draft-ietf-taps-transports-usage-09.txt   rfc8303.txt 
TAPS M. Welzl Internet Engineering Task Force (IETF) M. Welzl
Internet-Draft University of Oslo Request for Comments: 8303 University of Oslo
Intended status: Informational M. Tuexen Category: Informational M. Tuexen
Expires: April 29, 2018 Muenster Univ. of Appl. Sciences ISSN: 2070-1721 Muenster Univ. of Appl. Sciences
N. Khademi N. Khademi
University of Oslo University of Oslo
October 26, 2017 February 2018
On the Usage of Transport Features Provided by IETF Transport Protocols On the Usage of Transport Features
draft-ietf-taps-transports-usage-09 Provided by IETF Transport Protocols
Abstract Abstract
This document describes how the transport protocols Transmission This document describes how the transport protocols Transmission
Control Protocol (TCP), MultiPath TCP (MPTCP), Stream Control Control Protocol (TCP), MultiPath TCP (MPTCP), Stream Control
Transmission Protocol (SCTP), User Datagram Protocol (UDP) and Transmission Protocol (SCTP), User Datagram Protocol (UDP), and
Lightweight User Datagram Protocol (UDP-Lite) expose services to Lightweight User Datagram Protocol (UDP-Lite) expose services to
applications and how an application can configure and use the applications and how an application can configure and use the
features that make up these services. It also discusses the service features that make up these services. It also discusses the service
provided by the Low Extra Delay Background Transport (LEDBAT) provided by the Low Extra Delay Background Transport (LEDBAT)
congestion control mechanism. The description results in a set of congestion control mechanism. The description results in a set of
transport abstractions that can be exported in a TAPS API. transport abstractions that can be exported in a transport services
(TAPS) API.
Status of this Memo
This Internet-Draft is submitted in full conformance with the Status of This Memo
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This document is not an Internet Standards Track specification; it is
Task Force (IETF). Note that other groups may also distribute published for informational purposes.
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 7841.
This Internet-Draft will expire on April 29, 2018. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8303.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction ....................................................3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology .....................................................5
3. Pass 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Pass 1 ..........................................................6
3.1. Primitives Provided by TCP . . . . . . . . . . . . . . . . 5 3.1. Primitives Provided by TCP .................................6
3.1.1. Excluded Primitives or Parameters . . . . . . . . . . 9 3.1.1. Excluded Primitives or Parameters ...................9
3.2. Primitives Provided by MPTCP . . . . . . . . . . . . . . . 10 3.2. Primitives Provided by MPTCP ..............................10
3.3. Primitives Provided by SCTP . . . . . . . . . . . . . . . 11 3.3. Primitives Provided by SCTP ...............................11
3.3.1. Excluded Primitives or Parameters . . . . . . . . . . 18 3.3.1. Excluded Primitives or Parameters ..................18
3.4. Primitives Provided by UDP and UDP-Lite . . . . . . . . . 18 3.4. Primitives Provided by UDP and UDP-Lite ...................18
3.5. The service of LEDBAT . . . . . . . . . . . . . . . . . . 18 3.5. The Service of LEDBAT .....................................19
4. Pass 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4. Pass 2 .........................................................20
4.1. CONNECTION Related Primitives . . . . . . . . . . . . . . 20 4.1. CONNECTION-Related Primitives .............................21
4.2. DATA Transfer Related Primitives . . . . . . . . . . . . . 38 4.2. DATA-Transfer-Related Primitives ..........................38
5. Pass 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 5. Pass 3 .........................................................41
5.1. CONNECTION Related Transport Features . . . . . . . . . . 41 5.1. CONNECTION-Related Transport Features .....................41
5.2. DATA Transfer Related Transport Features . . . . . . . . . 47 5.2. DATA-Transfer-Related Transport Features ..................47
5.2.1. Sending Data . . . . . . . . . . . . . . . . . . . . . 47 5.2.1. Sending Data .......................................47
5.2.2. Receiving Data . . . . . . . . . . . . . . . . . . . . 48 5.2.2. Receiving Data .....................................48
5.2.3. Errors . . . . . . . . . . . . . . . . . . . . . . . . 49 5.2.3. Errors .............................................49
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 49 6. IANA Considerations ............................................49
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 49 7. Security Considerations ........................................49
8. Security Considerations . . . . . . . . . . . . . . . . . . . 50 8. References .....................................................50
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 50 8.1. Normative References ......................................50
9.1. Normative References . . . . . . . . . . . . . . . . . . . 50 8.2. Informative References ....................................52
9.2. Informative References . . . . . . . . . . . . . . . . . . 52 Appendix A. Overview of RFCs Used as Input for Pass 1 .............54
Appendix A. Overview of RFCs used as input for pass 1 . . . . . . 53 Appendix B. How This Document Was Developed .......................54
Appendix B. How this document was developed . . . . . . . . . . . 54 Acknowledgements ..................................................56
Appendix C. Revision information . . . . . . . . . . . . . . . . 55 Authors' Addresses ................................................56
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 57
1. Terminology
Transport Feature: a specific end-to-end feature that the transport
layer provides to an application. Examples include
confidentiality, reliable delivery, ordered delivery, message-
versus-stream orientation, etc.
Transport Service: a set of Transport Features, without an
association to any given framing protocol, which provides a
complete service to an application.
Transport Protocol: an implementation that provides one or more
transport services using a specific framing and header format on
the wire.
Transport Protocol Component: an implementation of a Transport
Feature within a protocol.
Transport Service Instance: an arrangement of transport protocols
with a selected set of features and configuration parameters that
implements a single transport service, e.g., a protocol stack (RTP
over UDP).
Application: an entity that uses the transport layer for end-to-end
delivery of data across the network (this may also be an upper
layer protocol or tunnel encapsulation).
Endpoint: an entity that communicates with one or more other
endpoints using a transport protocol.
Connection: shared state of two or more endpoints that persists
across messages that are transmitted between these endpoints.
Primitive: a function call that is used to locally communicate
between an application and a transport endpoint. A primitive is
related to one or more Transport Features.
Event: a primitive that is invoked by a transport endpoint.
Parameter: a value passed between an application and a transport
protocol by a primitive.
Socket: the combination of a destination IP address and a
destination port number.
Transport Address: the combination of an IP address, transport
protocol and the port number used by the transport protocol.
2. Introduction 1. Introduction
This specification describes an abstract interface for applications This specification describes how transport protocols offer transport
to make use of Transport Services, such that applications are no services, such that applications using them are no longer directly
longer directly tied to a specific protocol. Breaking this strict tied to a specific protocol. Breaking this strict connection can
connection can reduce the effort for an application programmer, yet reduce the effort for an application programmer, yet attain greater
attain greater transport flexibility by pushing complexity into an transport flexibility by pushing complexity into an underlying
underlying Transport Services (TAPS) system. transport services (TAPS) system.
This design process has started with a survey of the services This design process has started with a survey of the services
provided by IETF transport protocols and congestion control provided by IETF transport protocols and congestion control
mechanisms [RFC8095]. The present document and [FJ16] complement mechanisms [RFC8095]. The present document and [RFC8304] complement
this survey with an in-depth look at the defined interactions between this survey with an in-depth look at the defined interactions between
applications and the following unicast transport protocols: applications and the following unicast transport protocols:
Transmission Control Protocol (TCP), MultiPath TCP (MPTCP), Stream Transmission Control Protocol (TCP), MultiPath TCP (MPTCP), Stream
Control Transmission Protocol (SCTP), User Datagram Protocol (UDP), Control Transmission Protocol (SCTP), User Datagram Protocol (UDP),
Lightweight User Datagram Protocol (UDP-Lite). We also define a and Lightweight User Datagram Protocol (UDP-Lite). We also define a
primitive to enable/disable and configure the Low Extra Delay primitive to enable/disable and configure the Low Extra Delay
Background Transport (LEDBAT) unicast congestion control mechanism. Background Transport (LEDBAT) unicast congestion control mechanism.
For UDP and UDP-Lite, the first step of the protocol analysis -- a For UDP and UDP-Lite, the first step of the protocol analysis -- a
discussion of relevant RFC text -- is documented in [FJ16]. discussion of relevant RFC text -- is documented in [RFC8304].
This snapshot in time analysis of the IETF transport protocols is This snapshot in time of the IETF transport protocols is published as
published as an RFC to document the authors' and working group's an RFC to document the analysis by the authors and the TAPS Working
analysis, generating a set of transport abstractions that can be Group; this generates a set of transport abstractions that can be
exported in a TAPS API. It provides the basis for the minimal set of exported in a TAPS API. It provides the basis for the minimal set of
transport services that end systems supporting TAPS should implement transport services that end systems supporting TAPS should implement
[I-D.draft-gjessing-taps-minset]. [TAPS-MINSET].
The list of primitives, events and transport features in this The list of primitives, events, and transport features in this
document is strictly based on the parts of protocol specifications document is strictly based on the parts of protocol specifications
that describe what the protocol provides to an application using it that describe what the protocol provides to an application using it
and how the application interacts with it. Transport protocols and how the application interacts with it. Transport protocols
provide communication between processes that operate on network provide communication between processes that operate on network
endpoints, which means that they allow for multiplexing of endpoints, which means that they allow for multiplexing of
communication between the same IP addresses, and this multiplexing is communication between the same IP addresses, and this multiplexing is
achieved using port numbers. Port multiplexing is therefore assumed achieved using port numbers. Port multiplexing is therefore assumed
to be always provided and not discussed in this document. to be always provided and not discussed in this document.
Parts of a protocol that are explicitly stated as optional to Parts of a protocol that are explicitly stated as optional to
implement are not covered. Interactions between the application and implement are not covered. Interactions between the application and
a transport protocol that are not directly related to the operation a transport protocol that are not directly related to the operation
of the protocol are also not covered. For example, there are various of the protocol are also not covered. For example, there are various
ways for an application to use socket options to indicate its ways for an application to use socket options to indicate its
interest in receiving certain notifications [RFC6458]. However, for interest in receiving certain notifications [RFC6458]. However, for
the purpose of identifying primitives, events and transport features, the purpose of identifying primitives, events, and transport
the ability to enable or disable the reception of notifications is features, the ability to enable or disable the reception of
irrelevant. Similarly, "one-to-many style sockets" [RFC6458] just notifications is irrelevant. Similarly, "one-to-many style sockets"
affect the application programming style, not how the underlying
protocol operates, and they are therefore not discussed here. The [RFC6458] just affect the application programming style, not how the
same is true for the ability to obtain the unchanged value of a underlying protocol operates, and they are therefore not discussed
parameter that an application has previously set (e.g.,via "get" in here. The same is true for the ability to obtain the unchanged value
get/set operations [RFC6458]). of a parameter that an application has previously set (e.g., via
"get" in get/set operations [RFC6458]).
The document presents a three-pass process to arrive at a list of The document presents a three-pass process to arrive at a list of
transport features. In the first pass, the relevant RFC text is transport features. In the first pass (pass 1), the relevant RFC
discussed per protocol. In the second pass, this discussion is used text is discussed per protocol. In the second pass (pass 2), this
to derive a list of primitives and events that are uniformly discussion is used to derive a list of primitives and events that are
categorized across protocols. Here, an attempt is made to present or uniformly categorized across protocols. Here, an attempt is made to
-- where text describing primitives or events does not yet exist -- present or -- where text describing primitives or events does not yet
construct primitives or events in a slightly generalized form to exist -- construct primitives or events in a slightly generalized
highlight similarities. This is, for example, achieved by renaming form to highlight similarities. This is, for example, achieved by
primitives or events of protocols or by avoiding a strict 1:1-mapping renaming primitives or events of protocols or by avoiding a strict
between the primitives or events in the protocol specification and 1:1 mapping between the primitives or events in the protocol
primitives or events in the list. Finally, the third pass presents specification and primitives or events in the list. Finally, the
transport features based on pass 2, identifying which protocols third pass (pass 3) presents transport features based on pass 2,
implement them. identifying which protocols implement them.
In the list resulting from the second pass, some transport features In the list resulting from the second pass, some transport features
are missing because they are implicit in some protocols, and they are missing because they are implicit in some protocols, and they
only become explicit when we consider the superset of all transport only become explicit when we consider the superset of all transport
features offered by all protocols. For example, TCP always carries features offered by all protocols. For example, TCP always carries
out congestion control; we have to consider it together with a out congestion control; we have to consider it together with a
protocol like UDP (which does not have congestion control) before we protocol like UDP (which does not have congestion control) before we
can consider congestion control as a transport feature. The complete can consider congestion control as a transport feature. The complete
list of transport features across all protocols is therefore only list of transport features across all protocols is therefore only
available after pass 3. available after pass 3.
Some protocols are connection-oriented. Connection-oriented Some protocols are connection oriented. Connection-oriented
protocols often use an initial call to a specific primitive to open a protocols often use an initial call to a specific primitive to open a
connection before communication can progress, and require connection before communication can progress and require
communication to be explicitly terminated by issuing another call to communication to be explicitly terminated by issuing another call to
a primitive (usually called "close"). A "connection" is the common a primitive (usually called 'Close'). A "connection" is the common
state that some transport primitives refer to, e.g., to adjust state that some transport primitives refer to, e.g., to adjust
general configuration settings. Connection establishment, general configuration settings. Connection establishment,
maintenance and termination are therefore used to categorize maintenance, and termination are therefore used to categorize
transport primitives of connection-oriented transport protocols in transport primitives of connection-oriented transport protocols in
pass 2 and pass 3. For this purpose, UDP is assumed to be used with pass 2 and pass 3. For this purpose, UDP is assumed to be used with
"connected" sockets, i.e. sockets that are bound to a specific pair "connected" sockets, i.e., sockets that are bound to a specific pair
of addresses and ports [FJ16]. of addresses and ports [RFC8304].
2. Terminology
Transport Feature: a specific end-to-end feature that the transport
layer provides to an application. Examples include
confidentiality, reliable delivery, ordered delivery, message-
versus-stream orientation, etc.
Transport Service: a set of transport features, without an
association to any given framing protocol, which provides a
complete service to an application.
Transport Protocol: an implementation that provides one or more
transport services using a specific framing and header format on
the wire.
Transport Protocol Component: an implementation of a transport
feature within a protocol.
Transport Service Instance: an arrangement of transport protocols
with a selected set of features and configuration parameters that
implement a single transport service, e.g., a protocol stack (RTP
over UDP).
Application: an entity that uses the transport layer for end-to-end
delivery of data across the network (this may also be an upper-
layer protocol or tunnel encapsulation).
Endpoint: an entity that communicates with one or more other
endpoints using a transport protocol.
Connection: shared state of two or more endpoints that persists
across messages that are transmitted between these endpoints.
Primitive: a function call that is used to locally communicate
between an application and a transport endpoint. A primitive is
related to one or more transport features.
Event: a primitive that is invoked by a transport endpoint.
Parameter: a value passed between an application and a transport
protocol by a primitive.
Socket: the combination of a destination IP address and a
destination port number.
Transport Address: the combination of an IP address, transport
protocol, and the port number used by the transport protocol.
3. Pass 1 3. Pass 1
This first iteration summarizes the relevant text parts of the RFCs This first iteration summarizes the relevant text parts of the RFCs
describing the protocols, focusing on what each transport protocol describing the protocols, focusing on what each transport protocol
provides to the application and how it is used (abstract API provides to the application and how it is used (abstract API
descriptions, where they are available). When presenting primitives, descriptions, where they are available). When presenting primitives,
events and parameters, the use of lower- and upper-case characters is events, and parameters, the use of lower- and upper-case characters
made uniform for the sake of readability. is made uniform for the sake of readability.
3.1. Primitives Provided by TCP 3.1. Primitives Provided by TCP
The initial TCP specification [RFC0793] states: "The Transmission The initial TCP specification [RFC0793] states:
Control Protocol (TCP) is intended for use as a highly reliable host-
to-host protocol between hosts in packet-switched computer
communication networks, and in interconnected systems of such
networks". Section 3.8 in this specification [RFC0793] further
specifies the interaction with the application by listing several
transport primitives. It is also assumed that an Operating System
provides a means for TCP to asynchronously signal the application;
the primitives representing such signals are called 'events' in this
section. This section describes the relevant primitives.
Open: this is either active or passive, to initiate a connection or The Transmission Control Protocol (TCP) is intended for use as a
highly reliable host-to-host protocol between hosts in packet-
switched computer communication networks, and in interconnected
systems of such networks.
Section 3.8 of [RFC0793] further specifies the interaction with the
application by listing several transport primitives. It is also
assumed that an Operating System provides a means for TCP to
asynchronously signal the application; the primitives representing
such signals are called 'events' in this section. This section
describes the relevant primitives.
Open: This is either active or passive, to initiate a connection or
listen for incoming connections. All other primitives are listen for incoming connections. All other primitives are
associated with a specific connection, which is assumed to first associated with a specific connection, which is assumed to first
have been opened. An active open call contains a socket. A have been opened. An active open call contains a socket. A
passive open call with a socket waits for a particular connection; passive open call with a socket waits for a particular connection;
alternatively, a passive open call can leave the socket alternatively, a passive open call can leave the socket
unspecified to accept any incoming connection. A fully specified unspecified to accept any incoming connection. A fully specified
passive call can later be made active by calling 'Send'. passive call can later be made active by calling 'Send'.
Optionally, a timeout can be specified, after which TCP will abort Optionally, a timeout can be specified, after which TCP will abort
the connection if data has not been successfully delivered to the the connection if data has not been successfully delivered to the
destination (else a default timeout value is used). A procedure destination (else a default timeout value is used). A procedure
skipping to change at page 6, line 35 skipping to change at page 7, line 5
threshold may be measured in time units or as a count of threshold may be measured in time units or as a count of
retransmission [RFC1122]. This indicates that the timeout could retransmission [RFC1122]. This indicates that the timeout could
also be specified as a count of retransmission. also be specified as a count of retransmission.
Also optional, for multihomed hosts, the local IP address can be Also optional, for multihomed hosts, the local IP address can be
provided [RFC1122]. If it is not provided, a default choice will provided [RFC1122]. If it is not provided, a default choice will
be made in case of active open calls. A passive open call will be made in case of active open calls. A passive open call will
await incoming connection requests to all local addresses and then await incoming connection requests to all local addresses and then
maintain usage of the local IP address where the incoming maintain usage of the local IP address where the incoming
connection request has arrived. Finally, the 'options' parameter connection request has arrived. Finally, the 'options' parameter
allows the application to specify IP options such as source route, allows the application to specify IP options such as Source Route,
record route, or timestamp [RFC1122]. It is not stated on which Record Route, or Timestamp [RFC1122]. It is not stated on which
segments of a connection these options should be applied, but segments of a connection these options should be applied, but
probably all segments, as this is also stated in a specification probably on all segments, as this is also stated in a
given for the usage of source route (section 4.2.3.8 of specification given for the usage of the Source Route IP option
[RFC1122]). Source route is the only non-optional IP option in (Section 4.2.3.8 of [RFC1122]). Source Route is the only non-
this parameter, allowing an application to specify a source route optional IP option in this parameter, allowing an application to
when it actively opens a TCP connection. specify a source route when it actively opens a TCP connection.
Master Key Tuples (MKTs) for authentication can optionally be Master Key Tuples (MKTs) for authentication can optionally be
configured when calling open (section 7.1 of [RFC5925]). When configured when calling 'Open' (Section 7.1 of [RFC5925]). When
authentication is in use, complete TCP segments are authenticated, authentication is in use, complete TCP segments are authenticated,
including the TCP IPv4 pseudoheader, TCP header, and TCP data. including the TCP IPv4 pseudoheader, TCP header, and TCP data.
TCP Fast Open (TFO) [RFC7413] allows applications to immediately TCP Fast Open (TFO) [RFC7413] allows applications to immediately
hand over a message from the active open to the passive open side hand over a message from the active open to the passive open side
of a TCP connection together with the first message establishment of a TCP connection together with the first message establishment
packet (the SYN). This can be useful for applications that are packet (the SYN). This can be useful for applications that are
sensitive to TCP's connection setup delay. [RFC7413] states that sensitive to TCP's connection setup delay. [RFC7413] states that
"TCP implementations MUST NOT use TFO by default, but only use TFO "TCP implementations MUST NOT use TFO by default, but only use TFO
if requested explicitly by the application on a per-service-port if requested explicitly by the application on a per-service-port
basis". The size of the message sent with TFO cannot be more than basis." The size of the message sent with TFO cannot be more than
TCP's maximum segment size (minus options used in the SYN). For TCP's maximum segment size (minus options used in the SYN). For
the active open side, it is recommended to change or replace the the active open side, it is recommended to change or replace the
connect() call in order to support a user data buffer argument connect() call in order to support a user data buffer argument
[RFC7413]. For the passive open side, the application needs to [RFC7413]. For the passive open side, the application needs to
enable the reception of Fast Open requests, e.g. via a new enable the reception of Fast Open requests, e.g., via a new
TCP_FASTOPEN setsockopt() socket option before listen(). The TCP_FASTOPEN setsockopt() socket option before listen(). The
receiving application must be prepared to accept duplicates of the receiving application must be prepared to accept duplicates of the
TFO message, as the first data written to a socket can be TFO message, as the first data written to a socket can be
delivered more than once to the application on the remote host. delivered more than once to the application on the remote host.
Send: this is the primitive that an application uses to give the Send: This is the primitive that an application uses to give the
local TCP transport endpoint a number of bytes that TCP should local TCP transport endpoint a number of bytes that TCP should
reliably send to the other side of the connection. The 'urgent' reliably send to the other side of the connection. The 'urgent'
flag, if set, states that the data handed over by this send call flag, if set, states that the data handed over by this send call
is urgent and this urgency should be indicated to the receiving is urgent and this urgency should be indicated to the receiving
process in case the receiving application has not yet consumed all process in case the receiving application has not yet consumed all
non-urgent data preceding it. An optional timeout parameter can non-urgent data preceding it. An optional timeout parameter can
be provided that updates the connection's timeout (see 'open'). be provided that updates the connection's timeout (see 'Open').
Additionally, optional parameters allow to indicate the preferred Additionally, optional parameters allow the ability to indicate
outgoing MKT (current_key) and/or the preferred incoming MKT the preferred outgoing MKT (current_key) and/or the preferred
(rnext_key) of a connection (section 7.1 of [RFC5925]). incoming MKT (rnext_key) of a connection (Section 7.1 of
[RFC5925]).
Receive: This primitive allocates a receiving buffer for a provided Receive: This primitive allocates a receiving buffer for a provided
number of bytes. It returns the number of received bytes provided number of bytes. It returns the number of received bytes provided
in the buffer when these bytes have been received and written into in the buffer when these bytes have been received and written into
the buffer by TCP. The application is informed of urgent data via the buffer by TCP. The application is informed of urgent data via
an 'urgent' flag: if it is on, there is urgent data. If it is an 'urgent' flag: if it is on, there is urgent data; if it is off,
off, there is no urgent data or this call to 'receive' has there is no urgent data or this call to 'Receive' has returned all
returned all the urgent data. The application is also informed the urgent data. The application is also informed about the
about the current_key and rnext_key information carried in a current_key and rnext_key information carried in a recently
recently received segment via an optional parameter (section 7.1 received segment via an optional parameter (Section 7.1 of
of [RFC5925]). [RFC5925]).
Close: This primitive closes one side of a connection. It is Close: This primitive closes one side of a connection. It is
semantically equivalent to "I have no more data to send" but does semantically equivalent to "I have no more data to send" but does
not mean "I will not receive any more", as the other side may not mean "I will not receive any more", as the other side may
still have data to send. This call reliably delivers any data still have data to send. This call reliably delivers any data
that has already been given to TCP (and if that fails, 'close' that has already been given to TCP (and if that fails, 'Close'
becomes 'abort'). becomes 'abort').
Abort: This primitive causes all pending 'send' and 'receive' calls Abort: This primitive causes all pending 'Send' and 'Receive' calls
to be aborted. A TCP "RESET" message is sent to the TCP endpoint to be aborted. A TCP "RESET" message is sent to the TCP endpoint
on the other side of the connection [RFC0793]. on the other side of the connection [RFC0793].
Close Event: TCP uses this primitive to inform an application that Close Event: TCP uses this primitive to inform an application that
the application on the other side has called the 'close' the application on the other side has called the 'Close'
primitive, so the local application can also issue a 'close' and primitive, so the local application can also issue a 'Close' and
terminate the connection gracefully. See [RFC0793], Section 3.5. terminate the connection gracefully. See [RFC0793], Section 3.5.
Abort Event: When TCP aborts a connection upon receiving a "RESET" Abort Event: When TCP aborts a connection upon receiving a "RESET"
from the peer, it "advises the user and goes to the CLOSED state." from the peer, it "advises the user and goes to the CLOSED state."
See [RFC0793], Section 3.4. See [RFC0793], Section 3.4.
User Timeout Event: This event is executed when the user timeout User Timeout Event: This event is executed when the user timeout
expires (see 'open') (section 3.9 of [RFC0793]). All queues are (Section 3.9 of [RFC0793]) expires (see the definition of 'Open'
flushed and the application is informed that the connection had to in this section). All queues are flushed, and the application is
be aborted due to user timeout. informed that the connection had to be aborted due to user
timeout.
Error_Report event: This event informs the application of "soft Error_Report event: This event informs the application of "soft
errors" that can be safely ignored [RFC5461], including the errors" that can be safely ignored [RFC5461], including the
arrival of an ICMP error message or excessive retransmissions arrival of an ICMP error message or excessive retransmissions
(reaching a threshold below the threshold where the connection is (reaching a threshold below the threshold where the connection is
aborted). See section 4.2.4.1 of [RFC1122]. aborted). See Section 4.2.4.1 of [RFC1122].
Type-of-Service: Section 4.2.4.2 of the requirements for Internet Type-of-Service: Section 4.2.4.2 of the requirements for Internet
hosts [RFC1122] states that "the application layer MUST be able to hosts [RFC1122] states that "The application layer MUST be able to
specify the Type-of-Service (TOS) for segments that are sent on a specify the Type-of-Service (TOS) for segments that are sent on a
connection". The application should be able to change the TOS connection." The application should be able to change the TOS
during the connection lifetime, and the TOS value should be passed during the connection lifetime, and the TOS value should be passed
to the IP layer unchanged. Since then the TOS field has been to the IP layer unchanged. Since then, the TOS field has been
redefined. The Differentiated Services (DiffServ) model [RFC2475] redefined. The Differentiated Services (Diffserv) model [RFC2475]
[RFC3260] replaces this field in the IP Header, assigning the six [RFC3260] replaces this field in the IP header, assigning the six
most significant bits to carry the Differentiated Services Code most significant bits to carry the Differentiated Services Code
Point (DSCP) field [RFC2474]. Point (DSCP) field [RFC2474].
Nagle: The Nagle algorithm delays sending data for some time to Nagle: The Nagle algorithm delays sending data for some time to
increase the likelihood of sending a full-sized segment (section increase the likelihood of sending a full-sized segment
4.2.3.4 of [RFC1122]). An application can disable the Nagle (Section 4.2.3.4 of [RFC1122]). An application can disable the
algorithm for an individual connection. Nagle algorithm for an individual connection.
User Timeout Option: The User Timeout Option (UTO) [RFC5482] allows User Timeout Option: The User Timeout Option (UTO) [RFC5482] allows
one end of a TCP connection to advertise its current user timeout one end of a TCP connection to advertise its current user timeout
value so that the other end of the TCP connection can adapt its value so that the other end of the TCP connection can adapt its
own user timeout accordingly. In addition to the configurable own user timeout accordingly. In addition to the configurable
value of the User Timeout (see 'send'), there are three per- value of the user timeout (see 'Send'), there are three per-
connection state variables that an application can adjust to connection state variables that an application can adjust to
control the operation of the User Timeout Option (UTO): 'adv_uto' control the operation of the UTO: 'adv_uto' is the value of the
is the value of the UTO advertised to the remote TCP peer UTO advertised to the remote TCP peer (default: system-wide
(default: system-wide default user timeout); 'enabled' (default default user timeout); 'enabled' (default false) is a boolean-type
false) is a boolean-type flag that controls whether the UTO option flag that controls whether the UTO option is enabled for a
is enabled for a connection. This applies to both sending and connection. This applies to both sending and receiving.
receiving. 'changeable' is a boolean-type flag (default true) that 'changeable' is a boolean-type flag (default true) that controls
controls whether the user timeout may be changed based on a UTO whether the user timeout may be changed based on a UTO option
option received from the other end of the connection. 'changeable' received from the other end of the connection. 'changeable'
becomes false when an application explicitly sets the user timeout becomes false when an application explicitly sets the user timeout
(see 'send'). (see 'Send').
Set / Get Authentication Parameters: The preferred outgoing MKT Set/Get Authentication Parameters: The preferred outgoing MKT
(current_key) and/or the preferred incoming MKT (rnext_key) of a (current_key) and/or the preferred incoming MKT (rnext_key) of a
connection can be configured. Information about current_key and connection can be configured. Information about current_key and
rnext_key carried in a recently received segment can be retrieved rnext_key carried in a recently received segment can be retrieved
(section 7.1 of [RFC5925]). (Section 7.1 of [RFC5925]).
3.1.1. Excluded Primitives or Parameters 3.1.1. Excluded Primitives or Parameters
The 'open' primitive can be handed optional Precedence or security/ The 'Open' primitive can be handed optional precedence or security/
compartment information [RFC0793], but this was not included here compartment information [RFC0793], but this was not included here
because it is mostly irrelevant today [RFC7414]. because it is mostly irrelevant today [RFC7414].
The 'Status' primitive was not included because the initial TCP The 'Status' primitive was not included because the initial TCP
specification describes this primitive as "implementation dependent" specification describes this primitive as "implementation dependent"
and states that it "could be excluded without adverse effect" and states that it "could be excluded without adverse effect"
[RFC0793]. Moreover, while a data block containing specific [RFC0793]. Moreover, while a data block containing specific
information is described, it is also stated that not all of this information is described, it is also stated that not all of this
information may always be available. While [RFC5925] states that information may always be available. While [RFC5925] states that
'Status' "SHOULD be augmented to allow the MKTs of a current or 'Status' "SHOULD be augmented to allow the MKTs of a current or
pending connection to be read (for confirmation)", the same pending connection to be read (for confirmation)", the same
information is also available via 'Receive', which, following information is also available via 'Receive', which, following
[RFC5925], "MUST be augmented" with that functionality. The 'Send' [RFC5925], "MUST be augmented" with that functionality. The 'Send'
primitive includes an optional 'push' flag which, if set, requires primitive includes an optional 'push' flag which, if set, requires
data to be promptly transmitted to the receiver without delay data to be promptly transmitted to the receiver without delay
[RFC0793]; the 'Receive' primitive described in can (under some [RFC0793]; the 'Receive' primitive described in can (under some
conditions) yield the status of the 'push' flag. Because "push" conditions) yield the status of the 'push' flag. Because "push"
functionality is optional to implement for both the 'send' and functionality is optional to implement for both the 'Send' and
'receive' primitives [RFC1122], this functionality is not included 'Receive' primitives [RFC1122], this functionality is not included
here. The requirements for Internet hosts [RFC1122] also introduce here. The requirements for Internet hosts [RFC1122] also introduce
keep-alives to TCP, but these are optional to implement and hence not keep-alives to TCP, but these are optional to implement and hence not
considered here. The same document also describes that "some TCP considered here. The same document also describes that "some TCP
implementations have included a FLUSH call", indicating that this implementations have included a FLUSH call", indicating that this
call is also optional to implement. It is therefore not considered call is also optional to implement; therefore, it is not considered
here. here.
3.2. Primitives Provided by MPTCP 3.2. Primitives Provided by MPTCP
Multipath TCP (MPTCP) is an extension to TCP that allows the use of MPTCP is an extension to TCP that allows the use of multiple paths
multiple paths for a single data-stream. It achieves this by for a single data stream. It achieves this by creating different so-
creating different so-called TCP subflows for each of the interfaces called TCP subflows for each of the interfaces and scheduling the
and scheduling the traffic across these TCP subflows. The service traffic across these TCP subflows. The service provided by MPTCP is
provided by MPTCP is described as follows in [RFC6182]: "Multipath described as follows in [RFC6182]:
TCP MUST follow the same service model as TCP [RFC0793]: in- order,
reliable, and byte-oriented delivery. Furthermore, a Multipath TCP
connection SHOULD provide the application with no worse throughput or
resilience than it would expect from running a single TCP connection
over any one of its available paths."
Further, there are some constraints on the API exposed by MPTCP, Multipath TCP MUST follow the same service model as TCP [RFC0793]:
stated in [RFC6182]: "A multipath-capable equivalent of TCP MUST in-order, reliable, and byte-oriented delivery. Furthermore, a
retain some level of backward compatibility with existing TCP APIs, Multipath TCP connection SHOULD provide the application with no
so that existing applications can use the newer merely by upgrading worse throughput or resilience than it would expect from running a
the operating systems of the end hosts." As such, the primitives single TCP connection over any one of its available paths.
provided by MPTCP are equivalent to the ones provided by TCP.
Nevertheless, the MPTCP RFCs [RFC6824] and [RFC6897] clarify some Further, there are some constraints on the API exposed by MPTCP, as
parts of TCP's primitives with respect to MPTCP and add some stated in [RFC6182]:
extensions for better control on MPTCP's subflows. Hereafter is a
list of the clarifications and extensions the above cited RFCs A multipath-capable equivalent of TCP MUST retain some level of
provide to TCP's primitives. backward compatibility with existing TCP APIs, so that existing
applications can use the newer transport merely by upgrading the
operating systems of the end hosts.
As such, the primitives provided by MPTCP are equivalent to the ones
provided by TCP. Nevertheless, the MPTCP RFCs [RFC6824] and
[RFC6897] clarify some parts of TCP's primitives with respect to
MPTCP and add some extensions for better control on MPTCP's subflows.
Hereafter is a list of the clarifications and extensions the above-
cited RFCs provide to TCP's primitives.
Open: "An application should be able to request to turn on or turn Open: "An application should be able to request to turn on or turn
off the usage of MPTCP" [RFC6897]. This functionality can be off the usage of MPTCP" [RFC6897]. This functionality can be
provided through a socket-option called 'tcp_multipath_enable'. provided through a socket option called 'tcp_multipath_enable'.
Further, MPTCP must be disabled in case the application is binding Further, MPTCP must be disabled in case the application is binding
to a specific address [RFC6897]. to a specific address [RFC6897].
Send/Receive: The sending and receiving of data does not require any Send/Receive: The sending and receiving of data does not require any
changes to the application when MPTCP is being used [RFC6824]. changes to the application when MPTCP is being used [RFC6824].
The MPTCP-layer will "take one input data stream from an The MPTCP-layer will take one input data stream from an
application, and split it into one or more subflows, with application, and split it into one or more subflows, with
sufficient control information to allow it to be reassembled and sufficient control information to allow it to be reassembled and
delivered reliably and in order to the recipient application." delivered reliably and in order to the recipient application.
The use of the Urgent Pointer is special in MPTCP [RFC6824], which The use of the Urgent Pointer is special in MPTCP [RFC6824], which
states: "a TCP subflow MUST NOT use the Urgent Pointer to states: "a TCP subflow MUST NOT use the Urgent Pointer to
interrupt an existing mapping." interrupt an existing mapping."
Address and Subflow Management: MPTCP uses different addresses and Address and Subflow Management: MPTCP uses different addresses and
allows a host to announce these addresses as part of the protocol. allows a host to announce these addresses as part of the protocol.
The MPTCP API Considerations RFC [RFC6897] says "An application The MPTCP API Considerations RFC [RFC6897] says "An application
should be able to restrict MPTCP to binding to a given set of should be able to restrict MPTCP to binding to a given set of
addresses" and thus allows applications to limit the set of addresses" and thus allows applications to limit the set of
addresses that are being used by MPTCP. Further, "An application addresses that are being used by MPTCP. Further, "An application
should be able to obtain information on the pairs of addresses should be able to obtain information on the pairs of addresses
used by the MPTCP subflows". used by the MPTCP subflows."
3.3. Primitives Provided by SCTP 3.3. Primitives Provided by SCTP
TCP has a number of limitations that SCTP removes (section 1.1 of TCP has a number of limitations that SCTP removes (Section 1.1 of
[RFC4960]). The following three removed limitations directly [RFC4960]). The following three removed limitations directly
translate into transport features that are visible to an application translate into transport features that are visible to an application
using SCTP: 1) it allows for preservation of message delimiters; 2) using SCTP: 1) it allows for preservation of message delimiters; 2)
it does not provide in-order or reliable delivery unless the it does not provide in-order or reliable delivery unless the
application wants that; 3) multi-homing is supported. In SCTP, application wants that; 3) multihoming is supported. In SCTP,
connections are called "associations" and they can be between not connections are called "associations" and they can be between not
only two (as in TCP) but multiple addresses at each endpoint. only two (as in TCP) but multiple addresses at each endpoint.
Section 10 of the SCTP base protocol specification [RFC4960] Section 10 of the SCTP base protocol specification [RFC4960]
specifies the interaction with the application (which SCTP calls the specifies the interaction with the application (which SCTP calls the
"Upper Layer Protocol" (ULP)). It is assumed that the Operating "Upper-Layer Protocol (ULP)"). It is assumed that the Operating
System provides a means for SCTP to asynchronously signal the System provides a means for SCTP to asynchronously signal the
application; the primitives representing such signals are called application; the primitives representing such signals are called
'events' in this section. Here, we describe the relevant primitives. 'events' in this section. Here, we describe the relevant primitives.
In addition to the abstract API described in the section 10 of the In addition to the abstract API described in Section 10 of [RFC4960],
SCTP base protocol specification [RFC4960], an extension to the an extension to the sockets API is described in [RFC6458]. This
socket API is described in [RFC6458]. This covers the functionality covers the functionality of the base protocol [RFC4960] and some of
of the base protocol [RFC4960] and some of its extensions [RFC3758], its extensions [RFC3758] [RFC4895] [RFC5061]. For other protocol
[RFC4895], [RFC5061]. For other protocol extensions [RFC6525], extensions [RFC6525] [RFC6951] [RFC7053] [RFC7496] [RFC7829]
[RFC6951], [RFC7053], [RFC7496], [RFC7829],
[I-D.ietf-tsvwg-sctp-ndata], the corresponding extensions of the [RFC8260], the corresponding extensions of the sockets API are
socket API are specified in these protocol specifications. The specified in these protocol specifications. The functionality
functionality exposed to the ULP through all these APIs is considered exposed to the ULP through all these APIs is considered here.
here.
The abstract API contains a 'SetProtocolParameters' primitive that The abstract API contains a 'SetProtocolParameters' primitive that
allows to adjust elements of a parameter list [RFC4960]; it is stated allows elements of a parameter list [RFC4960] to be adjusted; it is
that SCTP implementations "may allow ULP to customize some of these stated that SCTP implementations "may allow ULP to customize some of
protocol parameters", indicating that none of the elements of this these protocol parameters", indicating that none of the elements of
parameter list are mandatory to make ULP-configurable. Thus, we only this parameter list are mandatory to make ULP configurable. Thus, we
consider the parameters in the abstract API that are also covered in only consider the parameters in the abstract API that are also
one of the other RFCs listed above, which leads us to exclude the covered in one of the other RFCs listed above, which leads us to
parameters RTO.Alpha, RTO.Beta and HB.Max.Burst. For clarity, we exclude the parameters 'RTO.Alpha', 'RTO.Beta', and 'HB.Max.Burst'.
also replace 'SetProtocolParameters' itself with primitives that For clarity, we also replace 'SetProtocolParameters' itself with
adjust parameters or groups of parameters that fit together. primitives that adjust parameters or groups of parameters that fit
together.
Initialize: Initialize creates a local SCTP instance that it binds Initialize: Initialize creates a local SCTP instance that it binds
to a set of local addresses (and, if provided, a local port to a set of local addresses (and, if provided, a local port
number) [RFC4960]. Initialize needs to be called only once per number) [RFC4960]. Initialize needs to be called only once per
set of local addresses. A number of per-association set of local addresses. A number of per-association
initialization parameters can be used when an association is initialization parameters can be used when an association is
created, but before it is connected (via the primitive 'Associate' created, but before it is connected (via the primitive 'Associate'
below): the maximum number of inbound streams the application is below): the maximum number of inbound streams the application is
prepared to support, the maximum number of attempts to be made prepared to support, the maximum number of attempts to be made
when sending the INIT (the first message of association when sending the INIT (the first message of association
establishment), and the maximum retransmission timeout (RTO) value establishment), and the maximum retransmission timeout (RTO) value
to use when attempting an INIT [RFC6458]. At this point, before to use when attempting an INIT [RFC6458]. At this point, before
connecting, an application can also enable UDP encapsulation by connecting, an application can also enable UDP encapsulation by
configuring the remote UDP encapsulation port number [RFC6951]. configuring the remote UDP encapsulation port number [RFC6951].
Associate: This creates an association (the SCTP equivalent of a Associate: This creates an association (the SCTP equivalent of a
connection) that connects the local SCTP instance and a remote connection) that connects the local SCTP instance and a remote
SCTP instance. To identify the remote endpoint, it can be given SCTP instance. To identify the remote endpoint, it can be given
one or multiple (using "connectx") sockets (section 9.9 of one or multiple (using "connectx") sockets (Section 9.9 of
[RFC6458]). Most primitives are associated with a specific [RFC6458]). Most primitives are associated with a specific
association, which is assumed to first have been created. association, which is assumed to first have been created.
Associate can return a list of destination transport addresses so Associate can return a list of destination transport addresses so
that multiple paths can later be used. One of the returned that multiple paths can later be used. One of the returned
sockets will be selected by the local endpoint as default primary sockets will be selected by the local endpoint as the default
path for sending SCTP packets to this peer, but this choice can be primary path for sending SCTP packets to this peer, but this
changed by the application using the list of destination choice can be changed by the application using the list of
addresses. Associate is also given the number of outgoing streams destination addresses. Associate is also given the number of
to request and optionally returns the number of negotiated outgoing streams to request and optionally returns the number of
outgoing streams. An optional parameter of 32 bits, the negotiated outgoing streams. An optional parameter of 32 bits,
adaptation layer indication, can be provided [RFC5061]. If the adaptation layer indication, can be provided [RFC5061]. If
authenticated chunks are used, the chunk types required to be sent authenticated chunks are used, the chunk types required to be sent
authenticated by the peer can be provided [RFC4895]. A authenticated by the peer can be provided [RFC4895]. An
'SCTP_Cant_Str_Assoc' notification is used to inform the 'SCTP_Cant_Str_Assoc' notification is used to inform the
application of a failure to create an association [RFC6458]. An application of a failure to create an association [RFC6458]. An
application could use sendto() or sendmsg() to implicitly setup an application could use sendto() or sendmsg() to implicitly set up
association, thereby handing over a message that SCTP might send an association, thereby handing over a message that SCTP might
during the association setup phase [RFC6458]. Note that this send during the association setup phase [RFC6458]. Note that this
mechanism is different from TCP's TFO mechanism: the message would mechanism is different from TCP's TFO mechanism: the message would
arrive only once, after at least one RTT, as it is sent together arrive only once, after at least one RTT, as it is sent together
with the third message exchanged during association setup, the with the third message exchanged during association setup, the
COOKIE-ECHO chunk). COOKIE-ECHO chunk).
Send: This sends a message of a certain length in bytes over an Send: This sends a message of a certain length in bytes over an
association. A number can be provided to later refer to the association. A number can be provided to later refer to the
correct message when reporting an error, and a stream id is correct message when reporting an error, and a stream id is
provided to specify the stream to be used inside an association provided to specify the stream to be used inside an association
(we consider this as a mandatory parameter here for simplicity: if (we consider this as a mandatory parameter here for simplicity: if
not provided, the stream id defaults to 0). A condition to not provided, the stream id defaults to 0). A condition to
abandon the message can be specified (for example limiting the abandon the message can be specified (for example limiting the
number of retransmissions or the lifetime of the user message). number of retransmissions or the lifetime of the user message).
This allows to control the partial reliability extension This allows control of the partial reliability extension [RFC3758]
[RFC3758], [RFC7496]. An optional maximum life time can specify [RFC7496]. An optional maximum lifetime can specify the time
the time after which the message should be discarded rather than after which the message should be discarded rather than sent. A
sent. A choice (advisory, i.e. not guaranteed) of the preferred choice (advisory, i.e., not guaranteed) of the preferred path can
path can be made by providing a socket, and the message can be be made by providing a socket, and the message can be delivered
delivered out-of-order if the unordered flag is set. An advisory out-of-order if the 'unordered' flag is set. An advisory flag
flag indicates that the peer should not delay the acknowledgement indicates that the peer should not delay the acknowledgement of
of the user message provided [RFC7053]. Another advisory flag the user message provided [RFC7053]. Another advisory flag
indicates whether the application prefers to avoid bundling user indicates whether the application prefers to avoid bundling user
data with other outbound DATA chunks (i.e., in the same packet). data with other outbound DATA chunks (i.e., in the same packet).
A payload protocol-id can be provided to pass a value that A payload protocol-id can be provided to pass a value that
indicates the type of payload protocol data to the peer. If indicates the type of payload protocol data to the peer. If
authenticated chunks are used, the key identifier for authenticated chunks are used, the key identifier for
authenticating DATA chunks can be provided [RFC4895]. authenticating DATA chunks can be provided [RFC4895].
Receive: Messages are received from an association, and optionally a Receive: Messages are received from an association, and optionally a
stream within the association, with their size returned. The stream within the association, with their size returned. The
application is notified of the availability of data via a 'Data application is notified of the availability of data via a 'Data
Arrive' notification. If the sender has included a payload Arrive' notification. If the sender has included a payload
protocol-id, this value is also returned. If the received message protocol-id, this value is also returned. If the received message
is only a partial delivery of a whole message, a partial flag will is only a partial delivery of a whole message, a 'partial' flag
indicate so, in which case the stream id and a stream sequence will indicate so, in which case the stream id and a stream
number are provided to the application. sequence number are provided to the application.
Shutdown: This primitive gracefully closes an association, reliably Shutdown: This primitive gracefully closes an association, reliably
delivering any data that has already been handed over to SCTP. A delivering any data that has already been handed over to SCTP. A
parameter lets the application control whether further receive or parameter lets the application control whether further receive or
send operations or both are disabled when the call is issued. A send operations or both are disabled when the call is issued. A
return code informs about success or failure of this procedure. return code informs about success or failure of this procedure.
Abort: This ungracefully closes an association, by discarding any Abort: This ungracefully closes an association, by discarding any
locally queued data and informing the peer that the association locally queued data and informing the peer that the association
was aborted. Optionally, an abort reason to be passed to the peer was aborted. Optionally, an abort reason to be passed to the peer
may be provided by the application. A return code informs about may be provided by the application. A return code informs about
success or failure of this procedure. success or failure of this procedure.
Change Heartbeat / Request Heartbeat: This allows the application to Change Heartbeat / Request Heartbeat: This allows the application to
enable/disable heartbeats and optionally specify a heartbeat enable/disable heartbeats and optionally specify a heartbeat
frequency as well as requesting a single heartbeat to be carried frequency as well as requesting a single heartbeat to be carried
out upon a function call, with a notification about success or out upon a function call, with a notification about success or
failure of transmitting the HEARTBEAT chunk to the destination. failure of transmitting the HEARTBEAT chunk to the destination.
Configure Max. Retransmissions of an Association: The parameter Configure Max. Retransmissions of an Association: The parameter
Association.Max.Retrans [RFC4960] (called "sasoc_maxrxt" in the 'Association.Max.Retrans' [RFC4960] (called "sasoc_maxrxt" in the
SCTP socket API extensions [RFC6458]), allows to configure the SCTP sockets API extensions [RFC6458]) allows the configuration of
number of unsuccessful retransmissions after which an entire the number of unsuccessful retransmissions after which an entire
association is considered as failed; this should invoke a association is considered as failed; this should invoke a
'Communication Lost' notification. 'Communication Lost' notification.
Set Primary: This allows to set a new primary default path for an Set Primary: This allows the ability to set a new primary default
association by providing a socket. Optionally, a default source path for an association by providing a socket. Optionally, a
address to be used in IP datagrams can be provided. default source address to be used in IP datagrams can be provided.
Change Local Address / Set Peer Primary: This allows an endpoint to Change Local Address / Set Peer Primary: This allows an endpoint to
add/remove local addresses to/from an association. In addition, add/remove local addresses to/from an association. In addition,
the peer can be given a hint which address to use as the primary the peer can be given a hint for which address to use as the
address [RFC5061]. primary address [RFC5061].
Configure Path Switchover: The abstract API contains a primitive Configure Path Switchover: The abstract API contains a primitive
called 'Set Failure Threshold' [RFC4960]. This configures the called 'Set Failure Threshold' [RFC4960]. This configures the
parameter "Path.Max.Retrans", which determines after how many parameter 'Path.Max.Retrans', which determines after how many
retransmissions a particular transport address is considered as retransmissions a particular transport address is considered as
unreachable. If there are more transport addresses available in unreachable. If there are more transport addresses available in
an association, reaching this limit will invoke a path switchover. an association, reaching this limit will invoke a path switchover.
An extension called "SCTP-PF" adds a concept of "Potentially An extension called "SCTP-PF" adds a concept of "Potentially
Failed" (PF) paths to this method [RFC7829]. When a path is in PF Failed (PF)" paths to this method [RFC7829]. When a path is in PF
state, SCTP will not entirely give up sending on that path, but it state, SCTP will not entirely give up sending on that path, but it
will preferably send data on other active paths if such paths are will preferably send data on other active paths if such paths are
available. Entering the PF state is done upon exceeding a available. Entering the PF state is done upon exceeding a
configured maximum number of retransmissions. Thus, for all paths configured maximum number of retransmissions. Thus, for all paths
where this mechanism is used, there are two configurable error where this mechanism is used, there are two configurable error
thresholds: one to decide that a path is in PF state, and one to thresholds: one to decide that a path is in PF state, and one to
decide that the transport address is unreachable. decide that the transport address is unreachable.
Set / Get Authentication Parameters: This allows an endpoint to add/ Set/Get Authentication Parameters: This allows an endpoint to add/
remove key material to/from an association. In addition, the remove key material to/from an association. In addition, the
chunk types being authenticated can be queried [RFC4895]. chunk types being authenticated can be queried [RFC4895].
Add / Reset Streams, Reset Association: This allows an endpoint to Add/Reset Streams, Reset Association: This allows an endpoint to add
add streams to an existing association or or to reset them streams to an existing association or to reset them individually.
individually. Additionally, the association can be reset Additionally, the association can be reset [RFC6525].
[RFC6525].
Status: The 'Status' primitive returns a data block with information Status: The 'Status' primitive returns a data block with information
about a specified association, containing: association connection about a specified association, containing: an association
state; destination transport address list; destination transport connection state; a destination transport address list;
address reachability states; current local and peer receiver destination transport address reachability states; current local
window sizes; current local congestion window sizes; number of and peer receiver window sizes; current local congestion window
unacknowledged DATA chunks; number of DATA chunks pending receipt; sizes; number of unacknowledged DATA chunks; number of DATA chunks
primary path; most recent SRTT on primary path; RTO on primary pending receipt; a primary path; the most recent Smoothed Round-
path; SRTT and RTO on other destination addresses [RFC4960] and Trip Time (SRTT) on a primary path; RTO on a primary path; SRTT
MTU per path [RFC6458]. and RTO on other destination addresses [RFC4960]; and an MTU per
path [RFC6458].
Enable / Disable Interleaving: This allows to enable or disable the Enable/Disable Interleaving: This allows the negotiation of user
negotiation of user message interleaving support for future message interleaving support for future associations to be enabled
associations. For existing associations it is possible to query or disabled. For existing associations, it is possible to query
whether user message interleaving support was negotiated or not on whether user message interleaving support was negotiated or not on
a particular association [I-D.ietf-tsvwg-sctp-ndata]. a particular association [RFC8260].
Set Stream Scheduler: This allows to select a stream scheduler per Set Stream Scheduler: This allows the ability to select a stream
association, with a choice of: First Come First Serve, Round scheduler per association, with a choice of: First-Come, First-
Robin, Round Robin per Packet, Priority Based, Fair Bandwidth, Served; Round-Robin; Round-Robin per Packet; Priority-Based; Fair
Weighted Fair Queuing [I-D.ietf-tsvwg-sctp-ndata]. Bandwidth; and Weighted Fair Queuing [RFC8260].
Configure Stream Scheduler: This allows to change a parameter per Configure Stream Scheduler: This allows the ability to change a
stream for the schedulers: a priority value for the Priority Based parameter per stream for the schedulers: a priority value for the
scheduler and a weight for the Weighted Fair Queuing scheduler. Priority-Based scheduler and a weight for the Weighted Fair
Queuing scheduler.
Enable / Disable NoDelay: This turns on/off any Nagle-like algorithm Enable/Disable NoDelay: This turns on/off any Nagle-like algorithm
for an association [RFC6458]. for an association [RFC6458].
Configure Send Buffer Size: This controls the amount of data SCTP Configure Send Buffer Size: This controls the amount of data SCTP
may have waiting in internal buffers to be sent or retransmitted may have waiting in internal buffers to be sent or retransmitted
[RFC6458]. [RFC6458].
Configure Receive Buffer Size: This sets the receive buffer size in Configure Receive Buffer Size: This sets the receive buffer size in
octets, thereby controlling the receiver window for an association octets, thereby controlling the receiver window for an association
[RFC6458]. [RFC6458].
Configure Message Fragmentation: If a user message causes an SCTP Configure Message Fragmentation: If a user message causes an SCTP
packet to exceed the maximum fragmentation size (which can be packet to exceed the maximum fragmentation size (which can be
provided by the application, and is otherwise the PMTU size), then provided by the application and is otherwise the Path MTU (PMTU)
the message will be fragmented by SCTP. Disabling message size), then the message will be fragmented by SCTP. Disabling
fragmentation will produce an error instead of fragmenting the message fragmentation will produce an error instead of fragmenting
message [RFC6458]. the message [RFC6458].
Configure Path MTU Discovery: Path MTU Discovery can be enabled or Configure Path MTU Discovery: Path MTU Discovery (PMTUD) can be
disabled per peer address of an association (section 8.1.12 of enabled or disabled per peer address of an association
[RFC6458]). When it is enabled, the current Path MTU value can be (Section 8.1.12 of [RFC6458]). When it is enabled, the current
obtained. When it is disabled, the Path MTU to be used can be Path MTU value can be obtained. When it is disabled, the Path MTU
controlled by the application. to be used can be controlled by the application.
Configure Delayed SACK Timer: The time before sending a SACK can be Configure Delayed SACK Timer: The time before sending a SACK can be
adjusted; delaying SACKs can be disabled; the number of packets adjusted; delaying SACKs can be disabled; and the number of
that must be received before a SACK is sent without waiting for packets that must be received before a SACK is sent without
the delay timer to expire can be configured [RFC6458]. waiting for the delay timer to expire can be configured [RFC6458].
Set Cookie Life Value: The Cookie life value can be adjusted Set Cookie Life Value: The cookie life value can be adjusted
(section 8.1.2 of [RFC6458]). "Valid.Cookie.Life" is also one of (Section 8.1.2 of [RFC6458]). 'Valid.Cookie.Life' is also one of
the parameters that is potentially adjustable with the parameters that is potentially adjustable with
'SetProtocolParameters' [RFC4960]. 'SetProtocolParameters' [RFC4960].
Set Maximum Burst: The maximum burst of packets that can be emitted Set Maximum Burst: The maximum burst of packets that can be emitted
by a particular association (default 4, and values above 4 are by a particular association (default 4, and values above 4 are
optional to implement) can be adjusted (section 8.1.2 of optional to implement) can be adjusted (Section 8.1.2 of
[RFC6458]). "Max.Burst" is also one of the parameters that is [RFC6458]). 'Max.Burst' is also one of the parameters that is
potentially adjustable with 'SetProtocolParameters' [RFC4960]. potentially adjustable with 'SetProtocolParameters' [RFC4960].
Configure RTO Calculation: The abstract API contains the following Configure RTO Calculation: The abstract API contains the following
adjustable parameters: RTO.Initial; RTO.Min; RTO.Max; RTO.Alpha; adjustable parameters: 'RTO.Initial'; 'RTO.Min'; 'RTO.Max';
RTO.Beta. Only the initial, minimum and maximum RTO are also 'RTO.Alpha'; and 'RTO.Beta'. Only the initial, minimum and
described as configurable in the SCTP sockets API extensions maximum RTOs are also described as configurable in the SCTP
[RFC6458]. sockets API extensions [RFC6458].
Set DSCP Value: The DSCP value can be set per peer address of an Set DSCP Value: The DSCP value can be set per peer address of an
association (section 8.1.12 of [RFC6458]). association (Section 8.1.12 of [RFC6458]).
Set IPv6 Flow Label: The flow label field can be set per peer Set IPv6 Flow Label: The flow label field can be set per peer
address of an association (section 8.1.12 of [RFC6458]). address of an association (Section 8.1.12 of [RFC6458]).
Set Partial Delivery Point: This allows to specify the size of a Set Partial Delivery Point: This allows the ability to specify the
message where partial delivery will be invoked. Setting this to a size of a message where partial delivery will be invoked. Setting
lower value will cause partial deliveries to happen more often this to a lower value will cause partial deliveries to happen more
[RFC6458]. often [RFC6458].
Communication Up Notification: When a lost communication to an Communication Up Notification: When a lost communication to an
endpoint is restored or when SCTP becomes ready to send or receive endpoint is restored or when SCTP becomes ready to send or receive
user messages, this notification informs the application process user messages, this notification informs the application process
about the affected association, the type of event that has about the affected association, the type of event that has
occurred, the complete set of sockets of the peer, the maximum occurred, the complete set of sockets of the peer, the maximum
number of allowed streams and the inbound stream count (the number number of allowed streams, and the inbound stream count (the
of streams the peer endpoint has requested). If interleaving is number of streams the peer endpoint has requested). If
supported by both endpoints, this information is also included in interleaving is supported by both endpoints, this information is
this notification. also included in this notification.
Restart Notification: When SCTP has detected that the peer has Restart Notification: When SCTP has detected that the peer has
restarted, this notification is passed to the upper layer restarted, this notification is passed to the upper layer
[RFC6458]. [RFC6458].
Data Arrive Notification: When a message is ready to be retrieved Data Arrive Notification: When a message is ready to be retrieved
via the 'Receive' primitive, the application is informed by this via the 'Receive' primitive, the application is informed by this
notification. notification.
Send Failure Notification / Receive Unsent Message / Receive Send Failure Notification / Receive Unsent Message / Receive
Unacknowledged Message: When a message cannot be delivered via an Unacknowledged Message: When a message cannot be delivered via an
association, the sender can be informed about it and learn whether association, the sender can be informed about it and learn whether
the message has just not been acknowledged or (e.g. in case of the message has just not been acknowledged or (e.g., in case of
lifetime expiry) if it has not even been sent. This can also lifetime expiry) if it has not even been sent. This can also
inform the sender that a part of the message has been successfully inform the sender that a part of the message has been successfully
delivered. delivered.
Network Status Change Notification: This informs the application Network Status Change Notification: This informs the application
about a socket becoming active/inactive [RFC4960] or "Potentially about a socket becoming active/inactive [RFC4960] or "Potentially
Failed" [RFC7829]. Failed" [RFC7829].
Communication Lost Notification: When SCTP loses communication to an Communication Lost Notification: When SCTP loses communication to an
endpoint (e.g. via Heartbeats or excessive retransmission) or endpoint (e.g., via heartbeats or excessive retransmission) or
detects an abort, this notification informs the application detects an abort, this notification informs the application
process of the affected association and the type of event (failure process of the affected association and the type of event (failure
OR termination in response to a shutdown or abort request). OR termination in response to a shutdown or abort request).
Shutdown Complete Notification: When SCTP completes the shutdown Shutdown Complete Notification: When SCTP completes the shutdown
procedures, this notification is passed to the upper layer, procedures, this notification is passed to the upper layer,
informing it about the affected assocation. informing it about the affected association.
Authentication Notification: When SCTP wants to notify the upper Authentication Notification: When SCTP wants to notify the upper
layer regarding the key management related to authenticated chunks layer regarding the key management related to authenticated chunks
[RFC4895], this notification is passed to the upper layer. [RFC4895], this notification is passed to the upper layer.
Adaptation Layer Indication Notification: When SCTP completes the Adaptation Layer Indication Notification: When SCTP completes the
association setup and the peer provided an adaptation layer association setup and the peer provided an adaptation layer
indication, this is passed to the upper layer [RFC5061], indication, this is passed to the upper layer [RFC5061] [RFC6458].
[RFC6458].
Stream Reset Notification: When SCTP completes the procedure for Stream Reset Notification: When SCTP completes the procedure for
resetting streams [RFC6525], this notification is passed to the resetting streams [RFC6525], this notification is passed to the
upper layer, informing it about the result. upper layer, informing it about the result.
Assocation Reset Notification: When SCTP completes the association Association Reset Notification: When SCTP completes the association
reset procedure [RFC6525], this notification is passed to the reset procedure [RFC6525], this notification is passed to the
upper layer, informing it about the result. upper layer, informing it about the result.
Stream Change Notification: When SCTP completes the procedure used Stream Change Notification: When SCTP completes the procedure used
to increase the number of streams [RFC6525], this notification is to increase the number of streams [RFC6525], this notification is
passed to the upper layer, informing it about the result. passed to the upper layer, informing it about the result.
Sender Dry Notification: When SCTP has no more user data to send or Sender Dry Notification: When SCTP has no more user data to send or
retransmit on a particular association, this notification is retransmit on a particular association, this notification is
passed to the upper layer [RFC6458]. passed to the upper layer [RFC6458].
Partial Delivery Aborted Notification: When a receiver has begun to Partial Delivery Aborted Notification: When a receiver has begun to
receive parts of a user message but the delivery of this message receive parts of a user message but the delivery of this message
is then aborted, this notification is passed to the upper layer is then aborted, this notification is passed to the upper layer
(section 6.1.7 of [RFC6458]). (Section 6.1.7 of [RFC6458]).
3.3.1. Excluded Primitives or Parameters 3.3.1. Excluded Primitives or Parameters
The 'Receive' primitive can return certain additional information, The 'Receive' primitive can return certain additional information,
but this is optional to implement and therefore not considered. With but this is optional to implement and therefore not considered. With
a 'Communication Lost' notification, some more information may a 'Communication Lost' notification, some more information may
optionally be passed to the application (e.g., identification to optionally be passed to the application (e.g., identification to
retrieve unsent and unacknowledged data). SCTP "can invoke" a retrieve unsent and unacknowledged data). SCTP "can invoke" a
'Communication Error' notification and "may send" a 'Restart' 'Communication Error' notification and "may send" a 'Restart'
notification, making these two notifications optional to implement. notification, making these two notifications optional to implement.
The list provided under 'Status' includes "etc", indicating that more The list provided under 'Status' includes "etc.", indicating that
information could be provided. The primitive 'Get SRTT Report' more information could be provided. The primitive 'Get SRTT Report'
returns information that is included in the information that 'Status' returns information that is included in the information that 'Status'
provides and is therefore not discussed. The 'Destroy SCTP Instance' provides and is therefore not discussed. The 'Destroy SCTP Instance'
API function was excluded: it erases the SCTP instance that was API function was excluded: it erases the SCTP instance that was
created by 'Initialize', but is not a Primitive as defined in this created by 'Initialize' but is not a primitive as defined in this
document because it does not relate to a transport feature. The document because it does not relate to a transport feature. The
'Shutdown' event informs an application that the peer has sent a 'Shutdown' event informs an application that the peer has sent a
SHUTDOWN, and hence no further data should be sent on this socket SHUTDOWN, and hence no further data should be sent on this socket
(section 6.1 of [RFC6458]). However, if an application would try to (Section 6.1 of [RFC6458]). However, if an application would try to
send data on the socket, it would get an error message anyway; thus, send data on the socket, it would get an error message anyway; thus,
this event is classified as "just affecting the application this event is classified as "just affecting the application
programming style, not how the underlying protocol operates" and not programming style, not how the underlying protocol operates" and is
included here. not included here.
3.4. Primitives Provided by UDP and UDP-Lite 3.4. Primitives Provided by UDP and UDP-Lite
The set of pass 1 primitives for UDP and UDP-Lite is documented in The set of pass 1 primitives for UDP and UDP-Lite is documented in
[FJ16]. [RFC8304].
3.5. The service of LEDBAT 3.5. The Service of LEDBAT
The service of the Low Extra Delay Background Transport (LEDBAT) The service of the LEDBAT congestion control mechanism is described
congestion control mechanism is described as follows: "LEDBAT is as follows:
designed for use by background bulk-transfer applications to be no
more aggressive than standard TCP congestion control (as specified in LEDBAT is designed for use by background bulk-transfer
RFC 5681) and to yield in the presence of competing flows, thus applications to be no more aggressive than standard TCP congestion
limiting interference with the network performance of competing control (as specified in RFC 5681) and to yield in the presence of
flows" [RFC6817]. competing flows, thus limiting interference with the network
performance of competing flows [RFC6817].
LEDBAT does not have any primitives, as LEDBAT is not a transport LEDBAT does not have any primitives, as LEDBAT is not a transport
protocol. According to its specification [RFC6817], "LEDBAT can be protocol. According to its specification [RFC6817]:
used as part of a transport protocol or as part of an application, as
long as the data transmission mechanisms are capable of carrying
timestamps and acknowledging data frequently. LEDBAT can be used
with TCP, Stream Control Transmission Protocol (SCTP), and Datagram
Congestion Control Protocol (DCCP), with appropriate extensions where
necessary; and it can be used with proprietary application protocols,
such as those built on top of UDP for peer-to- peer (P2P)
applications." At the time of writing, the appropriate extensions
for TCP, SCTP or DCCP do not exist.
A numer of configurable parameters exist in the LEDBAT specification: LEDBAT can be used as part of a transport protocol or as part of
TARGET, which is the queuing delay target at which LEDBAT tries to an application, as long as the data transmission mechanisms are
operate, must be set to 100ms or less. 'allowed_increase' (should be capable of carrying timestamps and acknowledging data frequently.
1, must be greater than 0) limits the speed at which LEDBAT increases LEDBAT can be used with TCP, Stream Control Transmission Protocol
its rate. 'gain', which, according to [RFC6817], "MUST be set to 1 or (SCTP), and Datagram Congestion Control Protocol (DCCP), with
less" to avoid a faster ramp-up than TCP Reno, determines how quickly appropriate extensions where necessary; and it can be used with
the sender responds to changes in queueing delay. Implementations proprietary application protocols, such as those built on top of
may divide 'gain' into two parameters, one for increase and a UDP for peer-to-peer (P2P) applications.
possibly larger one for decrease. We call these parameters
'Gain_Inc' and 'Gain_Dec' here. 'Base_History' is the size of the At the time of writing, the appropriate extensions for TCP, SCTP, or
list of measured base delays, and, according to [RFC6817], "SHOULD be DCCP do not exist.
10". This list can be filtered using a 'Filter' function which is
not prescribed [RFC6817], yielding a list of size 'Current_Filter'. A number of configurable parameters exist in the LEDBAT
The initial and minimum congestion windows, 'Init_CWND' and specification: TARGET, which is the queuing delay target at which
'Min_CWND', should both be 2. LEDBAT tries to operate, must be set to 100 ms or less.
'allowed_increase' (should be 1, must be greater than 0) limits the
speed at which LEDBAT increases its rate. 'gain', which according to
[RFC6817] "MUST be set to 1 or less" to avoid a faster ramp-up than
TCP Reno, determines how quickly the sender responds to changes in
queueing delay. Implementations may divide 'gain' into two
parameters: one for increase and a possibly larger one for decrease.
We call these parameters 'Gain_Inc' and 'Gain_Dec' here.
'Base_History' is the size of the list of measured base delays, and,
according to [RFC6817], "SHOULD be 10". This list can be filtered
using a 'Filter' function, which is not prescribed [RFC6817], that
yields a list of size 'Current_Filter'. The initial and minimum
congestion windows, 'Init_CWND' and 'Min_CWND', should both be 2.
Regarding which of these parameters should be under control of an Regarding which of these parameters should be under control of an
application, the possible range goes from exposing nothing on the one application, the possible range goes from exposing nothing on the one
hand, to considering everything that is not prescribed with a "MUST" hand to considering everything that is not prescribed with a "MUST"
in the specification as a parameter on the other hand. Function in the specification as a parameter on the other hand. Function
implementations are not provided as a parameter to any of the implementations are not provided as a parameter to any of the
transport protocols discussed here, and hence we do not regard the transport protocols discussed here; hence, we do not regard the
'Filter' function as a parameter. However, to avoid unnecessarily 'Filter' function as a parameter. However, to avoid unnecessarily
limiting future implementations, we consider all other parameters limiting future implementations, we consider all other parameters
above as tunable parameters that should be exposed. above as tunable parameters that should be exposed.
4. Pass 2 4. Pass 2
This pass categorizes the primitives from pass 1 based on whether This pass categorizes the primitives from pass 1 based on whether
they relate to a connection or to data transmission. Primitives are they relate to a connection or to data transmission. Primitives are
presented following the nomenclature presented following the nomenclature
"CATEGORY.[SUBCATEGORY].PRIMITIVENAME.PROTOCOL". The CATEGORY can be "CATEGORY.[SUBCATEGORY].PRIMITIVENAME.PROTOCOL". The CATEGORY can be
CONNECTION or DATA. Within the CONNECTION category, ESTABLISHMENT, CONNECTION or DATA. Within the CONNECTION category, ESTABLISHMENT,
AVAILABILITY, MAINTENANCE and TERMINATION subcategories can be AVAILABILITY, MAINTENANCE, and TERMINATION subcategories can be
considered. The DATA category does not have any SUBCATEGORY. The considered. The DATA category does not have any SUBCATEGORY. The
PROTOCOL name "UDP(-Lite)" is used when primitives are equivalent for PROTOCOL name "UDP(-Lite)" is used when primitives are equivalent for
UDP and UDP-Lite; the PROTOCOL name "TCP" refers to both TCP and UDP and UDP-Lite; the PROTOCOL name "TCP" refers to both TCP and
MPTCP. We present "connection" as a general protocol-independent MPTCP. We present "connection" as a general protocol-independent
concept and use it to refer to, e.g., TCP connections (identifiable concept and use it to refer to, e.g., TCP connections (identifiable
by a unique pair of IP addresses and TCP port numbers), SCTP by a unique pair of IP addresses and TCP port numbers), SCTP
associations (identifiable by multiple IP address and port number associations (identifiable by multiple IP address and port number
pairs), as well UDP and UDP-Lite connections (identifiable by a pairs), as well UDP and UDP-Lite connections (identifiable by a
unique socket pair). unique socket pair).
Some minor details are omitted for the sake of generalization -- Some minor details are omitted for the sake of generalization --
e.g., SCTP's 'Close' [RFC4960] returns success or failure, and lets e.g., SCTP's 'Close' [RFC4960] returns success or failure and lets
the application control whether further receive or send operations or the application control whether further receive or send operations,
both are disabled [RFC6458]. This is not described in the same way or both, are disabled [RFC6458]. This is not described in the same
for TCP [RFC0793], but these details play no significant role for the way for TCP [RFC0793], but these details play no significant role for
primitives provided by either TCP or SCTP (for the sake of being the primitives provided by either TCP or SCTP (for the sake of being
generic, it could be assumed that both receive and send operations generic, it could be assumed that both receive and send operations
are disabled in both cases). are disabled in both cases).
The TCP 'Send' and 'Receive' primitives include usage of an 'urgent' The TCP 'Send' and 'Receive' primitives include usage of an 'urgent'
parameter. This parameter controls a mechanism that is required to parameter. This parameter controls a mechanism that is required to
implement the "synch signal" used by telnet [RFC0854], but [RFC6093] implement the "synch signal" used by telnet [RFC0854], but [RFC6093]
states that "new applications SHOULD NOT employ the TCP urgent states that "new applications SHOULD NOT employ the TCP urgent
mechanism". Because pass 2 is meant as a basis for the creation of mechanism." Because pass 2 is meant as a basis for the creation of
future systems, the "urgent" mechanism is excluded. This also future systems, the "urgent" mechanism is excluded. This also
concerns the notification 'Urgent Pointer Advance' in the concerns the notification 'Urgent Pointer Advance' in the
'Error_Report' (section 4.2.4.1 of [RFC1122]). 'Error_Report' (Section 4.2.4.1 of [RFC1122]).
Since LEDBAT is a congestion control mechanism and not a protocol, it Since LEDBAT is a congestion control mechanism and not a protocol, it
is not currently defined when to enable / disable or configure the is not currently defined when to enable/disable or configure the
mechanism. For instance, it could be a one-time choice upon mechanism. For instance, it could be a one-time choice upon
connection establishment or when listening for incoming connections, connection establishment or when listening for incoming connections,
in which case it should be categorized under CONNECTION.ESTABLISHMENT in which case it should be categorized under CONNECTION.ESTABLISHMENT
or CONNECTION.AVAILABILITY, respectively. To avoid unnecessarily or CONNECTION.AVAILABILITY, respectively. To avoid unnecessarily
limiting future implementations, it was decided to place it under limiting future implementations, it was decided to place it under
CONNECTION.MAINTENANCE, with all parameters that are described in the CONNECTION.MAINTENANCE, with all parameters that are described in the
specification [RFC6817] made configurable. specification [RFC6817] made configurable.
4.1. CONNECTION Related Primitives 4.1. CONNECTION-Related Primitives
ESTABLISHMENT: ESTABLISHMENT:
Active creation of a connection from one transport endpoint to one or Active creation of a connection from one transport endpoint to one or
more transport endpoints. more transport endpoints. Interfaces to UDP and UDP-Lite allow both
Interfaces to UDP and UDP-Lite allow both connection-oriented and connection-oriented and connection-less usage of the API [RFC8085].
connection-less usage of the API [RFC8085].
o CONNECT.TCP: o CONNECT.TCP:
Pass 1 primitive / event: 'Open' (active) or 'Open' (passive) with Pass 1 primitive/event: 'Open' (active) or 'Open' (passive) with
socket, followed by 'Send' socket, followed by 'Send'
Parameters: 1 local IP address (optional); 1 destination transport Parameters: 1 local IP address (optional); 1 destination transport
address (for active open; else the socket and the local IP address address (for active open; else the socket and the local IP address
of the succeeding incoming connection request will be maintained); of the succeeding incoming connection request will be maintained);
timeout (optional); options (optional); MKT configuration timeout (optional); options (optional); MKT configuration
(optional); user message (optional) (optional); and user message (optional)
Comments: If the local IP address is not provided, a default Comments: if the local IP address is not provided, a default
choice will automatically be made. The timeout can also be a choice will automatically be made. The timeout can also be a
retransmission count. The options are IP options to be used on retransmission count. The options are IP options to be used on
all segments of the connection. At least the Source Route option all segments of the connection. At least the Source Route option
is mandatory for TCP to provide. 'MKT configuration' refers to is mandatory for TCP to provide. 'MKT configuration' refers to
the ability to configure Master Key Tuples (MKTs) for the ability to configure MKTs for authentication. The user
authentication. The user message may be transmitted to the peer message may be transmitted to the peer application immediately
application immediately upon reception of the TCP SYN packet. To upon reception of the TCP SYN packet. To benefit from the lower
benefit from the lower latency this provides as part of the latency this provides as part of the experimental TFO mechanism,
experimental TFO mechanism, its length must be at most the TCP's its length must be at most the TCP's maximum segment size (minus
maximum segment size (minus TCP options used in the SYN). The TCP options used in the SYN). The message may also be delivered
message may also be delivered more than once to the application on more than once to the application on the remote host.
the remote host.
o CONNECT.SCTP: o CONNECT.SCTP:
Pass 1 primitive / event: 'Initialize', followed by 'Enable / Pass 1 primitive/event: 'Initialize', followed by 'Enable/Disable
Disable Interleaving' (optional), followed by 'Associate' Interleaving' (optional), followed by 'Associate'
Parameters: list of local SCTP port number / IP address pairs Parameters: list of local SCTP port number / IP address pairs
('Initialize'); one or several sockets (identifying the peer); ('Initialize'); one or several sockets (identifying the peer);
outbound stream count; maximum allowed inbound stream count; outbound stream count; maximum allowed inbound stream count;
adaptation layer indication (optional); chunk types required to be adaptation layer indication (optional); chunk types required to be
authenticated (optional); request interleaving on/off; maximum authenticated (optional); request interleaving on/off; maximum
number of INIT attemps (optional); maximum init. RTO for INIT number of INIT attempts (optional); maximum init. RTO for INIT
(optional); user message (optional); remote UDP port number (optional); user message (optional); and remote UDP port number
(optional) (optional)
Returns: socket list or failure Returns: socket list or failure
Comments: 'Initialize' needs to be called only once per list of Comments: 'Initialize' needs to be called only once per list of
local SCTP port number / IP address pairs. One socket will local SCTP port number / IP address pairs. One socket will
automatically be chosen; it can later be changed in MAINTENANCE. automatically be chosen; it can later be changed in MAINTENANCE.
The user message may be transmitted to the peer application The user message may be transmitted to the peer application
immediately upon reception of the packet containing the COOKIE- immediately upon reception of the packet containing the
ECHO chunk. To benefit from the lower latency this provides, its COOKIE-ECHO chunk. To benefit from the lower latency this
length must be limited such that it fits into the packet provides, its length must be limited such that it fits into the
containing the COOKIE-ECHO chunk. If a remote UDP port number is packet containing the COOKIE-ECHO chunk. If a remote UDP port
provided, SCTP packets will be encapsulated in UDP. number is provided, SCTP packets will be encapsulated in UDP.
o CONNECT.MPTCP: o CONNECT.MPTCP:
This is similar to CONNECT.TCP except for one additional boolean This is similar to CONNECT.TCP except for one additional boolean
parameter that allows to enable or disable MPTCP for a particular parameter that allows the ability to enable or disable MPTCP for a
connection or socket (default: enabled). particular connection or socket (default: enabled).
o CONNECT.UDP(-Lite): o CONNECT.UDP(-Lite):
Pass 1 primitive / event: 'Connect' followed by 'Send'. Pass 1 primitive/event: 'Connect' followed by 'Send'
Parameters: 1 local IP address (default (ANY), or specified); 1 Parameters: 1 local IP address (default (ANY) or specified); 1
destination transport address; 1 local port (default (OS chooses), destination transport address; 1 local port (default (OS chooses)
or specified); 1 destination port (default (OS chooses), or or specified); and 1 destination port (default (OS chooses) or
specified). specified).
Comments: Associates a transport address creating a UDP(-Lite) Comments: associates a transport address creating a UDP(-Lite)
socket connection. This can be called again with a new transport socket connection. This can be called again with a new transport
address to create a new connection. The CONNECT function allows address to create a new connection. The CONNECT function allows
an application to receive errors from messages sent to a transport an application to receive errors from messages sent to a transport
address. address.
AVAILABILITY: AVAILABILITY:
Preparing to receive incoming connection requests. Preparing to receive incoming connection requests.
o LISTEN.TCP: o LISTEN.TCP:
Pass 1 primitive / event: 'Open' (passive) Pass 1 primitive/event: 'Open' (passive)
Parameters: 1 local IP address (optional); 1 socket (optional); Parameters: 1 local IP address (optional); 1 socket (optional);
timeout (optional); buffer to receive a user message (optional); timeout (optional); buffer to receive a user message (optional);
MKT configuration (optional) and MKT configuration (optional)
Comments: if the socket and/or local IP address is provided, this Comments: if the socket and/or local IP address is provided, this
waits for incoming connections from only and/or to only the waits for incoming connections from only and/or to only the
provided address. Else this waits for incoming connections provided address. Else this waits for incoming connections
without this / these constraint(s). ESTABLISHMENT can later be without this/these constraint(s). ESTABLISHMENT can later be
performed with 'Send'. If a buffer is provided to receive a user performed with 'Send'. If a buffer is provided to receive a user
message, a user message can be received from a TFO-enabled sender message, a user message can be received from a TFO-enabled sender
before TCP's connection handshake is completed. This message may before the TCP's connection handshake is completed. This message
arrive multiple times. 'MKT configuration' refers to the ability may arrive multiple times. 'MKT configuration' refers to the
to configure Master Key Tuples (MKTs) for authentication. ability to configure MKTs for authentication.
o LISTEN.SCTP: o LISTEN.SCTP:
Pass 1 primitive / event: 'Initialize', followed by 'Communication Pass 1 primitive/event: 'Initialize', followed by the
Up' or 'Restart' notification and possibly 'Adaptation Layer' 'Communication Up' or 'Restart' notification and possibly the
notification 'Adaptation Layer' notification
Parameters: list of local SCTP port number / IP address pairs Parameters: list of local SCTP port number / IP address pairs
(initialize) (initialize)
Returns: socket list; outbound stream count; inbound stream count; Returns: socket list; outbound stream count; inbound stream count;
adaptation layer indication; chunks required to be authenticated; adaptation layer indication; chunks required to be authenticated;
interleaving supported on both sides yes/no and interleaving supported on both sides yes/no
Comments: 'Initialize' needs to be called only once per list of Comments: 'Initialize' needs to be called only once per list of
local SCTP port number / IP address pairs. 'Communication Up' can local SCTP port number / IP address pairs. 'Communication Up' can
also follow a 'Communication Lost' notification, indicating that also follow a 'Communication Lost' notification, indicating that
the lost communication is restored. If the peer has provided an the lost communication is restored. If the peer has provided an
adaptation layer indication, an 'Adaptation Layer' notification is adaptation layer indication, an 'Adaptation Layer' notification is
issued. issued.
o LISTEN.MPTCP: o LISTEN.MPTCP:
This is similar to LISTEN.TCP except for one additional boolean This is similar to LISTEN.TCP except for one additional boolean
parameter that allows to enable or disable MPTCP for a particular parameter that allows the ability to enable or disable MPTCP for a
connection or socket (default: enabled). particular connection or socket (default: enabled).
o LISTEN.UDP(-Lite): o LISTEN.UDP(-Lite):
Pass 1 primitive / event: 'Receive'. Pass 1 primitive/event: 'Receive'
Parameters: 1 local IP address (default (ANY), or specified); 1 Parameters: 1 local IP address (default (ANY) or specified); 1
destination transport address; local port (default (OS chooses), destination transport address; local port (default (OS chooses) or
or specified); destination port (default (OS chooses), or specified); and destination port (default (OS chooses) or
specified). specified)
Comments: The 'Receive' function registers the application to Comments: the 'Receive' function registers the application to
listen for incoming UDP(-Lite) datagrams at an endpoint. listen for incoming UDP(-Lite) datagrams at an endpoint.
MAINTENANCE: MAINTENANCE:
Adjustments made to an open connection, or notifications about it. Adjustments made to an open connection, or notifications about it.
These are out-of-band messages to the protocol that can be issued at These are out-of-band messages to the protocol that can be issued at
any time, at least after a connection has been established and before any time, at least after a connection has been established and before
it has been terminated (with one exception: CHANGE_TIMEOUT.TCP can it has been terminated (with one exception: CHANGE_TIMEOUT.TCP can
only be issued for an open connection when DATA.SEND.TCP is called). only be issued for an open connection when DATA.SEND.TCP is called).
In some cases, these primitives can also be immediately issued during In some cases, these primitives can also be immediately issued during
ESTABLISHMENT or AVAILABILITY, without waiting for the connection to ESTABLISHMENT or AVAILABILITY, without waiting for the connection to
be opened (e.g. CHANGE_TIMEOUT.TCP can be done using TCP's 'Open' be opened (e.g., CHANGE_TIMEOUT.TCP can be done using TCP's 'Open'
primitive). For UDP and UDP-Lite, these functions may establish a primitive). For UDP and UDP-Lite, these functions may establish a
setting per connection, but may also be changed per datagram message. setting per connection but may also be changed per datagram message.
o CHANGE_TIMEOUT.TCP: o CHANGE_TIMEOUT.TCP:
Pass 1 primitive / event: 'Open' or 'Send' combined with Pass 1 primitive/event: 'Open' or 'Send' combined with unspecified
unspecified control of per-connection state variables control of per-connection state variables
Parameters: timeout value (optional); adv_uto (optional); boolean Parameters: timeout value (optional); adv_uto (optional); boolean
uto_enabled (optional, default false); boolean changeable uto_enabled (optional, default false); and boolean changeable
(optional, default true) (optional, default true)
Comments: when sending data, an application can adjust the Comments: when sending data, an application can adjust the
connection's timeout value (time after which the connection will connection's timeout value (the time after which the connection
be aborted if data could not be delivered). If 'uto_enabled' is will be aborted if data could not be delivered). If 'uto_enabled'
true, the 'timeout value' (or, if provided, the value 'adv_uto') is true, the 'timeout value' (or, if provided, the value
will be advertised for the TCP on the other side of the connection 'adv_uto') will be advertised for the TCP on the other side of the
to adapt its own user timeout accordingly. 'uto_enabled' controls connection to adapt its own user timeout accordingly.
whether the UTO option is enabled for a connection. This applies 'uto_enabled' controls whether the UTO option is enabled for a
to both sending and receiving. 'changeable' controls whether the connection. This applies to both sending and receiving.
user timeout may be changed based on a UTO option received from 'changeable' controls whether the user timeout may be changed
the other end of the connection; it becomes false when 'timeout based on a UTO option received from the other end of the
value' is used. connection; it becomes false when the 'timeout value' is used.
o CHANGE_TIMEOUT.SCTP: o CHANGE_TIMEOUT.SCTP:
Pass 1 primitive / event: 'Change HeartBeat' combined with Pass 1 primitive/event: 'Change Heartbeat' combined with
'Configure Max. Retransmissions of an Association' 'Configure Max. Retransmissions of an Association'
Parameters: 'Change Heartbeat': heartbeat frequency; 'Configure Parameters: 'Change Heartbeat': heartbeat frequency and 'Configure
Max. Retransmissions of an Association': association.max.retrans Max. Retransmissions of an Association': Association.Max.Retrans
Comments: 'Change Heartbeat' can enable / disable heartbeats in Comments: 'Change Heartbeat' can enable/disable heartbeats in SCTP
SCTP as well as change their frequency. The parameter as well as change their frequency. The parameter
'association.max.retrans' defines after how many unsuccessful 'Association.Max.Retrans' defines after how many unsuccessful
transmissions of any packets (including heartbeats) the transmissions of any packets (including heartbeats) the
association will be terminated; thus these two primitives / association will be terminated; thus, these two primitives/
parameters together can yield a similar behavior for SCTP parameters together can yield a similar behavior for SCTP
associations as CHANGE_TIMEOUT.TCP does for TCP connections. associations as CHANGE_TIMEOUT.TCP does for TCP connections.
o DISABLE_NAGLE.TCP: o DISABLE_NAGLE.TCP:
Pass 1 primitive / event: not specified Pass 1 primitive/event: not specified
Parameters: one boolean value Parameters: one boolean value
Comments: the Nagle algorithm delays data transmission to increase Comments: the Nagle algorithm delays data transmission to increase
the chance to send a full-sized segment. An application must be the chance of sending a full-sized segment. An application must
able to disable this algorithm for a connection. be able to disable this algorithm for a connection.
o DISABLE_NAGLE.SCTP: o DISABLE_NAGLE.SCTP:
Pass 1 primitive / event: 'Enable / Disable NoDelay' Pass 1 primitive/event: 'Enable/Disable NoDelay'
Parameters: one boolean value Parameters: one boolean value
Comments: Nagle-like algorithms delay data transmission to Comments: Nagle-like algorithms delay data transmission to
increase the chance to send a full-sized packet. increase the chance of sending a full-sized packet.
o REQUEST_HEARTBEAT.SCTP: o REQUEST_HEARTBEAT.SCTP:
Pass 1 primitive / event: 'Request HeartBeat' Pass 1 primitive/event: 'Request Heartbeat'
Parameters: socket Parameters: socket
Returns: success or failure Returns: success or failure
Comments: requests an immediate heartbeat on a path, returning Comments: requests an immediate heartbeat on a path, returning
success or failure. success or failure.
o ADD_PATH.MPTCP: o ADD_PATH.MPTCP:
Pass 1 primitive / event: not specified Pass 1 primitive/event: not specified
Parameters: local IP address and optionally the local port number Parameters: local IP address and optionally the local port number
Comments: the application specifies the local IP address and port Comments: the application specifies the local IP address and port
number that must be used for a new subflow. number that must be used for a new subflow.
o ADD_PATH.SCTP: o ADD_PATH.SCTP:
Pass 1 primitive / event: 'Change Local Address / Set Peer Pass 1 primitive/event: 'Change Local Address / Set Peer Primary'
Primary'
Parameters: local IP address Parameters: local IP address
o REM_PATH.MPTCP: o REM_PATH.MPTCP:
Pass 1 primitive / event: not specified Pass 1 primitive/event: not specified
Parameters: local IP address; local port number; remote IP Parameters: local IP address; local port number; remote IP
address; remote port number address; and remote port number
Comments: the application removes the subflow specified by the IP/ Comments: the application removes the subflow specified by the IP/
port-pair. The MPTCP implementation must trigger a removal of the port-pair. The MPTCP implementation must trigger a removal of the
subflow that belongs to this IP/port-pair. subflow that belongs to this IP/port-pair.
o REM_PATH.SCTP: o REM_PATH.SCTP:
Pass 1 primitive / event: 'Change Local Address / Set Peer Pass 1 primitive/event: 'Change Local Address / Set Peer Primary'
Primary'
Parameters: local IP address Parameters: local IP address
o SET_PRIMARY.SCTP: o SET_PRIMARY.SCTP:
Pass 1 primitive / event: 'Set Primary' Pass 1 primitive/event: 'Set Primary'
Parameters: socket Parameters: socket
Returns: result of attempting this operation Returns: result of attempting this operation
Comments: update the current primary address to be used, based on Comments: update the current primary address to be used, based on
the set of available sockets of the association. the set of available sockets of the association.
o SET_PEER_PRIMARY.SCTP: o SET_PEER_PRIMARY.SCTP:
Pass 1 primitive / event: 'Change Local Address / Set Peer Pass 1 primitive/event: 'Change Local Address / Set Peer Primary'
Primary'
Parameters: local IP address Parameters: local IP address
Comments: this is only advisory for the peer. Comments: this is only advisory for the peer.
o CONFIG_SWITCHOVER.SCTP: o CONFIG_SWITCHOVER.SCTP:
Pass 1 primitive / event: 'Configure Path Switchover' Pass 1 primitive/event: 'Configure Path Switchover'
Parameters: primary max retrans (no. of retransmissions after
which a path is considered inactive); PF max retrans (no. of Parameters: primary max retrans (number of retransmissions after
which a path is considered inactive) and PF max retrans (number of
retransmissions after which a path is considered to be retransmissions after which a path is considered to be
"Potentially Failed", and others will be preferably used) "Potentially Failed", and others will be preferably used)
(optional) (optional)
o STATUS.SCTP: o STATUS.SCTP:
Pass 1 primitive / event: 'Status', 'Enable / Disable Pass 1 primitive/event: 'Status', 'Enable/Disable Interleaving',
Interleaving' and 'Network Status Change' notification. and 'Network Status Change' notification
Returns: data block with information about a specified Returns: data block with information about a specified
association, containing: association connection state; destination association, containing: association connection state; destination
transport address list; destination transport address reachability transport address list; destination transport address reachability
states; current local and peer receiver window sizes; current states; current local and peer receiver window sizes; current
local congestion window sizes; number of unacknowledged DATA local congestion window sizes; number of unacknowledged DATA
chunks; number of DATA chunks pending receipt; primary path; most chunks; number of DATA chunks pending receipt; primary path; most
recent SRTT on primary path; RTO on primary path; SRTT and RTO on recent SRTT on primary path; RTO on primary path; SRTT and RTO on
other destination addresses; MTU per path; interleaving supported other destination addresses; MTU per path; and interleaving
yes/no. supported yes/no
Comments: The 'Network Status Change' notification informs the Comments: the 'Network Status Change' notification informs the
application about a socket becoming active/inactive; this only application about a socket becoming active/inactive; this only
affects the programming style, as the same information is also affects the programming style, as the same information is also
available via 'Status'. available via 'Status'.
o STATUS.MPTCP: o STATUS.MPTCP:
Pass 1 primitive / event: not specified Pass 1 primitive/event: not specified
Returns: list of pairs of tuples of IP address and TCP port number Returns: list of pairs of tuples of IP address and TCP port number
of each subflow. The first of the pair is the local IP and port of each subflow. The first of the pair is the local IP and port
number, while the second is the remote IP and port number. number, while the second is the remote IP and port number.
o SET_DSCP.TCP: o SET_DSCP.TCP:
Pass 1 primitive / event: not specified Pass 1 primitive/event: not specified
Parameters: DSCP value Parameters: DSCP value
Comments: this allows an application to change the DSCP value for Comments: this allows an application to change the DSCP value for
outgoing segments. outgoing segments.
o SET_DSCP.SCTP: o SET_DSCP.SCTP:
Pass 1 primitive / event: 'Set DSCP value' Pass 1 primitive/event: 'Set DSCP value'
Parameters: DSCP value Parameters: DSCP value
Comments: this allows an application to change the DSCP value for Comments: this allows an application to change the DSCP value for
outgoing packets on a path. outgoing packets on a path.
o SET_DSCP.UDP(-Lite): o SET_DSCP.UDP(-Lite):
Pass 1 primitive / event: 'Set_DSCP' Pass 1 primitive/event: 'Set_DSCP'
Parameter: DSCP value Parameter: DSCP value
Comments: This allows an application to change the DSCP value for Comments: this allows an application to change the DSCP value for
outgoing UDP(-Lite) datagrams. [RFC7657] and [RFC8085] provide outgoing UDP(-Lite) datagrams. [RFC7657] and [RFC8085] provide
current guidance on using this value with UDP. current guidance on using this value with UDP.
o ERROR.TCP: o ERROR.TCP:
Pass 1 primitive / event: 'Error_Report' Pass 1 primitive/event: 'Error_Report'
Returns: reason (encoding not specified); subreason (encoding not Returns: reason (encoding not specified) and subreason (encoding
specified) not specified)
Comments: soft errors that can be ignored without harm by many Comments: soft errors that can be ignored without harm by many
applications; an application should be able to disable these applications; an application should be able to disable these
notifications. The reported conditions include at least: ICMP notifications. The reported conditions include at least: ICMP
error message arrived; Excessive Retransmissions. error message arrived and excessive retransmissions.
o ERROR.UDP(-Lite): o ERROR.UDP(-Lite):
Pass 1 primitive / event: 'Error_Report' Pass 1 primitive/event: 'Error_Report'
Returns: Error report Returns: Error report
Comments: This returns soft errors that may be ignored without Comments: this returns soft errors that may be ignored without
harm by many applications; An application must connect to be able harm by many applications; an application must connect to be able
receive these notifications. receive these notifications.
o SET_AUTH.TCP: o SET_AUTH.TCP:
Pass 1 primitive / event: not specified Pass 1 primitive/event: not specified
Parameters: current_key; rnext_key
Parameters: current_key and rnext_key
Comments: current_key and rnext_key are the preferred outgoing MKT Comments: current_key and rnext_key are the preferred outgoing MKT
and the preferred incoming MKT, respectively, for a segment that and the preferred incoming MKT, respectively, for a segment that
is sent on the connection. is sent on the connection.
o SET_AUTH.SCTP: o SET_AUTH.SCTP:
Pass 1 primitive / event: 'Set / Get Authentication Parameters' Pass 1 primitive/event: 'Set/Get Authentication Parameters'
Parameters: key_id; key; hmac_id Parameters: key_id; key; and hmac_id
o GET_AUTH.TCP: o GET_AUTH.TCP:
Pass 1 primitive / event: not specified Pass 1 primitive/event: not specified
Parameters: current_key; rnext_key Parameters: current_key and rnext_key
Comments: current_key and rnext_key are the preferred outgoing MKT Comments: current_key and rnext_key are the preferred outgoing MKT
and the preferred incoming MKT, respectively, that were carried on and the preferred incoming MKT, respectively, that were carried on
a recently received segment. a recently received segment.
o GET_AUTH.SCTP: o GET_AUTH.SCTP:
Pass 1 primitive / event: 'Set / Get Authentication Parameters' Pass 1 primitive/event: 'Set/Get Authentication Parameters'
Parameters: key_id; chunk_list Parameters: key_id and chunk_list
o RESET_STREAM.SCTP: o RESET_STREAM.SCTP:
Pass 1 primitive / event: 'Add / Reset Streams, Reset Association' Pass 1 primitive/event: 'Add/Reset Streams, Reset Association'
Parameters: sid; direction Parameters: sid and direction
o RESET_STREAM-EVENT.SCTP: o RESET_STREAM-EVENT.SCTP:
Pass 1 primitive / event: 'Stream Reset' notification Pass 1 primitive/event: 'Stream Reset' notification
Parameters: information about the result of RESET_STREAM.SCTP. Parameters: information about the result of RESET_STREAM.SCTP
Comments: This is issued when the procedure for resetting streams Comments: this is issued when the procedure for resetting streams
has completed. has completed.
o RESET_ASSOC.SCTP: o RESET_ASSOC.SCTP:
Pass 1 primitive / event: 'Add / Reset Streams, Reset Association' Pass 1 primitive/event: 'Add/Reset Streams, Reset Association'
Parameters: information related to the extension, defined in Parameters: information related to the extension, as defined in
[RFC3260]. [RFC3260]
o RESET_ASSOC-EVENT.SCTP: o RESET_ASSOC-EVENT.SCTP:
Pass 1 primitive / event: 'Association Reset' notification Pass 1 primitive/event: 'Association Reset' notification
Parameters: information about the result of RESET_ASSOC.SCTP. Parameters: information about the result of RESET_ASSOC.SCTP
Comments: this is issued when the procedure for resetting an Comments: this is issued when the procedure for resetting an
association has completed. association has completed.
o ADD_STREAM.SCTP: o ADD_STREAM.SCTP:
Pass 1 primitive / event: 'Add / Reset Streams, Reset Association' Pass 1 primitive/event: 'Add/Reset Streams, Reset Association'
Parameters: number if outgoing and incoming streams to be added Parameters: number of outgoing and incoming streams to be added
o ADD_STREAM-EVENT.SCTP: o ADD_STREAM-EVENT.SCTP:
Pass 1 primitive / event: 'Stream Change' notification Pass 1 primitive/event: 'Stream Change' notification
Parameters: information about the result of ADD_STREAM.SCTP. Parameters: information about the result of ADD_STREAM.SCTP
Comments: this is issued when the procedure for adding a stream Comments: this is issued when the procedure for adding a stream
has completed. has completed.
o SET_STREAM_SCHEDULER.SCTP: o SET_STREAM_SCHEDULER.SCTP:
Pass 1 primitive / event: 'Set Stream Scheduler' Pass 1 primitive/event: 'Set Stream Scheduler'
Parameters: scheduler identifier Parameters: scheduler identifier
Comments: choice of First Come First Serve, Round Robin, Round Comments: choice of First-Come, First-Served; Round-Robin; Round-
Robin per Packet, Priority Based, Fair Bandwidth, Weighted Fair Robin per Packet; Priority-Based; Fair Bandwidth; and Weighted
Queuing. Fair Queuing.
o CONFIGURE_STREAM_SCHEDULER.SCTP: o CONFIGURE_STREAM_SCHEDULER.SCTP:
Pass 1 primitive / event: 'Configure Stream Scheduler' Pass 1 primitive/event: 'Configure Stream Scheduler'
Parameters: priority Parameters: priority
Comments: the priority value only applies when Priority Based or Comments: the priority value only applies when Priority-Based or
Weighted Fair Queuing scheduling is chosen with Weighted Fair Queuing scheduling is chosen with
SET_STREAM_SCHEDULER.SCTP. The meaning of the parameter differs SET_STREAM_SCHEDULER.SCTP. The meaning of the parameter differs
between these two schedulers but in both cases it realizes some between these two schedulers, but in both cases, it realizes some
form of prioritization regarding how bandwidth is divided among form of prioritization regarding how bandwidth is divided among
streams. streams.
o SET_FLOWLABEL.SCTP: o SET_FLOWLABEL.SCTP:
Pass 1 primitive / event: 'Set IPv6 Flow Label' Pass 1 primitive/event: 'Set IPv6 Flow Label'
Parameters: flow label Parameters: flow label
Comments: this allows an application to change the IPv6 header's Comments: this allows an application to change the IPv6 header's
flow label field for outgoing packets on a path. flow label field for outgoing packets on a path.
o AUTHENTICATION_NOTIFICATION-EVENT.SCTP: o AUTHENTICATION_NOTIFICATION-EVENT.SCTP:
Pass 1 primitive / event: 'Authentication' notification Pass 1 primitive/event: 'Authentication' notification
Returns: information regarding key management. Returns: information regarding key management
o CONFIG_SEND_BUFFER.SCTP: o CONFIG_SEND_BUFFER.SCTP:
Pass 1 primitive / event: 'Configure Send Buffer Size' Pass 1 primitive/event: 'Configure Send Buffer Size'
Parameters: size value in octets Parameters: size value in octets
o CONFIG_RECEIVE_BUFFER.SCTP: o CONFIG_RECEIVE_BUFFER.SCTP:
Pass 1 primitive / event: 'Configure Receive Buffer Size' Pass 1 primitive/event: 'Configure Receive Buffer Size'
Parameters: size value in octets Parameters: size value in octets
Comments: this controls the receiver window. Comments: this controls the receiver window.
o CONFIG_FRAGMENTATION.SCTP: o CONFIG_FRAGMENTATION.SCTP:
Pass 1 primitive / event: 'Configure Message Fragmentation' Pass 1 primitive/event: 'Configure Message Fragmentation'
Parameters: one boolean value (enable/disable); maximum Parameters: one boolean value (enable/disable) and maximum
fragmentation size (optional; default: PMTU) fragmentation size (optional; default: PMTU)
Comments: if fragmentation is enabled, messages exceeding the Comments: if fragmentation is enabled, messages exceeding the
maximum fragmentation size will be fragmented. If fragmentation maximum fragmentation size will be fragmented. If fragmentation
is disabled, trying to send a message that exceeds the maximum is disabled, trying to send a message that exceeds the maximum
fragmentation size will produce an error. fragmentation size will produce an error.
o CONFIG_PMTUD.SCTP: o CONFIG_PMTUD.SCTP:
Pass 1 primitive / event: 'Configure Path MTU Discovery' Pass 1 primitive/event: 'Configure Path MTU Discovery'
Parameters: one boolean value (PMTUD on/off); PMTU value Parameters: one boolean value (PMTUD on/off) and PMTU value
(optional) (optional)
Returns: PMTU value Returns: PMTU value
Comments: this returns a meaningful PMTU value when PMTUD is Comments: this returns a meaningful PMTU value when PMTUD is
enabled (the boolean is true), and the PMTU value can be set if enabled (the boolean is true), and the PMTU value can be set if
PMTUD is disabled (the boolean is false) PMTUD is disabled (the boolean is false).
o CONFIG_DELAYED_SACK.SCTP: o CONFIG_DELAYED_SACK.SCTP:
Pass 1 primitive / event: 'Configure Delayed SACK Timer' Pass 1 primitive/event: 'Configure Delayed SACK Timer'
Parameters: one boolean value (delayed SACK on/off); timer value Parameters: one boolean value (delayed SACK on/off); timer value
(optional); number of packets to wait for (default 2) (optional); and number of packets to wait for (default 2)
Comments: if delayed SACK is enabled, SCTP will send a SACK upon Comments: if delayed SACK is enabled, SCTP will send a SACK either
either receiving the provided number of packets or when the timer upon receiving the provided number of packets or when the timer
expires, whatever occurs first. expires, whatever occurs first.
o CONFIG_RTO.SCTP: o CONFIG_RTO.SCTP:
Pass 1 primitive / event: 'Configure RTO Calculation' Pass 1 primitive/event: 'Configure RTO Calculation'
Parameters: init (optional); min (optional); max (optional) Parameters: init (optional); min (optional); and max (optional)
Comments: this adjusts the initial, minimum and maximum RTO Comments: this adjusts the initial, minimum, and maximum RTO
values. values.
o SET_COOKIE_LIFE.SCTP: o SET_COOKIE_LIFE.SCTP:
Pass 1 primitive / event: 'Set Cookie Life Value' Pass 1 primitive/event: 'Set Cookie Life Value'
Parameters: cookie life value Parameters: cookie life value
o SET_MAX_BURST.SCTP: o SET_MAX_BURST.SCTP:
Pass 1 primitive / event: 'Set Maximum Burst' Pass 1 primitive/event: 'Set Maximum Burst'
Parameters: max burst value Parameters: max burst value
Comments: not all implementations allow values above the default Comments: not all implementations allow values above the default
of 4. of 4.
o SET_PARTIAL_DELIVERY_POINT.SCTP: o SET_PARTIAL_DELIVERY_POINT.SCTP:
Pass 1 primitive / event: 'Set Partial Delivery Point' Pass 1 primitive/event: 'Set Partial Delivery Point'
Parameters: partial delivery point (integer) Parameters: partial delivery point (integer)
Comments: this parameter must be smaller or equal to the socket Comments: this parameter must be smaller or equal to the socket
receive buffer size. receive buffer size.
o SET_CHECKSUM_ENABLED.UDP: o SET_CHECKSUM_ENABLED.UDP:
Pass 1 primitive / event: 'Checksum_Enabled'. Pass 1 primitive/event: 'Checksum_Enabled'
Parameters: 0 when zero checksum is used at sender, 1 for checksum Parameters: 0 when zero checksum is used at sender, 1 for checksum
at sender (default) at sender (default)
o SET_CHECKSUM_REQUIRED.UDP: o SET_CHECKSUM_REQUIRED.UDP:
Pass 1 primitive / event: 'Require_Checksum'. Pass 1 primitive/event: 'Require_Checksum'
Parameter: 0 to allow zero checksum, 1 when a non-zero checksum is Parameter: 0 to allow zero checksum, 1 when a non-zero checksum is
required (default) at receiver required (default) at the receiver
o SET_CHECKSUM_COVERAGE.UDP-Lite: o SET_CHECKSUM_COVERAGE.UDP-Lite:
Pass 1 primitive / event: 'Set_Checksum_Coverage' Pass 1 primitive/event: 'Set_Checksum_Coverage'
Parameters: coverage length at sender (default maximum coverage) Parameters: coverage length at sender (default maximum coverage)
o SET_MIN_CHECKSUM_COVERAGE.UDP-Lite: o SET_MIN_CHECKSUM_COVERAGE.UDP-Lite:
Pass 1 primitive / event: 'Set_Min_Coverage'. Pass 1 primitive/event: 'Set_Min_Coverage'
Parameter: coverage length at receiver (default minimum coverage) Parameter: coverage length at receiver (default minimum coverage)
o SET_DF.UDP(-Lite): o SET_DF.UDP(-Lite):
Pass 1 primitive event: 'Set_DF'. Pass 1 primitive event: 'Set_DF'
Parameter: 0 when DF is not set (default) in the IPv4 header, 1 Parameter: 0 when DF is not set (default) in the IPv4 header, 1
when DF is set when DF is set
o GET_MMS_S.UDP(-Lite): o GET_MMS_S.UDP(-Lite):
Pass 1 primitive event: 'Get_MM_S'. Pass 1 primitive event: 'Get_MM_S'
Comments: this retrieves the maximum transport-message size that Comments: this retrieves the maximum transport-message size that
may be sent using a non-fragmented IP packet from the configured may be sent using a non-fragmented IP packet from the configured
interface. interface.
o GET_MMS_R.UDP(-Lite): o GET_MMS_R.UDP(-Lite):
Pass 1 primitive event: 'Get_MMS_R'. Pass 1 primitive event: 'Get_MMS_R'
Comments: this retrieves the maximum transport-message size that Comments: this retrieves the maximum transport-message size that
may be received from the configured interface. may be received from the configured interface.
o SET_TTL.UDP(-Lite) (IPV6_UNICAST_HOPS): o SET_TTL.UDP(-Lite) (IPV6_UNICAST_HOPS):
Pass 1 primitive / event: 'Set_TTL' and 'Set_IPV6_Unicast_Hops' Pass 1 primitive/event: 'Set_TTL' and 'Set_IPV6_Unicast_Hops'
Parameters: IPv4 TTL value or IPv6 Hop Count value Parameters: IPv4 TTL value or IPv6 Hop Count value
Comments: this allows an application to change the IPv4 TTL of Comments: this allows an application to change the IPv4 TTL of
IPv6 Hop count value for outgoing UDP(-Lite) datagrams. IPv6 Hop Count value for outgoing UDP(-Lite) datagrams.
o GET_TTL.UDP(-Lite) (IPV6_UNICAST_HOPS): o GET_TTL.UDP(-Lite) (IPV6_UNICAST_HOPS):
Pass 1 primitive / event: 'Get_TTL' and 'Get_IPV6_Unicast_Hops' Pass 1 primitive/event: 'Get_TTL' and 'Get_IPV6_Unicast_Hops'
Returns: IPv4 TTL value or IPv6 Hop Count value Returns: IPv4 TTL value or IPv6 Hop Count value
Comments: this allows an application to read the the IPv4 TTL of
IPv6 Hop count value from a received UDP(-Lite) datagram. Comments: this allows an application to read the IPv4 TTL of the
IPv6 Hop Count value from a received UDP(-Lite) datagram.
o SET_ECN.UDP(-Lite): o SET_ECN.UDP(-Lite):
Pass 1 primitive / event: 'Set_ECN' Pass 1 primitive/event: 'Set_ECN'
Parameters: ECN value Parameters: ECN value
Comments: this allows a UDP(-Lite) application to set the ECN Comments: this allows a UDP(-Lite) application to set the Explicit
codepoint field for outgoing UDP(-Lite) datagrams. Defaults to Congestion Notification (ECN) code point field for outgoing
sending '00'. UDP(-Lite) datagrams. It defaults to sending '00'.
o GET_ECN.UDP(-Lite): o GET_ECN.UDP(-Lite):
Pass 1 primitive / event: 'Get_ECN' Pass 1 primitive/event: 'Get_ECN'
Parameters: ECN value Parameters: ECN value
Comments: this allows a UDP(-Lite) application to read the ECN Comments: this allows a UDP(-Lite) application to read the ECN
codepoint field from a received UDP(-Lite) datagram. code point field from a received UDP(-Lite) datagram.
o SET_IP_OPTIONS.UDP(-Lite): o SET_IP_OPTIONS.UDP(-Lite):
Pass 1 primitive / event: 'Set_IP_Options' Pass 1 primitive/event: 'Set_IP_Options'
Parameters: options Parameters: options
Comments: this allows a UDP(-Lite) application to set IP Options Comments: this allows a UDP(-Lite) application to set IP options
for outgoing UDP(-Lite) datagrams. These options can at least be for outgoing UDP(-Lite) datagrams. These options can at least be
the Source Route, Record Route, and Time Stamp option. the Source Route, Record Route, and Timestamp option.
o GET_IP_OPTIONS.UDP(-Lite): o GET_IP_OPTIONS.UDP(-Lite):
Pass 1 primitive / event: 'Get_IP_Options' Pass 1 primitive/event: 'Get_IP_Options'
Returns: options Returns: options
Comments: this allows a UDP(-Lite) application to receive any IP Comments: this allows a UDP(-Lite) application to receive any IP
options that are contained in a received UDP(-Lite) datagram. options that are contained in a received UDP(-Lite) datagram.
o CONFIGURE.LEDBAT: o CONFIGURE.LEDBAT:
Pass 1 primitive / event: N/A Pass 1 primitive/event: N/A
Parameters: enable (boolean); target; allowed_increase; gain_inc; Parameters: enable (boolean); target; allowed_increase; gain_inc;
gain_dec; base_history; current_filter; init_cwnd; min_cwnd gain_dec; base_history; current_filter; init_cwnd; and min_cwnd
Comments: 'enable' is a newly invented parameter that enables or Comments: 'enable' is a newly invented parameter that enables or
disables the whole LEDBAT service. disables the whole LEDBAT service.
TERMINATION: TERMINATION:
Gracefully or forcefully closing a connection, or being informed Gracefully or forcefully closing a connection or being informed about
about this event happening. this event happening.
o CLOSE.TCP: o CLOSE.TCP:
Pass 1 primitive / event: 'Close' Pass 1 primitive/event: 'Close'
Comments: this terminates the sending side of a connection after Comments: this terminates the sending side of a connection after
reliably delivering all remaining data. reliably delivering all remaining data.
o CLOSE.SCTP: o CLOSE.SCTP:
Pass 1 primitive / event: 'Shutdown' Pass 1 primitive/event: 'Shutdown'
Comments: this terminates a connection after reliably delivering Comments: this terminates a connection after reliably delivering
all remaining data. all remaining data.
o ABORT.TCP: o ABORT.TCP:
Pass 1 primitive / event: 'Abort' Pass 1 primitive/event: 'Abort'
Comments: this terminates a connection without delivering Comments: this terminates a connection without delivering
remaining data and sends an error message to the other side. remaining data and sends an error message to the other side.
o ABORT.SCTP: o ABORT.SCTP:
Pass 1 primitive / event: 'Abort' Pass 1 primitive/event: 'Abort'
Parameters: abort reason to be given to the peer (optional) Parameters: abort reason to be given to the peer (optional)
Comments: this terminates a connection without delivering Comments: this terminates a connection without delivering
remaining data and sends an error message to the other side. remaining data and sends an error message to the other side.
o ABORT.UDP(-Lite): o ABORT.UDP(-Lite):
Pass 1 primitive event: 'Close' Pass 1 primitive event: 'Close'
Comments: this terminates a connection without delivering Comments: this terminates a connection without delivering
remaining data. No further UDP(-Lite) datagrams are sent/received remaining data. No further UDP(-Lite) datagrams are sent/received
for this transport service instance. for this transport service instance.
o TIMEOUT.TCP: o TIMEOUT.TCP:
Pass 1 primitive / event: 'User Timeout' event Pass 1 primitive/event: 'User Timeout' event
Comments: the application is informed that the connection is Comments: the application is informed that the connection is
aborted. This event is executed on expiration of the timeout set aborted. This event is executed on expiration of the timeout set
in CONNECTION.ESTABLISHMENT.CONNECT.TCP (possibly adjusted in in CONNECTION.ESTABLISHMENT.CONNECT.TCP (possibly adjusted in
CONNECTION.MAINTENANCE.CHANGE_TIMEOUT.TCP). CONNECTION.MAINTENANCE.CHANGE_TIMEOUT.TCP).
o TIMEOUT.SCTP: o TIMEOUT.SCTP:
Pass 1 primitive / event: 'Communication Lost' event Pass 1 primitive/event: 'Communication Lost' event
Comments: the application is informed that the connection is Comments: the application is informed that the connection is
aborted. this event is executed on expiration of the timeout that aborted. This event is executed on expiration of the timeout that
should be enabled by default (see the beginning of section 8.3 in should be enabled by default (see the beginning of Section 8.3 in
[RFC4960]) and was possibly adjusted in [RFC4960]) and was possibly adjusted in
CONNECTION.MAINTENANCE.CHANGE_TIMEOOUT.SCTP. CONNECTION.MAINTENANCE.CHANGE_TIMEOOUT.SCTP.
o ABORT-EVENT.TCP: o ABORT-EVENT.TCP:
Pass 1 primitive / event: not specified. Pass 1 primitive/event: not specified
o ABORT-EVENT.SCTP: o ABORT-EVENT.SCTP:
Pass 1 primitive / event: 'Communication Lost' event Pass 1 primitive/event: 'Communication Lost' event
Returns: abort reason from the peer (if available) Returns: abort reason from the peer (if available)
Comments: the application is informed that the other side has Comments: the application is informed that the other side has
aborted the connection using CONNECTION.TERMINATION.ABORT.SCTP. aborted the connection using CONNECTION.TERMINATION.ABORT.SCTP.
o CLOSE-EVENT.TCP: o CLOSE-EVENT.TCP:
Pass 1 primitive / event: not specified. Pass 1 primitive/event: not specified
o CLOSE-EVENT.SCTP: o CLOSE-EVENT.SCTP:
Pass 1 primitive / event: 'Shutdown Complete' event Pass 1 primitive/event: 'Shutdown Complete' event
Comments: the application is informed that Comments: the application is informed that
CONNECTION.TERMINATION.CLOSE.SCTP was successfully completed. CONNECTION.TERMINATION.CLOSE.SCTP was successfully completed.
4.2. DATA Transfer Related Primitives 4.2. DATA-Transfer-Related Primitives
All primitives in this section refer to an existing connection, i.e. All primitives in this section refer to an existing connection, i.e.,
a connection that was either established or made available for a connection that was either established or made available for
receiving data (although this is optional for the primitives of UDP(- receiving data (although this is optional for the primitives of
Lite)). In addition to the listed parameters, all sending primitives UDP(-Lite)). In addition to the listed parameters, all sending
contain a reference to a data block and all receiving primitives primitives contain a reference to a data block, and all receiving
contain a reference to available buffer space for the data. Note primitives contain a reference to available buffer space for the
that CONNECT.TCP and LISTEN.TCP in the ESTABLISHMENT and AVAILABILITY data. Note that CONNECT.TCP and LISTEN.TCP in the ESTABLISHMENT and
category also allow to transfer data (an optional user message) AVAILABILITY categories also allow to transfer data (an optional user
before the connection is fully established. message) before the connection is fully established.
o SEND.TCP: o SEND.TCP:
Pass 1 primitive / event: 'Send' Pass 1 primitive/event: 'Send'
Parameters: timeout (optional); current_key (optional); rnext_key Parameters: timeout (optional); current_key (optional); and
(optional) rnext_key (optional)
Comments: this gives TCP a data block for reliable transmission to Comments: this gives TCP a data block for reliable transmission to
the TCP on the other side of the connection. The timeout can be the TCP on the other side of the connection. The timeout can be
configured with this call (see also configured with this call (see also
CONNECTION.MAINTENANCE.CHANGE_TIMEOUT.TCP). 'current_key' and CONNECTION.MAINTENANCE.CHANGE_TIMEOUT.TCP). 'current_key' and
'rnext_key' are authentication parameters that can be configured 'rnext_key' are authentication parameters that can be configured
with this call (see also CONNECTION.MAINTENANCE.SET_AUTH.TCP). with this call (see also CONNECTION.MAINTENANCE.SET_AUTH.TCP).
o SEND.SCTP: o SEND.SCTP:
Pass 1 primitive / event: 'Send' Pass 1 primitive/event: 'Send'
Parameters: stream number; context (optional); socket (optional); Parameters: stream number; context (optional); socket (optional);
unordered flag (optional); no-bundle flag (optional); payload unordered flag (optional); no-bundle flag (optional); payload
protocol-id (optional); pr-policy (optional) pr-value (optional); protocol-id (optional); pr-policy (optional) pr-value (optional);
sack-immediately flag (optional); key-id (optional) sack-immediately flag (optional); and key-id (optional)
Comments: this gives SCTP a data block for transmission to the Comments: this gives SCTP a data block for transmission to the
SCTP on the other side of the connection (SCTP association). The SCTP on the other side of the connection (SCTP association). The
'stream number' denotes the stream to be used. The 'context' 'stream number' denotes the stream to be used. The 'context'
number can later be used to refer to the correct message when an number can later be used to refer to the correct message when an
error is reported. The 'socket' can be used to state which path error is reported. The 'socket' can be used to state which path
should be preferred, if there are multiple paths available (see should be preferred, if there are multiple paths available (see
also CONNECTION.MAINTENANCE.SETPRIMARY.SCTP). The data block can also CONNECTION.MAINTENANCE.SETPRIMARY.SCTP). The data block can
be delivered out-of-order if the 'unordered flag' is set. The be delivered out of order if the 'unordered' flag is set. The
'no-bundle flag' can be set to indicate a preference to avoid 'no-bundle flag' can be set to indicate a preference to avoid
bundling. The 'payload protocol-id' is a number that will, if bundling. The 'payload protocol-id' is a number that will, if
provided, be handed over to the receiving application. Using pr- provided, be handed over to the receiving application. Using
policy and pr-value the level of reliability can be controlled. pr-policy and pr-value, the level of reliability can be
The 'sack-immediately' flag can be used to indicate that the peer controlled. The 'sack-immediately' flag can be used to indicate
should not delay the sending of a SACK corresponding to the that the peer should not delay the sending of a SACK corresponding
provided user message. If specified, the provided key-id is used to the provided user message. If specified, the provided key-id
for authenticating the user message. is used for authenticating the user message.
o SEND.UDP(-Lite): o SEND.UDP(-Lite):
Pass 1 primitive / event: 'Send' Pass 1 primitive/event: 'Send'
Parameters: IP Address and Port Number of the destination endpoint Parameters: IP address and port number of the destination endpoint
(optional if connected) (optional if connected)
Comments: this provides a message for unreliable transmission Comments: this provides a message for unreliable transmission
using UDP(-Lite) to the specified transport address. IP address using UDP(-Lite) to the specified transport address. The IP
and Port may be omitted for connected UDP(-Lite) sockets. All address and port number may be omitted for connected UDP(-Lite)
CONNECTION.MAINTENANCE.SET_*.UDP(-Lite) primitives apply per sockets. All CONNECTION.MAINTENANCE.SET_*.UDP(-Lite) primitives
message sent. apply per message sent.
o RECEIVE.TCP: o RECEIVE.TCP:
Pass 1 primitive / event: 'Receive'. Pass 1 primitive/event: 'Receive'
Parameters: current_key (optional); rnext_key (optional) Parameters: current_key (optional) and rnext_key (optional)
Comments: 'current_key' and 'rnext_key' are authentication Comments: 'current_key' and 'rnext_key' are authentication
parameters that can be read with this call (see also parameters that can be read with this call (see also
CONNECTION.MAINTENANCE.GET_AUTH.TCP). CONNECTION.MAINTENANCE.GET_AUTH.TCP).
o RECEIVE.SCTP: o RECEIVE.SCTP:
Pass 1 primitive / event: 'Data Arrive' notification, followed by Pass 1 primitive/event: 'Data Arrive' notification, followed by
'Receive' 'Receive'
Parameters: stream number (optional) Parameters: stream number (optional)
Returns: stream sequence number (optional); partial flag Returns: stream sequence number (optional) and partial flag
(optional) (optional)
Comments: if the 'stream number' is provided, the call to receive Comments: if the 'stream number' is provided, the call to receive
only receives data on one particular stream. If a partial message only receives data on one particular stream. If a partial message
arrives, this is indicated by the 'partial flag', and then the arrives, this is indicated by the 'partial flag', and then the
'stream sequence number' must be provided such that an application 'stream sequence number' must be provided such that an application
can restore the correct order of data blocks that comprise an can restore the correct order of data blocks that comprise an
entire message. entire message.
o RECEIVE.UDP(-Lite): o RECEIVE.UDP(-Lite):
Pass 1 primitive / event: 'Receive', Pass 1 primitive/event: 'Receive'
Parameters: buffer for received datagram Parameters: buffer for received datagram
Comments: all CONNECTION.MAINTENANCE.GET_*.UDP(-Lite) primitives Comments: all CONNECTION.MAINTENANCE.GET_*.UDP(-Lite) primitives
apply per message received. apply per message received.
o SENDFAILURE-EVENT.SCTP: o SENDFAILURE-EVENT.SCTP:
Pass 1 primitive / event: 'Send Failure' notification, optionally Pass 1 primitive/event: 'Send Failure' notification, optionally
followed by 'Receive Unsent Message' or 'Receive Unacknowledged followed by 'Receive Unsent Message' or 'Receive Unacknowledged
Message' Message'
Returns: cause code; context; unsent or unacknowledged message Returns: cause code; context; and unsent or unacknowledged message
(optional) (optional)
Comments: 'cause code' indicates the reason of the failure, and Comments: 'cause code' indicates the reason of the failure, and
'context' is the context number if such a number has been provided 'context' is the context number if such a number has been provided
in DATA.SEND.SCTP, for later use with 'Receive Unsent Message' or in DATA.SEND.SCTP, for later use with 'Receive Unsent Message' or
'Receive Unacknowledged Message', respectively. These primitives 'Receive Unacknowledged Message', respectively. These primitives
can be used to retrieve the unsent or unacknowledged message (or can be used to retrieve the unsent or unacknowledged message (or
part of the message, in case a part was delivered) if desired. part of the message, in case a part was delivered) if desired.
o SEND_FAILURE.UDP(-Lite): o SEND_FAILURE.UDP(-Lite):
Pass 1 primitive / event: 'Send' Pass 1 primitive/event: 'Send'
Comments: this may be used to probe for the effective PMTU when Comments: this may be used to probe for the effective PMTU when
using in combination with the 'MAINTENANCE.SET_DF' primitive. using in combination with the 'MAINTENANCE.SET_DF' primitive.
o SENDER_DRY-EVENT.SCTP: o SENDER_DRY-EVENT.SCTP:
Pass 1 primitive / event: 'Sender Dry' notification Pass 1 primitive/event: 'Sender Dry' notification
Comments: this informs the application that the stack has no more Comments: this informs the application that the stack has no more
user data to send. user data to send.
o PARTIAL_DELIVERY_ABORTED-EVENT.SCTP: o PARTIAL_DELIVERY_ABORTED-EVENT.SCTP:
Pass 1 primitive / event: 'Partial Delivery Aborted' notification Pass 1 primitive/event: 'Partial Delivery Aborted' notification
Comments: this informs the receiver of a partial message that the Comments: this informs the receiver of a partial message that the
further delivery of the message has been aborted. further delivery of the message has been aborted.
5. Pass 3 5. Pass 3
This section presents the superset of all transport features in all This section presents the superset of all transport features in all
protocols that were discussed in the preceding sections, based on the protocols that were discussed in the preceding sections, based on the
list of primitives in pass 2 but also on text in pass 1 to include list of primitives in pass 2 but also on text in pass 1 to include
transport features that can be configured in one protocol and are transport features that can be configured in one protocol and are
static properties in another (congestion control, for example). static properties in another (congestion control, for example).
Again, some minor details are omitted for the sake of generalization Again, some minor details are omitted for the sake of generalization
-- e.g., TCP may provide various different IP options, but only -- e.g., TCP may provide various different IP options, but only
source route is mandatory to implement, and this detail is not source route is mandatory to implement, and this detail is not
visible in the Pass 3 transport feature "Specify IP Options". As visible in the pass 3 transport feature "Specify IP options". As
before, "UDP(-Lite)" represents both UDP and UDP-Lite, and TCP refers before, "UDP(-Lite)" represents both UDP and UDP-Lite, and "TCP"
to both TCP and MPTCP. refers to both TCP and MPTCP.
5.1. CONNECTION Related Transport Features 5.1. CONNECTION-Related Transport Features
ESTABLISHMENT: ESTABLISHMENT:
Active creation of a connection from one transport endpoint to one or Active creation of a connection from one transport endpoint to one or
more transport endpoints. more transport endpoints.
o Connect o Connect
Protocols: TCP, SCTP, UDP(-Lite) Protocols: TCP, SCTP, and UDP(-Lite)
o Specify which IP Options must always be used o Specify which IP options must always be used
Protocols: TCP, UDP(-Lite) Protocols: TCP and UDP(-Lite)
o Request multiple streams o Request multiple streams
Protocols: SCTP Protocols: SCTP
o Limit the number of inbound streams o Limit the number of inbound streams
Protocols: SCTP Protocols: SCTP
o Specify number of attempts and/or timeout for the first o Specify number of attempts and/or timeout for the first
establishment message establishment message
Protocols: TCP, SCTP Protocols: TCP and SCTP
o Obtain multiple sockets o Obtain multiple sockets
Protocols: SCTP Protocols: SCTP
o Disable MPTCP o Disable MPTCP
Protocols: MPTCP Protocols: MPTCP
o Configure authentication o Configure authentication
Protocols: TCP, SCTP Protocols: TCP and SCTP
Comments: with TCP, this allows to configure Master Key Tuples Comments: with TCP, this allows the configuration of MKTs. In
(MKTs). In SCTP, this allows to specify which chunk types must SCTP, this allows the specification of which chunk types must
always be authenticated. DATA, ACK etc. are different 'chunks' in always be authenticated. DATA, ACK, etc., are different 'chunks'
SCTP; one or more chunks may be included in a single packet. in SCTP; one or more chunks may be included in a single packet.
o Indicate an Adaptation Layer (via an adaptation code point) o Indicate an Adaptation Layer (via an adaptation code point)
Protocols: SCTP Protocols: SCTP
o Request to negotiate interleaving of user messages o Request to negotiate interleaving of user messages
Protocols: SCTP Protocols: SCTP
o Hand over a message to reliably transfer (possibly multiple times) o Hand over a message to reliably transfer (possibly multiple times)
before connection establishment before connection establishment
Protocols: TCP Protocols: TCP
skipping to change at page 42, line 40 skipping to change at page 42, line 30
Protocols: TCP Protocols: TCP
o Hand over a message to reliably transfer during connection o Hand over a message to reliably transfer during connection
establishment establishment
Protocols: SCTP Protocols: SCTP
o Enable UDP encapsulation with a specified remote UDP port number o Enable UDP encapsulation with a specified remote UDP port number
Protocols: SCTP Protocols: SCTP
AVAILABILITY: AVAILABILITY:
Preparing to receive incoming connection requests. Preparing to receive incoming connection requests.
o Listen, 1 specified local interface o Listen, 1 specified local interface
Protocols: TCP, SCTP, UDP(-Lite) Protocols: TCP, SCTP, and UDP(-Lite)
o Listen, N specified local interfaces o Listen, N specified local interfaces
Protocols: SCTP Protocols: SCTP
o Listen, all local interfaces o Listen, all local interfaces
Protocols: TCP, SCTP, UDP(-Lite) Protocols: TCP, SCTP, and UDP(-Lite)
o Obtain requested number of streams o Obtain requested number of streams
Protocols: SCTP Protocols: SCTP
o Limit the number of inbound streams o Limit the number of inbound streams
Protocols: SCTP Protocols: SCTP
o Specify which IP Options must always be used o Specify which IP options must always be used
Protocols: TCP, UDP(-Lite) Protocols: TCP and UDP(-Lite)
o Disable MPTCP o Disable MPTCP
Protocols: MPTCP Protocols: MPTCP
o Configure authentication o Configure authentication
Protocols: TCP, SCTP Protocols: TCP and SCTP
Comments: with TCP, this allows to configure Master Key Tuples Comments: with TCP, this allows the configuration of MKTs. In
(MKTs). In SCTP, this allows to specify which chunk types must SCTP, this allows the specification of which chunk types must
always be authenticated. DATA, ACK etc. are different 'chunks' in always be authenticated. DATA, ACK, etc., are different 'chunks'
SCTP; one or more chunks may be included in a single packet. in SCTP; one or more chunks may be included in a single packet.
o Indicate an Adaptation Layer (via an adaptation code point) o Indicate an Adaptation Layer (via an adaptation code point)
Protocols: SCTP Protocols: SCTP
MAINTENANCE: MAINTENANCE:
Adjustments made to an open connection, or notifications about it. Adjustments made to an open connection, or notifications about it.
o Change timeout for aborting connection (using retransmit limit or o Change timeout for aborting connection (using retransmit limit or
time value) time value)
Protocols: TCP, SCTP Protocols: TCP and SCTP
o Suggest timeout to the peer o Suggest timeout to the peer
Protocols: TCP Protocols: TCP
o Disable Nagle algorithm o Disable Nagle algorithm
Protocols: TCP, SCTP Protocols: TCP and SCTP
o Request an immediate heartbeat, returning success/failure o Request an immediate heartbeat, returning success/failure
Protocols: SCTP Protocols: SCTP
o Notification of Excessive Retransmissions (early warning below o Notification of excessive retransmissions (early warning below
abortion threshold) abortion threshold)
Protocols: TCP Protocols: TCP
o Add path o Add path
Protocols: MPTCP, SCTP Protocols: MPTCP and SCTP
MPTCP Parameters: source-IP; source-Port; destination-IP; MPTCP Parameters: source-IP; source-Port; destination-IP; and
destination-Port destination-Port
SCTP Parameters: local IP address SCTP Parameters: local IP address
o Remove path o Remove path
Protocols: MPTCP, SCTP Protocols: MPTCP and SCTP
MPTCP Parameters: source-IP; source-Port; destination-IP; MPTCP Parameters: source-IP; source-Port; destination-IP; and
destination-Port destination-Port
SCTP Parameters: local IP address SCTP Parameters: local IP address
o Set primary path o Set primary path
Protocols: SCTP Protocols: SCTP
o Suggest primary path to the peer o Suggest primary path to the peer
Protocols: SCTP Protocols: SCTP
o Configure Path Switchover o Configure Path Switchover
Protocols: SCTP Protocols: SCTP
o Obtain status (query or notification) o Obtain status (query or notification)
Protocols: SCTP, MPTCP Protocols: SCTP and MPTCP
SCTP parameters: association connection state; destination SCTP parameters: association connection state; destination
transport address list; destination transport address reachability transport address list; destination transport address reachability
states; current local and peer receiver window sizes; current states; current local and peer receiver window sizes; current
local congestion window sizes; number of unacknowledged DATA local congestion window sizes; number of unacknowledged DATA
chunks; number of DATA chunks pending receipt; primary path; most chunks; number of DATA chunks pending receipt; primary path; most
recent SRTT on primary path; RTO on primary path; SRTT and RTO on recent SRTT on primary path; RTO on primary path; SRTT and RTO on
other destination addresses; MTU per path; interleaving supported other destination addresses; MTU per path; and interleaving
yes/no supported yes/no
MPTCP parameters: subflow-list (identified by source-IP; source- MPTCP parameters: subflow-list (identified by source-IP;
Port; destination-IP; destination-Port) source-Port; destination-IP; and destination-Port)
o Specify DSCP field o Specify DSCP field
Protocols: TCP, SCTP, UDP(-Lite) Protocols: TCP, SCTP, and UDP(-Lite)
o Notification of ICMP error message arrival o Notification of ICMP error message arrival
Protocols: TCP, UDP(-Lite) Protocols: TCP and UDP(-Lite)
o Change authentication parameters o Change authentication parameters
Protocols: TCP, SCTP Protocols: TCP and SCTP
o Obtain authentication information o Obtain authentication information
Protocols: TCP, SCTP Protocols: TCP and SCTP
o Reset Stream o Reset Stream
Protocols: SCTP Protocols: SCTP
o Notification of Stream Reset o Notification of Stream Reset
Protocols: STCP Protocols: STCP
o Reset Association o Reset Association
Protocols: SCTP Protocols: SCTP
skipping to change at page 46, line 25 skipping to change at page 46, line 16
Protocols: UDP(-Lite) Protocols: UDP(-Lite)
o Get max. transport-message size that may be sent using a non- o Get max. transport-message size that may be sent using a non-
fragmented IP packet from the configured interface fragmented IP packet from the configured interface
Protocols: UDP(-Lite) Protocols: UDP(-Lite)
o Get max. transport-message size that may be received from the o Get max. transport-message size that may be received from the
configured interface configured interface
Protocols: UDP(-Lite) Protocols: UDP(-Lite)
o Specify TTL/Hop count field o Specify TTL/Hop Count field
Protocols: UDP(-Lite) Protocols: UDP(-Lite)
o Obtain TTL/Hop count field o Obtain TTL/Hop Count field
Protocols: UDP(-Lite) Protocols: UDP(-Lite)
o Specify ECN field o Specify ECN field
Protocols: UDP(-Lite) Protocols: UDP(-Lite)
o Obtain ECN field o Obtain ECN field
Protocols: UDP(-Lite) Protocols: UDP(-Lite)
o Specify IP Options o Specify IP options
Protocols: UDP(-Lite) Protocols: UDP(-Lite)
o Obtain IP Options o Obtain IP options
Protocols: UDP(-Lite) Protocols: UDP(-Lite)
o Enable and configure "Low Extra Delay Background Transfer" o Enable and configure "Low Extra Delay Background Transfer"
Protocols: A protocol implementing the LEDBAT congestion control Protocols: A protocol implementing the LEDBAT congestion control
mechanism mechanism
TERMINATION: TERMINATION:
Gracefully or forcefully closing a connection, or being informed Gracefully or forcefully closing a connection, or being informed
about this event happening. about this event happening.
o Close after reliably delivering all remaining data, causing an o Close after reliably delivering all remaining data, causing an
event informing the application on the other side event informing the application on the other side
Protocols: TCP, SCTP Protocols: TCP and SCTP
Comments: a TCP endpoint locally only closes the connection for Comments: a TCP endpoint locally only closes the connection for
sending; it may still receive data afterwards. sending; it may still receive data afterwards.
o Abort without delivering remaining data, causing an event o Abort without delivering remaining data, causing an event that
informing the application on the other side informs the application on the other side
Protocols: TCP, SCTP Protocols: TCP and SCTP
Comments: in SCTP a reason can optionally be given by the Comments: in SCTP, a reason can optionally be given by the
application on the aborting side, which can then be received by application on the aborting side, which can then be received by
the application on the other side. the application on the other side.
o Abort without delivering remaining data, not causing an event o Abort without delivering remaining data, not causing an event that
informing the application on the other side informs the application on the other side
Protocols: UDP(-Lite) Protocols: UDP(-Lite)
o Timeout event when data could not be delivered for too long o Timeout event when data could not be delivered for too long
Protocols: TCP, SCTP Protocols: TCP and SCTP
Comments: the timeout is configured with CONNECTION.MAINTENANCE Comments: the timeout is configured with CONNECTION.MAINTENANCE
"Change timeout for aborting connection (using retransmit limit or "Change timeout for aborting connection (using retransmit limit or
time value)". time value)".
5.2. DATA Transfer Related Transport Features 5.2. DATA-Transfer-Related Transport Features
All transport features in this section refer to an existing All transport features in this section refer to an existing
connection, i.e. a connection that was either established or made connection, i.e., a connection that was either established or made
available for receiving data. Note that TCP allows to transfer data available for receiving data. Note that TCP allows the transfer of
(a single optional user message, possibly arriving multiple times) data (a single optional user message, possibly arriving multiple
before the connection is fully established. Reliable data transfer times) before the connection is fully established. Reliable data
entails delay -- e.g. for the sender to wait until it can transmit transfer entails delay -- e.g., for the sender to wait until it can
data, or due to retransmission in case of packet loss. transmit data or due to retransmission in case of packet loss.
5.2.1. Sending Data 5.2.1. Sending Data
All transport features in this section are provided by DATA.SEND from All transport features in this section are provided by DATA.SEND from
pass 2. DATA.SEND is given a data block from the application, which pass 2. DATA.SEND is given a data block from the application, which
we here call a "message" if the beginning and end of the data block here we call a "message" if the beginning and end of the data block
can be identified at the receiver, and "data" otherwise. can be identified at the receiver, and "data" otherwise.
o Reliably transfer data, with congestion control o Reliably transfer data, with congestion control
Protocols: TCP Protocols: TCP
o Reliably transfer a message, with congestion control o Reliably transfer a message, with congestion control
Protocols: SCTP Protocols: SCTP
o Unreliably transfer a message, with congestion control o Unreliably transfer a message, with congestion control
Protocols: SCTP Protocols: SCTP
skipping to change at page 48, line 24 skipping to change at page 48, line 15
o Choice of stream o Choice of stream
Protocols: SCTP Protocols: SCTP
o Choice of path (destination address) o Choice of path (destination address)
Protocols: SCTP Protocols: SCTP
o Ordered message delivery (potentially slower than unordered) o Ordered message delivery (potentially slower than unordered)
Protocols: SCTP Protocols: SCTP
o Unordered message delivery (potentially faster than ordered) o Unordered message delivery (potentially faster than ordered)
Protocols: SCTP, UDP(-Lite) Protocols: SCTP and UDP(-Lite)
o Request not to bundle messages o Request not to bundle messages
Protocols: SCTP Protocols: SCTP
o Specifying a "payload protocol-id" (handed over as such by the o Specifying a 'payload protocol-id' (handed over as such by the
receiver) receiver)
Protocols: SCTP Protocols: SCTP
o Specifying a key id to be used to authenticate a message o Specifying a key identifier to be used to authenticate a message
Protocols: SCTP Protocols: SCTP
o Request not to delay the acknowledgement (SACK) of a message o Request not to delay the acknowledgement (SACK) of a message
Protocols: SCTP Protocols: SCTP
5.2.2. Receiving Data 5.2.2. Receiving Data
All transport features in this section are provided by DATA.RECEIVE All transport features in this section are provided by DATA.RECEIVE
from pass 2. DATA.RECEIVE fills a buffer provided by the from pass 2. DATA.RECEIVE fills a buffer provided by the
application, with what we here call a "message" if the beginning and application, with what here we call a "message" if the beginning and
end of the data block can be identified at the receiver, and "data" end of the data block can be identified at the receiver, and "data"
otherwise. otherwise.
o Receive data (with no message delimiting) o Receive data (with no message delimiting)
Protocols: TCP Protocols: TCP
o Receive a message o Receive a message
Protocols: SCTP, UDP(-Lite) Protocols: SCTP and UDP(-Lite)
o Choice of stream to receive from o Choice of stream to receive from
Protocols: SCTP Protocols: SCTP
o Information about partial message arrival o Information about partial message arrival
Protocols: SCTP Protocols: SCTP
Comments: in SCTP, partial messages are combined with a stream Comments: in SCTP, partial messages are combined with a stream
sequence number so that the application can restore the correct sequence number so that the application can restore the correct
order of data blocks an entire message consists of. order of data blocks an entire message consists of.
5.2.3. Errors 5.2.3. Errors
This section describes sending failures that are associated with a This section describes sending failures that are associated with a
specific call to DATA.SEND from pass 2. specific call to DATA.SEND from pass 2.
o Notification of an unsent (part of a) message o Notification of an unsent (part of a) message
Protocols: SCTP, UDP(-Lite) Protocols: SCTP and UDP(-Lite)
o Notification of an unacknowledged (part of a) message o Notification of an unacknowledged (part of a) message
Protocols: SCTP Protocols: SCTP
o Notification that the stack has no more user data to send o Notification that the stack has no more user data to send
Protocols: SCTP Protocols: SCTP
o Notification to a receiver that a partial message delivery has o Notification to a receiver that a partial message delivery has
been aborted been aborted
Protocols: SCTP Protocols: SCTP
6. Acknowledgements 6. IANA Considerations
The authors would like to thank (in alphabetical order) Bob Briscoe,
Spencer Dawkins, Aaron Falk, David Hayes, Karen Nielsen, Tommy Pauly,
Joe Touch and Brian Trammell for providing valuable feedback on this
document. We especially thank Christoph Paasch for providing input
related to Multipath TCP, and Gorry Fairhurst and Tom Jones for
providing input related to UDP(-Lite). This work has received
funding from the European Union's Horizon 2020 research and
innovation programme under grant agreement No. 644334 (NEAT).
7. IANA Considerations
This memo includes no request to IANA. This document does not require any IANA actions.
8. Security Considerations 7. Security Considerations
Authentication, confidentiality protection, and integrity protection Authentication, confidentiality protection, and integrity protection
are identified as transport features [RFC8095]. These transport are identified as transport features [RFC8095]. These transport
features are generally provided by a protocol or layer on top of the features are generally provided by a protocol or layer on top of the
transport protocol; none of the transport protocols considered in transport protocol; none of the transport protocols considered in
this document provides these transport features on its own. this document provides these transport features on its own.
Therefore, these transport features are not considered in this Therefore, these transport features are not considered in this
document, with the exception of native authentication capabilities of document, with the exception of native authentication capabilities of
TCP and SCTP for which the security considerations in [RFC5925] and TCP and SCTP for which the security considerations in [RFC5925] and
[RFC4895] apply. [RFC4895] apply.
Security considerations for the use of UDP and UDP-Lite are provided Security considerations for the use of UDP and UDP-Lite are provided
in the referenced RFCs. Security guidance for application usage is in the referenced RFCs. Security guidance for application usage is
provided in the UDP-Guidelines [RFC8085]. provided in the UDP Guidelines [RFC8085].
9. References
9.1. Normative References
[FJ16] Fairhurst, G. and T. Jones, "Features of the User Datagram 8. References
Protocol (UDP) and Lightweight UDP (UDP-Lite) Transport
Protocols", draft-ietf-taps-transports-usage-udp-04 (work
in progress), July 2017.
[I-D.ietf-tsvwg-sctp-ndata] 8.1. Normative References
Stewart, R., Tuexen, M., Loreto, S., and R. Seggelmann,
"Stream Schedulers and User Message Interleaving for the
Stream Control Transmission Protocol",
draft-ietf-tsvwg-sctp-ndata-08 (work in progress),
October 2016.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981, RFC 793, DOI 10.17487/RFC0793, September 1981,
<https://www.rfc-editor.org/info/rfc793>. <https://www.rfc-editor.org/info/rfc793>.
[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, DOI 10.17487/ Communication Layers", STD 3, RFC 1122,
RFC1122, October 1989, DOI 10.17487/RFC1122, October 1989,
<https://www.rfc-editor.org/info/rfc1122>. <https://www.rfc-editor.org/info/rfc1122>.
[RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P. [RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
Conrad, "Stream Control Transmission Protocol (SCTP) Conrad, "Stream Control Transmission Protocol (SCTP)
Partial Reliability Extension", RFC 3758, DOI 10.17487/ Partial Reliability Extension", RFC 3758,
RFC3758, May 2004, DOI 10.17487/RFC3758, May 2004,
<https://www.rfc-editor.org/info/rfc3758>. <https://www.rfc-editor.org/info/rfc3758>.
[RFC4895] Tuexen, M., Stewart, R., Lei, P., and E. Rescorla, [RFC4895] Tuexen, M., Stewart, R., Lei, P., and E. Rescorla,
"Authenticated Chunks for the Stream Control Transmission "Authenticated Chunks for the Stream Control Transmission
Protocol (SCTP)", RFC 4895, DOI 10.17487/RFC4895, Protocol (SCTP)", RFC 4895, DOI 10.17487/RFC4895, August
August 2007, <https://www.rfc-editor.org/info/rfc4895>. 2007, <https://www.rfc-editor.org/info/rfc4895>.
[RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol", [RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol",
RFC 4960, DOI 10.17487/RFC4960, September 2007, RFC 4960, DOI 10.17487/RFC4960, September 2007,
<https://www.rfc-editor.org/info/rfc4960>. <https://www.rfc-editor.org/info/rfc4960>.
[RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M. [RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
Kozuka, "Stream Control Transmission Protocol (SCTP) Kozuka, "Stream Control Transmission Protocol (SCTP)
Dynamic Address Reconfiguration", RFC 5061, DOI 10.17487/ Dynamic Address Reconfiguration", RFC 5061,
RFC5061, September 2007, DOI 10.17487/RFC5061, September 2007,
<https://www.rfc-editor.org/info/rfc5061>. <https://www.rfc-editor.org/info/rfc5061>.
[RFC5482] Eggert, L. and F. Gont, "TCP User Timeout Option", [RFC5482] Eggert, L. and F. Gont, "TCP User Timeout Option",
RFC 5482, DOI 10.17487/RFC5482, March 2009, RFC 5482, DOI 10.17487/RFC5482, March 2009,
<https://www.rfc-editor.org/info/rfc5482>. <https://www.rfc-editor.org/info/rfc5482>.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925, Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <https://www.rfc-editor.org/info/rfc5925>. June 2010, <https://www.rfc-editor.org/info/rfc5925>.
[RFC6182] Ford, A., Raiciu, C., Handley, M., Barre, S., and J. [RFC6182] Ford, A., Raiciu, C., Handley, M., Barre, S., and J.
Iyengar, "Architectural Guidelines for Multipath TCP Iyengar, "Architectural Guidelines for Multipath TCP
Development", RFC 6182, DOI 10.17487/RFC6182, March 2011, Development", RFC 6182, DOI 10.17487/RFC6182, March 2011,
<https://www.rfc-editor.org/info/rfc6182>. <https://www.rfc-editor.org/info/rfc6182>.
[RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V. [RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V.
Yasevich, "Sockets API Extensions for the Stream Control Yasevich, "Sockets API Extensions for the Stream Control
Transmission Protocol (SCTP)", RFC 6458, DOI 10.17487/ Transmission Protocol (SCTP)", RFC 6458,
RFC6458, December 2011, DOI 10.17487/RFC6458, December 2011,
<https://www.rfc-editor.org/info/rfc6458>. <https://www.rfc-editor.org/info/rfc6458>.
[RFC6525] Stewart, R., Tuexen, M., and P. Lei, "Stream Control [RFC6525] Stewart, R., Tuexen, M., and P. Lei, "Stream Control
Transmission Protocol (SCTP) Stream Reconfiguration", Transmission Protocol (SCTP) Stream Reconfiguration",
RFC 6525, DOI 10.17487/RFC6525, February 2012, RFC 6525, DOI 10.17487/RFC6525, February 2012,
<https://www.rfc-editor.org/info/rfc6525>. <https://www.rfc-editor.org/info/rfc6525>.
[RFC6817] Shalunov, S., Hazel, G., Iyengar, J., and M. Kuehlewind, [RFC6817] Shalunov, S., Hazel, G., Iyengar, J., and M. Kuehlewind,
"Low Extra Delay Background Transport (LEDBAT)", RFC 6817, "Low Extra Delay Background Transport (LEDBAT)", RFC 6817,
DOI 10.17487/RFC6817, December 2012, DOI 10.17487/RFC6817, December 2012,
skipping to change at page 52, line 11 skipping to change at page 51, line 32
"TCP Extensions for Multipath Operation with Multiple "TCP Extensions for Multipath Operation with Multiple
Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013, Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013,
<https://www.rfc-editor.org/info/rfc6824>. <https://www.rfc-editor.org/info/rfc6824>.
[RFC6897] Scharf, M. and A. Ford, "Multipath TCP (MPTCP) Application [RFC6897] Scharf, M. and A. Ford, "Multipath TCP (MPTCP) Application
Interface Considerations", RFC 6897, DOI 10.17487/RFC6897, Interface Considerations", RFC 6897, DOI 10.17487/RFC6897,
March 2013, <https://www.rfc-editor.org/info/rfc6897>. March 2013, <https://www.rfc-editor.org/info/rfc6897>.
[RFC6951] Tuexen, M. and R. Stewart, "UDP Encapsulation of Stream [RFC6951] Tuexen, M. and R. Stewart, "UDP Encapsulation of Stream
Control Transmission Protocol (SCTP) Packets for End-Host Control Transmission Protocol (SCTP) Packets for End-Host
to End-Host Communication", RFC 6951, DOI 10.17487/ to End-Host Communication", RFC 6951,
RFC6951, May 2013, DOI 10.17487/RFC6951, May 2013,
<https://www.rfc-editor.org/info/rfc6951>. <https://www.rfc-editor.org/info/rfc6951>.
[RFC7053] Tuexen, M., Ruengeler, I., and R. Stewart, "SACK- [RFC7053] Tuexen, M., Ruengeler, I., and R. Stewart, "SACK-
IMMEDIATELY Extension for the Stream Control Transmission IMMEDIATELY Extension for the Stream Control Transmission
Protocol", RFC 7053, DOI 10.17487/RFC7053, November 2013, Protocol", RFC 7053, DOI 10.17487/RFC7053, November 2013,
<https://www.rfc-editor.org/info/rfc7053>. <https://www.rfc-editor.org/info/rfc7053>.
[RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP [RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP
Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014, Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014,
<https://www.rfc-editor.org/info/rfc7413>. <https://www.rfc-editor.org/info/rfc7413>.
skipping to change at page 52, line 40 skipping to change at page 52, line 15
[RFC7829] Nishida, Y., Natarajan, P., Caro, A., Amer, P., and K. [RFC7829] Nishida, Y., Natarajan, P., Caro, A., Amer, P., and K.
Nielsen, "SCTP-PF: A Quick Failover Algorithm for the Nielsen, "SCTP-PF: A Quick Failover Algorithm for the
Stream Control Transmission Protocol", RFC 7829, Stream Control Transmission Protocol", RFC 7829,
DOI 10.17487/RFC7829, April 2016, DOI 10.17487/RFC7829, April 2016,
<https://www.rfc-editor.org/info/rfc7829>. <https://www.rfc-editor.org/info/rfc7829>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage [RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>. March 2017, <https://www.rfc-editor.org/info/rfc8085>.
9.2. Informative References [RFC8260] Stewart, R., Tuexen, M., Loreto, S., and R. Seggelmann,
"Stream Schedulers and User Message Interleaving for the
Stream Control Transmission Protocol", RFC 8260,
DOI 10.17487/RFC8260, November 2017,
<https://www.rfc-editor.org/info/rfc8260>.
[I-D.draft-gjessing-taps-minset] [RFC8304] Fairhurst, G. and T. Jones, "Transport Features of the
Gjessing, S. and M. Welzl, "A Minimal Set of Transport User Datagram Protocol (UDP) and Lightweight UDP (UDP-
Services for TAPS Systems", draft-gjessing-taps-minset-05 Lite)", RFC 8304, DOI 10.17487/RFC8304, February 2018,
(work in progress), June 2017. <https://www.rfc-editor.org/info/rfc8304>.
8.2. Informative References
[RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol [RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol
Specification", STD 8, RFC 854, DOI 10.17487/RFC0854, Specification", STD 8, RFC 854, DOI 10.17487/RFC0854, May
May 1983, <https://www.rfc-editor.org/info/rfc854>. 1983, <https://www.rfc-editor.org/info/rfc854>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119,
RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS "Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474, Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998, DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>. <https://www.rfc-editor.org/info/rfc2474>.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated and W. Weiss, "An Architecture for Differentiated
skipping to change at page 53, line 32 skipping to change at page 53, line 15
[RFC5461] Gont, F., "TCP's Reaction to Soft Errors", RFC 5461, [RFC5461] Gont, F., "TCP's Reaction to Soft Errors", RFC 5461,
DOI 10.17487/RFC5461, February 2009, DOI 10.17487/RFC5461, February 2009,
<https://www.rfc-editor.org/info/rfc5461>. <https://www.rfc-editor.org/info/rfc5461>.
[RFC6093] Gont, F. and A. Yourtchenko, "On the Implementation of the [RFC6093] Gont, F. and A. Yourtchenko, "On the Implementation of the
TCP Urgent Mechanism", RFC 6093, DOI 10.17487/RFC6093, TCP Urgent Mechanism", RFC 6093, DOI 10.17487/RFC6093,
January 2011, <https://www.rfc-editor.org/info/rfc6093>. January 2011, <https://www.rfc-editor.org/info/rfc6093>.
[RFC7414] Duke, M., Braden, R., Eddy, W., Blanton, E., and A. [RFC7414] Duke, M., Braden, R., Eddy, W., Blanton, E., and A.
Zimmermann, "A Roadmap for Transmission Control Protocol Zimmermann, "A Roadmap for Transmission Control Protocol
(TCP) Specification Documents", RFC 7414, DOI 10.17487/ (TCP) Specification Documents", RFC 7414,
RFC7414, February 2015, DOI 10.17487/RFC7414, February 2015,
<https://www.rfc-editor.org/info/rfc7414>. <https://www.rfc-editor.org/info/rfc7414>.
[RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services [RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services
(Diffserv) and Real-Time Communication", RFC 7657, (Diffserv) and Real-Time Communication", RFC 7657,
DOI 10.17487/RFC7657, November 2015, DOI 10.17487/RFC7657, November 2015,
<https://www.rfc-editor.org/info/rfc7657>. <https://www.rfc-editor.org/info/rfc7657>.
[RFC8095] Fairhurst, G., Ed., Trammell, B., Ed., and M. Kuehlewind, [RFC8095] Fairhurst, G., Ed., Trammell, B., Ed., and M. Kuehlewind,
Ed., "Services Provided by IETF Transport Protocols and Ed., "Services Provided by IETF Transport Protocols and
Congestion Control Mechanisms", RFC 8095, DOI 10.17487/ Congestion Control Mechanisms", RFC 8095,
RFC8095, March 2017, DOI 10.17487/RFC8095, March 2017,
<https://www.rfc-editor.org/info/rfc8095>. <https://www.rfc-editor.org/info/rfc8095>.
Appendix A. Overview of RFCs used as input for pass 1 [TAPS-MINSET]
TCP: [RFC0793], [RFC1122], [RFC5482], [RFC5925], [RFC7413] Welzl, M. and S. Gjessing, "A Minimal Set of Transport
MPTCP: [RFC6182], [RFC6824], [RFC6897] Services for TAPS Systems", Work in Progress, draft-ietf-
SCTP: RFCs without a socket API specification: [RFC3758], [RFC4895], taps-minset-01, February 2018.
[RFC4960], [RFC5061].
RFCs that include a socket API specification: [RFC6458],
[RFC6525], [RFC6951], [RFC7053], [RFC7496] [RFC7829].
UDP(-Lite): See [FJ16]
LEDBAT: [RFC6817].
Appendix B. How this document was developed Appendix A. Overview of RFCs Used as Input for Pass 1
TCP: [RFC0793], [RFC1122], [RFC5482], [RFC5925], and
[RFC7413].
MPTCP: [RFC6182], [RFC6824], and [RFC6897].
SCTP: RFCs without a sockets API specification:
[RFC3758], [RFC4895], [RFC4960], and [RFC5061].
RFCs that include a sockets API specification:
[RFC6458], [RFC6525], [RFC6951], [RFC7053], [RFC7496],
and [RFC7829].
UDP(-Lite): See [RFC8304].
LEDBAT: [RFC6817].
Appendix B. How This Document Was Developed
This section gives an overview of the method that was used to develop This section gives an overview of the method that was used to develop
this document. It was given to contributors for guidance, and it can this document. It was given to contributors for guidance, and it can
be helpful for future updates or extensions. be helpful for future updates or extensions.
This document is only concerned with transport features that are This document is only concerned with transport features that are
explicitly exposed to applications via primitives. It also strictly explicitly exposed to applications via primitives. It also strictly
follows RFC text: if a transport feature is truly relevant for an follows RFC text: if a transport feature is truly relevant for an
application, the RFCs should say so, and they should describe how to application, the RFCs should say so, and they should describe how to
use and configure it. Thus, the approach followed for developing use and configure it. Thus, the approach followed for developing
this document was to identify the right RFCs, then analyze and this document was to identify the right RFCs, then analyze and
process their text. process their text.
Primitives that "MAY" be implemented by a transport protocol were Primitives that "MAY" be implemented by a transport protocol were
excluded. To be included, the minimum requirement level for a excluded. To be included, the minimum requirement level for a
primitive to be implemented by a protocol was "SHOULD". Where primitive to be implemented by a protocol was "SHOULD". Where style
[RFC2119]-style requirements levels are not used, primitives were requirement levels as described in [RFC2119] are not used, primitives
excluded when they are described in conjunction with statements like, were excluded when they are described in conjunction with statements
e.g.: "some implementations also provide" or "an implementation may like, e.g., "some implementations also provide" or "an implementation
also". Excluded primitives or parameters were briefly described in a may also". Excluded primitives or parameters were briefly described
dedicated subsection. in a dedicated subsection.
Pass 1: This began by identifying text that talks about primitives. Pass 1: This began by identifying text that talks about primitives.
An API specification, abstract or not, obviously describes primitives An API specification, abstract or not, obviously describes primitives
-- but we are not *only* interested in API specifications. The text -- but we are not *only* interested in API specifications. The text
describing the 'send' primitive in the API specified in [RFC0793], describing the 'Send' primitive in the API specified in [RFC0793],
for instance, does not say that data transfer is reliable. TCP's for instance, does not say that data transfer is reliable. TCP's
reliability is clear, however, from this text in Section 1 of reliability is clear, however, from this text in Section 1 of
[RFC0793]: "The Transmission Control Protocol (TCP) is intended for [RFC0793]:
use as a highly reliable host-to-host protocol between hosts in
packet-switched computer communication networks, and in
interconnected systems of such networks."
Some text for pass 1 subsections was developed copy+pasting all the The Transmission Control Protocol (TCP) is intended for use as a
relevant text parts from the relevant RFCs, then adjusting highly reliable host-to-host protocol between hosts in packet-
terminology to match the terminology in Section 1 and adjusting switched computer communication networks, and in interconnected
(shortening!) phrasing to match the general style of the document. systems of such networks.
An effort was made to formulate everything as a primitive description Some text for the pass 1 subsections was developed by copying and
such that the primitive descriptions became as complete as possible pasting all the relevant text parts from the relevant RFCs then
(e.g., the "SEND.TCP" primitive in pass 2 is explicitly described as adjusting the terminology to match that in Section 2 and shortening
reliably transferring data); text that is relevant for the primitives phrasing to match the general style of the document. An effort was
made to formulate everything as a primitive description such that the
primitive descriptions became as complete as possible (e.g., the
'SEND.TCP' primitive in pass 2 is explicitly described as reliably
transferring data); text that is relevant for the primitives
presented in this pass but still does not fit directly under any presented in this pass but still does not fit directly under any
primitive was used in a subsection's introduction. primitive was used in a subsection's introduction.
Pass 2: The main goal of this pass is unification of primitives. As Pass 2: The main goal of this pass is unification of primitives. As
input, only text from pass 1 was used (no exterior sources). The input, only text from pass 1 was used (no exterior sources). The
list in pass 2 is not arranged by protocol ("first protocol X, here list in pass 2 is not arranged by protocol (i.e., "first protocol X,
are all the primitives; then protocol Y, here are all the primitives, here are all the primitives; then protocol Y, here are all the
..") but by primitive ("primitive A, implemented this way in protocol primitives, ...") but by primitive (i.e., "primitive A, implemented
X, this way in protocol Y, ..."). It was a goal to obtain as many this way in protocol X, this way in protocol Y, ..."). It was a goal
similar pass 2 primitives as possible. For instance, this was to obtain as many similar pass 2 primitives as possible. For
sometimes achieved by not always maintaining a 1:1 mapping between instance, this was sometimes achieved by not always maintaining a 1:1
pass 1 and pass 2 primitives, renaming primitives etc. For every new mapping between pass 1 and pass 2 primitives, renaming primitives,
primitive, the already existing primitives were considered to try to etc. For every new primitive, the already-existing primitives were
make them as coherent as possible. considered to try to make them as coherent as possible.
For each primitive, the following style was used: For each primitive, the following style was used:
o PRIMITIVENAME.PROTOCOL: o PRIMITIVENAME.PROTOCOL:
Pass 1 primitive / event: Pass 1 primitive/event:
Parameters: Parameters:
Returns: Returns:
Comments: Comments:
The entries "Parameters", "Returns" and "Comments" were skipped when The entries "Parameters", "Returns", and "Comments" were skipped when
a primitive had no parameters, no described return value or no a primitive had no parameters, no described return value, or no
comments seemed necessary, respectively. Optional parameters are comments seemed necessary, respectively. Optional parameters are
followed by "(optional)". When a default value is known, this was followed by "(optional)". When known, default values were provided.
also provided.
Pass 3: the main point of this pass is to identify transport features Pass 3: The main point of this pass is to identify transport features
that are the result of static properties of protocols, for which all that are the result of static properties of protocols, for which all
protocols have to be listed together; this is then the final list of protocols have to be listed together; this is then the final list of
all available transport features. This list was primarily based on all available transport features. This list was primarily based on
text from pass 2, with additional input from pass 1 (but no external text from pass 2, with additional input from pass 1 (but no external
sources). sources).
Appendix C. Revision information Acknowledgements
XXX RFC-Ed please remove this section prior to publication.
-00 (from draft-welzl-taps-transports): this now covers TCP based on
all TCP RFCs (this means: if you know of something in any TCP RFC
that you think should be addressed, please speak up!) as well as
SCTP, exclusively based on [RFC4960]. We decided to also incorporate
[RFC6458] for SCTP, but this hasn't happened yet. Terminology made
in line with [RFC8095]. Addressed comments by Karen Nielsen and
Gorry Fairhurst; various other fixes. Appendices (TCP overview and
how-to-contribute) added.
-01: this now also covers MPTCP based on [RFC6182], [RFC6824] and
[RFC6897].
-02: included UDP, UDP-Lite, and all extensions of SCTPs. This
includes fixing the [RFC6458] omission from -00.
-03: wrote security considerations. The "how to contribute" section
was updated to reflect how the document *was* created, not how it
*should be* created; it also no longer wrongly says that Experimental
RFCs are excluded. Included LEDBAT. Changed abstract and intro to
reflect which protocols/mechanisms are covered (TCP, MPTCP, SCTP,
UDP, UDP-Lite, LEDBAT) instead of talking about "transport
protocols". Interleaving and stream scheduling added
(draft-ietf-tsvwg-sctp-ndata). TFO added. "Set protocol parameters"
in SCTP replaced with per-parameter (or parameter group) primitives.
More primitives added, mostly previously overlooked ones from
[RFC6458]. Updated terminology (s/transport service feature/
transport feature) in line with an update of [RFC8095]. Made
sequence of transport features / primitives more logical. Combined
MPTCP's add/rem subflow with SCTP's add/remove local address.
-04: changed UDP's close into an ABORT (to better fit with the
primitives of TCP and SCTP), and incorporated the corresponding
transport feature in step 3 (this addresses a comment from Gorry
Fairhurst). Added TCP Authentication (RFC 5925, section 7.1).
Changed TFO from looking like a primitive in pass 1 to be a part of
'open'. Changed description of SCTP authentication in pass 3 to
encompass both TCP and SCTP. Added citations of [RFC8095] and minset
[I-D.draft-gjessing-taps-minset] to the intro, to give the context of
this document.
-05: minor fix to TCP authentication (comment from Joe Touch),
several fixes from Gorry Fairhurst and Tom Jones. Language fixes;
updated to align with latest taps-transport-usage-udp ID.
-06: addressed WGLC comments from Aaron Falk and Tommy Pauly.
-07: addressed AD review comments from Spencer Dawkins.
-08: removed "delivery number" which was based on an error in RFC
4960: https://tools.ietf.org/html/
draft-ietf-tsvwg-rfc4960-errata-02#section-3.34.
-09: for consistency with the draft-ietf-taps-minset-00, adjusted the The authors would like to thank (in alphabetical order) Bob Briscoe,
following transport features in "pass 3": "Choice between unordered Spencer Dawkins, Aaron Falk, David Hayes, Karen Nielsen, Tommy Pauly,
(potentially faster) or ordered delivery of messages" divided into Joe Touch, and Brian Trammell for providing valuable feedback on this
two transport features (one for unordered, one for ordered); the word document. We especially thank Christoph Paasch for providing input
"reliably" was added to the transport features "Hand over a message related to Multipath TCP and Gorry Fairhurst and Tom Jones for
to reliably transfer (possibly multiple times) before connection providing input related to UDP(-Lite). This work has received
establishment" and "Hand over a message to reliably transfer during funding from the European Union's Horizon 2020 research and
connection establishment". Fixed RFC2119-style language into innovation programme under grant agreement No. 644334 (NEAT).
explicit citations (comment by Eric Rescorla and others). Addressed
editorial comments by Mirja Kuehlewind, Ben Campbell, Benoit Claise
and the Gen-ART reviewer Roni Even, except for moving terminology
section after the intro because the terminology is already used in
the intro text.
Authors' Addresses Authors' Addresses
Michael Welzl Michael Welzl
University of Oslo University of Oslo
PO Box 1080 Blindern PO Box 1080 Blindern
Oslo, N-0316 Oslo N-0316
Norway Norway
Email: michawe@ifi.uio.no Email: michawe@ifi.uio.no
Michael Tuexen Michael Tuexen
Muenster University of Applied Sciences Muenster University of Applied Sciences
Stegerwaldstrasse 39 Stegerwaldstrasse 39
Steinfurt 48565 Steinfurt 48565
Germany Germany
Email: tuexen@fh-muenster.de Email: tuexen@fh-muenster.de
Naeem Khademi Naeem Khademi
University of Oslo University of Oslo
PO Box 1080 Blindern PO Box 1080 Blindern
Oslo, N-0316 Oslo N-0316
Norway Norway
Email: naeemk@ifi.uio.no Email: naeemk@ifi.uio.no
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