draft-ietf-mmusic-sctp-sdp-08.txt   draft-ietf-mmusic-sctp-sdp-09.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: June 1, 2015 Ericsson Expires: June 8, 2015 Ericsson
November 28, 2014 December 5, 2014
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-08 draft-ietf-mmusic-sctp-sdp-09
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' and 'DTLS/SCTP'. 'SCTP/DTLS' and 'DTLS/SCTP'.
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 June 1, 2015. This Internet-Draft will expire on June 8, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 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
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
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 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
4.5. 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
6. SDP 'fmtp' Attribute . . . . . . . . . . . . . . . . . . . . 7 6. SDP 'max-message-size' Attribute . . . . . . . . . . . . . . 7
6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7 6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 7 6.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. SCTP Association Management . . . . . . . . . . . . . . . . . 7 7. SDP 'fmtp' Attribute . . . . . . . . . . . . . . . . . . . . 7
7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7 7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.2. SDP setup Attribute . . . . . . . . . . . . . . . . . . . 7 7.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.3. SDP connection Attribute . . . . . . . . . . . . . . . . 8 8. SCTP Association Management . . . . . . . . . . . . . . . . . 8
8. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 8
8.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 8 8.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.2. Generating the Initial SDP Offer . . . . . . . . . . . . 9 8.2. SDP sendrecv/sendonly/sendrecv/inactive Attribute . . . . 8
8.3. Generating the SDP Answer . . . . . . . . . . . . . . . . 9 8.3. SDP setup Attribute . . . . . . . . . . . . . . . . . . . 8
8.4. Offerer Processing of the SDP Answer . . . . . . . . . . 10 8.3.1. General . . . . . . . . . . . . . . . . . . . . . . . 8
8.5. Modifying the Session . . . . . . . . . . . . . . . . . . 10 8.3.2. SCTP Association Initiation . . . . . . . . . . . . . 9
9. Multihoming Considerations . . . . . . . . . . . . . . . . . 10 8.3.3. TLS Role Determination . . . . . . . . . . . . . . . 9
10. NAT Considerations . . . . . . . . . . . . . . . . . . . . . 11 8.4. SDP connection Attribute . . . . . . . . . . . . . . . . 9
10.1. General . . . . . . . . . . . . . . . . . . . . . . . . 11 9. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 10
10.2. ICE Considerations . . . . . . . . . . . . . . . . . . . 11 9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 10
11. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 11 9.2. Generating the Initial SDP Offer . . . . . . . . . . . . 11
12. Security Considerations . . . . . . . . . . . . . . . . . . . 12 9.3. Generating the SDP Answer . . . . . . . . . . . . . . . . 11
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 9.4. Offerer Processing of the SDP Answer . . . . . . . . . . 12
13.1. New SDP proto values . . . . . . . . . . . . . . . . . . 12 9.5. Modifying the Session . . . . . . . . . . . . . . . . . . 12
13.2. New SDP Attribute . . . . . . . . . . . . . . . . . . . 12 10. Multihoming Considerations . . . . . . . . . . . . . . . . . 13
13.3. association-usage Name Registry . . . . . . . . . . . . 13 11. NAT Considerations . . . . . . . . . . . . . . . . . . . . . 13
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 11.1. General . . . . . . . . . . . . . . . . . . . . . . . . 13
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 11.2. ICE Considerations . . . . . . . . . . . . . . . . . . . 13
15.1. Normative References . . . . . . . . . . . . . . . . . . 14
15.2. Informative References . . . . . . . . . . . . . . . . . 15 12. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 13. Security Considerations . . . . . . . . . . . . . . . . . . . 14
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
14.1. New SDP proto values . . . . . . . . . . . . . . . . . . 14
14.2. New SDP Attribute . . . . . . . . . . . . . . . . . . . 14
14.3. association-usage Name Registry . . . . . . . . . . . . 15
15. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
16. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 16
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
17.1. Normative References . . . . . . . . . . . . . . . . . . 16
17.2. Informative References . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
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 (Transmission Control Protocol) [RFC5246]
streams. Connection-Oriented Media Transport over the Transport streams. Connection-Oriented Media Transport over the Transport
Layer Security (TLS) Protocol in the Session Description Protocol Layer Security (TLS) Protocol in the Session Description Protocol
skipping to change at page 6, line 22 skipping to change at page 6, line 26
sctp-port = port sctp-port = port
udp-port = port udp-port = port
sctp-fmt = association-usage sctp-fmt = association-usage
association-usage = token association-usage = token
4.5. Example 4.5. Example
TEMP:
m=application 12345 DTLS/SCTP webrtc-datachannel
a=max-message-size=100000
m=application 12345 DTLS/SCTP webrtc-datachannel m=application 12345 DTLS/SCTP webrtc-datachannel
a=fmtp:webrtc-datachannel max-message-size=100000 a=fmtp:webrtc-datachannel 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 descriptor (m-
line) with a 'DTLS/SCTP' proto value, in which case the m- line port line) with a 'DTLS/SCTP' proto value, in which case the m- line port
value indicates the port of the underlying transport protocol (UDP or value indicates the port of the underlying transport protocol (UDP or
TCP). TCP).
If the SDP sctp-port attribute is not present, the default value is TEMP: If the SDP sctp-port attribute is not present, the m- line
5000. SHOULD be discarded. If the SDP sctp-port attribute is not present,
the default value is 5000.
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
sctp-port-attr = "a=sctp-port:" portnumber sctp-port-attr = "a=sctp-port:" port
port-number = port
port = 1*DIGIT port = 1*DIGIT
6. SDP 'fmtp' 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-
line to indicate the maximum message size that an SCTP endpoint is
willing to receive on the SCTP association associated with the m-
line.
The remote peer MUST assume that larger messages will be rejected by
the SCTP endpoint. SCTP endpoints need to decide on appropriate
behaviour in case a message that exceeds the maximum size needs to be
sent.
If the SDP 'max-message-size' attribute contains a maximum message
size value of zero, it indicates the SCTP endpoint will handle
messages of any size, subject to memory capacity etc.
If the SDP 'max-message-size' attribute is not present, the default
value is 64K.
6.2. Syntax
max-message-size-attr = "a=max-message-size:" max-message-size
max-message-size = 1*DIGIT
7. SDP 'fmtp' Attribute
7.1. General
The SDP 'fmtp' attribute can be used with an m- line, associated with The SDP 'fmtp' attribute can be used with an m- line, associated with
an SCTP association, to indicate the maximum message size that an an SCTP association, to indicate the maximum message size that an
SCTP endpoint is willing to receive, for a particular SCTP SCTP endpoint is willing to receive, for a particular SCTP
association usage, on that SCTP association. association usage, on that SCTP association.
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
behaviour in case a message that exceeds the maximum size needs to be behaviour in case a message that exceeds the maximum size needs to be
sent. sent.
If the SDP 'fmtp' attribute contains a maximum message size value of If the SDP 'fmtp' attribute contains a maximum message size value of
zero, it indicates the SCTP endpoint will handle messages of any zero, it indicates the SCTP endpoint will handle messages of any
size, subject to memory capacity etc. size, subject to memory capacity etc.
If the SDP 'fmtp' attribute is not present, the default value is 64K. If the SDP 'fmtp' attribute is not present, the default value is 64K.
6.2. Syntax NOTE: This specification only defines the usage of the SDP 'max-
message-size' attribute when associated with an m- line containing
one of the following proto field values: 'SCTP', 'SCTP/DTLS' or
'DTLS/SCTP'. Usage of the attribute with other proto field values
needs to be defined in a separate specification.
7.2. Syntax
sctpmap-attr = "a=fmtp:" association-usage [max-message-size] sctpmap-attr = "a=fmtp:" association-usage [max-message-size]
max-message-size = "max-message-size" EQUALS 1*DIGIT max-message-size = "max-message-size" EQUALS 1*DIGIT
7. SCTP Association Management 8. SCTP Association Management
7.1. General 8.1. 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 endpoints 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.
7.2. SDP setup Attribute 8.2. SDP sendrecv/sendonly/sendrecv/inactive Attribute
This specification does not define any semantics for the SDP
direction attributes [RFC4566]. Specifications for an individual
SCTP association usage MAY define how the attributes can be used with
that association usage. If the semantics of these attributes for an
SCTP association usage has not been defined, SDP direction attributes
MUST be discarded if present.
8.3. SDP setup Attribute
8.3.1. General
The SDP setup attribute is used to determine the 'active/passive'
status of the endpoints, following the procedures for TCP in
[RFC4145].
8.3.2. 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].
If the m- line proto field value is 'DTLS/SCTP', and if SCTP is
carried on top of TCP, only the 'active' endpoint will initiate the
TCP connection, following the procedures in [RFC4145], while both
endpoints will initiate the SCTP association carried on top of the
TCP connection.
8.3.3. TLS Role Determination
If the m- line proto field value is 'SCTP/DTLS' or 'DTLS/SCTP', the If the m- line proto field value is 'SCTP/DTLS' or 'DTLS/SCTP', the
SDP setup attribute [RFC4145] is used to determine the TLS roles, 'active/passive' status is used to determine the TLS roles.
following the proceduresin [RFC4572] (the 'active' endpoint will take Following the procedures in [RFC4572], the 'active' endpoint will
the TLS client role). take the TLS client role.
The SDP setup attribute is not used to determine which endpoint Once a DTLS connection has been established, if the 'active/passive'
initiates the SCTP association. Instead, both endpoints MUST status of the endpoints change during a session, a new DTLS
initiate the SCTP association, and MUST use the same SCTP port as connection MUST be established. Therefore, endpoints SHOULD NOT
client port and server port (in order to prevent two separate SCTP change the 'active/passive' status in subsequent offers and answers,
associations from being established). unless they want to establish a new DTLS connection.
However, if the proto field value is 'DTLS/SCTP', and the transport If the transport parameters or the key fingerprints change, the
layer protocol is TCP (SCTP is carried on top of TCP), the SDP setup endpoints MUST establish a new DTLS connection. In such case the
attribute is also used to negotiate which endpoint will initiate the 'active/passive' status of the endpoints will again be determined
TCP connection (send TCP SYN), following the procedures in [RFC4145]. following the procedures in [RFC4145], and the new status will be
used to determine the TLS roles associated with the new DTLS
connection.
7.3. SDP connection Attribute NOTE: The procedure above is identical to the one defined for SRTP-
DTLS in [RFC5763].
NOTE: A new DTLS connection needs to be established if the transport
parameters or the key fingerprints change.
8.4. 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.
In general, the SDP connection attribute only applies to an SCTP The SDP connection attribute only applies to an SCTP association and,
association. Therefore, if the m- line proto field value is 'DTLS/ if the m- line proto field value is 'DTLS/SCTP', also to the TCP
SCTP', a connection attribute 'new' value will not automatically re- connection which is used to carry the SCTP association. An attribute
establish an existing DTLS connection, unless some DTLS properties 'new' value indicates that a new SCTP association (and, if
are also changed in a way which require the DTLS connection to be re- applicable, the TCP connection, have to be established, following the
established. procedures in [RFC4145].
However, if the m- line proto field value is 'SCTP/DTLS', if the SCTP OPEN ISSUE #3: We need to determine whether the SDP connection
association is re-established, the DTLS connection also needs to be attribute only applies to the transport-layer protocol, and not e.g.
re-established. to an SCTP assocation carried on top of UDP or TCP.
The SDP connection attribute value does not impact an existing DTLS
connection. Section 8.3.3 describes in which cases a new DTLS
connections will be established.
NOTE: if the m- line proto field value is 'SCTP/DTLS', and if the
SCTP association is re-established, the DTLS connection also needs to
be re-established.
OPEN ISSUE #2: Verify that the above statement regarding 'SCTP/DTLS' OPEN ISSUE #2: Verify that the above statement regarding 'SCTP/DTLS'
is correct. is correct.
8. SDP Offer/Answer Procedures 9. SDP Offer/Answer Procedures
8.1. General 9.1. 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 protocol identifier values stated, the procedures apply to all m- line proto values ('SCTP',
('SCTP', 'SCTP/DTLS' and 'DTLS/SCTP') defined in this specification. 'SCTP/DTLS' and 'DTLS/SCTP') defined in this specification.
If the m- line proto value is 'SCTP/DTLS' or 'DTLS/SCTP', each If the m- line proto value is 'SCTP/DTLS' or 'DTLS/SCTP', each
endpoint MUST provide a certificate fingerprint, using the SDP endpoint MUST provide a certificate fingerprint, using the SDP
'fingerprint' attribute [RFC4145], if the endpoint supports, and is 'fingerprint' attribute [RFC4145], if the endpoint supports, and is
willing to use, a cipher suite with an associated certificate. willing to use, a cipher suite with an 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 NOTE: The procedures apply to a specific m- line describing an SCTP
association. If an offer or answer contains multiple m- line association. If an offer or answer contains multiple m- line
describing SCTP associations, the procedures are applied separately describing SCTP associations, the procedures are applied separately
to each m- line. The procedures related to SDP attributes apply to to each m- line.
attributes associated with the m- line describing the SCTP
association.
EDITOR'S NOTE: The offer/answer proceudres for the max-message-size 9.2. Generating the Initial SDP Offer
value still need to be added.
8.2. Generating the Initial SDP Offer When the offerer creates an initial offer, the offerer:
When the offerer creates an offer, if the m- line proto field value o MUST, if the m- line proto field value is 'SCTP/DTLS' or 'DTLS/
is 'SCTP/DTLS' or 'DTLS/SCTP', the offerer MUST insert an SDP setup SCTP', associate an SDP setup attribute [Section 8.3], with an
attribute in the offer, in order to determine the TLS roles, and in 'actpass' value, with the m- line;
cases where SCTP is transported on TCP, determine which endpoint is
responsible for establishing the TCP connection [Section 7.2].
The offerer MAY insert an SDP connection attribute, with a 'new' o MUST, if the m- line proto field is 'DTLS/SCTP', associate an SDP
value, in the offer. sctp-port attribute[Section 5] with the m- line;
If the value of the m- line proto field is set to 'DTLS/SCTP', the o MUST associate an SDP 'connection' attribute [Section 8.4], with a
offerer MAY insert an SDP sctp-port attribute, with a value 'new' value, with the m- line; and
indicating the local SCTP port, in the offer.
8.3. Generating the SDP Answer o MAY associate an SDP 'max-message-size' attribute [Section 7] with
the m- line.
9.3. 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, it MUST insert a corresponding m- describing an SCTP association, if the answerer accepts the m- line
line, with an identical m- line proto field value, in the associated it:
answer, following the procedures in [RFC3264].
If the answerer accepts the offered m- line, it assigns the other m- o MUST insert a corresponiding m- line in the answer, with an
line field values according to Section 4. identical m- line proto value [RFC3264];
If the offer contains an SDP setup attribute, the answerer MUST o MUST, if the m- line proto field value is 'SCTP/DTLS' or 'DTLS/
insert a setup attribute in the answer, following the rules in SCTP', associate an SDP setup attribute [Section 8.3], with an
[RFC4572] and [RFC4145] (if applicable). 'active' or 'passive' value, with the m- line;
If the value of the m- line proto field is set to 'DTLS/SCTP', the o MUST, if the m- line proto field is 'DTLS/SCTP', associate an SDP
answerer MAY insert an SDP sctp-port attribute, with a value sctp-port attribute[Section 5] with the m- line;
indicating the local SCTP port, in the answer.
Once the answerer has sent the answer, if the SCTP association o MAY associate an SDP 'max-message-size' attribute [Section 7] with
associated with the m- line has yet not been established, or if an the m- line.
existing SCTP association is to be re-established, the answer MUST
start establishing the SCTP association towards the peer. Once the answerer has sent the answer, the answerer:
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
re-established, initiate the establishing of the SCTP association;
and
o MUST, if the answerer is the 'active' endpoint, and if an DTLS
connection associated with the m- line is to be established (or
re-established), initiate the establishing of the DTLS connection
(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 value to the port field of the corresponding m- line in assign a zero port value to the corresponding m- line in the answer.
the answer. In addition, the answerer MUST NOT insert an SDP setup In addition, the answerer MUST NOT establish an SCTP association, or
attribute, or an SDP sctp-port attribute, in the answer. a DTLS connection, associated with the m- line.
8.4. Offerer Processing of the SDP Answer 9.4. Offerer Processing of the SDP Answer
When the offerer receives an answer, if the SCTP association When the offerer receives an answer, which contains an m- line with a
associated with the m- line has not yet been established, or if an non-zero port value, describing an SCTP association, the offerer:
existing SCTP association is to be re-established, the offerer MUST
start establishing the SCTP association towards the peer.
If the m- line port field value in the answer is zero, the offerer o MUST, if an SCTP association associated with the m- line has yet
MUST terminate the SCTP association (if it exists) associated with not been established, or if an existing SCTP association is to be
the m- line. re-established, initiate the establishing of the SCTP association;
and
8.5. Modifying the Session o MUST, if the offerer is the 'active' endpoint, and if an DTLS
connection associated with the m- line is to be established (or
re-established), initiate the establishing of the DTLS connection
(by sending a ClientHello message).
When an offerer sends an updated offer, in order to modify a If the m- line in the answer contains a zero port value, the offerer
previously negotiated SCTP association, it follows the rules in MUST NOT establish an SCTP association, or a DTLS connection,
Section 8.2, with the following exceptions: associated with the m- line.
If the offerer wants to re-establish an existing SCTP association 9.5. Modifying the Session
associated with the m- line, the offerer MUST insert an SDP
connection attribute, with a 'new' value, in the offer.
If the m- line proto field value is 'SCTP/DTLS' or 'DTLS/SCTP', and When an offerer sends an updated offer, in order to modify a
the offer is not intended to re-establish the DTLS connection, the previously established SCTP assiciation, it follows the procedures in
offerer MUST NOT insert a SDP setup attribute with a value that Section 9.2, with the following exceptions:
changes the previously determined TLS roles in the offer.
If the offerer wants to disable a previously established SCTP o Unless the offerer wants to re-establish an existing SCTP
association, it MUST set the port value of the m- line associated association, the offerer MUST associate an SDP connection
with the SCTP association to zero, following the procedures in attribute, with an 'existing' value, with the m- line; and
[RFC3264]. The offerer MUST NOT insert an SDP setup attribute, or an
SDP sctp-port attribute, in the offer.
NOTE: Different SCTP association applications might define protocol o If the offerer wants to disable a previously established SCTP
association, it MUST assign a zero port value to the m- line
associated with the SCTP association, following the procedures in
[RFC3264].
NOTE: Different SCTP association usages might define protocol
procedures etc that need to be performed before an SCTP association procedures etc that need to be performed before an SCTP association
is terminated. Such procedures are outside the scope of this is terminated. Such procedures are outside the scope of this
specification. specification.
9. Multihoming Considerations 10. 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
skipping to change at page 11, line 24 skipping to change at page 13, line 31
and firewall control use the address information in the SDP "c=" and and firewall control use the address information in the SDP "c=" and
"m=" lines to authorize media, and will not pass media sent using "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 environment, 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 to its upper layer.
10. NAT Considerations 11. NAT Considerations
10.1. General 11.1. 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.
10.2. ICE Considerations 11.2. 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 ICE (Interactive Connectivity Establishment) defined for using ICE ICE (Interactive Connectivity Establishment)
[RFC5768] together with SCTP. Such procedures, including the [RFC5768] together with SCTP. Such procedures, including the
associated SDP Offer/Answer procedures, are outside the scope of this associated SDP Offer/Answer procedures, are outside the scope of this
specification, and might be defined in a future specification. specification, and might be defined in a future specification.
11. Examples 12. Examples
TODO: ADD EXAMPLES HERE TODO: ADD EXAMPLES HERE
12. Security Considerations 13. 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. security
considerations on SCTP in general, while [RFC6083] defines security considerations on SCTP in general, while [RFC6083] defines security
considerations when using DTLS on top of SCTP. considerations when using DTLS on top of 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.
13. IANA Considerations 14. IANA Considerations
13.1. New SDP proto values 14.1. 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 | DTLS/SCTP | [RFCXXXX] | | proto | DTLS/SCTP | [RFCXXXX] |
+-------+-----------+-----------+ +-------+-----------+-----------+
Table 1: SDP "proto" field values Table 1: SDP "proto" field values
13.2. New SDP Attribute 14.2. New SDP Attribute
[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 Subject to charset: No
Purpose: Indicate the SCTP port value associated Purpose: Indicate the SCTP port value associated
with the SDP Media Description. with the SDP Media Description.
Appropriate values: Integer Appropriate values: Integer
Contact name: Christer Holmberg Contact name: Christer Holmberg
Contact e-mail: christer.holmberg@ericsson.com Contact e-mail: christer.holmberg@ericsson.com
Reference: RFCXXXX Reference: RFCXXXX
13.3. association-usage Name Registry 14.3. 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' and 'DTLS/SCTP' protocol identifiers. Each "fmt" 'SCTP', 'SCTP/DTLS' and 'DTLS/SCTP' protocol identifiers. Each "fmt"
value describes the usage of an entire SCTP association, including value describes the usage of an entire SCTP association, including
all SCTP streams associated with the SCTP association. all SCTP streams associated with the SCTP association.
skipping to change at page 14, line 12 skipping to change at page 16, line 12
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 |
-+----------------------------------------------------------| -+----------------------------------------------------------|
Figure 1 Figure 1
14. Acknowledgments 15. 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 for their comments and useful feedback.
15. References 16. Change Log
15.1. Normative References [RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-ietf-mmusic-sctp-sdp-08
o Default SCTP port removed
o - Usage of SDP sctp-port attribute mandatory
o SDP max-message-size attribute defined
o - Attribute definition
o - SDP Offer/Answer procedures
o Text about SDP direction attributes added
o Text about TLS role determination added
17. References
17.1. 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 15, line 24 skipping to change at page 17, line 43
[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-06 (work in progress), November 2014.
15.2. Informative References 17.2. Informative References
[RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
Transport Layer Security (DTLS) for Stream Control for Establishing a Secure Real-time Transport Protocol
Transmission Protocol (SCTP)", RFC 6083, January 2011. (SRTP) Security Context Using Datagram Transport Layer
Security (DTLS)", RFC 5763, May 2010.
[RFC5768] Rosenberg, J., "Indicating Support for Interactive [RFC5768] Rosenberg, J., "Indicating Support for Interactive
Connectivity Establishment (ICE) in the Session Initiation Connectivity Establishment (ICE) in the Session Initiation
Protocol (SIP)", RFC 5768, April 2010. Protocol (SIP)", RFC 5768, April 2010.
[RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram
Transport Layer Security (DTLS) for Stream Control
Transmission Protocol (SCTP)", RFC 6083, January 2011.
[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. 64 change blocks. 
142 lines changed or deleted 267 lines changed or added

This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/