draft-ietf-mmusic-sctp-sdp-16.txt   draft-ietf-mmusic-sctp-sdp-17.txt 
MMUSIC C. Holmberg MMUSIC C. Holmberg
Internet-Draft S. Loreto Internet-Draft S. Loreto
Intended status: Standards Track G. Camarillo Intended status: Standards Track G. Camarillo
Expires: September 1, 2016 Ericsson Expires: March 3, 2017 Ericsson
February 29, 2016 August 30, 2016
Stream Control Transmission Protocol (SCTP)-Based Media Transport in the Stream Control Transmission Protocol (SCTP)-Based Media Transport in the
Session Description Protocol (SDP) Session Description Protocol (SDP)
draft-ietf-mmusic-sctp-sdp-16 draft-ietf-mmusic-sctp-sdp-17
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.
This specification describes how to describe SCTP associations using This specification describes how to describe SCTP associations using
the Session Description Protocol (SDP), and defines the following new the Session Description Protocol (SDP), and defines the following new
SDP Media Description protocol identifiers (proto values):'SCTP', SDP Media Description protocol identifiers (proto values):'SCTP',
'SCTP/DTLS', 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP'. 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP'.
The specification also describes how to use the new proto values The specification also describes how to use the new proto values
together with the SDP Offer/Answer mechanism in order to negotiate together with the SDP Offer/Answer mechanism in order to negotiate
and establish SCTP associations, and how to indicate the SCTP and establish SCTP associations, and how to indicate the SCTP
application usage. application usage.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
skipping to change at page 1, line 43 skipping to change at page 1, line 43
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 September 1, 2016. This Internet-Draft will expire on March 3, 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
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publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.4.1. General . . . . . . . . . . . . . . . . . . . . . . . 6 4.4.1. General . . . . . . . . . . . . . . . . . . . . . . . 6
4.4.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . 6 4.4.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . 6
4.5. Example . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.5. Example . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. SDP 'sctp-port' Attribute . . . . . . . . . . . . . . . . . . 7 5. SDP 'sctp-port' Attribute . . . . . . . . . . . . . . . . . . 6
5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7 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 . . . . . . . . . . . . . . 8 6. SDP 'max-message-size' Attribute . . . . . . . . . . . . . . 7
6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 8 6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 8 6.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.3. Mux Category . . . . . . . . . . . . . . . . . . . . . . 8 6.3. Mux Category . . . . . . . . . . . . . . . . . . . . . . 8
7. UDP/DTLS/SCTP Transport Realization . . . . . . . . . . . . . 9 7. UDP/DTLS/SCTP Transport Realization . . . . . . . . . . . . . 8
8. TCP/DTLS/SCTP Transport Realization . . . . . . . . . . . . . 9 8. TCP/DTLS/SCTP Transport Realization . . . . . . . . . . . . . 9
9. SCTP Association Management . . . . . . . . . . . . . . . . . 9 9. Association And Connection Management . . . . . . . . . . . . 9
9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 9 9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.2. SDP sendrecv/sendonly/recvonly/inactive Attribute . . . . 10 9.2. SDP sendrecv/sendonly/recvonly/inactive Attribute . . . . 9
9.3. SDP setup Attribute . . . . . . . . . . . . . . . . . . . 10 9.3. SCTP Association . . . . . . . . . . . . . . . . . . . . 9
9.3.1. General . . . . . . . . . . . . . . . . . . . . . . . 10 9.4. DTLS Association (UDP/DTLS/SCTP And TCP/DTLS/SCTP) . . . 10
9.3.2. SCTP Association Initiation . . . . . . . . . . . . . 10 9.5. TCP Connection (TCP/DTLS/SCTP) . . . . . . . . . . . . . 10
9.3.3. TLS Role Determination . . . . . . . . . . . . . . . 10
9.4. SDP connection Attribute . . . . . . . . . . . . . . . . 11
10. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 11 10. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 11
10.1. General . . . . . . . . . . . . . . . . . . . . . . . . 11 10.1. General . . . . . . . . . . . . . . . . . . . . . . . . 11
10.2. Generating the Initial SDP Offer . . . . . . . . . . . . 12 10.2. Generating the Initial SDP Offer . . . . . . . . . . . . 11
10.3. Generating the SDP Answer . . . . . . . . . . . . . . . 12 10.3. Generating the SDP Answer . . . . . . . . . . . . . . . 12
10.4. Offerer Processing of the SDP Answer . . . . . . . . . . 13 10.4. Offerer Processing of the SDP Answer . . . . . . . . . . 12
10.5. Modifying the Session . . . . . . . . . . . . . . . . . 14 10.5. Modifying the Session . . . . . . . . . . . . . . . . . 13
11. Multihoming Considerations . . . . . . . . . . . . . . . . . 14 11. Multihoming Considerations . . . . . . . . . . . . . . . . . 13
12. NAT Considerations . . . . . . . . . . . . . . . . . . . . . 15 12. NAT Considerations . . . . . . . . . . . . . . . . . . . . . 14
12.1. General . . . . . . . . . . . . . . . . . . . . . . . . 15 12.1. General . . . . . . . . . . . . . . . . . . . . . . . . 14
12.2. ICE Considerations . . . . . . . . . . . . . . . . . . . 15 12.2. ICE Considerations . . . . . . . . . . . . . . . . . . . 14
13. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 15 13. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 15
13.1. Establishment of UDP/DTLS/SCTP association . . . . . . . 16 13.1. Establishment of UDP/DTLS/SCTP association . . . . . . . 15
14. Security Considerations . . . . . . . . . . . . . . . . . . . 16 14. Security Considerations . . . . . . . . . . . . . . . . . . . 15
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
15.1. New SDP proto values . . . . . . . . . . . . . . . . . . 17 15.1. New SDP proto values . . . . . . . . . . . . . . . . . . 16
15.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 17 15.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 16
15.2.1. sctp-port . . . . . . . . . . . . . . . . . . . . . 17 15.2.1. sctp-port . . . . . . . . . . . . . . . . . . . . . 16
15.2.2. max-message-size . . . . . . . . . . . . . . . . . . 18 15.2.2. max-message-size . . . . . . . . . . . . . . . . . . 17
15.3. association-usage Name Registry . . . . . . . . . . . . 18 15.3. association-usage Name Registry . . . . . . . . . . . . 17
16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18
17. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 19 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
18. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
18.1. Normative References . . . . . . . . . . . . . . . . . . 21 18.1. Normative References . . . . . . . . . . . . . . . . . . 20
18.2. Informative References . . . . . . . . . . . . . . . . . 23 18.2. Informative References . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23
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
streams that are protected using TLS. streams that are protected using TLS.
The Stream Control Transmission Protocol (SCTP) [RFC4960] is a The Stream Control Transmission Protocol (SCTP) [RFC4960] is a
transport protocol used to establish associations between two transport protocol used to establish associations between two
endpoints. endpoints.
This specification defines how to describe SCTP associations using This specification defines how to describe SCTP associations using
the Session Description Protocol (SDP) [RFC4566], and defines the the Session Description Protocol (SDP) [RFC4566], and defines the
following new SDP Media Description [RFC4566] protocol identifiers following new SDP Media Description [RFC4566] protocol identifiers
(proto values):'SCTP', 'SCTP/DTLS', 'UDP/DTLS/SCTP' and 'TCP/DTLS/ (proto values):'SCTP', 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP'.
SCTP'.
The specification also describes how to use the new proto values The specification also describes how to use the new proto values
together with the SDP Offer/Answer mechanism [RFC3264] in order to together with the SDP Offer/Answer mechanism [RFC3264] in order to
negotiate and establish SCTP associations, and how to indicate the negotiate and establish SCTP associations, and how to indicate the
SCTP application usage. SCTP application usage.
NOTE: TLS is designed to run on top of a byte-stream oriented NOTE: TLS is designed to run on top of a byte-stream oriented
transport protocol providing a reliable, in-sequence delivery like transport protocol providing a reliable, in-sequence delivery like
TCP. [RFC6083] presents serious limitations with transporting TLS on TCP. [RFC6083] presents serious limitations with transporting TLS on
top of SCTP. Therefore, defining a mechanism to negotiate media top of SCTP. Therefore, defining a mechanism to negotiate media
streams transported using TLS on top of SCTP, i.e. 'SCTP/TLS', is streams transported using TLS on top of SCTP, i.e. 'SCTP/TLS', is
outside the scope of this specification. outside the scope of this specification.
2. Terminology 2. Conventions
In this document, the key words "MUST", "MUST NOT", "REQUIRED", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as document are to be interpreted as described in [RFC2119].
described in BCP 14, RFC 2119 [RFC2119] and indicate requirement
levels for compliant implementations.
3. SCTP Terminology 3. SCTP Terminology
SCTP Association: A protocol relationship between SCTP endpoints, SCTP Association: A protocol relationship between SCTP endpoints,
composed of the two SCTP endpoints and protocol state information composed of the two SCTP endpoints and protocol state information
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.
skipping to change at page 4, line 42 skipping to change at page 4, line 37
transport-layer port number. In the case of SCTP running over IP, 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 transport address is defined by the combination of an IP address and
an SCTP port number (where SCTP is the transport protocol). an SCTP port number (where SCTP is the transport protocol).
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: 'SCTP', 'SCTP/DTLS', 'UDP/DTLS/SCTP' and 'TCP/DTLS/ association: 'SCTP', 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP'. The
SCTP'. The section also describes how an m- line, associated with section also describes how an m- line, associated with the proto
the proto values, is created. values, is 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 'SCTP', 'SCTP/DTLS', 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' proto The 'SCTP', 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' proto values are
values are similar to both the 'UDP' and 'TCP' proto values in that similar to both the 'UDP' and 'TCP' proto values in that they only
they only describe the transport-layer protocol and not the upper- describe the transport-layer protocol and not the upper-layer
layer protocol. protocol.
NOTE: When the 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' proto values are NOTE: When the 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' proto values are
used, the underlying transport protocol is respectively UDP and TCP; used, the underlying transport protocol is respectively UDP and TCP;
SCTP is carried on top of DTLS which is on top of those transport- SCTP is carried on top of DTLS which is on top of those transport-
layer protocols. layer protocols.
The m- line fmt value, identifying the application-layer protocol, The m- line fmt value, identifying the application-layer protocol,
MUST be registered by IANA. MUST be registered by IANA.
4.2. Protocol Identifiers 4.2. Protocol Identifiers
The new proto values are defined as below: The new proto values are defined as below:
o The 'SCTP' proto value describes an SCTP association, as defined o The 'SCTP' proto value describes an SCTP association, as defined
in [RFC4960]. in [RFC4960].
o The 'SCTP/DTLS' proto value describes a Datagram Transport Layer
Security (DTLS) [RFC6347] connection on top of an SCTP
association, as defined in [RFC6083].
o The 'UDP/DTLS/SCTP' proto value describes an SCTP association on o The 'UDP/DTLS/SCTP' proto value describes an SCTP association on
top of a DTLS connection on top of UDP, as defined in Section 7. top of a DTLS association on top of UDP, as defined in Section 7.
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 connection 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 [RFC6838]
[RFC4289] by production of, or reference to, a standards-track RFC [RFC4289] by production of, or reference to, a standards-track RFC
that defines the transport protocol for the format. that defines the transport protocol for the format.
An m- line with a proto value of 'SCTP', 'SCTP/DTLS', 'UDP/DTLS/SCTP' An m- line with a proto value of 'SCTP', 'UDP/DTLS/SCTP' or
or 'TCP/DTLS/SCTP' always describe a single SCTP association. 'TCP/DTLS/SCTP' always describe 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
skipping to change at page 6, line 26 skipping to change at page 6, line 17
when associated with any of the proto values defined in this when associated with any of the proto values defined in this
document. document.
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. ABNF
sctp-m-line = %x6d "=" sctp-m-line = %x6d "="
("application" SP sctp-port SP "SCTP" SP fmt CRLF) / ("application" SP sctp-port SP "SCTP" SP fmt CRLF) /
("application" SP sctp-port SP "SCTP/DTLS" SP fmt CRLF) /
("application" SP udp-port SP "UDP/DTLS/SCTP" SP fmt CRLF) / ("application" SP udp-port SP "UDP/DTLS/SCTP" SP fmt CRLF) /
("application" SP tcp-port SP "TCP/DTLS/SCTP" SP fmt CRLF) ("application" SP tcp-port SP "TCP/DTLS/SCTP" SP fmt CRLF)
sctp-port = port sctp-port = port
udp-port = port udp-port = port
tcp-port = port tcp-port = port
fmt = association-usage fmt = association-usage
skipping to change at page 7, line 20 skipping to change at page 7, line 9
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 Usage of the SDP 'sctp-port' attribute with other proto values is not
specified, and MUST be discarded if received. specified, and MUST be discarded if received.
5.2. Syntax 5.2. Syntax
The ABNF for the SDP 'sctp-port' attribute is: The ABNF for the SDP 'sctp-port' attribute is:
sctp-port-attr = "a=sctp-port:" port sctp-port-attr = "a=sctp-port:" port
port = (1*5)DIGIT port = (1*5)DIGIT
The SCTP port range is between 0 and 65535 (both included). The SCTP port range is between 0 and 65535 (both included).
Leading zeroes MUST NOT be used. Leading zeroes MUST NOT be used.
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. Usage of the attribute is only
applicable when associated with 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' applicable when associated with 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP'
proto value m- lines. 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
connection 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 connection, 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 message size (indicated in bytes) that an SCTP endpoint
is willing to receive on the SCTP association associated with the m- is willing to receive on the SCTP association associated with the m-
skipping to change at page 8, line 29 skipping to change at page 8, line 14
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: 'SCTP', 'SCTP/DTLS', 'UDP/DTLS/ one of the following proto values: 'SCTP', 'UDP/DTLS/SCTP' or
SCTP' or 'TCP/DTLS/SCTP'. Usage of the attribute with other proto 'TCP/DTLS/SCTP'. Usage of the attribute with other proto values
values needs to be defined in a separate specification. needs to be defined in a separate specification.
6.2. Syntax 6.2. Syntax
The ABNF for the SDP 'max-message-size' attribute is: The ABNF for the SDP 'max-message-size' attribute is:
max-message-size-attr = "a=max-message-size:" max-message-size max-message-size-attr = "a=max-message-size:" max-message-size
max-message-size = 1*40DIGIT max-message-size = 1*40DIGIT
Leading zeroes MUST NOT be used. Leading zeroes MUST NOT be used.
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. The mux rules depends on the proto value of the associated m- line.
If the proto value is 'SCTP' or 'SCTP/DTLS' the rules are identical If the proto value is 'SCTP' the rules are identical to the rules
to the rules associated with the TRANSPORT mux category. associated with the TRANSPORT mux category.
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
connection 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 connection, 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 supports the negotiation of a single SCTP
association on top of any given DTLS connection. 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
[RFC4571], with DTLS packets being sent instead of RTP/RTCP [RFC4571], with DTLS packets being sent instead of RTP/RTCP
packets, and SDP signaling according to the procedures defined in packets, and SDP signaling according to the procedures defined in
this specification. this specification.
NOTE: DTLS on top of TCP, without using the framing method defined in NOTE: DTLS on top of TCP, without using the framing method defined in
[RFC4571] is outside the scope of this specification. A separate [RFC4571] is outside the scope of this specification. A separate
proto value would need to be registered for such transport proto value would need to be registered for such transport
realization. realization.
9. SCTP Association Management 9. Association And Connection Management
9.1. General 9.1. General
The management of an SCTP association is identical to the management This section describes how to mange an SCTP association, DTLS
of a TCP connection. An SCTP endpoint MUST follow the rules in association and TCP connection using SDP attributes.
Section 6 of [RFC4145] to manage SCTP associations. Whether to use
the SCTP ordered or unordered delivery service is up to the In case of UDP/DTLS/SCTP and TCP/DTLS/SCTP the SCTP association, DTLS
applications using the SCTP association, and this specification does association and TCP connection are managed independetly for each
not define a mechanism to indicate the type of delivery service using other. An assocation/connection can be re-established without
SDP. impacting other assocations/connections.
The detailed SDP Offer/Answer [RFC3264] procedures for the SDP
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 discarded if present.
9.3. SDP setup Attribute 9.3. SCTP Association
9.3.1. General
The SDP setup attribute is used to determine the 'active/passive'
status of the endpoints, following the procedures for TCP in
[RFC4145].
9.3.2. SCTP Association Initiation
Both the 'active' and 'passive' endpoint MUST initiate the SCTP
association, and MUST use the same SCTP port as client port and
server port (in order to prevent two separate SCTP associations from
being established).
NOTE: The procedure above is different from TCP, where only the
'active' endpoint initiates the TCP connection [RFC4145].
NOTE: If the underlying transport protocol is UDP or TCP (e.g. if the When an SCTP association is established/re-established, both SCTP
m- line proto value is 'UDP/DTLS/SCTP' or 'TCP/DTLS/SCTP'), when the endpoints MUST initiate the SCTP association (i.e. both SCTP
SCTP association is established it is assumed that any NAT traversal endpoints take the 'active' role), and MUST use the same SCTP port as
procedures for the underlying transport protocol has successfully client port and server port (in order to prevent two separate SCTP
been performed. associations from being established).
If the m- line proto value is 'TCP/DTLS/SCTP', the 'active' endpoint As both SCTP endpoints take the 'active' role, this specification
only MUST initiate the TCP connection, following the procedures in does not define usage of the SDP 'setup' attribute [RFC4145] for
[RFC4145]. Both endpoints MUST still initiate the SCTP association SCTP.
on top of the TCP connection.
9.3.3. TLS Role Determination NOTE: The procedure above is different from TCP, where one endpoint
takes the 'active' role, the other endpoint takes the 'passive' role,
and only the 'active' endpoint initiates the TCP connection
[RFC4145].
If the m- line proto value is 'SCTP/DTLS', 'UDP/DTLS/SCTP' or NOTE: If the underlying transport protocol is UDP or TCP (UDP/DTLS/
'TCP/DTLS/SCTP', the 'active/passive' status is used to determine the SCTP or TCP/DTLS/SCTP), when the SCTP association is established it
(D)TLS roles of the endpoints. Following the procedures in is assumed that any NAT traversal procedures for the underlying
[RFC4572], the 'active' endpoint will take the (D)TLS client role. transport protocol has successfully been performed.
Once the DTLS connection has been established, the endpoints MUST NOT Usage of the SDP 'connection' attribute [RFC4145] is not defined for
modify (as result of an offer/answer exchange) the TLS roles, or the SCTP. In order to trigger the re-establishment of an SCTP
'active/passive' status, of the endpoints, unless the underlying association, the SDP 'sctp-port' attribute (Section 5) is used to
transport protocol is also modified (e.g. if an IP address- or port indicate a new (different than the ones currently used) SCTP ports.
value associated with the transport protocol is modified).
If the underlying transport protocol is modified, the endpoints MUST NOTE: This specification does not define procedures for re-
establish a new DTLS connection. In such case the 'active/passive' establishing an SCTP association using the SCTP ports currently used
status of the endpoints will again be determined following the for the SCTP association.
procedures in [RFC4145], and the new status will be used to determine
the (D)TLS roles of the endpoints associated with the new DTLS
connection.
NOTE: The procedure above is identical to the one defined for SRTP- 9.4. DTLS Association (UDP/DTLS/SCTP And TCP/DTLS/SCTP)
DTLS in [RFC5763].
NOTE: As described in [add-reference], if the Interactive An DTLS association is managed according to the procedures in
Connectivity Establishment (ICE) mechanism [RFC5245] is used, all ICE [I-D.ietf-mmusic-dtls-sdp]. Hence, the SDP 'setup' attribute is used
candidates associated with an SCTP association on top of a DTLS to negotiate the (D)TLS roles ('client' and 'server') [RFC4572].
connection as part of the same DTLS connection. Thus, a switch from
one candidate pair to another candidate pair will not trigger the
establishment of a new DTLS connection.
9.4. SDP connection Attribute NOTE: The SDP 'setup' attribute is used both to negotiate both the
DTLS roles and the TCP roles (Section 9.5).
The SDP connection attribute is used following the procedures in NOTE: As described in [RFC5245], if the Interactive Connectivity
[RFC4145], with the additional SCTP specific considerations described Establishment (ICE) mechanism [RFC5245] is used, all ICE candidates
in this section. associated with an DTLS association as considered part of the same
DTLS association. Thus, a switch from one candidate pair to another
candidate pair will not trigger the establishment of a new DTLS
association.
If the m- line proto value is 'TCP/DTLS/SCTP', an SDP connection 9.5. TCP Connection (TCP/DTLS/SCTP)
attribute associated with that m- line applies to both the SCTP
association and the TCP connection. Therefore, an attribute 'new'
value indicates that both a new SCTP association and new TCP
connection have to be established, following the procedures in
[RFC4145].
NOTE: This specification does not define a mechanism which allows re- The TCP connection is managed according to the procedures in
establishing of a new SCTP association, while maintaining the [RFC4145]. Hence, the SDP 'setup' attribute is used to negotiate the
underlying TCP connection. TCP roles ('active' and 'passive'), and the SDP 'connection'
attribute is used to indicate whether to use an existing TCP
connection, or create a new one.
The SDP connection attribute value does not automatically impact an NOTE: A change of the TCP roles will also trigger a re-establishment
existing DTLS connection. Section 9.3.3 describes in which cases a of the DTLS association, according to the procedures in
new DTLS connections will have to be re-established. [I-D.ietf-mmusic-dtls-sdp].
10. SDP Offer/Answer Procedures 10. SDP Offer/Answer Procedures
10.1. General 10.1. General
This section defines the SDP Offer/Answer [RFC3264] procedures for This section defines the SDP Offer/Answer [RFC3264] procedures for
negotiating and establishing an SCTP association. Unless explicitly negotiating and establishing an SCTP association. Unless explicitly
stated, the procedures apply to all m- line proto values ('SCTP', stated, the procedures apply to SCTP, UDP/DTLS/SCTP and TCP/DTLS/
'SCTP/DTLS', 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP') defined in this SCTP.
specification.
If the m- line proto value is 'SCTP/DTLS', 'UDP/DTLS/SCTP' or In case of UDP/DTLS/SCTP or TCP/DTLS/SCTP, each endpoint MUST
'TCP/DTLS/SCTP', each endpoint MUST provide a certificate associate one or more certificate fingerprints, using the SDP
fingerprint, using the SDP 'fingerprint' attribute [RFC4572], if the 'fingerprint' attribute with the m- line, following the procedures in
endpoint supports, and is willing to use, a cipher suite with an [RFC4572] and [I-D.ietf-mmusic-4572-update].
associated certificate.
The authentication certificates are interpreted and validated as The authentication certificates are interpreted and validated as
defined in [RFC4572]. Self-signed certificates can be used securely, defined in [RFC4572]. Self-signed certificates can be used securely,
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].
NOTE: The procedures apply to a specific m- line describing an SCTP In case of UDP/DTLS/SCTP or TCP/DTLS/SCTP, each endpoint MUST
association. If an offer or answer contains multiple m- lines associate an SDP 'dtls-id' attribute with the m- line, following the
describing SCTP associations, the procedures are applied separately procedures in [I-D.ietf-mmusic-dtls-sdp].
to each m- line.
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, if the m- line proto value is 'SCTP/DTLS', 'UDP/DTLS/SCTP' o MUST, in the case of UDP/DTLS/SCTP or TCP/DTLS/SCTP, associate an
or 'TCP/DTLS/SCTP', associate an SDP setup attribute, with an SDP setup attribute, with an 'actpass' value, with the m- line;
'actpass' value, with the m- line (see Section 9.3);
o MUST, if the m- line proto is 'UDP/DTLS/SCTP' or 'TCP/DTLS/SCTP', o MUST, in the case of UDP/DTLS/SCTP or TCP/DTLS/SCTP, associate an
associate an SDP 'sctp-port' attribute with the m- line (see SDP 'sctp-port' attribute with the m- line;
Section 5);
o MUST associate an SDP 'connection' attribute, with a 'new' value, o MUST, in the case of TCP/DTLS/SCTP, associate an SDP 'connection'
with the m- line (see Section 9.4); and attribute, with a 'new' attribute value, with the m- line; and
o MAY associate an SDP 'max-message-size' attribute with the m- line o MAY associate an SDP 'max-message-size' attribute (Section 6) with
(see Section 6). 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 association, if the answerer accepts the m- line describing an SCTP association, if the answerer accepts the m- line
it: it:
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, if the m- line proto value is 'SCTP/DTLS', 'UDP/DTLS/SCTP' o MUST, in the case of UDP/DTLS/SCTP or TCP/DTLS/SCTP associate an
or 'TCP/DTLS/SCTP', associate an SDP 'setup' attribute, with an SDP 'setup' attribute, with an 'active' or 'passive' value, with
'active' or 'passive' value, with the m- line (see Section 9.3); the m- line;
o MUST, if the m- line proto is 'UDP/DTLS/SCTP' or 'TCP/DTLS/SCTP', o MUST, in the case of UDP/DTLS/SCTP or TCP/DTLS/SCTP, associate an
associate an SDP 'sctp-port' attribute with the m- line (see SDP 'sctp-port' attribute with the m- line; and
Section 5); and
o MAY associate an SDP 'max-message-size' attribute with the m- line o MAY associate an SDP 'max-message-size' attribute (Section 6)with
(see Section 6). 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: Once the answerer has sent the answer, the answerer MUST, if an SCTP
association has yet not been established, or if an existing SCTP
association is to be re-established, initiate the establishement of
the SCTP association.
o MUST, if an SCTP association associated with the m- line has yet In the case of UDP/DTLS/SCTP or TCP/DTLS/SCTP, the answerer follows
not been established, or if an existing SCTP association is to be the procedures in [I-D.ietf-mmusic-dtls-sdp] regarding the
re-established, initiate the establishing of the SCTP association; establishment/re-establishemnt of the DTLS association.
and
o MUST, if the answerer is the 'active' endpoint, and if an DTLS In the case of TCP/DTLS/SCTP, the answerer follows the procedures in
connection associated with the m- line is to be established (or [RFC4145] regarding the establishment/re-establishemnt of the TCP
re-established), initiate the establishing of the DTLS connection conection association.
(by sending a ClientHello message).
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,
In addition, the answerer MUST NOT establish an SCTP association, or following the procedures in [RFC3264]. In addition, the answerer
a DTLS connection, associated with the m- line. MUST NOT initiate the establishment of an SCTP 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
When the offerer receives an answer, which contains an m- line with a Once the offerer has received the answer, which contains an m- line
non-zero port value, describing an SCTP association, 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, if the offerer is the 'active' endpoint, if the m- line to be re-established, initiate the establishement of the SCTP
proto value is 'TCP/DTLS/SCTP', and if a TCP connection used to association.
carry the SCTP association has not yet been established (or if an
existing TCP connection is to be re-established), initiate the
establishing of the TCP connection;
o MUST, if an SCTP association associated with the m- line has not
yet been established (or if an existing SCTP association is to be
re-established), initiate the establishing of the SCTP
association; and
o MUST, if the offerer is the 'active' endpoint, and if a DTLS In the case of UDP/DTLS/SCTP or TCP/DTLS/SCTP, the offerer follows
connection associated with the m- line is to be established (or if the procedures in [I-D.ietf-mmusic-dtls-sdp] regarding the
an existing DTLS connection is to be re-established), initiate the establishment/re-establishemnt of the DTLS association.
establishing of the DTLS connection (by sending a ClientHello
message).
o NOTE: If the m- line proto value is 'UDP/DTLS/SCTP' or 'TCP/DTLS/ In the case of TCP/DTLS/SCTP, the offerer follows the procedures in
SCTP', the underlying DTLS connection needs to be established [RFC4145] regarding the establishment/re-establishemnt of the TCP
before the SCTP association can be established. conection 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 establish a TCP connection, an SCTP association, or a DTLS
connection, associated with the m- line. association, associated with the m- line.
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 Unless the offerer wants to re-establish an existing SCTP o Unless the offerer wants to re-establish an SCTP association, the
association, the offerer MUST associate an SDP connection offerer MUST associate an SDP 'sctp-port' attribute, with a new
attribute, with an 'existing' value, with the m- line; and attribute value, with the m- line; and
o If the offerer wants to disable a previously established SCTP o If the offerer wants to disable a previously established SCTP
association, it MUST assign a zero port value to the m- line association, it MUST assign a zero port value to the m- line
associated with the SCTP association, following the procedures in associated with the SCTP association, following the procedures in
[RFC3264]. [RFC3264].
In the case of UDP/DTLS/SCTP or TCP/DTLS/SCTP, the offer follows the
procedures in [I-D.ietf-mmusic-dtls-sdp] regarding the DTLS
association impacts when modifying a session.
In the case of TCP/DTLS/SCTP, the offer follows the procedures in
[RFC4145] regarding the TCP connection impacts when modifying a
session;
11. Multihoming Considerations 11. Multihoming Considerations
SCTP supports multihoming. An SCTP endpoint is considered multihomed SCTP supports multihoming. An SCTP endpoint is considered multihomed
if it has more than one IP address on which SCTP can be used. An if it has more than one IP address on which SCTP can be used. An
SCTP endpoint inform the remote peer about its IP addresses using the SCTP endpoint inform the remote peer about its IP addresses using the
address parameters in the INIT/INIT-ACK chunk. Therefore, when SDP address parameters in the INIT/INIT-ACK chunk. Therefore, when SDP
is used to describe an SCTP association, while the "c=" line contains is used to describe an SCTP association, while the "c=" line contains
the address which was used to negotiate the SCTP association, the address which was used to negotiate the SCTP association,
multihomed SCTP endpoints might end up using other IP addresses. multihomed SCTP endpoints might end up using other IP addresses.
skipping to change at page 15, line 16 skipping to change at page 14, line 26
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
SCTP features not present in UDP or TCP, including the checksum SCTP features not present in UDP or TCP, including the checksum
(CRC32c) value calculated on the whole packet (rather than just the (CRC32c) value calculated on the whole packet (rather than just the
header), and multihoming, introduce new challenges for NAT traversal. header), and multihoming, introduce new challenges for NAT traversal.
[I-D.ietf-tsvwg-natsupp] defines an SCTP specific variant of NAT, [I-D.ietf-behave-sctpnat] defines an SCTP specific variant of NAT,
which provides similar features of Network Address and Port which provides similar features of Network Address and Port
Translation (NAPT). Translation (NAPT).
Current NATs typically do not support SCTP. [RFC6951] defines a Current NATs typically do not support SCTP. [RFC6951] defines a
mechanism for sending SCTP on top of UDP, which makes it possible to mechanism for sending SCTP on top of UDP, which makes it possible to
use SCTP with NATs and firewalls that do not support SCTP. use SCTP with NATs and firewalls that do not support SCTP.
12.2. ICE Considerations 12.2. ICE Considerations
At the time of writing this specification, no procedures have been At the time of writing this specification, no procedures have been
defined for using ICE [RFC5245] together with SCTP as transport layer defined for using ICE [RFC5245] together with SCTP as transport layer
protocol. Such procedures, including the associated SDP Offer/Answer protocol. Such procedures, including the associated SDP Offer/Answer
procedures, are outside the scope of this specification, and might be procedures, are outside the scope of this specification, and might be
defined in a future specification. defined in a future specification.
When the transport layer protocol is UDP (in case of an SCTP When the transport layer protocol is UDP (UDP/DTLS/SCTP), if ICE is
association on top of a DTLS connection on top of UDP), if ICE is
used, the ICE procedures defined in [RFC5245] are used. used, the ICE procedures defined in [RFC5245] are used.
When the transport layer protocol is TCP (in case of an SCTP When the transport layer protocol is TCP (TCP/DTLS/SCTP), if ICE is
association on top of a DTLS connection on top of TCP), if ICE is
used, the ICE procedures defined in [RFC6544] are used. used, the ICE procedures defined in [RFC6544] are used.
Implementations MUST treat all ICE candidate pairs associated with a Implementations MUST treat all ICE candidate pairs associated with a
an SCTP association on top of a DTLS connection as part of the same an SCTP association on top of a DTLS association as part of the same
DTLS connection. Thus, there will only be one DTLS handshake even if DTLS association. Thus, there will only be one DTLS handshake even
there are multiple valid candidate pairs, and shifting from one if there are multiple valid candidate pairs, and shifting from one
candidate pair to another will not impact the DTLS connection. If candidate pair to another will not impact the DTLS association. If
new candidates are added, they will also be part of the same DTLS new candidates are added, they will also be part of the same DTLS
connection. association.
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=setup:actpass a=setup:actpass
a=connection:new
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
UDP/DTLS/SCTP association will be as defined UDP/DTLS/SCTP association will be as defined
for the 'webrtc-datachannel' format value. for the 'webrtc-datachannel' format value.
- The offerer UDP port value is 54111. - The offerer UDP port value is 54111.
- The offerer SCTP port value is 5000. - The offerer SCTP port value is 5000.
- The offerer indicates that it can take either the - The offerer indicates that it can take either the
active or the passive role. client or the server DTLS role.
SDP Answer: SDP Answer:
m=application 64300 UDP/DTLS/SCTP webrtc-datachannel m=application 64300 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4 192.0.2.2 c=IN IP4 192.0.2.2
a=dtls-id:ggr4rd
a=setup:passive a=setup:passive
a=sctp-port:6000 a=sctp-port:6000
a=max-message-size:100000 a=max-message-size:100000
- The answerer UDP port value is 64300. - The answerer UDP port value is 64300.
- The answerer SCTP port value is 6000. - The answerer SCTP port value is 6000.
- The answerer takes the passive role. - The answerer takes the server DTLS role.
14. Security Considerations 14. Security Considerations
[RFC4566] defines general SDP security considerations, while [RFC4566] defines general SDP security considerations, while
[RFC3264], [RFC4145] and [RFC4572] define security considerations [RFC3264], [RFC4145] and [RFC4572] define security considerations
when using the SDP offer/answer mechanism to negotiate media streams. when using the SDP offer/answer mechanism to negotiate media streams.
[RFC4960] defines general SCTP security considerations, while [RFC4960] defines general SCTP security considerations, while
[RFC6083] defines security considerations when using DTLS on top of [RFC6083] defines security considerations when using DTLS on top of
SCTP, and [I-D.ietf-tsvwg-sctp-dtls-encaps] defines security SCTP, and [I-D.ietf-tsvwg-sctp-dtls-encaps] defines security
skipping to change at page 17, line 21 skipping to change at page 16, line 29
This document updates the "Session Description Protocol (SDP) This document updates the "Session Description Protocol (SDP)
Parameters" registry, following the procedures in [RFC4566], by Parameters" registry, following the procedures in [RFC4566], by
adding the following values to the table in the SDP "proto" field adding the following values to the table in the SDP "proto" field
registry: registry:
+-------+---------------+-----------+ +-------+---------------+-----------+
| Type | SDP Name | Reference | | Type | SDP Name | Reference |
+-------+---------------+-----------+ +-------+---------------+-----------+
| proto | SCTP | [RFCXXXX] | | proto | SCTP | [RFCXXXX] |
| proto | SCTP/DTLS | [RFCXXXX] |
| 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
skipping to change at page 18, line 33 skipping to change at page 17, line 44
Contact e-mail: christer.holmberg@ericsson.com Contact e-mail: christer.holmberg@ericsson.com
Reference: RFCXXXX 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
'SCTP', 'SCTP/DTLS', 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' protocol 'SCTP', 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' protocol identifiers.
identifiers. Each "fmt" value describes the usage of an entire SCTP Each "fmt" value describes the usage of an entire SCTP association,
association, including all SCTP streams associated with the SCTP including all SCTP streams associated with the SCTP association.
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" is
required. It is defined in [Section 4]. 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
skipping to change at page 19, line 25 skipping to change at page 18, line 36
[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.]
Figure 1 Figure 1
16. Acknowledgments 16. Acknowledgments
The authors wish to thank Harald Alvestrand, Randell Jesup, Paul The authors wish to thank Roman Shpount, Harald Alvestrand, Randell
Kyzivat, Michael Tuexen, Juergen Stoetzer-Bradler, Flemming Andreasen Jesup, Paul Kyzivat, Michael Tuexen, Juergen Stoetzer-Bradler,
and Ari Keranen for their comments and useful feedback. Flemming Andreasen and Ari Keranen for their comments and useful
feedback.
17. Change Log 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-15 Changes from draft-ietf-mmusic-sctp-sdp-15
o Re-submission due to expiration of previous version. o Chapter about SCTP, DTLS and TCP association/connection management
modified.
o Reference updates. o Removal of SCTP/DTLS.
Changes from draft-ietf-mmusic-sctp-sdp-14 Changes from draft-ietf-mmusic-sctp-sdp-14
o Changes based on WGLC comments from Magnus Westerlund. o Changes based on WGLC comments from Magnus Westerlund.
o - ABNF clarification that token and port are defined in RFC4566. o - ABNF clarification that token and port are defined in RFC4566.
o - Specify 40 as maximum digit character length for the SDP max- o - Specify 40 as maximum digit character length for the SDP max-
message-size value. message-size value.
o - Editorial clarification. o - Editorial clarification.
o Changes based on discussions at IETF#92. o Changes based on discussions at IETF#92.
o - Specify that all ICE candidate pairs belong to the same DTLS o - Specify that all ICE candidate pairs belong to the same DTLS
connection. association.
Changes from draft-ietf-mmusic-sctp-sdp-13 Changes from draft-ietf-mmusic-sctp-sdp-13
o Changes based on comments from Paul Kyzivat. o Changes based on comments from Paul Kyzivat.
o - Text preventing usage of well-known ports removed. o - Text preventing usage of well-known ports removed.
o - Editorial clarification. o - Editorial clarification.
Changes from draft-ietf-mmusic-sctp-sdp-12 Changes from draft-ietf-mmusic-sctp-sdp-12
skipping to change at page 20, line 34 skipping to change at page 19, line 47
o - Specify that fingerprint or setup roles must not be modified, o - Specify that fingerprint or setup roles must not be modified,
unless underlying transport protocol is also modified. unless underlying transport protocol is also modified.
o Changes based on comments from Ari Keranen: o Changes based on comments from Ari Keranen:
o - Editorial corrections. o - Editorial corrections.
o Changes based on comments from Flemming Andreasen: o Changes based on comments from Flemming Andreasen:
o - Clarify that, if UDP/DTLS/SCTP or TCP/DTLS/SCTP is used, the o - Clarify that, if UDP/DTLS/SCTP or TCP/DTLS/SCTP is used, the
DTLS connection is established before the SCTP association. DTLS association is established before the SCTP association.
o - Clarify that max-message-size value is given in bytes, and that o - Clarify that max-message-size value is given in bytes, and that
different values can be used per direction. different values can be used per direction.
o - Section on fmtp attribute removed. o - Section on fmtp attribute removed.
o - Editorial corrections. o - Editorial corrections.
Changes from draft-ietf-mmusic-sctp-sdp-11 Changes from draft-ietf-mmusic-sctp-sdp-11
skipping to change at page 22, line 49 skipping to change at page 22, line 19
[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]
Holmberg, C., "Updates to RFC 4572", draft-ietf-mmusic-
4572-update-05 (work in progress), June 2016.
[I-D.ietf-mmusic-dtls-sdp]
Holmberg, C. and R. Shpount, "Using the SDP Offer/Answer
Mechanism for DTLS", draft-ietf-mmusic-dtls-sdp-14 (work
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-12 Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-13
(work in progress), January 2016. (work in progress), June 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 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT) (ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245, Traversal for Offer/Answer Protocols", RFC 5245,
DOI 10.17487/RFC5245, April 2010, DOI 10.17487/RFC5245, April 2010,
<http://www.rfc-editor.org/info/rfc5245>. <http://www.rfc-editor.org/info/rfc5245>.
[RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
for Establishing a Secure Real-time Transport Protocol
(SRTP) Security Context Using Datagram Transport Layer
Security (DTLS)", RFC 5763, DOI 10.17487/RFC5763, May
2010, <http://www.rfc-editor.org/info/rfc5763>.
[RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram [RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram
Transport Layer Security (DTLS) for Stream Control Transport Layer Security (DTLS) for Stream Control
Transmission Protocol (SCTP)", RFC 6083, Transmission Protocol (SCTP)", RFC 6083,
DOI 10.17487/RFC6083, January 2011, DOI 10.17487/RFC6083, January 2011,
<http://www.rfc-editor.org/info/rfc6083>. <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>.
[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, to End-Host Communication", RFC 6951,
DOI 10.17487/RFC6951, May 2013, DOI 10.17487/RFC6951, May 2013,
<http://www.rfc-editor.org/info/rfc6951>. <http://www.rfc-editor.org/info/rfc6951>.
[I-D.ietf-tsvwg-natsupp] [I-D.ietf-behave-sctpnat]
Stewart, R., Tuexen, M., and I. Ruengeler, "Stream Control Stewart, R., Tuexen, M., and I. Ruengeler, "Stream Control
Transmission Protocol (SCTP) Network Address Translation Transmission Protocol (SCTP) Network Address Translation",
Support", draft-ietf-tsvwg-natsupp-08 (work in progress), draft-ietf-behave-sctpnat-09 (work in progress), September
July 2015. 2013.
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
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