draft-ietf-mmusic-sctp-sdp-18.txt   draft-ietf-mmusic-sctp-sdp-19.txt 
MMUSIC C. Holmberg MMUSIC C. Holmberg
Internet-Draft Ericsson Internet-Draft Ericsson
Intended status: Standards Track R. Shpount Intended status: Standards Track R. Shpount
Expires: April 10, 2017 TurboBridge Expires: April 29, 2017 TurboBridge
S. Loreto S. Loreto
G. Camarillo G. Camarillo
Ericsson Ericsson
October 7, 2016 October 26, 2016
Session Description Protocol (SDP) Offer/Answer Procedures For Stream Session Description Protocol (SDP) Offer/Answer Procedures For Stream
Control Transmission Protocol (SCTP) over Datagram Transport Layer Control Transmission Protocol (SCTP) over Datagram Transport Layer
Security (DTLS) Transport. Security (DTLS) Transport.
draft-ietf-mmusic-sctp-sdp-18 draft-ietf-mmusic-sctp-sdp-19
Abstract Abstract
The Stream Control Transmission Protocol (SCTP) is a transport The Stream Control Transmission Protocol (SCTP) is a transport
protocol used to establish associations between two endpoints. protocol used to establish associations between two endpoints.
draft-ietf-tsvwg-sctp-dtls-encaps-09 specifies how SCTP can be used draft-ietf-tsvwg-sctp-dtls-encaps-09 specifies how SCTP can be used
on top of the Datagram Transport Layer Security (DTLS) protocol, on top of the Datagram Transport Layer Security (DTLS) protocol,
referred to as SCTP-over-DTLS. referred to as SCTP-over-DTLS.
This specification defines the following new Session Description This specification defines the following new Session Description
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 10, 2017. This Internet-Draft will expire on April 29, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. SCTP Terminology . . . . . . . . . . . . . . . . . . . . . . 4 3. SCTP Terminology . . . . . . . . . . . . . . . . . . . . . . 4
4. SDP Media Descriptions . . . . . . . . . . . . . . . . . . . 4 4. SDP Media Descriptions . . . . . . . . . . . . . . . . . . . 4
4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Protocol Identifiers . . . . . . . . . . . . . . . . . . 5 4.2. Protocol Identifiers . . . . . . . . . . . . . . . . . . 5
4.3. Media Format Management . . . . . . . . . . . . . . . . . 5 4.3. Media Format Management . . . . . . . . . . . . . . . . . 5
4.4. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.4. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.4.1. General . . . . . . . . . . . . . . . . . . . . . . . 6 4.4.1. General . . . . . . . . . . . . . . . . . . . . . . . 6
4.4.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . 6 4.4.2. SDP Media Description values . . . . . . . . . . . . 6
4.5. Example . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.5. Example . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. SDP 'sctp-port' Attribute . . . . . . . . . . . . . . . . . . 6 5. SDP 'sctp-port' Attribute . . . . . . . . . . . . . . . . . . 6
5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.3. Mux Category . . . . . . . . . . . . . . . . . . . . . . 7 5.3. Mux Category . . . . . . . . . . . . . . . . . . . . . . 7
6. SDP 'max-message-size' Attribute . . . . . . . . . . . . . . 7 6. SDP 'max-message-size' Attribute . . . . . . . . . . . . . . 8
6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7 6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 8 6.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.3. Mux Category . . . . . . . . . . . . . . . . . . . . . . 8 6.3. Mux Category . . . . . . . . . . . . . . . . . . . . . . 9
7. UDP/DTLS/SCTP Transport Realization . . . . . . . . . . . . . 8 7. UDP/DTLS/SCTP Transport Realization . . . . . . . . . . . . . 9
8. TCP/DTLS/SCTP Transport Realization . . . . . . . . . . . . . 9 8. TCP/DTLS/SCTP Transport Realization . . . . . . . . . . . . . 10
9. Association And Connection Management . . . . . . . . . . . . 9 9. Association And Connection Management . . . . . . . . . . . . 10
9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 9 9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.2. SDP sendrecv/sendonly/recvonly/inactive Attribute . . . . 9 9.2. SDP sendrecv/sendonly/recvonly/inactive Attribute . . . . 10
9.3. SCTP Association . . . . . . . . . . . . . . . . . . . . 9 9.3. SCTP Association . . . . . . . . . . . . . . . . . . . . 10
9.4. DTLS Association (UDP/DTLS/SCTP And TCP/DTLS/SCTP) . . . 10 9.4. DTLS Association (UDP/DTLS/SCTP And TCP/DTLS/SCTP) . . . 11
9.5. TCP Connection (TCP/DTLS/SCTP) . . . . . . . . . . . . . 11 9.5. TCP Connection (TCP/DTLS/SCTP) . . . . . . . . . . . . . 12
10. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 11 10. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 12
10.1. General . . . . . . . . . . . . . . . . . . . . . . . . 11 10.1. General . . . . . . . . . . . . . . . . . . . . . . . . 12
10.2. Generating the Initial SDP Offer . . . . . . . . . . . . 11 10.2. Generating the Initial SDP Offer . . . . . . . . . . . . 13
10.3. Generating the SDP Answer . . . . . . . . . . . . . . . 12 10.3. Generating the SDP Answer . . . . . . . . . . . . . . . 13
10.4. Offerer Processing of the SDP Answer . . . . . . . . . . 13 10.4. Offerer Processing of the SDP Answer . . . . . . . . . . 14
10.5. Modifying the Session . . . . . . . . . . . . . . . . . 13 10.5. Modifying the Session . . . . . . . . . . . . . . . . . 15
11. Multihoming Considerations . . . . . . . . . . . . . . . . . 14 11. Multihoming Considerations . . . . . . . . . . . . . . . . . 16
12. NAT Considerations . . . . . . . . . . . . . . . . . . . . . 14 12. NAT Considerations . . . . . . . . . . . . . . . . . . . . . 16
12.1. General . . . . . . . . . . . . . . . . . . . . . . . . 14 12.1. General . . . . . . . . . . . . . . . . . . . . . . . . 16
12.2. ICE Considerations . . . . . . . . . . . . . . . . . . . 14 12.2. ICE Considerations . . . . . . . . . . . . . . . . . . . 16
13. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 15 13. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 17
13.1. Establishment of UDP/DTLS/SCTP association . . . . . . . 15 13.1. Establishment of UDP/DTLS/SCTP association . . . . . . . 17
14. Security Considerations . . . . . . . . . . . . . . . . . . . 16 14. Security Considerations . . . . . . . . . . . . . . . . . . . 18
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
15.1. New SDP proto values . . . . . . . . . . . . . . . . . . 17 15.1. New SDP proto values . . . . . . . . . . . . . . . . . . 18
15.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 17 15.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 18
15.2.1. sctp-port . . . . . . . . . . . . . . . . . . . . . 17 15.2.1. sctp-port . . . . . . . . . . . . . . . . . . . . . 18
15.2.2. max-message-size . . . . . . . . . . . . . . . . . . 18 15.2.2. max-message-size . . . . . . . . . . . . . . . . . . 18
15.3. association-usage Name Registry . . . . . . . . . . . . 18 15.3. association-usage Name Registry . . . . . . . . . . . . 19
16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
18. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
18.1. Normative References . . . . . . . . . . . . . . . . . . 21 18.1. Normative References . . . . . . . . . . . . . . . . . . 22
18.2. Informative References . . . . . . . . . . . . . . . . . 23 18.2. Informative References . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction 1. Introduction
SDP (Session Description Protocol) [RFC4566] provides a general- SDP (Session Description Protocol) [RFC4566] provides a general-
purpose format for describing multimedia sessions in announcements or purpose format for describing multimedia sessions in announcements or
invitations. TCP-Based Media Transport in the Session Description invitations. TCP-Based Media Transport in the Session Description
Protocol (SDP) [RFC4145] specifies a general mechanism for describing Protocol (SDP) [RFC4145] specifies a general mechanism for describing
and establishing TCP [RFC0793] streams. Connection-Oriented Media and establishing TCP [RFC0793] streams. Connection-Oriented Media
Transport over the Transport Layer Security (TLS) Protocol in SDP Transport over the Transport Layer Security (TLS) Protocol in SDP
[RFC4572] extends RFC4145 [RFC4145] for describing TCP-based media [RFC4572] extends RFC4145 [RFC4145] for describing TCP-based media
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endpoints. [I-D.ietf-tsvwg-sctp-dtls-encaps] specifies how SCTP can endpoints. [I-D.ietf-tsvwg-sctp-dtls-encaps] specifies how SCTP can
be used on top of the Datagram Transport Layer Security (DTLS) be used on top of the Datagram Transport Layer Security (DTLS)
protocol, referred to as SCTP-over-DTLS. protocol, referred to as SCTP-over-DTLS.
This specification defines the following new Session Description This specification defines the following new Session Description
Protocol (SDP) [RFC4566] protocol identifiers (proto Protocol (SDP) [RFC4566] protocol identifiers (proto
values):'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP'. This specification also values):'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP'. This specification also
specifies how to use the new proto values with the SDP Offer/Answer specifies how to use the new proto values with the SDP Offer/Answer
mechanism [RFC3264] for negotiating SCTP-over-DTLS associations. mechanism [RFC3264] for negotiating SCTP-over-DTLS associations.
NOTE: TLS is designed to run on top of a byte-stream oriented NOTE: Due to the characteristics of TCP, usage of 'TCP/DTLS/SCTP'
transport protocol providing a reliable, in-sequence delivery like will always force ordered and reliable delivery of the SCTP packets,
TCP. [RFC6083] presents serious limitations with transporting TLS on which limits the usage of the SCTP options. Therefore, it is
top of SCTP. Therefore, defining a mechanism to negotiate media strongly RECOMMENDED that TCP is only used in situations where UDP
streams transported using TLS on top of SCTP, i.e., 'SCTP/TLS', is traffic is blocked.
outside the scope of this specification. In addition, defining a
mechanism to negotiate non-protected SCTP associations is also
outside the scope of this specification.
2. Conventions 2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
3. SCTP Terminology 3. SCTP Terminology
SCTP Association: A protocol relationship between SCTP endpoints, SCTP Association: A protocol relationship between SCTP endpoints,
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including Verification Tags and the currently active set of including Verification Tags and the currently active set of
Transmission Sequence Numbers (TSNs), etc. An association can be Transmission Sequence Numbers (TSNs), etc. An association can be
uniquely identified by the transport addresses used by the endpoints uniquely identified by the transport addresses used by the endpoints
in the association. in the association.
SCTP Stream: A unidirectional logical channel established from one to SCTP Stream: A unidirectional logical channel established from one to
another associated SCTP endpoint, within which all user messages are another associated SCTP endpoint, within which all user messages are
delivered in sequence except for those submitted to the unordered delivered in sequence except for those submitted to the unordered
delivery service. delivery service.
SCTP Transport address: A transport address is traditionally defined
by a network-layer address, a transport-layer protocol, and a
transport-layer port number. In the case of SCTP running over IP, a
transport address is defined by the combination of an IP address and
an SCTP port number (where SCTP is the transport protocol).
SCTP-over-DTLS: SCTP used on top of DTLS, as specified in SCTP-over-DTLS: SCTP used on top of DTLS, as specified in
[I-D.ietf-tsvwg-sctp-dtls-encaps]. [I-D.ietf-tsvwg-sctp-dtls-encaps].
4. SDP Media Descriptions 4. SDP Media Descriptions
4.1. General 4.1. General
This section defines the following new SDP Media Description (m- This section defines the following new SDP Media Description (m-
line) protocol identifiers (proto values) for describing an SCTP line) protocol identifiers (proto values) for describing an SCTP
association: UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP'. The section also association: 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP'. The section also
describes how an m- line, associated with the proto values, is describes how an m- line, associated with the proto values, is
created. created.
The following is the format for an 'm' line, as specified in RFC4566 The following is the format for an 'm' line, as specified in RFC4566
[RFC4566]: [RFC4566]:
m=<media> <port> <proto> <fmt> ... m=<media> <port> <proto> <fmt> ...
The 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' proto values are similar to The 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' proto values are similar to
both the 'UDP' and 'TCP' proto values in that they only describe the both the 'UDP' and 'TCP' proto values in that they only describe the
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o The 'TCP/DTLS/SCTP' proto value describes an SCTP association on o The 'TCP/DTLS/SCTP' proto value describes an SCTP association on
top of a DTLS association on top of TCP, as defined in Section 8. top of a DTLS association on top of TCP, as defined in Section 8.
4.3. Media Format Management 4.3. Media Format Management
[RFC4566] defines that specifications defining new proto values must [RFC4566] defines that specifications defining new proto values must
define the rules by which their media format (fmt) namespace is define the rules by which their media format (fmt) namespace is
managed. Use of an existing MIME subtype for the format is managed. Use of an existing MIME subtype for the format is
encouraged. If no MIME subtype exists, it is recommended that a encouraged. If no MIME subtype exists, it is recommended that a
suitable one is registered through the IETF process [RFC6838] suitable one is registered through the IETF process defined in
[RFC4289] by production of, or reference to, a standards-track RFC [RFC6838] and [RFC4289] by production of, or reference to, a
that defines the transport protocol for the format. standards-track RFC that defines the transport protocol for the
format.
An m- line with a proto value of UDP/DTLS/SCTP' or 'TCP/DTLS/SCTP' An m- line with a proto value of 'UDP/DTLS/SCTP' or 'TCP/DTLS/SCTP'
always describe a single SCTP association. always describes a single SCTP association.
In addition, such m- line MUST further indicate the application-layer In addition, such m- line MUST further indicate the application-layer
protocol using an 'fmt' identifier. There MUST be exactly one 'fmt' protocol using an 'fmt' identifier. There MUST be exactly one 'fmt'
value per m- line associated with the proto values defined in this value per m- line associated with the proto values defined in this
specification. The "fmt" namespace associated with those proto specification. The "fmt" namespace associated with those proto
values describes the generic application usage of the entire SCTP values describes the generic application usage of the entire SCTP
association, including the associated SCTP streams. association, including the associated SCTP streams.
NOTE: A mechanism on how to describe, and manage, individual SCTP NOTE: A mechanism on how to describe, and manage, individual SCTP
streams within an SCTP association, is outside the scope of this streams within an SCTP association, is outside the scope of this
specification. specification. [I-D.ietf-mmusic-data-channel-sdpneg] defines a
mechanism for negotiating individual SCTP streams used to realize
WebRTC data channels [I-D.ietf-rtcweb-data-channel].
4.4. Syntax 4.4. Syntax
4.4.1. General 4.4.1. General
This section defines the ABNF [RFC5234] for the SDP media description This section defines the values that can be used within an SDP media
when associated with any of the proto values defined in this description ("m=" line) associated with an SCTP-over-DTLS
document. association.
This specification creates an IANA registry for 'association-usage' This specification creates an IANA registry for 'association-usage'
values. values.
4.4.2. ABNF 4.4.2. SDP Media Description values
sctp-m-line = %x6d "="
("application" SP udp-port SP "UDP/DTLS/SCTP" SP fmt CRLF) /
("application" SP tcp-port SP "TCP/DTLS/SCTP" SP fmt CRLF)
udp-port = port
tcp-port = port
fmt = association-usage
association-usage = token
token and port as defined in RFC4566 m= line parameter parameter value(s)
------------------------------------------------------------------
<media>: "application"
<proto>: "UDP/DTLS/SCTP" or "TCP/DTLS/SCTP"
<port>: UDP port number (for "UDP/DTLS/SCTP")
TCP port number (for ""UDP/DTLS/SCTP")
<fmt>: a string denoting the association-usage,
limited to the syntax of a 'token' as
defined in RFC4566.
4.5. Example 4.5. Example
m=application 12345 UDP/DTLS/SCTP webrtc-datachannel m=application 12345 UDP/DTLS/SCTP webrtc-datachannel
a=max-message-size: 100000 a=max-message-size: 100000
5. SDP 'sctp-port' Attribute 5. SDP 'sctp-port' Attribute
5.1. General 5.1. General
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The attribute can be associated with an SDP media description (m- The attribute can be associated with an SDP media description (m-
line) with a 'UDP/DTLS/SCTP' or a 'TCP/DTLS/SCTP' proto value. In line) with a 'UDP/DTLS/SCTP' or a 'TCP/DTLS/SCTP' proto value. In
that case the m- line port value indicates the port of the underlying that case the m- line port value indicates the port of the underlying
transport layer protocol (UDP or TCP), and the 'sctp-port' value transport layer protocol (UDP or TCP), and the 'sctp-port' value
indicates the SCTP port. indicates the SCTP port.
No default value is defined for the SDP sctp-port attribute. No default value is defined for the SDP sctp-port attribute.
Therefore, if the attribute is not present, the associated m- line Therefore, if the attribute is not present, the associated m- line
MUST be considered invalid. MUST be considered invalid.
Usage of the SDP 'sctp-port' attribute with other proto values is not NOTE: This specification only defines the usage of the SDP 'sctp-
specified, and MUST be discarded if received. port' attribute when associated with an m- line containing one of the
following proto values: 'UDP/DTLS/SCTP' or 'TCP/DTLS/SCTP'. Usage of
the attribute with other proto values needs to be defined in a
separate specification.
5.2. Syntax 5.2. Syntax
The ABNF for the SDP 'sctp-port' attribute is: [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this
document.]
sctp-port-attr = "a=sctp-port:" port The definition of the SDP 'sctp-port' attribute is:
port = (1*5)DIGIT
The SCTP port range is between 0 and 65535 (both included). Attribute name: sctp-port
Leading zeroes MUST NOT be used. Type of attribute: media
Mux category: SPECIAL
Subject to charset: No
Purpose: Indicate the SCTP port value associated with
the SDP Media Description.
Appropriate values: Integer
Contact name: Christer Holmberg
Contact e-mail: christer.holmberg@ericsson.com
Reference: RFCXXXX
Syntax:
sctp-port-value = 1*5<DIGIT defined in RFC4566>
The SCTP port range is between 0 and 65535 (both included).
Leading zeroes MUST NOT be used.
Example:
a=sctp-port:5000
5.3. Mux Category 5.3. Mux Category
The mux category [I-D.ietf-mmusic-sdp-mux-attributes] for the SDP The mux category [I-D.ietf-mmusic-sdp-mux-attributes] for the SDP
sctp-port' attribute is SPECIAL. Usage of the attribute is only 'sctp-port' attribute is SPECIAL.
applicable when associated with 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP'
proto value m- lines.
As the usage of multiple SCTP associations on top of a single DTLS As the usage of multiple SCTP associations on top of a single DTLS
association is outside the scope of this specification, no mux rules association is outside the scope of this specification, no mux rules
are specified for the 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' proto are specified for the 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' proto
values. Future extensions, that define how to negotiate multiplexing values. Future extensions, that define how to negotiate multiplexing
of multiple SCTP associations of top of a single DTLS association, of multiple SCTP associations of top of a single DTLS association,
need to also define the mux rules for the attribute. need to also define the mux rules for the attribute.
6. SDP 'max-message-size' Attribute 6. SDP 'max-message-size' Attribute
6.1. General 6.1. General
This section defines a new SDP media-level attribute, 'max-message- This section defines a new SDP media-level attribute, 'max-message-
size'. The attribute can be associated with an m- line to indicate size'. The attribute can be associated with an m- line to indicate
the maximum message size (indicated in bytes) that an SCTP endpoint the maximum SCTP user message size (indicated in bytes) that an SCTP
is willing to receive on the SCTP association associated with the m- endpoint is willing to receive on the SCTP association associated
line. Different attribute values can be used in each direction. with the m- line. Different attribute values can be used in each
direction.
The remote peer MUST assume that larger messages will be rejected by An SCTP endpoint MUST assume that larger SCTP user message sizes will
the SCTP endpoint. SCTP endpoints need to decide on appropriate be rejected by the peer SCTP endpoint. SCTP endpoints need to decide
behavior in case a message that exceeds the maximum size needs to be on appropriate behavior in case a message needs to be sent in which
sent. the SCTP user message size exceeds the maximumv SCTP user message
size.
If the SDP 'max-message-size' attribute contains a maximum message If the SDP 'max-message-size' attribute contains a maximum message
size value of zero, it indicates the SCTP endpoint will handle size value of zero, it indicates the SCTP endpoint will handle
messages of any size, subject to memory capacity etc. messages of any size, subject to memory capacity etc.
If the SDP 'max-message-size' attribute is not present, the default If the SDP 'max-message-size' attribute is not present, the default
value is 64K. value is 64K.
NOTE: This specification only defines the usage of the SDP 'max- NOTE: This specification only defines the usage of the SDP 'max-
message-size' attribute when associated with an m- line containing message-size' attribute when associated with an m- line containing
one of the following proto values: 'UDP/DTLS/SCTP' or 'TCP/DTLS/ one of the following proto values: 'UDP/DTLS/SCTP' or 'TCP/DTLS/
SCTP'. Usage of the attribute with other proto values needs to be SCTP'. Usage of the attribute with other proto values needs to be
defined in a separate specification. defined in a separate specification.
6.2. Syntax 6.2. Syntax
The ABNF for the SDP 'max-message-size' attribute is: [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this
document.]
max-message-size-attr = "a=max-message-size:" max-message-size The definition of the SDP 'max-message-size' attribute is:
max-message-size = 1*40DIGIT
Attribute name: max-message-size
Type of attribute: media
Mux category: SPECIAL
Subject to charset: No
Purpose: Indicate the maximum message size that
an SCTP endpoint is willing to receive
on the SCTP association associated
with the SDP Media Description.
Appropriate values: Integer
Contact name: Christer Holmberg
Contact e-mail: christer.holmberg@ericsson.com
Reference: RFCXXXX
Syntax:
max-message-size-value = 1*<DIGIT defined in RFC4566>
Leading zeroes MUST NOT be used. Leading zeroes MUST NOT be used.
Example:
a=max-message-size:100000
6.3. Mux Category 6.3. Mux Category
The mux category for the SDP 'max-message-size' attribute is SPECIAL. The mux category for the SDP 'max-message-size' attribute is SPECIAL.
The mux rules depends on the proto value of the associated m- line.
As the usage of multiple SCTP associations on top of a single DTLS As the usage of multiple SCTP associations on top of a single DTLS
association is outside the scope of this specification, no mux rules association is outside the scope of this specification, no mux rules
are specified for the 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' proto are specified for the 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' proto
values. values.
7. UDP/DTLS/SCTP Transport Realization 7. UDP/DTLS/SCTP Transport Realization
The UDP/DTLS/SCTP transport is realized as described below: The UDP/DTLS/SCTP transport is realized as described below:
o SCTP on top of DTLS is realized according to the procedures o SCTP on top of DTLS is realized according to the procedures
defined in [I-D.ietf-tsvwg-sctp-dtls-encaps]; and defined in [I-D.ietf-tsvwg-sctp-dtls-encaps]; and
o DTLS on top of UDP is realized according to the procedures in o DTLS on top of UDP is realized according to the procedures in
defined in [RFC6347]. defined in [RFC6347].
NOTE: While [I-D.ietf-tsvwg-sctp-dtls-encaps] allows multiple SCTP NOTE: While [I-D.ietf-tsvwg-sctp-dtls-encaps] allows multiple SCTP
associations on top of a single DTLS association, the procedures in associations on top of a single DTLS association, the procedures in
this specification only supports the negotiation of a single SCTP this specification only support the negotiation of a single SCTP
association on top of any given DTLS association. association on top of any given DTLS association.
8. TCP/DTLS/SCTP Transport Realization 8. TCP/DTLS/SCTP Transport Realization
The TCP/DTLS/SCTP transport is realized as described below: The TCP/DTLS/SCTP transport is realized as described below:
o SCTP on top of DTLS is realized according to the procedures o SCTP on top of DTLS is realized according to the procedures
defined in [I-D.ietf-tsvwg-sctp-dtls-encaps]; and defined in [I-D.ietf-tsvwg-sctp-dtls-encaps]; and
o DTLS on top of TCP is realized using the framing method defined in o DTLS on top of TCP is realized using the framing method defined in
skipping to change at page 9, line 29 skipping to change at page 10, line 29
proto value would need to be registered for such transport proto value would need to be registered for such transport
realization. realization.
9. Association And Connection Management 9. Association And Connection Management
9.1. General 9.1. General
This section describes how to mange an SCTP association, DTLS This section describes how to mange an SCTP association, DTLS
association and TCP connection using SDP attributes. association and TCP connection using SDP attributes.
In case of UDP/DTLS/SCTP and TCP/DTLS/SCTP the SCTP association, DTLS The SCTP association, the DTLS association and the TCP connection are
association and TCP connection are managed independently for each managed independently from each other. Each can be established and
other. An association/connection can be re-established without closed without impacting others.
impacting other associations/connections.
The detailed SDP Offer/Answer [RFC3264] procedures for the SDP The detailed SDP Offer/Answer [RFC3264] procedures for the SDP
attributes are described in (Section 10). attributes are described in Section 10.
9.2. SDP sendrecv/sendonly/recvonly/inactive Attribute 9.2. SDP sendrecv/sendonly/recvonly/inactive Attribute
This specification does not define semantics for the SDP direction This specification does not define semantics for the SDP direction
attributes [RFC4566]. Unless semantics of these attributes for an attributes [RFC4566]. Unless semantics of these attributes for an
SCTP association usage have been defined, SDP direction attributes SCTP association usage have been defined, SDP direction attributes
MUST be discarded if present. MUST be ignored if present.
9.3. SCTP Association 9.3. SCTP Association
When an SCTP association is established/re-established, both SCTP When an SCTP association is established, both SCTP endpoints MUST
endpoints MUST initiate the SCTP association (i.e. both SCTP initiate the SCTP association (i.e. both SCTP endpoints take the
endpoints take the 'active' role), and MUST use the same SCTP port as 'active' role), and MUST use the same SCTP port as client port and
client port and server port (in order to prevent two separate SCTP server port (in order to prevent two separate SCTP associations from
associations from being established). being established).
As both SCTP endpoints take the 'active' role, this specification As both SCTP endpoints take the 'active' role, the SDP 'setup'
does not define usage of the SDP 'setup' attribute [RFC4145] for attribute [RFC4145] does not apply to SCTP association establishment.
SCTP.
However the 'setup' attribute does apply to establishment of the
underlying DTLS association and TCP connection.
NOTE: The procedure above is different from TCP, where one endpoint NOTE: The procedure above is different from TCP, where one endpoint
takes the 'active' role, the other endpoint takes the 'passive' role, takes the 'active' role, the other endpoint takes the 'passive' role,
and only the 'active' endpoint initiates the TCP connection and only the 'active' endpoint initiates the TCP connection
[RFC4145]. [RFC4145].
NOTE: In case of SCTP-over-DTLS, when the SCTP association is NOTE: When the SCTP association is established it is assumed that any
established it is assumed that any NAT traversal procedures for the NAT traversal procedures for the underlying transport protocol (UDP
underlying transport protocol (UDP or TCP) has successfully been or TCP) have successfully been performed.
performed.
Usage of the SDP 'connection' attribute [RFC4145] is not defined for The SDP 'connection' attribute [RFC4145] does not apply to the SCTP
SCTP. In order to trigger the closure and re-establishment of an association. In order to trigger the closure of an existing SCTP
SCTP association, the SDP 'sctp-port' attribute (Section 5) is used association, and establishment of a new SCTP association, the SDP
to indicate a new (different than the ones currently used) SCTP port. 'sctp-port' attribute [Section 5] is used to indicate a new
(different than the ones currently used) SCTP port. The existing
SCTP association is closed, and the new SCTP association is
established, if one or both endpoints signal a new SCTP port. The
'connection' attribute does apply to establishment of underlying TCP
connections.
Alternatively, an SCTP association can be closed using the SDP 'sctp- Alternatively, an SCTP association can be closed using the SDP 'sctp-
port' attribute with a zero attribute value. Later, the SCTP port' attribute with a zero attribute value. Later, a new SCTP
association can be re-established using the procedures in this association can be established using the procedures in this section
section for establishing an SCTP association. for establishing an SCTP association.
SCTP associations might be closed without SDP signalling, e.g, in SCTP associations might be closed without SDP signalling, e.g, in
case of a failure. When such SCTP association is re-established the case of a failure. The procedures in this section MUST be followed
SCTP endpoints MUST use the procedures in this section for to establish a new SCTP association. This requires a new SDP Offer/
establishing an SCTP association. New (different than the ones Answer exchange. New (different than the ones currently used) SCTP
currently used) SCTP ports MUST be used. ports MUST be used.
NOTE: Closing and re-establishing the SCTP association using the SDP NOTE: Closing and establishing a new SCTP association using the SDP
'sctp-port' attribute will not impact the underlying DTLS 'sctp-port' attribute will not impact the underlying DTLS
association. association.
9.4. DTLS Association (UDP/DTLS/SCTP And TCP/DTLS/SCTP) 9.4. DTLS Association (UDP/DTLS/SCTP And TCP/DTLS/SCTP)
An DTLS association is managed according to the procedures in A DTLS association is managed according to the procedures in
[I-D.ietf-mmusic-dtls-sdp]. Hence, the SDP 'setup' attribute is used [I-D.ietf-mmusic-dtls-sdp]. Hence, the SDP 'setup' attribute is used
to negotiate the (D)TLS roles ('client' and 'server') [RFC4572]. to negotiate the (D)TLS roles ('client' and 'server') [RFC4572].
NOTE: The SDP 'setup' attribute is used both to negotiate both the NOTE: The SDP 'setup' attribute is used both to negotiate both the
DTLS roles and the TCP roles (Section 9.5). DTLS roles and the TCP roles (Section 9.5).
NOTE: As described in [RFC5245], if the Interactive Connectivity NOTE: As described in [I-D.ietf-ice-rfc5245bis], if the Interactive
Establishment (ICE) mechanism [RFC5245] is used, all ICE candidates Connectivity Establishment (ICE) mechanism [I-D.ietf-ice-rfc5245bis]
associated with an DTLS association as considered part of the same is used, all ICE candidates associated with a DTLS association as
DTLS association. Thus, a switch from one candidate pair to another considered part of the same DTLS association. Thus, a switch from
candidate pair will not trigger the establishment of a new DTLS one candidate pair to another candidate pair will not trigger the
association. establishment of a new DTLS association.
9.5. TCP Connection (TCP/DTLS/SCTP) 9.5. TCP Connection (TCP/DTLS/SCTP)
The TCP connection is managed according to the procedures in The TCP connection is managed according to the procedures in
[RFC4145]. Hence, the SDP 'setup' attribute is used to negotiate the [RFC4145]. Hence, the SDP 'setup' attribute is used to negotiate the
TCP roles ('active' and 'passive'), and the SDP 'connection' TCP roles ('active' and 'passive'), and the SDP 'connection'
attribute is used to indicate whether to use an existing TCP attribute is used to indicate whether to use an existing TCP
connection, or create a new one. The SDP 'setup' attribute connection, or create a new one. The SDP 'setup' attribute
'holdconn' value MUST NOT be used. 'holdconn' value MUST NOT be used.
NOTE: A change of the TCP roles will also trigger a re-establishment NOTE: A change of the TCP roles will also trigger a closure of the
of the DTLS association, according to the procedures in DTLS association, and establishment of a new DTLS association,
[I-D.ietf-mmusic-dtls-sdp]. according to the procedures in [I-D.ietf-mmusic-dtls-sdp].
NOTE: As specified in [I-D.ietf-mmusic-dtls-sdp], usage of the SDP NOTE: As specified in [I-D.ietf-mmusic-dtls-sdp], usage of the SDP
'setup' attribute 'holdconn' value is not allowed. Therefore this 'setup' attribute 'holdconn' value is not allowed. Therefore this
specification also forbids usage of the attribute value for TCP, as specification also forbids usage of the attribute value for TCP, as
DTLS is transported on top of TCP. DTLS is transported on top of TCP.
10. SDP Offer/Answer Procedures 10. SDP Offer/Answer Procedures
10.1. General 10.1. General
skipping to change at page 11, line 50 skipping to change at page 13, line 9
provided that the integrity of the SDP description is assured as provided that the integrity of the SDP description is assured as
defined in [RFC4572]. defined in [RFC4572].
Each endpoint MUST associate an SDP 'dtls-id' attribute with the m- Each endpoint MUST associate an SDP 'dtls-id' attribute with the m-
line, following the procedures in [I-D.ietf-mmusic-dtls-sdp]. line, following the procedures in [I-D.ietf-mmusic-dtls-sdp].
10.2. Generating the Initial SDP Offer 10.2. Generating the Initial SDP Offer
When the offerer creates an initial offer, the offerer: When the offerer creates an initial offer, the offerer:
o MUST associate an SDP setup attribute, with an 'actpass' value, o MUST associate an SDP setup attribute with the m- line;
with the m- line;
o MUST associate an SDP 'sctp-port' attribute with the m- line; o MUST associate an SDP 'sctp-port' attribute with the m- line;
o MUST, in the case of TCP/DTLS/SCTP, associate an SDP 'connection' o MUST, in the case of TCP/DTLS/SCTP, associate an SDP 'connection'
attribute, with a 'new' attribute value, with the m- line; and attribute, with a 'new' attribute value, with the m- line; and
o MAY associate an SDP 'max-message-size' attribute (Section 6) with o MAY associate an SDP 'max-message-size' attribute [Section 6] with
the m- line. the m- line.
10.3. Generating the SDP Answer 10.3. Generating the SDP Answer
When the answerer receives an offer, which contains an m- line When the answerer receives an offer, which contains an m- line
describing an SCTP-over-DTLS association, if the answerer accepts the describing an SCTP-over-DTLS association, if the answerer accepts the
association line it: association, the answerer:
o MUST insert a corresponding m- line in the answer, with an o MUST insert a corresponding m- line in the answer, with an
identical m- line proto value [RFC3264]; identical m- line proto value [RFC3264];
o MUST associate an SDP 'setup' attribute, with an 'active' or o MUST associate an SDP 'setup' attribute, with an 'active' or
'passive' value, with the m- line; 'passive' value, with the m- line;
o MUST associate an SDP 'sctp-port' attribute with the m- line. If o MUST associate an SDP 'sctp-port' attribute with the m- line. If
the offer contained a new (different than the one currently used) the offer contained a new (different than the one currently used)
SCTP port value the answerer MUST also associate a new SCTP port SCTP port value the answerer MUST also associate a new SCTP port
value. If the offer contained a zero SCTP port value the answerer value. If the offer contained a zero SCTP port value, or if the
MUST also associate a zero SCTP port value; and answerer does not accept the SCTP association, the answerer MUST
also associate a zero SCTP port value; and
o MAY associate an SDP 'max-message-size' attribute (Section 6)with o MAY associate an SDP 'max-message-size' attribute [Section 6] with
the m- line. The attribute value in the answer is independent the m- line. The attribute value in the answer is independent
from the value (if present) in the corresponding m- line of the from the value (if present) in the corresponding m- line of the
offer. offer.
Once the answerer has sent the answer the answerer MUST, if an SCTP Once the answerer has sent the answer the answerer:
association has yet not been established, or if an existing SCTP
association is to be re-established, initiate the establishment of
the SCTP association.
The answerer follows the procedures in [I-D.ietf-mmusic-dtls-sdp] o MUST, in the case of TCP/DTLS/SCTP, if a TCP connection has yet
regarding the establishment/re-establishment of the DTLS association. not been established, or if an existing TCP connection is to be
closed and replaced by a new TCP connection, follow the procedures
in [RFC4145] for closing and establishing a TCP connection;
In the case of TCP/DTLS/SCTP, the answerer follows the procedures in o MUST, if a DTLS association has yet not been established, or if an
[RFC4145] regarding the establishment/re-establishment of the TCP existing DTLS association is to be closed and replaced by a new
connection association. DTLS association, follow the procedures in
[I-D.ietf-mmusic-dtls-sdp] for closing establishing a DTLS
association; and
o MUST, if an SCTP association has yet not been established, or if
an existing SCTP association is to be closed and replaced by a new
SCTP association, initiate the closing of the existing SCTP
association (if applicable) and establishment of the SCTP
association.
If the SDP 'sctp-port' attribute in the answer contains a zero
attribute value, the answerer MUST NOT establish an SCTP association.
If an SCTP association exists, the offerer MUST close it.
If the answerer does not accept the m- line in the offer, it MUST If the answerer does not accept the m- line in the offer, it MUST
assign a zero port value to the corresponding m- line in the answer, assign a zero port value to the corresponding m- line in the answer,
following the procedures in [RFC3264]. In addition, the answerer following the procedures in [RFC3264]. In addition, the answerer
MUST NOT initiate the establishment of an SCTP association, or a DTLS MUST NOT initiate the establishment of a TCP connection, a DTLS
association, associated with the m- line. association or a DTLS association associated with the m- line.
10.4. Offerer Processing of the SDP Answer 10.4. Offerer Processing of the SDP Answer
Once the offerer has received the answer, which contains an m- line Once the offerer has received the answer the offerer:
with a non-zero port value, the offerer MUST, if an SCTP association
has yet not been established, or if an existing SCTP association is o MUST, in the case of TCP/DTLS/SCTP, if a TCP connection has yet
to be re-established, initiate the establishment of the SCTP not been established, or if an existing TCP connection is to be
association. closed and replaced by a new TCP connection, follow the procedures
in [RFC4145] for closing and establishing a TCP connection;
o MUST, if a DTLS association has yet not been established, or if an
existing DTLS association is to be closed and replaced by a new
DTLS association, follow the procedures in
[I-D.ietf-mmusic-dtls-sdp] for closing establishing a DTLS
association; and
o MUST, if an SCTP association has yet not been established, or if
an existing SCTP association is to be closed and replaced by a new
SCTP association, initiate the closing of the existing SCTP
association (if applicable) and establishment of the SCTP
association.
If the SDP 'sctp-port' attribute in the answer contains a zero If the SDP 'sctp-port' attribute in the answer contains a zero
attribute value, the offerer MUST NOT establish an SCTP association. attribute value, the offerer MUST NOT establish an SCTP association.
If an SCTP association exists, the offerer MUST close it. If an SCTP association exists, the offerer MUST close it.
The offerer follows the procedures in [I-D.ietf-mmusic-dtls-sdp]
regarding the establishment/re-establishment of the DTLS association.
In the case of TCP/DTLS/SCTP, the offerer follows the procedures in
[RFC4145] regarding the establishment/re-establishment of the TCP
connection association.
If the m- line in the answer contains a zero port value, the offerer If the m- line in the answer contains a zero port value, the offerer
MUST NOT establish a TCP connection, an SCTP association, or a DTLS MUST NOT initiate the establishment a TCP connection, a DTLS
association, associated with the m- line. If an SCTP association, association or an SCTP association associated with the m- line. If a
DTLS association and/or TCP connection exists, the offerer MUST close TCP connection, or a DTLS association or an SCTP association exists,
it. the offerer MUST close it.
10.5. Modifying the Session 10.5. Modifying the Session
When an offerer sends an updated offer, in order to modify a When an offerer sends an updated offer, in order to modify a
previously established SCTP association, it follows the procedures in previously established SCTP association, it follows the procedures in
Section 10.2, with the following exceptions: Section 10.2, with the following exceptions:
o If the offerer wants to close and immediately re-establish an o If the offerer wants to close an SCTP association, and immediately
existing SCTP association, the offerer MUST associate an SDP establish a new SCTP association, the offerer MUST associate an
'sctp-port' attribute with a new (different than the one currently SDP 'sctp-port' attribute with a new (different than the one
used) attribute value. This will not impact the underlying DTLS currently used) attribute value. This will not impact the
association (and TCP connection in case of TCP/DTLS/SCTP).
o If the offerer wants to close, but not re-establish an existing
SCTP association, the offerer MUST associate an SDP 'sctp-port'
attribute with a zero attribute value. This will not impact the
underlying DTLS association (and TCP connection in case of underlying DTLS association (and TCP connection in case of
TCP/DTLS/SCTP). TCP/DTLS/SCTP).
o If the offerer wants to re-establish a previously closed SCTP o If the offerer wants to close an SCTP association, without
association, the offerer MUST associate an SDP 'sctp-port' immediately establishing a new SCTP association, the offerer MUST
attribute with a new (different than the one currently used) associate an SDP 'sctp-port' attribute with a zero attribute
attribute value. If the SCTP association was previously closed value. This will not impact the underlying DTLS association (and
using an SDP 'sctp-port' attribute with a zero attribute value, TCP connection in case of TCP/DTLS/SCTP).
the offerer MAY use the same attribute value that was used prior
to the SCTP association was closed. This will not impact the o If the offerer wants to establish an SCTP association, and another
underlying DTLS association (and TCP connection in case of SCTP association was previously closed, the offerer MUST associate
TCP/DTLS/SCTP). an SDP 'sctp-port' attribute with a new attribute value (different
than the value associated with the previous SCTP association). If
the previous SCTP association was closed using an SDP 'sctp-port'
attribute with a zero attribute value, the offerer MAY use the
same attribute value for the new SCTP association that was used
with the previous SCTP association before it was closed. This
will not impact the underlying DTLS association (and TCP
connection in case of TCP/DTLS/SCTP).
o If the offerer wants to close an existing SCTP association, and o If the offerer wants to close an existing SCTP association, and
the underlying DTLS association (and the underlying TCP connection the underlying DTLS association (and the underlying TCP connection
in case of TCP/DTLS/SCTP) it MUST assign a zero port value to the in case of TCP/DTLS/SCTP) it MUST assign a zero port value to the
m- line associated with the SCTP and DTLS associations (and TCP m- line associated with the SCTP and DTLS associations (and TCP
connection in case of TCP/DTLS/SCTP), following the procedures in connection in case of TCP/DTLS/SCTP), following the procedures in
[RFC3264]. [RFC3264].
o NOTE: This specification does not define a mechanism for o NOTE: This specification does not define a mechanism for
explicitly closing an DTLS association while maintaining the explicitly closing a DTLS association while maintaining the
overlying SCTP association. However, if a DTLS association is re- overlying SCTP association. However, if a DTLS association is
established as a result of some other action closed and replaced with a new DTLS association, as a result of
[I-D.ietf-mmusic-dtls-sdp] the SCTP association is not affected. some other action [I-D.ietf-mmusic-dtls-sdp], the SCTP association
is not affected.
The offer follows the procedures in [I-D.ietf-mmusic-dtls-sdp] The offer follows the procedures in [I-D.ietf-mmusic-dtls-sdp]
regarding the DTLS association impacts when modifying a session. regarding the DTLS association impacts when modifying a session.
In the case of TCP/DTLS/SCTP, the offer follows the procedures in In the case of TCP/DTLS/SCTP, the offer follows the procedures in
[RFC4145] regarding the TCP connection impacts when modifying a [RFC4145] regarding the TCP connection impacts when modifying a
session; session.
11. Multihoming Considerations 11. Multihoming Considerations
Multihoming is not supported when sending SCTP on top of DTLS, as Multihoming is not supported when sending SCTP on top of DTLS, as
DTLS does not expose address management of the underlying transport DTLS does not expose address management of the underlying transport
protocols (UDP or TCP) to its upper layer. protocols (UDP or TCP) to its upper layer.
12. NAT Considerations 12. NAT Considerations
12.1. General 12.1. General
When SCTP-over-DTLS is used in NAT environment, it relies on the NAT When SCTP-over-DTLS is used in NAT environment, it relies on the NAT
traversal procedures for the underlying transport protocol (UDP or traversal procedures for the underlying transport protocol (UDP or
TCP). TCP).
12.2. ICE Considerations 12.2. ICE Considerations
When SCTP-over-DTLS is used with UDP based ICE candidates as defined When SCTP-over-DTLS is used with UDP based ICE candidates
in [RFC5245] procedures for UDP/DTLS/SCTP, as defined in Section 7 [I-D.ietf-ice-rfc5245bis] then the procedures for UDP/DTLS/SCTP
are used. [Section 7] are used.
When SCTP-over-DTLS is used with TCP based ICE candidates as defined When SCTP-over-DTLS is used with TCP based ICE candidates [RFC6544]
in [RFC6544] procedures for TCP/DTLS/SCTP, as defined in Section 8 then the procedures for TCP/DTLS/SCTP [Section 8] are used.
are used.
Implementations MUST treat all ICE candidate pairs associated with a The generic ICE rules defined in [I-D.ietf-mmusic-ice-sip-sdp] apply
an SCTP association on top of a DTLS association as part of the same also to SCTP-over-DTLS. Therefore, implementations must treat all
DTLS association. Thus, there will only be one SCTP handshake and ICE candidate pairs associated with an SCTP association on top of a
one DTLS handshake even if there are multiple valid candidate pairs, DTLS association as part of the same DTLS association. Thus, there
and shifting from one candidate pair to another will not impact the will only be one SCTP handshake and one DTLS handshake even if there
SCTP or DTLS associations. If new candidates are added, they will are multiple valid candidate pairs, and shifting from one candidate
also be part of the same SCTP and DTLS associations. When pair to another will not impact the SCTP or DTLS associations. If
transitioning between candidate pairs, different candidate pairs can new candidates are added, they will also be part of the same SCTP and
be currently active in different directions and implementations MUST DTLS associations. Note that, depending on which candidiates are
be ready to receive data on any of the candidates, even if this means used at any given time, TCP-based and UDP-based candidiates might be
sending and receiving data using UDP/DTLS/SCTP and TCP/DTLS/SCTP at used simultaneously for sending and receiving data.
the same time in different directions.
When an SDP offer or answer is sent, the proto value MUST match the When an SDP offer or answer is sent, the rules in
transport protocol associated with the default candidate. Hence, if [I-D.ietf-mmusic-ice-sip-sdp] apply regarding when the proto value
UDP transport is used for the default candidate the 'UDP/DTLS/SCTP' must match the transport protocol associated with the default
proto value MUST be used. If TCP transport is used for the default candidate.
candidate the 'TCP/DTLS/SCTP' proto value MUST be used. However, if
an endpoint switch between TCP-based and UDP-based candidates during If an endpoint switches between TCP-based and UDP-based candidates
a session the endpoint is not required to send an SDP offer in order during a session the endpoint is not required to send an SDP offer in
to modify that proto value of the associated m- line. order to modify that proto value of the associated m- line.
NOTE: The text in the paragraph above only applies when the usage of NOTE: The text in the paragraph above only applies when the usage of
ICE has been negotiated. If ICE is not used, the proto value MUST ICE has been negotiated. If ICE is not used, the proto value MUST
always reflect the transport protocol used at any given time. always reflect the transport protocol used at any given time.
13. Examples 13. Examples
13.1. Establishment of UDP/DTLS/SCTP association 13.1. Establishment of UDP/DTLS/SCTP association
SDP Offer: SDP Offer:
m=application 54111 UDP/DTLS/SCTP webrtc-datachannel m=application 54111 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4 192.0.2.1 c=IN IP4 192.0.2.1
a=dtls-id:abc3dl a=dtls-id:abc3dl
a=setup:actpass a=setup:actpass
a=sctp-port:5000 a=sctp-port:5000
a=max-message-size:100000 a=max-message-size:100000
- The offerer indicates that the usage of the - The offerer indicates that the usage of the
skipping to change at page 17, line 30 skipping to change at page 18, line 43
| proto | UDP/DTLS/SCTP | [RFCXXXX] | | proto | UDP/DTLS/SCTP | [RFCXXXX] |
| proto | TCP/DTLS/SCTP | [RFCXXXX] | | proto | TCP/DTLS/SCTP | [RFCXXXX] |
+-------+---------------+-----------+ +-------+---------------+-----------+
Table 1: SDP "proto" field values Table 1: SDP "proto" field values
15.2. New SDP Attributes 15.2. New SDP Attributes
15.2.1. sctp-port 15.2.1. sctp-port
[RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this This document defines a new SDP media-level attribute,'sctp-port'.
document.] The details of the attribute are defined in Section 5.2.
This document defines a new SDP media-level attribute,'sctp-port', as
follows:
Attribute name: sctp-port
Type of attribute: media
Mux category: SPECIAL
Subject to charset: No
Purpose: Indicate the SCTP port value associated
with the SDP Media Description.
Appropriate values: Integer
Contact name: Christer Holmberg
Contact e-mail: christer.holmberg@ericsson.com
Reference: RFCXXXX
15.2.2. max-message-size 15.2.2. max-message-size
[RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this
document.]
This document defines a new SDP media-level attribute,'max-message- This document defines a new SDP media-level attribute,'max-message-
size', as follows: size'. The details of the attribute are defined in Section 6.2.
Attribute name: max-message-size
Type of attribute: media
Mux category: SPECIAL
Subject to charset: No
Purpose: Indicate the maximum message size that
an SCTP endpoint is willing to receive
on the SCTP association associated
with the SDP Media Description.
Appropriate values: Integer
Contact name: Christer Holmberg
Contact e-mail: christer.holmberg@ericsson.com
Reference: RFCXXXX
15.3. association-usage Name Registry 15.3. association-usage Name Registry
[RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this
document.] document.]
This specification creates a new IANA registry, following the This specification creates a new IANA registry, following the
procedures in [RFC5226], for the "fmt" namespace associated with the procedures in [RFC5226], for the "fmt" namespace associated with the
'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' protocol identifiers. Each "fmt" 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' protocol identifiers. Each "fmt"
value describes the usage of an entire SCTP association, including value describes the usage of an entire SCTP association, including
all SCTP streams associated with the SCTP association. all SCTP streams associated with the SCTP association.
NOTE: Usage indication of individual SCTP streams is outside the NOTE: Usage indication of individual SCTP streams is outside the
scope of this specification. scope of this specification.
The "fmt" value, "association-usage", used with these "proto" is The "fmt" value, "association-usage", used with these "proto" values
required. It is defined in [Section 4]. is required. It is defined in Section 4.
As part of this registry, IANA maintains the following information: As part of this registry, IANA maintains the following information:
association-usage name: The identifier of the subprotocol, as will association-usage name: The identifier of the subprotocol, as will
be used as the "fmt" value. be used as the "fmt" value.
association-usage reference: A reference to the document in which association-usage reference: A reference to the document in which
the association-usage is defined. the association-usage is defined.
association-usage names are to be subject to the "First Come First association-usage names are to be subject to the "First Come First
Served" IANA registration policy [RFC5226]. Served" IANA registration policy [RFC5226].
IANA is asked to add initial values to the registry. IANA is asked to add initial values to the registry.
|----------------------------------------------------------| |----------------------------------------------------------|
| name | Reference | | name | Reference |
|----------------------------------------------------------| |----------------------------------------------------------|
| webrtc-datachannel | draft-ietf-rtcweb-data-protocol-xx | | webrtc-datachannel | draft-ietf-rtcweb-data-protocol-xx, |
| | RFCXXX |
|----------------------------------------------------------| |----------------------------------------------------------|
[RFC EDITOR NOTE: Please hold the publication of this draft [RFC EDITOR NOTE: Please hold the publication of this draft
until draft-ietf-rtcweb-data-protocol has been published as an RFC. until draft-ietf-rtcweb-data-protocol has been published as an RFC.
Then, replace the reference to draft-ietf-rtcweb-data-protocol Then, replace the reference to draft-ietf-rtcweb-data-protocol
with the RFC number.] with the RFC number.]
[RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number
of this document.]
Figure 1 Figure 1
16. Acknowledgments 16. Acknowledgments
The authors wish to thank Harald Alvestrand, Randell Jesup, Paul The authors wish to thank Harald Alvestrand, Randell Jesup, Paul
Kyzivat, Michael Tuexen, Juergen Stoetzer-Bradler, Flemming Andreasen Kyzivat, Michael Tuexen, Juergen Stoetzer-Bradler, Flemming Andreasen
and Ari Keranen for their comments and useful feedback. and Ari Keranen for their comments and useful feedback.
17. 17.
[RFC EDITOR NOTE: Please remove this section when publishing] [RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-ietf-mmusic-sctp-sdp-18
o Changes based on WGLC comments from Paul Kyzivat.
Changes from draft-ietf-mmusic-sctp-sdp-17 Changes from draft-ietf-mmusic-sctp-sdp-17
o Removal of 'SCTP'. o Removal of 'SCTP'.
o Document title changed. o Document title changed.
o Disallow usage of SDP 'setup' attribute 'holdconn' value. o Disallow usage of SDP 'setup' attribute 'holdconn' value.
o Roman Shpount added as co-editor. o Roman Shpount added as co-editor.
skipping to change at page 22, line 39 skipping to change at page 23, line 25
[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,
<http://www.rfc-editor.org/info/rfc4960>. <http://www.rfc-editor.org/info/rfc4960>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008, DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>. <http://www.rfc-editor.org/info/rfc5226>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <http://www.rfc-editor.org/info/rfc6347>. January 2012, <http://www.rfc-editor.org/info/rfc6347>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13, Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013, RFC 6838, DOI 10.17487/RFC6838, January 2013,
<http://www.rfc-editor.org/info/rfc6838>. <http://www.rfc-editor.org/info/rfc6838>.
[I-D.ietf-mmusic-4572-update] [I-D.ietf-mmusic-4572-update]
skipping to change at page 23, line 22 skipping to change at page 23, line 51
Mechanism for DTLS", draft-ietf-mmusic-dtls-sdp-14 (work Mechanism for DTLS", draft-ietf-mmusic-dtls-sdp-14 (work
in progress), July 2016. in progress), July 2016.
[I-D.ietf-tsvwg-sctp-dtls-encaps] [I-D.ietf-tsvwg-sctp-dtls-encaps]
Tuexen, M., Stewart, R., Jesup, R., and S. Loreto, "DTLS Tuexen, M., Stewart, R., Jesup, R., and S. Loreto, "DTLS
Encapsulation of SCTP Packets", draft-ietf-tsvwg-sctp- Encapsulation of SCTP Packets", draft-ietf-tsvwg-sctp-
dtls-encaps-09 (work in progress), January 2015. dtls-encaps-09 (work in progress), January 2015.
[I-D.ietf-mmusic-sdp-mux-attributes] [I-D.ietf-mmusic-sdp-mux-attributes]
Nandakumar, S., "A Framework for SDP Attributes when Nandakumar, S., "A Framework for SDP Attributes when
Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-13 Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-14
(work in progress), June 2016. (work in progress), September 2016.
18.2. Informative References 18.2. Informative References
[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,
<http://www.rfc-editor.org/info/rfc793>. <http://www.rfc-editor.org/info/rfc793>.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245,
DOI 10.17487/RFC5245, April 2010,
<http://www.rfc-editor.org/info/rfc5245>.
[RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram
Transport Layer Security (DTLS) for Stream Control
Transmission Protocol (SCTP)", RFC 6083,
DOI 10.17487/RFC6083, January 2011,
<http://www.rfc-editor.org/info/rfc6083>.
[RFC6544] Rosenberg, J., Keranen, A., Lowekamp, B., and A. Roach, [RFC6544] Rosenberg, J., Keranen, A., Lowekamp, B., and A. Roach,
"TCP Candidates with Interactive Connectivity "TCP Candidates with Interactive Connectivity
Establishment (ICE)", RFC 6544, DOI 10.17487/RFC6544, Establishment (ICE)", RFC 6544, DOI 10.17487/RFC6544,
March 2012, <http://www.rfc-editor.org/info/rfc6544>. March 2012, <http://www.rfc-editor.org/info/rfc6544>.
[I-D.ietf-ice-rfc5245bis]
Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive
Connectivity Establishment (ICE): A Protocol for Network
Address Translator (NAT) Traversal", draft-ietf-ice-
rfc5245bis-04 (work in progress), June 2016.
[I-D.ietf-mmusic-ice-sip-sdp]
Petit-Huguenin, M., Keranen, A., and S. Nandakumar, "Using
Interactive Connectivity Establishment (ICE) with Session
Description Protocol (SDP) offer/answer and Session
Initiation Protocol (SIP)", draft-ietf-mmusic-ice-sip-
sdp-10 (work in progress), July 2016.
[I-D.ietf-rtcweb-data-channel]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data
Channels", draft-ietf-rtcweb-data-channel-13 (work in
progress), January 2015.
[I-D.ietf-mmusic-data-channel-sdpneg]
Drage, K., Makaraju, M., Stoetzer-Bradler, J., Ejzak, R.,
and (. (Unknown), "SDP-based Data Channel Negotiation",
draft-ietf-mmusic-data-channel-sdpneg-10 (work in
progress), September 2016.
Authors' Addresses Authors' Addresses
Christer Holmberg Christer Holmberg
Ericsson Ericsson
Hirsalantie 11 Hirsalantie 11
Jorvas 02420 Jorvas 02420
Finland Finland
Email: christer.holmberg@ericsson.com Email: christer.holmberg@ericsson.com
Roman Shpount Roman Shpount
TurboBridge TurboBridge
4905 Del Ray Avenue, Suite 300 4905 Del Ray Avenue, Suite 300
Bethesda, MD 20814 Bethesda, MD 20814
USA USA
Phone: +1 (240) 292-6632 Phone: +1 (240) 292-6632
Email: rshpount@turbobridge.com Email: rshpount@turbobridge.com
Salvatore Loreto Salvatore Loreto
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