draft-ietf-mmusic-sctp-sdp-12.txt   draft-ietf-mmusic-sctp-sdp-13.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: July 19, 2015 Ericsson Expires: September 5, 2015 Ericsson
January 15, 2015 March 4, 2015
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-12 draft-ietf-mmusic-sctp-sdp-13
Abstract Abstract
SCTP (Stream Control Transmission Protocol) is a transport protocol SCTP (Stream Control Transmission Protocol) is a transport protocol
used to establish associations between two endpoints. 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'. 'SCTP/DTLS', 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP'.
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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 July 19, 2015. This Internet-Draft will expire on September 5, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 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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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 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
4.4.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.3. Mux Category . . . . . . . . . . . . . . . . . . . . . . 7
6. SDP 'max-message-size' Attribute . . . . . . . . . . . . . . 7 6. SDP 'max-message-size' Attribute . . . . . . . . . . . . . . 7
6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7 6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 7 6.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. SDP 'fmtp' Attribute . . . . . . . . . . . . . . . . . . . . 7 6.3. Mux Category . . . . . . . . . . . . . . . . . . . . . . 8
8. UDP/DTLS/SCTP Transport Realization . . . . . . . . . . . . . 7 7. UDP/DTLS/SCTP Transport Realization . . . . . . . . . . . . . 8
9. TCP/DTLS/SCTP Transport Realization . . . . . . . . . . . . . 8 8. TCP/DTLS/SCTP Transport Realization . . . . . . . . . . . . . 9
10. SCTP Association Management . . . . . . . . . . . . . . . . . 8 9. SCTP Association Management . . . . . . . . . . . . . . . . . 9
10.1. General . . . . . . . . . . . . . . . . . . . . . . . . 8 9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.2. SDP sendrecv/sendonly/sendrecv/inactive Attribute . . . 8 9.2. SDP sendrecv/sendonly/recvonly/inactive Attribute . . . . 9
10.3. SDP setup Attribute . . . . . . . . . . . . . . . . . . 8 9.3. SDP setup Attribute . . . . . . . . . . . . . . . . . . . 10
10.3.1. General . . . . . . . . . . . . . . . . . . . . . . 8 9.3.1. General . . . . . . . . . . . . . . . . . . . . . . . 10
10.3.2. SCTP Association Initiation . . . . . . . . . . . . 9 9.3.2. SCTP Association Initiation . . . . . . . . . . . . . 10
10.3.3. TLS Role Determination . . . . . . . . . . . . . . . 9 9.3.3. TLS Role Determination . . . . . . . . . . . . . . . 10
10.4. SDP connection Attribute . . . . . . . . . . . . . . . . 9 9.4. SDP connection Attribute . . . . . . . . . . . . . . . . 11
11. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 10 10. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 11
11.1. General . . . . . . . . . . . . . . . . . . . . . . . . 10 10.1. General . . . . . . . . . . . . . . . . . . . . . . . . 11
11.2. Generating the Initial SDP Offer . . . . . . . . . . . . 10 10.2. Generating the Initial SDP Offer . . . . . . . . . . . . 12
11.3. Generating the SDP Answer . . . . . . . . . . . . . . . 11 10.3. Generating the SDP Answer . . . . . . . . . . . . . . . 12
11.4. Offerer Processing of the SDP Answer . . . . . . . . . . 12 10.4. Offerer Processing of the SDP Answer . . . . . . . . . . 13
11.5. Modifying the Session . . . . . . . . . . . . . . . . . 12 10.5. Modifying the Session . . . . . . . . . . . . . . . . . 14
12. Multihoming Considerations . . . . . . . . . . . . . . . . . 13 11. Multihoming Considerations . . . . . . . . . . . . . . . . . 14
13. NAT Considerations . . . . . . . . . . . . . . . . . . . . . 13 12. NAT Considerations . . . . . . . . . . . . . . . . . . . . . 14
13.1. General . . . . . . . . . . . . . . . . . . . . . . . . 13 12.1. General . . . . . . . . . . . . . . . . . . . . . . . . 15
13.2. ICE Considerations . . . . . . . . . . . . . . . . . . . 14 12.2. ICE Considerations . . . . . . . . . . . . . . . . . . . 15
13. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 15
14. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 14 13.1. Establishment of UDP/DTLS/SCTP association . . . . . . . 15
14.1. Establishment of UDP/DTLS/SCTP association . . . . . . . 14 14. Security Considerations . . . . . . . . . . . . . . . . . . . 16
15. Security Considerations . . . . . . . . . . . . . . . . . . . 15 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 15.1. New SDP proto values . . . . . . . . . . . . . . . . . . 17
16.1. New SDP proto values . . . . . . . . . . . . . . . . . . 15 15.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 17
16.2. New SDP Attributes . . . . . . . . . . . . . . . . . . . 15 15.2.1. sctp-port . . . . . . . . . . . . . . . . . . . . . 17
16.2.1. sctp-port . . . . . . . . . . . . . . . . . . . . . 15 15.2.2. max-message-size . . . . . . . . . . . . . . . . . . 18
16.2.2. max-message-size . . . . . . . . . . . . . . . . . . 16 15.3. association-usage Name Registry . . . . . . . . . . . . 18
16.3. association-usage Name Registry . . . . . . . . . . . . 16 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19
17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17 17. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 19
18. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 17 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
19. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 18.1. Normative References . . . . . . . . . . . . . . . . . . 21
19.1. Normative References . . . . . . . . . . . . . . . . . . 18 18.2. Informative References . . . . . . . . . . . . . . . . . 22
19.2. Informative References . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
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 (Transmission Control Protocol) [RFC5246] and establishing TCP [RFC0793] streams. Connection-Oriented Media
streams. Connection-Oriented Media Transport over the Transport Transport over the Transport Layer Security (TLS) Protocol in SDP
Layer Security (TLS) Protocol in the Session Description Protocol [RFC4572] extends RFC4145 [RFC4145] for describing TCP-based media
(SDP) [RFC4572] extends RFC4145 [RFC4145] for describing TCP-based streams that are protected using TLS.
media streams that are protected using TLS.
SCTP (Stream Control Transmission Protocol) is a transport protocol SCTP (Stream Control Transmission Protocol) [RFC4960] is a transport
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 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', 'SCTP/DTLS', '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.
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described in BCP 14, RFC 2119 [RFC2119] and indicate requirement described in BCP 14, RFC 2119 [RFC2119] and indicate requirement
levels for compliant implementations. 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. Two SCTP endpoints MUST NOT have more than one in the association.
SCTP association between them at any given time.
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 SCTP Transport address: A transport address is traditionally defined
by a network-layer address, a transport-layer protocol, and a 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-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
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[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', 'SCTP/DTLS', 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' proto
values are similar to both the 'UDP' and 'TCP' proto values in that values are similar to both the 'UDP' and 'TCP' proto values in that
they only describe the transport-layer protocol and not the upper- they only describe the transport-layer protocol and not the upper-
layer protocol. layer 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 either UDP or TCP, SCTP is used, the underlying transport protocol is respectively UDP and TCP;
carried on top of either of those transport-layer protocols. SCTP is carried on top of DTLS which is on top of those transport-
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 o The 'SCTP/DTLS' proto value describes a Datagram Transport Layer
Security (DTLS) [RFC6347] connection on top of an SCTP Security (DTLS) [RFC6347] connection on top of an SCTP
association, as defined in [RFC6083]. 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 8. top of a DTLS connection 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 9. top of a DTLS connection 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.
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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.
4.4. Syntax 4.4. Syntax
4.4.1. General
This section defines the ABNF [RFC5234] for the SDP media description
when associated with any of the proto values defined in this
document.
This specification creates an IANA registry for 'association-usage'
values.
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 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
association-usage = token association-usage = token
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
This section defines a new SDP media-level attribute, 'sctp-port'. This section defines a new SDP media-level attribute, 'sctp-port'.
The attribute can be associated with an SDP media descriptor (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
which case the m- line port value indicates the port of the which case the m- line port value indicates the port of the
transport-layer protocol (UDP or TCP), on which SCTP is carried. underlying transport-layer protocol (UDP or TCP), on which SCTP is
carried, and the 'sctp-port' value indicates the SCTP port.
If the SDP sctp-port attribute is not present, the m- line MUST be No default value is defined for the SDP sctp-port attribute.
discarded. Therefore, if the attribute is not present, the associated m- line
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:
sctp-port-attr = "a=sctp-port:" port sctp-port-attr = "a=sctp-port:" port
port = 1*DIGIT port = (1*5)DIGIT
The SCTP port range is between 0 and 65535 (both included).
Applications MUST NOT use well-known port values, or port
values that have been registered for specific purposes.
Leading zeroes MUST NOT be used.
5.3. Mux Category
The mux category [I-D.ietf-mmusic-sdp-mux-attributes] for the SDP
sctp-port' attribute is SPECIAL. Usage of the attribute is only
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
connection is outside the scope of this specification, no mux rules
are specified for the 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' proto
values. Future extensions, that define how to negotiate multiplexing
of multiple SCTP associations of top of a single DTLS connection,
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
The SDP 'max-message-size' attribute can be associated with an m- This section defines a new SDP media-level attribute, 'max-message-
line to indicate the maximum message size that an SCTP endpoint is size'. The attribute can be associated with an m- line to indicate
willing to receive on the SCTP association associated with the m- the maximum message size (indicated in bytes) that an SCTP endpoint
line. is willing to receive on the SCTP association associated 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 The remote peer MUST assume that larger messages will be rejected by
the SCTP endpoint. SCTP endpoints need to decide on appropriate the SCTP endpoint. SCTP endpoints need to decide on appropriate
behavior in case a message that exceeds the maximum size needs to be behavior in case a message that exceeds the maximum size needs to be
sent. sent.
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.
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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', 'SCTP/DTLS', 'UDP/DTLS/
SCTP' or 'TCP/DTLS/SCTP'. Usage of the attribute with other proto SCTP' or 'TCP/DTLS/SCTP'. Usage of the attribute with other proto
values needs to be defined in a separate specification. values needs to be defined in a separate specification.
6.2. Syntax 6.2. Syntax
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*DIGIT max-message-size = 1*DIGIT
7. SDP 'fmtp' Attribute Leading zeroes MUST NOT be used.
The SDP 'fmtp' attribute [RFC4566] can be used to carry association- 6.3. Mux Category
usage specific parameters. If the attribute is used with a specific
association-usage, the usage and detailed syntax MUST be defined in
that association-usage specification.
8. UDP/DTLS/SCTP Transport Realization 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.
If the proto value is 'SCTP' or 'SCTP/DTLS' the rules are identical
to the rules associated with the TRANSPORT mux category.
As the usage of multiple SCTP associations on top of a single DTLS
connection is outside the scope of this specification, no mux rules
are specified for the 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' proto
values.
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].
9. TCP/DTLS/SCTP Transport Realization NOTE: While [I-D.ietf-tsvwg-sctp-dtls-encaps] allows multiple SCTP
associations on top of a single DTLS connection, the procedures in
this specification only supports the negotiation of a single SCTP
association on top of any given DTLS connection.
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]. [RFC4571], with DTLS packets being sent instead of RTP/RTCP
packets, and SDP signaling according to the procedures defined in
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.
10. SCTP Association Management 9. SCTP Association Management
10.1. General 9.1. General
The management of an SCTP association is identical to the management The management of an SCTP association is identical to the management
of a TCP connection. An SCTP endpoints MUST follow the rules in of a TCP connection. An SCTP endpoint MUST follow the rules in
Section 6 of [RFC4145] to manage SCTP associations. Whether to use Section 6 of [RFC4145] to manage SCTP associations. Whether to use
the SCTP ordered or unordered delivery service is up to the the SCTP ordered or unordered delivery service is up to the
applications using the SCTP association, and this specification does applications using the SCTP association, and this specification does
not define a mechanism to indicate the type of delivery service using not define a mechanism to indicate the type of delivery service using
SDP. SDP.
10.2. SDP sendrecv/sendonly/sendrecv/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]. Specifications for an individual SCTP attributes [RFC4566]. Unless semantics of these attributes for an
association usage MAY define how the attributes can be used with that SCTP association usage have been defined, SDP direction attributes
usage. Unless semantics of these attributes for an SCTP association MUST be discarded if present.
usage have been defined, SDP direction attributes MUST be discarded
if present.
10.3. SDP setup Attribute 9.3. SDP setup Attribute
10.3.1. General 9.3.1. General
The SDP setup attribute is used to determine the 'active/passive' The SDP setup attribute is used to determine the 'active/passive'
status of the endpoints, following the procedures for TCP in status of the endpoints, following the procedures for TCP in
[RFC4145]. [RFC4145].
10.3.2. SCTP Association Initiation 9.3.2. SCTP Association Initiation
Both the 'active' and 'passive' endpoint MUST initiate the SCTP Both the 'active' and 'passive' endpoint MUST initiate the SCTP
association, and MUST use the same SCTP port as client port and association, and MUST use the same SCTP port as client port and
server port (in order to prevent two separate SCTP associations from server port (in order to prevent two separate SCTP associations from
being established). being established).
NOTE: The procedure above is different from TCP, where only the NOTE: The procedure above is different from TCP, where only the
'active' endpoint initiates the TCP connection [RFC4145]. 'active' endpoint initiates the TCP connection [RFC4145].
If the m- line proto value is 'TCP/DTLS/SCTP', only the 'active' NOTE: If the underlying transport protocol is UDP or TCP (e.g. if the
endpoint will initiate the TCP connection, following the procedures m- line proto value is 'UDP/DTLS/SCTP' or 'TCP/DTLS/SCTP'), when the
in [RFC4145]. Both endpoints will still initiate the SCTP SCTP association is established it is assumed that any NAT traversal
association on top of the TCP connection. procedures for the underlying transport protocol has successfully
been performed.
10.3.3. TLS Role Determination If the m- line proto value is 'TCP/DTLS/SCTP', the 'active' endpoint
only MUST initiate the TCP connection, following the procedures in
[RFC4145]. Both endpoints MUST still initiate the SCTP association
on top of the TCP connection.
9.3.3. TLS Role Determination
If the m- line proto value is 'SCTP/DTLS', 'UDP/DTLS/SCTP' or If the m- line proto value is 'SCTP/DTLS', 'UDP/DTLS/SCTP' or
'TCP/DTLS/SCTP', the 'active/passive' status is used to determine the 'TCP/DTLS/SCTP', the 'active/passive' status is used to determine the
TLS roles of the endpoints. Following the procedures in [RFC4572], (D)TLS roles of the endpoints. Following the procedures in
the 'active' endpoint will take the TLS client role. [RFC4572], the 'active' endpoint will take the (D)TLS client role.
Once a DTLS connection has been established, if the 'active/passive' Once the DTLS connection has been established, the endpoints MUST NOT
status of the endpoints change (as result of an offer/answer modify (as result of an offer/answer exchange) the TLS roles, or the
transaction) during a session, a new DTLS connection MUST be 'active/passive' status, of the endpoints, unless the underlying
established. Therefore, endpoints SHOULD NOT change the 'active/ transport protocol is also modified (e.g. if an IP address- or port
passive' status during a session, unless they want to establish a new value associated with the transport protocol is modified).
DTLS connection.
If the transport parameters or the key fingerprints change, the If the underlying transport protocol is modified, the endpoints MUST
endpoints MUST establish a new DTLS connection. In such case the establish a new DTLS connection. In such case the 'active/passive'
'active/passive' status of the endpoints will again be determined status of the endpoints will again be determined following the
following the procedures in [RFC4145], and the new status will be procedures in [RFC4145], and the new status will be used to determine
used to determine the TLS roles of the endpoints associated with the the (D)TLS roles of the endpoints associated with the new DTLS
new DTLS connection. connection.
NOTE: The procedure above is identical to the one defined for SRTP- NOTE: The procedure above is identical to the one defined for SRTP-
DTLS in [RFC5763]. DTLS in [RFC5763].
10.4. SDP connection Attribute 9.4. SDP connection Attribute
The SDP connection attribute is used following the procedures in The SDP connection attribute is used following the procedures in
[RFC4145], with the additional SCTP specific considerations described [RFC4145], with the additional SCTP specific considerations described
in this section. in this section.
If the m- line proto value is 'TCP/DTLS/SCTP', an SDP connection If the m- line proto value is 'TCP/DTLS/SCTP', an SDP connection
attribute associated with that m- line applies to both the SCTP attribute associated with that m- line applies to both the SCTP
association and the TCP connection. Therefore, an attribute 'new' association and the TCP connection. Therefore, an attribute 'new'
value indicates that both a new SCTP association, and a new TCP value indicates that both a new SCTP association and new TCP
connection, have to be established, following the procedures in connection have to be established, following the procedures in
[RFC4145]. [RFC4145].
NOTE: This specification does not define a mechanism which allows re- NOTE: This specification does not define a mechanism which allows re-
establishing of a new SCTP association, while maintaining the TCP establishing of a new SCTP association, while maintaining the
connection. underlying TCP connection.
The SDP connection attribute value does not automatically impact an The SDP connection attribute value does not automatically impact an
existing DTLS connection. Section 10.3.3 describes in which cases a existing DTLS connection. Section 9.3.3 describes in which cases a
new DTLS connections will be established. new DTLS connections will have to be re-established.
NOTE: If the m- line proto value is 'SCTP/DTLS', and if the SCTP
association is re-established, the DTLS connection also needs to be
re-established.
11. SDP Offer/Answer Procedures 10. SDP Offer/Answer Procedures
11.1. 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 all m- line proto values ('SCTP',
'SCTP/DTLS', 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP') defined in this 'SCTP/DTLS', 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP') defined in this
specification. specification.
If the m- line proto value is 'SCTP/DTLS', 'UDP/DTLS/SCTP' or If the m- line proto value is 'SCTP/DTLS', 'UDP/DTLS/SCTP' or
'TCP/DTLS/SCTP', each endpoint MUST provide a certificate 'TCP/DTLS/SCTP', each endpoint MUST provide a certificate
fingerprint, using the SDP 'fingerprint' attribute [RFC4572], if the fingerprint, using the SDP 'fingerprint' attribute [RFC4572], if the
skipping to change at page 10, line 46 skipping to change at page 12, line 7
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 NOTE: The procedures apply to a specific m- line describing an SCTP
association. If an offer or answer contains multiple m- lines association. If an offer or answer contains multiple m- lines
describing SCTP associations, the procedures are applied separately describing SCTP associations, the procedures are applied separately
to each m- line. to each m- line.
11.2. 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, if the m- line proto value is 'SCTP/DTLS', 'UDP/DTLS/SCTP'
or 'TCP/DTLS/SCTP', associate an SDP setup attribute or 'TCP/DTLS/SCTP', associate an SDP setup attribute, with an
[Section 10.3], 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, if the m- line proto is 'UDP/DTLS/SCTP' or 'TCP/DTLS/SCTP',
associate an SDP 'sctp-port' attribute [Section 5] with the m- associate an SDP 'sctp-port' attribute with the m- line (see
line; Section 5);
o MUST associate an SDP 'connection' attribute [Section 10.4], with o MUST associate an SDP 'connection' attribute, with a 'new' value,
a 'new' value, with the m- line; and with the m- line (see Section 9.4); and
o MAY associate an SDP 'max-message-size' attribute [Section 6] with o MAY associate an SDP 'max-message-size' attribute with the m- line
the m- line. (see Section 6).
11.3. 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, if the m- line proto value is 'SCTP/DTLS', 'UDP/DTLS/SCTP'
or 'TCP/DTLS/SCTP', associate an SDP 'setup' attribute or 'TCP/DTLS/SCTP', associate an SDP 'setup' attribute, with an
[Section 10.3], with an 'active' or 'passive' value, with the m- 'active' or 'passive' value, with the m- line (see Section 9.3);
line;
o MUST, if the m- line proto is 'UDP/DTLS/SCTP' or 'TCP/DTLS/SCTP', o MUST, if the m- line proto is 'UDP/DTLS/SCTP' or 'TCP/DTLS/SCTP',
associate an SDP 'sctp-port' attribute[Section 5] with the m- associate an SDP 'sctp-port' attribute with the m- line (see
line; and Section 5); and
o MAY associate an SDP 'max-message-size' attribute [Section 6] with o MAY associate an SDP 'max-message-size' attribute with the m- line
the m- line. (see Section 6). The attribute value in the answer is independent
from the value (if present) in the corresponding m- line of the
offer.
Once the answerer has sent the answer, the answerer: Once the answerer has sent the answer, the answerer:
o MUST, if an SCTP association associated with the m- line has yet o MUST, if an SCTP association associated with the m- line has yet
not been established, or if an existing SCTP association is to be not been established, or if an existing SCTP association is to be
re-established, initiate the establishing of the SCTP association; re-established, initiate the establishing of the SCTP association;
and and
o MUST, if the answerer is the 'active' endpoint, and if an DTLS o MUST, if the answerer is the 'active' endpoint, and if an DTLS
connection associated with the m- line is to be established (or connection associated with the m- line is to be established (or
re-established), initiate the establishing of the DTLS connection re-established), initiate the establishing of the DTLS connection
(by sending a ClientHello message). (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 In addition, the answerer MUST NOT establish an SCTP association, or
a DTLS connection, associated with the m- line. a DTLS connection, associated with the m- line.
11.4. 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 When the offerer receives an answer, which contains an m- line with a
non-zero port value, describing an SCTP association, the offerer: non-zero port value, describing an SCTP association, the offerer:
o MUST, if the offerer is the 'active' endpoint, if the m- line o MUST, if the offerer is the 'active' endpoint, if the m- line
proto is 'TCP/DTLS/SCTP', and if a TCP connection used to carry proto value is 'TCP/DTLS/SCTP', and if a TCP connection used to
the SCTP association has yet not been established (or if an carry the SCTP association has not yet been established (or if an
existing TCP connection is to be re-established), initiate the existing TCP connection is to be re-established), initiate the
establishing of the TCP connection; establishing of the TCP connection;
o MUST, if an SCTP association associated with the m- line has yet o MUST, if an SCTP association associated with the m- line has not
not been established (or if an existing SCTP association is to be yet been established (or if an existing SCTP association is to be
re-established), initiate the establishing of the SCTP re-established), initiate the establishing of the SCTP
association; and association; and
o MUST, if the offerer is the 'active' endpoint, and if an DTLS o MUST, if the offerer is the 'active' endpoint, and if a DTLS
connection associated with the m- line is to be established (or if connection associated with the m- line is to be established (or if
an existing DTLS connection is to be re-established), initiate the an existing DTLS connection is to be re-established), initiate the
establishing of the DTLS connection (by sending a ClientHello establishing of the DTLS connection (by sending a ClientHello
message). message).
o NOTE: If the m- line proto value is 'UDP/DTLS/SCTP' or 'TCP/DTLS/
SCTP', the two actions above are performed in switch order, as the
underlying DTLS connection needs to be established before the SCTP
association can be established.
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. connection, associated with the m- line.
11.5. 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 11.2, 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 existing SCTP
association, the offerer MUST associate an SDP connection association, the offerer MUST associate an SDP connection
attribute, with an 'existing' value, with the m- line; and attribute, with an 'existing' 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].
NOTE: Different SCTP association usages might define protocol 11. Multihoming Considerations
procedures etc that need to be performed before an SCTP association
is terminated. Such procedures are outside the scope of this
specification.
12. 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.
If an endpoint removes the IP address [RFC5061] that it offered in If an endpoint removes the IP address [RFC5061] that it offered in
the SDP "c=" line associated with the SCTP association, it MUST send the SDP "c=" line associated with the SCTP association, it MUST send
a new Offer, in which the "c=" line contains an IP address with is a new Offer, in which the "c=" line contains an IP address which is
valid within the SCTP association. valid within the SCTP association.
NOTE: In some network environments, intermediaries performing gate- NOTE: In some network environments, intermediaries performing gate-
and firewall control use the address information in the SDP "c=" and and firewall control using the address information in the SDP "c="
"m=" lines to authorize media, and will not pass media sent using and "m=" lines to authorize media, and will not pass media sent using
other addresses. In such network environment, if an SCTP endpoints other addresses. In such network environments, if an SCTP endpoints
wants to change the address information on which media is sent and wants to change the address information on which media is sent and
received, it needs to send an updated Offer, in which the SDP "c=" received, it needs to send an updated Offer, in which the SDP "c="
and "m=" lines contain the new address information. and "m=" lines contain the new address information.
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 to its upper layer. DTLS does not expose address management of the underlying transport
protocols (UDP or TCP) to its upper layer.
13. NAT Considerations
13.1. General 12. NAT Considerations
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-behave-sctpnat] 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.
13.2. 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 (Interactive Connectivity Establishment) defined for using ICE (Interactive Connectivity Establishment)
[RFC5768] together with SCTP. Such procedures, including the [RFC5245] together with SCTP as transport layer protocol. Such
associated SDP Offer/Answer procedures, are outside the scope of this procedures, including the associated SDP Offer/Answer procedures, are
specification, and might be defined in a future specification. outside the scope of this specification, and might be defined in a
future specification.
14. Examples When the transport layer protocol is UDP (in case of an SCTP
association on top of a DTLS connection on top of UDP), if ICE is
used, the ICE procedures defined in [RFC5245] are used.
14.1. Establishment of UDP/DTLS/SCTP association When the transport layer protocol is TCP (in case of an SCTP
association on top of a DTLS connection on top of TCP), if ICE is
used, the ICE procedures defined in [RFC6544] are used.
13. Examples
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=setup:actpass a=setup:actpass
a=connection:new 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. active or the passive 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=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 passive role.
15. 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. security [RFC4960] defines general SCTP security considerations, while
considerations on SCTP in general, while [RFC6083] defines security [RFC6083] defines security considerations when using DTLS on top of
considerations when using DTLS on top of SCTP. SCTP.
This specification does not introduce new security considerations in This specification does not introduce new security considerations in
addition to those defined in the specifications listed above. addition to those defined in the specifications listed above.
16. IANA Considerations 15. IANA Considerations
16.1. New SDP proto values 15.1. New SDP proto values
[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 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 | 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
16.2. New SDP Attributes 15.2. New SDP Attributes
16.2.1. sctp-port 15.2.1. sctp-port
[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 document defines a new SDP media-level attribute,'sctp-port', as This document defines a new SDP media-level attribute,'sctp-port', as
follows: follows:
Attribute name: sctp-port Attribute name: sctp-port
Type of attribute: media Type of attribute: media
Subject to charset: No Mux category: SPECIAL
Purpose: Indicate the SCTP port value associated Subject to charset: No
with the SDP Media Description. Purpose: Indicate the SCTP port value associated
Appropriate values: Integer with the SDP Media Description.
Contact name: Christer Holmberg Appropriate values: Integer
Contact e-mail: christer.holmberg@ericsson.com Contact name: Christer Holmberg
Reference: RFCXXXX Contact e-mail: christer.holmberg@ericsson.com
Reference: RFCXXXX
16.2.2. max-message-size 15.2.2. max-message-size
[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 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', as follows:
Attribute name: max-message-size Attribute name: max-message-size
Type of attribute: media Type of attribute: media
Subject to charset: No Mux category: SPECIAL
Purpose: Indicate the maximum message size that Subject to charset: No
an SCTP endpoint is willing to receive Purpose: Indicate the maximum message size that
on the SCTP association associated an SCTP endpoint is willing to receive
with the SDP Media Description. on the SCTP association associated
Appropriate values: Integer with the SDP Media Description.
Contact name: Christer Holmberg Appropriate values: Integer
Contact e-mail: christer.holmberg@ericsson.com Contact name: Christer Holmberg
Reference: RFCXXXX Contact e-mail: christer.holmberg@ericsson.com
Reference: RFCXXXX
16.3. 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', 'SCTP/DTLS', 'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP' protocol
identifiers. Each "fmt" value describes the usage of an entire SCTP identifiers. Each "fmt" value describes the usage of an entire SCTP
association, including all SCTP streams associated with the SCTP association, 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
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 |
|----------------------------------------------------------|
[RFC EDITOR NOTE: Please hold the publication of this draft
until draft-ietf-rtcweb-data-protocol has been published as an RFC.
Then, replace the reference to draft-ietf-rtcweb-data-protocol
with the RFC number.]
Figure 1 Figure 1
17. 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 for their comments and useful feedback. Kyzivat, Michael Tuexen, Juergen Stoetzer-Bradler, Flemming Andreasen
and Ari Keranen for their comments and useful feedback.
18. Change Log 17. Change Log
[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-12
o Mux category rules added for new SDP attributes.
o Reference to draft-ietf-mmusic-sdp-mux-attributes added.
o Changes based on comments from Roman Shpount:
o - Specify that fingerprint or setup roles must not be modified,
unless underlying transport protocol is also modified.
o Changes based on comments from Ari Keranen:
o - Editorial corrections.
o Changes based on comments from Flemming Andreasen:
o - Clarify that, if UDP/DTLS/SCTP or TCP/DTLS/SCTP is used, the
DTLS connection is established before the SCTP association.
o - Clarify that max-message-size value is given in bytes, and that
different values can be used per direction.
o - Section on fmtp attribute removed.
o - Editorial corrections.
Changes from draft-ietf-mmusic-sctp-sdp-11 Changes from draft-ietf-mmusic-sctp-sdp-11
o Example added. o Example added.
Changes from draft-ietf-mmusic-sctp-sdp-10 Changes from draft-ietf-mmusic-sctp-sdp-10
o SDP max-message-size attribute added to IANA considerations. o SDP max-message-size attribute added to IANA considerations.
o Changes based on comments from Paul Kyzivat: o Changes based on comments from Paul Kyzivat:
skipping to change at page 18, line 25 skipping to change at page 21, line 5
o SDP max-message-size attribute defined: o SDP max-message-size attribute defined:
o - Attribute definition. o - Attribute definition.
o - SDP Offer/Answer procedures. o - SDP Offer/Answer procedures.
o Text about SDP direction attributes added. o Text about SDP direction attributes added.
o Text about TLS role determination added. o Text about TLS role determination added.
19. References 18. References
19.1. Normative References 18.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264, June with Session Description Protocol (SDP)", RFC 3264, June
2002. 2002.
[RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in
the Session Description Protocol (SDP)", RFC 4145, the Session Description Protocol (SDP)", RFC 4145,
skipping to change at page 19, line 21 skipping to change at page 21, line 47
[RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M. [RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
Kozuka, "Stream Control Transmission Protocol (SCTP) Kozuka, "Stream Control Transmission Protocol (SCTP)
Dynamic Address Reconfiguration", RFC 5061, September Dynamic Address Reconfiguration", RFC 5061, September
2007. 2007.
[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,
May 2008. May 2008.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008. (TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012. Security Version 1.2", RFC 6347, January 2012.
[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, RFC Specifications and Registration Procedures", BCP 13, RFC
6838, January 2013. 6838, January 2013.
[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-06 (work in progress), November 2014. dtls-encaps-09 (work in progress), January 2015.
19.2. Informative References [I-D.ietf-mmusic-sdp-mux-attributes]
Nandakumar, S., "A Framework for SDP Attributes when
Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-08
(work in progress), January 2015.
18.2. Informative References
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, September 1981.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245, April
2010.
[RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
for Establishing a Secure Real-time Transport Protocol for Establishing a Secure Real-time Transport Protocol
(SRTP) Security Context Using Datagram Transport Layer (SRTP) Security Context Using Datagram Transport Layer
Security (DTLS)", RFC 5763, May 2010. Security (DTLS)", RFC 5763, May 2010.
[RFC5768] Rosenberg, J., "Indicating Support for Interactive
Connectivity Establishment (ICE) in the Session Initiation
Protocol (SIP)", RFC 5768, April 2010.
[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, January 2011. Transmission Protocol (SCTP)", RFC 6083, January 2011.
[RFC6544] Rosenberg, J., Keranen, A., Lowekamp, B., and A. Roach,
"TCP Candidates with Interactive Connectivity
Establishment (ICE)", RFC 6544, March 2012.
[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, May 2013. to End-Host Communication", RFC 6951, May 2013.
[I-D.ietf-behave-sctpnat] [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",
draft-ietf-behave-sctpnat-09 (work in progress), September draft-ietf-behave-sctpnat-09 (work in progress), September
2013. 2013.
 End of changes. 103 change blocks. 
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