draft-ietf-mmusic-sctp-sdp-19.txt   draft-ietf-mmusic-sctp-sdp-20.txt 
MMUSIC C. Holmberg MMUSIC C. Holmberg
Internet-Draft Ericsson Internet-Draft Ericsson
Intended status: Standards Track R. Shpount Intended status: Standards Track R. Shpount
Expires: April 29, 2017 TurboBridge Expires: July 3, 2017 TurboBridge
S. Loreto S. Loreto
G. Camarillo G. Camarillo
Ericsson Ericsson
October 26, 2016 December 30, 2016
Session Description Protocol (SDP) Offer/Answer Procedures For Stream Session Description Protocol (SDP) Offer/Answer Procedures For Stream
Control Transmission Protocol (SCTP) over Datagram Transport Layer Control Transmission Protocol (SCTP) over Datagram Transport Layer
Security (DTLS) Transport. Security (DTLS) Transport.
draft-ietf-mmusic-sctp-sdp-19 draft-ietf-mmusic-sctp-sdp-20
Abstract Abstract
The Stream Control Transmission Protocol (SCTP) is a transport The Stream Control Transmission Protocol (SCTP) is a transport
protocol used to establish associations between two endpoints. protocol used to establish associations between two endpoints.
draft-ietf-tsvwg-sctp-dtls-encaps-09 specifies how SCTP can be used draft-ietf-tsvwg-sctp-dtls-encaps-09 specifies how SCTP can be used
on top of the Datagram Transport Layer Security (DTLS) protocol, on top of the Datagram Transport Layer Security (DTLS) protocol,
referred to as SCTP-over-DTLS. referred to as SCTP-over-DTLS.
This specification defines the following new Session Description This specification defines the following new Session Description
skipping to change at page 1, line 46 skipping to change at page 1, line 46
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 29, 2017. This Internet-Draft will expire on July 3, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(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
skipping to change at page 2, line 29 skipping to change at page 2, line 29
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. SCTP Terminology . . . . . . . . . . . . . . . . . . . . . . 4 3. SCTP Terminology . . . . . . . . . . . . . . . . . . . . . . 4
4. SDP Media Descriptions . . . . . . . . . . . . . . . . . . . 4 4. SDP Media Descriptions . . . . . . . . . . . . . . . . . . . 4
4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Protocol Identifiers . . . . . . . . . . . . . . . . . . 5 4.2. Protocol Identifiers . . . . . . . . . . . . . . . . . . 5
4.3. Media Format Management . . . . . . . . . . . . . . . . . 5 4.3. Media Format Management . . . . . . . . . . . . . . . . . 5
4.4. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.4. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.4.1. General . . . . . . . . . . . . . . . . . . . . . . . 6 4.4.1. General . . . . . . . . . . . . . . . . . . . . . . . 6
4.4.2. SDP Media Description values . . . . . . . . . . . . 6 4.4.2. SDP Media Description values . . . . . . . . . . . . 6
4.5. Example . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.5. Example . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. SDP 'sctp-port' Attribute . . . . . . . . . . . . . . . . . . 6 5. SDP 'sctp-port' Attribute . . . . . . . . . . . . . . . . . . 6
5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.3. Mux Category . . . . . . . . . . . . . . . . . . . . . . 7 5.3. Mux Category . . . . . . . . . . . . . . . . . . . . . . 7
6. SDP 'max-message-size' Attribute . . . . . . . . . . . . . . 8 6. SDP 'max-message-size' Attribute . . . . . . . . . . . . . . 8
6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 8 6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 8 6.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 8
skipping to change at page 3, line 41 skipping to change at page 3, line 41
Protocol (SDP) [RFC4145] specifies a general mechanism for describing Protocol (SDP) [RFC4145] specifies a general mechanism for describing
and establishing TCP [RFC0793] streams. Connection-Oriented Media and establishing TCP [RFC0793] streams. Connection-Oriented Media
Transport over the Transport Layer Security (TLS) Protocol in SDP Transport over the Transport Layer Security (TLS) Protocol in SDP
[RFC4572] extends RFC4145 [RFC4145] for describing TCP-based media [RFC4572] extends RFC4145 [RFC4145] for describing TCP-based media
streams that are protected using TLS. streams that are protected using TLS.
The Stream Control Transmission Protocol (SCTP) [RFC4960] is a The Stream Control Transmission Protocol (SCTP) [RFC4960] is a
transport protocol used to establish associations between two transport protocol used to establish associations between two
endpoints. endpoints.
The Stream Control Transmission Protocol (SCTP) [RFC4960] is a [I-D.ietf-tsvwg-sctp-dtls-encaps] specifies how SCTP can be used on
transport protocol used to establish associations between two top of the Datagram Transport Layer Security (DTLS) protocol,
endpoints. [I-D.ietf-tsvwg-sctp-dtls-encaps] specifies how SCTP can referred to as SCTP-over-DTLS.
be used on top of the Datagram Transport Layer Security (DTLS)
protocol, referred to as SCTP-over-DTLS.
This specification defines the following new Session Description This specification defines the following new Session Description
Protocol (SDP) [RFC4566] protocol identifiers (proto Protocol (SDP) [RFC4566] protocol identifiers (proto
values):'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP'. This specification also values):'UDP/DTLS/SCTP' and 'TCP/DTLS/SCTP'. This specification also
specifies how to use the new proto values with the SDP Offer/Answer specifies how to use the new proto values with the SDP Offer/Answer
mechanism [RFC3264] for negotiating SCTP-over-DTLS associations. mechanism [RFC3264] for negotiating SCTP-over-DTLS associations.
NOTE: Due to the characteristics of TCP, usage of 'TCP/DTLS/SCTP' NOTE: Due to the characteristics of TCP, usage of 'TCP/DTLS/SCTP'
will always force ordered and reliable delivery of the SCTP packets, will always force ordered and reliable delivery of the SCTP packets,
which limits the usage of the SCTP options. Therefore, it is which limits the usage of the SCTP options. Therefore, it is
skipping to change at page 5, line 27 skipping to change at page 5, line 27
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 association on top of UDP, as defined in Section 7. top of a DTLS association on top of UDP, as defined in Section 7.
o The 'TCP/DTLS/SCTP' proto value describes an SCTP association on o The 'TCP/DTLS/SCTP' proto value describes an SCTP association on
top of a DTLS association on top of TCP, as defined in Section 8. top of a DTLS association on top of TCP, as defined in Section 8.
4.3. Media Format Management 4.3. Media Format Management
[RFC4566] defines that specifications defining new proto values must [RFC4566] defines that specifications defining new proto values must
define the rules by which their media format (fmt) namespace is define the rules by which their media format (fmt) namespace is
managed. Use of an existing MIME subtype for the format is managed.
encouraged. If no MIME subtype exists, it is recommended that a
suitable one is registered through the IETF process defined in
[RFC6838] and [RFC4289] by production of, or reference to, a
standards-track RFC that defines the transport protocol for the
format.
An m- line with a proto value of 'UDP/DTLS/SCTP' or 'TCP/DTLS/SCTP' An m- line with a proto value of 'UDP/DTLS/SCTP' or 'TCP/DTLS/SCTP'
always describes a single SCTP association. always describes a single SCTP association.
In addition, such m- line MUST further indicate the application-layer In addition, such m- line MUST further indicate the application-layer
protocol using an 'fmt' identifier. There MUST be exactly one 'fmt' protocol using an 'fmt' identifier. There MUST be exactly one 'fmt'
value per m- line associated with the proto values defined in this value per m- line associated with the proto values defined in this
specification. The "fmt" namespace associated with those proto specification. The "fmt" namespace associated with those proto
values describes the generic application usage of the entire SCTP values describes the generic application usage of the entire SCTP
association, including the associated SCTP streams. association, including the associated SCTP streams.
Section 15.3 defines the IANA registry for the media format
namespace.
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. [I-D.ietf-mmusic-data-channel-sdpneg] defines a specification. [I-D.ietf-mmusic-data-channel-sdpneg] defines a
mechanism for negotiating individual SCTP streams used to realize mechanism for negotiating individual SCTP streams used to realize
WebRTC data channels [I-D.ietf-rtcweb-data-channel]. WebRTC data channels [I-D.ietf-rtcweb-data-channel].
4.4. Syntax 4.4. Syntax
4.4.1. General 4.4.1. General
This section defines the values that can be used within an SDP media This section defines the values that can be used within an SDP media
description ("m=" line) associated with an SCTP-over-DTLS description ("m=" line) associated with an SCTP-over-DTLS
association. association.
This specification creates an IANA registry for 'association-usage' This specification creates an IANA registry for 'association-usage'
values. values.
4.4.2. SDP Media Description values 4.4.2. SDP Media Description values
skipping to change at page 6, line 31 skipping to change at page 6, line 28
<proto>: "UDP/DTLS/SCTP" or "TCP/DTLS/SCTP" <proto>: "UDP/DTLS/SCTP" or "TCP/DTLS/SCTP"
<port>: UDP port number (for "UDP/DTLS/SCTP") <port>: UDP port number (for "UDP/DTLS/SCTP")
TCP port number (for ""UDP/DTLS/SCTP") TCP port number (for ""UDP/DTLS/SCTP")
<fmt>: a string denoting the association-usage, <fmt>: a string denoting the association-usage,
limited to the syntax of a 'token' as limited to the syntax of a 'token' as
defined in RFC4566. defined in RFC4566.
4.5. Example 4.5. Example
m=application 12345 UDP/DTLS/SCTP webrtc-datachannel m=application 12345 UDP/DTLS/SCTP webrtc-datachannel
a=max-message-size: 100000 a=max-message-size:100000
5. SDP 'sctp-port' Attribute 5. SDP 'sctp-port' Attribute
5.1. General 5.1. General
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 description (m- The attribute can be associated with an SDP media description (m-
line) with a 'UDP/DTLS/SCTP' or a 'TCP/DTLS/SCTP' proto value. In line) with a 'UDP/DTLS/SCTP' or a 'TCP/DTLS/SCTP' proto value. In
that case the m- line port value indicates the port of the underlying that case the m- line port value indicates the port of the underlying
transport layer protocol (UDP or TCP), and the 'sctp-port' value transport layer protocol (UDP or TCP), and the 'sctp-port' value
skipping to change at page 8, line 19 skipping to change at page 8, line 19
This section defines a new SDP media-level attribute, 'max-message- This section defines a new SDP media-level attribute, 'max-message-
size'. The attribute can be associated with an m- line to indicate size'. The attribute can be associated with an m- line to indicate
the maximum SCTP user message size (indicated in bytes) that an SCTP the maximum SCTP user message size (indicated in bytes) that an SCTP
endpoint is willing to receive on the SCTP association associated endpoint is willing to receive on the SCTP association associated
with the m- line. Different attribute values can be used in each with the m- line. Different attribute values can be used in each
direction. direction.
An SCTP endpoint MUST assume that larger SCTP user message sizes will An SCTP endpoint MUST assume that larger SCTP user message sizes will
be rejected by the peer SCTP endpoint. SCTP endpoints need to decide be rejected by the peer SCTP endpoint. SCTP endpoints need to decide
on appropriate behavior in case a message needs to be sent in which on appropriate behavior in case a message needs to be sent in which
the SCTP user message size exceeds the maximumv SCTP user message the SCTP user message size exceeds thevmaximum SCTP user message
size. size.
If the SDP 'max-message-size' attribute contains a maximum message If the SDP 'max-message-size' attribute contains a maximum message
size value of zero, it indicates the SCTP endpoint will handle size value of zero, it indicates the SCTP endpoint will handle
messages of any size, subject to memory capacity etc. messages of any size, subject to memory capacity etc.
If the SDP 'max-message-size' attribute is not present, the default If the SDP 'max-message-size' attribute is not present, the default
value is 64K. value is 64K.
NOTE: This specification only defines the usage of the SDP 'max- NOTE: This specification only defines the usage of the SDP 'max-
skipping to change at page 9, line 6 skipping to change at page 9, line 6
defined in a separate specification. defined in a separate specification.
6.2. Syntax 6.2. Syntax
[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.]
The definition of the SDP 'max-message-size' attribute is: The definition of the SDP 'max-message-size' attribute is:
Attribute name: max-message-size Attribute name: max-message-size
Type of attribute: media Type of attribute: media
Mux category: SPECIAL Mux category: SPECIAL
Subject to charset: No Subject to charset: No
Purpose: Indicate the maximum message size that Purpose: Indicate the maximum message size that
an SCTP endpoint is willing to receive an SCTP endpoint is willing to receive
on the SCTP association associated on the SCTP association 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
Syntax: Syntax:
max-message-size-value = 1*<DIGIT defined in RFC4566> max-message-size-value = 1*<DIGIT defined in RFC4566>
Leading zeroes MUST NOT be used. Leading zeroes MUST NOT be used.
Example: Example:
a=max-message-size:100000 a=max-message-size:100000
skipping to change at page 11, line 36 skipping to change at page 11, line 36
Alternatively, an SCTP association can be closed using the SDP 'sctp- Alternatively, an SCTP association can be closed using the SDP 'sctp-
port' attribute with a zero attribute value. Later, a new SCTP port' attribute with a zero attribute value. Later, a new SCTP
association can be established using the procedures in this section association can be established using the procedures in this section
for establishing an SCTP association. for establishing an SCTP association.
SCTP associations might be closed without SDP signalling, e.g, in SCTP associations might be closed without SDP signalling, e.g, in
case of a failure. The procedures in this section MUST be followed case of a failure. The procedures in this section MUST be followed
to establish a new SCTP association. This requires a new SDP Offer/ to establish a new SCTP association. This requires a new SDP Offer/
Answer exchange. New (different than the ones currently used) SCTP Answer exchange. New (different than the ones currently used) SCTP
ports MUST be used. ports MUST be used by both endpoints.
NOTE: Closing and establishing a new SCTP association using the SDP NOTE: Closing and establishing a new SCTP association using the SDP
'sctp-port' attribute will not impact the underlying DTLS 'sctp-port' attribute will not impact the underlying DTLS
association. association.
9.4. DTLS Association (UDP/DTLS/SCTP And TCP/DTLS/SCTP) 9.4. DTLS Association (UDP/DTLS/SCTP And TCP/DTLS/SCTP)
A DTLS association is managed according to the procedures in A DTLS association is managed according to the procedures in
[I-D.ietf-mmusic-dtls-sdp]. Hence, the SDP 'setup' attribute is used [I-D.ietf-mmusic-dtls-sdp]. Hence, the SDP 'setup' attribute is used
to negotiate the (D)TLS roles ('client' and 'server') [RFC4572]. to negotiate the (D)TLS roles ('client' and 'server') [RFC4572].
NOTE: The SDP 'setup' attribute is used both to negotiate both the NOTE: The SDP 'setup' attribute is used to negotiate both the DTLS
DTLS roles and the TCP roles (Section 9.5). roles and the TCP roles (Section 9.5).
NOTE: As described in [I-D.ietf-ice-rfc5245bis], if the Interactive NOTE: As described in [RFC5245], if the Interactive Connectivity
Connectivity Establishment (ICE) mechanism [I-D.ietf-ice-rfc5245bis] Establishment (ICE) mechanism [RFC5245] is used, all ICE candidates
is used, all ICE candidates associated with a DTLS association as associated with a DTLS association are considered part of the same
considered part of the same DTLS association. Thus, a switch from DTLS association. Thus, a switch from one candidate pair to another
one candidate pair to another candidate pair will not trigger the candidate pair will not trigger the establishment of a new DTLS
establishment of a new DTLS association. association.
9.5. TCP Connection (TCP/DTLS/SCTP) 9.5. TCP Connection (TCP/DTLS/SCTP)
The TCP connection is managed according to the procedures in The TCP connection is managed according to the procedures in
[RFC4145]. Hence, the SDP 'setup' attribute is used to negotiate the [RFC4145]. Hence, the SDP 'setup' attribute is used to negotiate the
TCP roles ('active' and 'passive'), and the SDP 'connection' TCP roles ('active' and 'passive'), and the SDP 'connection'
attribute is used to indicate whether to use an existing TCP attribute is used to indicate whether to use an existing TCP
connection, or create a new one. The SDP 'setup' attribute connection, or create a new one. The SDP 'setup' attribute
'holdconn' value MUST NOT be used. 'holdconn' value MUST NOT be used.
skipping to change at page 12, line 38 skipping to change at page 12, line 38
10.1. General 10.1. General
This section defines the SDP Offer/Answer [RFC3264] procedures for This section defines the SDP Offer/Answer [RFC3264] procedures for
negotiating and establishing an SCTP-over-DTLS association. Unless negotiating and establishing an SCTP-over-DTLS association. Unless
explicitly stated, the procedures apply to both the 'UDP/DTLS/SCTP' explicitly stated, the procedures apply to both the 'UDP/DTLS/SCTP'
and 'TCP/DTLS/SCTP' m- line proto values. and 'TCP/DTLS/SCTP' m- line proto values.
Each endpoint MUST associate one or more certificate fingerprints, Each endpoint MUST associate one or more certificate fingerprints,
using the SDP 'fingerprint' attribute with the m- line, following the using the SDP 'fingerprint' attribute with the m- line, following the
procedures in [RFC4572] and [I-D.ietf-mmusic-4572-update]. procedures in [I-D.ietf-mmusic-4572-update].
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 [I-D.ietf-mmusic-4572-update]. Self-signed certificates
provided that the integrity of the SDP description is assured as can be used securely, provided that the integrity of the SDP
defined in [RFC4572]. description is assured as defined in [I-D.ietf-mmusic-4572-update].
Each endpoint MUST associate an SDP 'dtls-id' attribute with the m- Each endpoint MUST associate an SDP 'dtls-id' attribute with the m-
line, following the procedures in [I-D.ietf-mmusic-dtls-sdp]. line, following the procedures in [I-D.ietf-mmusic-dtls-sdp].
10.2. Generating the Initial SDP Offer 10.2. Generating the Initial SDP Offer
When the offerer creates an initial offer, the offerer: When the offerer creates an initial offer, the offerer:
o MUST associate an SDP setup attribute with the m- line; o MUST associate an SDP setup attribute with the m- line;
skipping to change at page 13, line 28 skipping to change at page 13, line 28
10.3. Generating the SDP Answer 10.3. Generating the SDP Answer
When the answerer receives an offer, which contains an m- line When the answerer receives an offer, which contains an m- line
describing an SCTP-over-DTLS association, if the answerer accepts the describing an SCTP-over-DTLS association, if the answerer accepts the
association, the answerer: association, the answerer:
o MUST insert a corresponding m- line in the answer, with an o MUST insert a corresponding m- line in the answer, with an
identical m- line proto value [RFC3264]; identical m- line proto value [RFC3264];
o MUST associate an SDP 'setup' attribute, with an 'active' or o MUST associate an SDP 'setup' attribute with the m- line;
'passive' value, with the m- line;
o MUST associate an SDP 'sctp-port' attribute with the m- line. If o MUST associate an SDP 'sctp-port' attribute with the m- line. If
the offer contained a new (different than the one currently used) the offer contained a new (different than the one currently used)
SCTP port value the answerer MUST also associate a new SCTP port SCTP port value the answerer MUST also associate a new SCTP port
value. If the offer contained a zero SCTP port value, or if the value. If the offer contained a zero SCTP port value, or if the
answerer does not accept the SCTP association, the answerer MUST answerer does not accept the SCTP association, the answerer MUST
also associate a zero SCTP port value; and also associate a zero SCTP port value; and
o MAY associate an SDP 'max-message-size' attribute [Section 6] with o MAY associate an SDP 'max-message-size' attribute [Section 6] with
the m- line. The attribute value in the answer is independent the m- line. The attribute value in the answer is independent
from the value (if present) in the corresponding m- line of the from the value (if present) in the corresponding m- line of the
offer. offer.
Once the answerer has sent the answer the answerer: Once the answerer has sent the answer the answerer:
o MUST, in the case of TCP/DTLS/SCTP, if a TCP connection has yet o MUST, in the case of TCP/DTLS/SCTP, if a TCP connection has not
not been established, or if an existing TCP connection is to be yet been established, or if an existing TCP connection is to be
closed and replaced by a new TCP connection, follow the procedures closed and replaced by a new TCP connection, follow the procedures
in [RFC4145] for closing and establishing a TCP connection; in [RFC4145] for closing and establishing a TCP connection;
o MUST, if a DTLS association has yet not been established, or if an o MUST, if a DTLS association has not yet been established, or if an
existing DTLS association is to be closed and replaced by a new existing DTLS association is to be closed and replaced by a new
DTLS association, follow the procedures in DTLS association, follow the procedures in
[I-D.ietf-mmusic-dtls-sdp] for closing establishing a DTLS [I-D.ietf-mmusic-dtls-sdp] for closing establishing a DTLS
association; and association; and
o MUST, if an SCTP association has yet not been established, or if o MUST, if an SCTP association has not yet been established, or if
an existing SCTP association is to be closed and replaced by a new an existing SCTP association is to be closed and replaced by a new
SCTP association, initiate the closing of the existing SCTP SCTP association, initiate the closing of the existing SCTP
association (if applicable) and establishment of the SCTP association (if applicable) and establishment of the SCTP
association. association.
If the SDP 'sctp-port' attribute in the answer contains a zero If the SDP 'sctp-port' attribute in the answer contains a zero
attribute value, the answerer MUST NOT establish an SCTP association. attribute value, the answerer MUST NOT establish an SCTP association.
If an SCTP association exists, the offerer MUST close it. If an SCTP association exists, the offerer MUST close it.
If the answerer does not accept the m- line in the offer, it MUST If the answerer does not accept the m- line in the offer, it MUST
assign a zero port value to the corresponding m- line in the answer, assign a zero port value to the corresponding m- line in the answer,
following the procedures in [RFC3264]. In addition, the answerer following the procedures in [RFC3264]. In addition, the answerer
MUST NOT initiate the establishment of a TCP connection, a DTLS MUST NOT initiate the establishment of a TCP connection, a DTLS
association or a DTLS association associated with the m- line. association or a DTLS association associated with the m- line.
10.4. Offerer Processing of the SDP Answer 10.4. Offerer Processing of the SDP Answer
Once the offerer has received the answer the offerer: Once the offerer has received the answer the offerer:
o MUST, in the case of TCP/DTLS/SCTP, if a TCP connection has yet o MUST, in the case of TCP/DTLS/SCTP, if a TCP connection has not
not been established, or if an existing TCP connection is to be yet been established, or if an existing TCP connection is to be
closed and replaced by a new TCP connection, follow the procedures closed and replaced by a new TCP connection, follow the procedures
in [RFC4145] for closing and establishing a TCP connection; in [RFC4145] for closing and establishing a TCP connection;
o MUST, if a DTLS association has yet not been established, or if an o MUST, if a DTLS association has not yet been established, or if an
existing DTLS association is to be closed and replaced by a new existing DTLS association is to be closed and replaced by a new
DTLS association, follow the procedures in DTLS association, follow the procedures in
[I-D.ietf-mmusic-dtls-sdp] for closing establishing a DTLS [I-D.ietf-mmusic-dtls-sdp] for closing and establishing a DTLS
association; and association; and
o MUST, if an SCTP association has yet not been established, or if o MUST, if an SCTP association has not yet been established, or if
an existing SCTP association is to be closed and replaced by a new an existing SCTP association is to be closed and replaced by a new
SCTP association, initiate the closing of the existing SCTP SCTP association, initiate the closing of the existing SCTP
association (if applicable) and establishment of the SCTP association (if applicable) and establishment of the SCTP
association. association.
If the SDP 'sctp-port' attribute in the answer contains a zero If the SDP 'sctp-port' attribute in the answer contains a zero
attribute value, the offerer MUST NOT establish an SCTP association. attribute value, the offerer MUST NOT establish an SCTP association.
If an SCTP association exists, the offerer MUST close it. If an SCTP association exists in that case, the offerer MUST close
it.
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 initiate the establishment a TCP connection, a DTLS MUST NOT initiate the establishment a TCP connection, a DTLS
association or an SCTP association associated with the m- line. If a association or an SCTP association associated with the m- line. If a
TCP connection, or a DTLS association or an SCTP association exists, TCP connection, or a DTLS association or an SCTP association exists
the offerer MUST close it. in that case, the offerer MUST close it.
10.5. Modifying the Session 10.5. Modifying the Session
When an offerer sends an updated offer, in order to modify a When an offerer sends an updated offer, in order to modify a
previously established SCTP association, it follows the procedures in previously established SCTP association, it follows the procedures in
Section 10.2, with the following exceptions: Section 10.2, with the following exceptions:
o If the offerer wants to close an SCTP association, and immediately o If the offerer wants to close an SCTP association, and immediately
establish a new SCTP association, the offerer MUST associate an establish a new SCTP association, the offerer MUST associate an
SDP 'sctp-port' attribute with a new (different than the one SDP 'sctp-port' attribute with a new (different than the one
skipping to change at page 15, line 30 skipping to change at page 15, line 30
o If the offerer wants to close an SCTP association, without o If the offerer wants to close an SCTP association, without
immediately establishing a new SCTP association, the offerer MUST immediately establishing a new SCTP association, the offerer MUST
associate an SDP 'sctp-port' attribute with a zero attribute associate an SDP 'sctp-port' attribute with a zero attribute
value. This will not impact the underlying DTLS association (and value. This will not impact the underlying DTLS association (and
TCP connection in case of TCP/DTLS/SCTP). TCP connection in case of TCP/DTLS/SCTP).
o If the offerer wants to establish an SCTP association, and another o If the offerer wants to establish an SCTP association, and another
SCTP association was previously closed, the offerer MUST associate SCTP association was previously closed, the offerer MUST associate
an SDP 'sctp-port' attribute with a new attribute value (different an SDP 'sctp-port' attribute with a new attribute value (different
than the value associated with the previous SCTP association). If than the value associated with the previous SCTP association). If
the previous SCTP association was closed using an SDP 'sctp-port' the previous SCTP association was closed successfully following
attribute with a zero attribute value, the offerer MAY use the use of an SDP 'sctp-port' attribute with a zero attribute value,
same attribute value for the new SCTP association that was used the offerer MAY use the same attribute value for the new SCTP
with the previous SCTP association before it was closed. This association that was used with the previous SCTP association
will not impact the underlying DTLS association (and TCP before it was closed. This will not impact the underlying DTLS
connection in case of TCP/DTLS/SCTP). association (and TCP connection in case of TCP/DTLS/SCTP).
o If the offerer wants to close an existing SCTP association, and o If the offerer wants to close an existing SCTP association, and
the underlying DTLS association (and the underlying TCP connection the underlying DTLS association (and the underlying TCP connection
in case of TCP/DTLS/SCTP) it MUST assign a zero port value to the in case of TCP/DTLS/SCTP) it MUST assign a zero port value to the
m- line associated with the SCTP and DTLS associations (and TCP m- line associated with the SCTP and DTLS associations (and TCP
connection in case of TCP/DTLS/SCTP), following the procedures in connection in case of TCP/DTLS/SCTP), following the procedures in
[RFC3264]. [RFC3264].
o NOTE: This specification does not define a mechanism for o NOTE: This specification does not define a mechanism for
explicitly closing a DTLS association while maintaining the explicitly closing a DTLS association while maintaining the
overlying SCTP association. However, if a DTLS association is overlying SCTP association. However, if a DTLS association is
closed and replaced with a new DTLS association, as a result of closed and replaced with a new DTLS association, as a result of
some other action [I-D.ietf-mmusic-dtls-sdp], the SCTP association some other action [I-D.ietf-mmusic-dtls-sdp], the SCTP association
is not affected. is not affected.
The offer follows the procedures in [I-D.ietf-mmusic-dtls-sdp] The offer follows the procedures in [I-D.ietf-mmusic-dtls-sdp]
regarding the DTLS association impacts when modifying a session. regarding the DTLS association impacts when modifying a session.
In the case of TCP/DTLS/SCTP, the offer follows the procedures in In the case of TCP/DTLS/SCTP, the offerer follows the procedures in
[RFC4145] regarding the TCP connection impacts when modifying a [RFC4145] regarding the TCP connection impacts when modifying a
session. session.
11. Multihoming Considerations 11. Multihoming Considerations
Multihoming is not supported when sending SCTP on top of DTLS, as Multihoming is not supported when sending SCTP on top of DTLS, as
DTLS does not expose address management of the underlying transport DTLS does not expose address management of the underlying transport
protocols (UDP or TCP) to its upper layer. protocols (UDP or TCP) to its upper layer.
12. NAT Considerations 12. NAT Considerations
12.1. General 12.1. General
When SCTP-over-DTLS is used in NAT environment, it relies on the NAT When SCTP-over-DTLS is used in NAT environment, it relies on the NAT
traversal procedures for the underlying transport protocol (UDP or traversal procedures for the underlying transport protocol (UDP or
TCP). TCP).
12.2. ICE Considerations 12.2. ICE Considerations
When SCTP-over-DTLS is used with UDP based ICE candidates When SCTP-over-DTLS is used with UDP based ICE candidates [RFC5245]
[I-D.ietf-ice-rfc5245bis] then the procedures for UDP/DTLS/SCTP then the procedures for UDP/DTLS/SCTP [Section 7] are used.
[Section 7] are used.
When SCTP-over-DTLS is used with TCP based ICE candidates [RFC6544] When SCTP-over-DTLS is used with TCP based ICE candidates [RFC6544]
then the procedures for TCP/DTLS/SCTP [Section 8] are used. then the procedures for TCP/DTLS/SCTP [Section 8] are used.
The generic ICE rules defined in [I-D.ietf-mmusic-ice-sip-sdp] apply Implementations MUST treat all ICE candidate pairs associated with an
also to SCTP-over-DTLS. Therefore, implementations must treat all SCTP association on top of a DTLS association as part of the same
ICE candidate pairs associated with an SCTP association on top of a DTLS association. Thus, there will only be one SCTP handshake and
DTLS association as part of the same DTLS association. Thus, there one DTLS handshake even if there are multiple valid candidate pairs,
will only be one SCTP handshake and one DTLS handshake even if there and shifting from one candidate pair to another will not impact the
are multiple valid candidate pairs, and shifting from one candidate SCTP or DTLS associations. If new candidates are added, they will
pair to another will not impact the SCTP or DTLS associations. If also be part of the same SCTP and DTLS associations. When
new candidates are added, they will also be part of the same SCTP and transitioning between candidate pairs, different candidate pairs can
DTLS associations. Note that, depending on which candidiates are be currently active in different directions and implementations MUST
used at any given time, TCP-based and UDP-based candidiates might be be ready to receive data on any of the candidates, even if this means
used simultaneously for sending and receiving data. sending and receiving data using UDP/DTLS/SCTP and TCP/DTLS/SCTP at
the same time in different directions.
When an SDP offer or answer is sent, the rules in
[I-D.ietf-mmusic-ice-sip-sdp] apply regarding when the proto value
must match the transport protocol associated with the default
candidate.
If an endpoint switches between TCP-based and UDP-based candidates When an SDP offer or answer is sent, the proto value MUST match the
transport protocol associated with the default candidate. Hence, if
UDP transport is used for the default candidate the 'UDP/DTLS/SCTP'
proto value MUST be used. If TCP transport is used for the default
candidate the 'TCP/DTLS/SCTP' proto value MUST be used. However, if
an endpoint switches between TCP-based and UDP-based candidates
during a session the endpoint is not required to send an SDP offer in during a session the endpoint is not required to send an SDP offer in
order to modify that proto value of the associated m- line. order to modify that proto value of the associated m- line.
NOTE: The text in the paragraph above only applies when the usage of NOTE: The text in the paragraph above only applies when the usage of
ICE has been negotiated. If ICE is not used, the proto value MUST ICE has been negotiated. If ICE is not used, the proto value MUST
always reflect the transport protocol used at any given time. always reflect the transport protocol used at any given time.
13. Examples 13. Examples
13.1. Establishment of UDP/DTLS/SCTP association 13.1. Establishment of UDP/DTLS/SCTP association
skipping to change at page 20, line 15 skipping to change at page 20, line 15
16. Acknowledgments 16. Acknowledgments
The authors wish to thank Harald Alvestrand, Randell Jesup, Paul The authors wish to thank Harald Alvestrand, Randell Jesup, Paul
Kyzivat, Michael Tuexen, Juergen Stoetzer-Bradler, Flemming Andreasen Kyzivat, Michael Tuexen, Juergen Stoetzer-Bradler, Flemming Andreasen
and Ari Keranen for their comments and useful feedback. and Ari Keranen for their comments and useful feedback.
17. 17.
[RFC EDITOR NOTE: Please remove this section when publishing] [RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-ietf-mmusic-sctp-sdp-19
o Changes based on WG chair comments from Flemming Andreasen.
Changes from draft-ietf-mmusic-sctp-sdp-18 Changes from draft-ietf-mmusic-sctp-sdp-18
o Changes based on WGLC comments from Paul Kyzivat. o Changes based on WGLC comments from Paul Kyzivat.
Changes from draft-ietf-mmusic-sctp-sdp-17 Changes from draft-ietf-mmusic-sctp-sdp-17
o Removal of 'SCTP'. o Removal of 'SCTP'.
o Document title changed. o Document title changed.
skipping to change at page 22, line 42 skipping to change at page 22, line 49
[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, with Session Description Protocol (SDP)", RFC 3264,
DOI 10.17487/RFC3264, June 2002, DOI 10.17487/RFC3264, June 2002,
<http://www.rfc-editor.org/info/rfc3264>. <http://www.rfc-editor.org/info/rfc3264>.
[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,
DOI 10.17487/RFC4145, September 2005, DOI 10.17487/RFC4145, September 2005,
<http://www.rfc-editor.org/info/rfc4145>. <http://www.rfc-editor.org/info/rfc4145>.
[RFC4289] Freed, N. and J. Klensin, "Multipurpose Internet Mail
Extensions (MIME) Part Four: Registration Procedures",
BCP 13, RFC 4289, DOI 10.17487/RFC4289, December 2005,
<http://www.rfc-editor.org/info/rfc4289>.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, DOI 10.17487/RFC4566, Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <http://www.rfc-editor.org/info/rfc4566>. July 2006, <http://www.rfc-editor.org/info/rfc4566>.
[RFC4571] Lazzaro, J., "Framing Real-time Transport Protocol (RTP) [RFC4571] Lazzaro, J., "Framing Real-time Transport Protocol (RTP)
and RTP Control Protocol (RTCP) Packets over Connection- and RTP Control Protocol (RTCP) Packets over Connection-
Oriented Transport", RFC 4571, DOI 10.17487/RFC4571, July Oriented Transport", RFC 4571, DOI 10.17487/RFC4571, July
2006, <http://www.rfc-editor.org/info/rfc4571>. 2006, <http://www.rfc-editor.org/info/rfc4571>.
[RFC4572] Lennox, J., "Connection-Oriented Media Transport over the [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
skipping to change at page 23, line 29 skipping to change at page 23, line 29
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008, DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>. <http://www.rfc-editor.org/info/rfc5226>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <http://www.rfc-editor.org/info/rfc6347>. January 2012, <http://www.rfc-editor.org/info/rfc6347>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<http://www.rfc-editor.org/info/rfc6838>.
[I-D.ietf-mmusic-4572-update] [I-D.ietf-mmusic-4572-update]
Holmberg, C., "SDP Fingerprint Attribute Usage Lennox, J. and C. Holmberg, "Connection-Oriented Media
Clarifications", draft-ietf-mmusic-4572-update-07 (work in Transport over TLS in SDP", draft-ietf-mmusic-
progress), September 2016. 4572-update-08 (work in progress), November 2016.
[I-D.ietf-mmusic-dtls-sdp] [I-D.ietf-mmusic-dtls-sdp]
Holmberg, C. and R. Shpount, "Using the SDP Offer/Answer Holmberg, C. and R. Shpount, "Using the SDP Offer/Answer
Mechanism for DTLS", draft-ietf-mmusic-dtls-sdp-14 (work Mechanism for DTLS", draft-ietf-mmusic-dtls-sdp-15 (work
in progress), July 2016. in progress), October 2016.
[I-D.ietf-tsvwg-sctp-dtls-encaps] [I-D.ietf-tsvwg-sctp-dtls-encaps]
Tuexen, M., Stewart, R., Jesup, R., and S. Loreto, "DTLS Tuexen, M., Stewart, R., Jesup, R., and S. Loreto, "DTLS
Encapsulation of SCTP Packets", draft-ietf-tsvwg-sctp- Encapsulation of SCTP Packets", draft-ietf-tsvwg-sctp-
dtls-encaps-09 (work in progress), January 2015. dtls-encaps-09 (work in progress), January 2015.
[I-D.ietf-mmusic-sdp-mux-attributes] [I-D.ietf-mmusic-sdp-mux-attributes]
Nandakumar, S., "A Framework for SDP Attributes when Nandakumar, S., "A Framework for SDP Attributes when
Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-14 Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-16
(work in progress), September 2016. (work in progress), December 2016.
18.2. Informative References 18.2. Informative References
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981, RFC 793, DOI 10.17487/RFC0793, September 1981,
<http://www.rfc-editor.org/info/rfc793>. <http://www.rfc-editor.org/info/rfc793>.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245,
DOI 10.17487/RFC5245, April 2010,
<http://www.rfc-editor.org/info/rfc5245>.
[RFC6544] Rosenberg, J., Keranen, A., Lowekamp, B., and A. Roach, [RFC6544] Rosenberg, J., Keranen, A., Lowekamp, B., and A. Roach,
"TCP Candidates with Interactive Connectivity "TCP Candidates with Interactive Connectivity
Establishment (ICE)", RFC 6544, DOI 10.17487/RFC6544, Establishment (ICE)", RFC 6544, DOI 10.17487/RFC6544,
March 2012, <http://www.rfc-editor.org/info/rfc6544>. March 2012, <http://www.rfc-editor.org/info/rfc6544>.
[I-D.ietf-ice-rfc5245bis]
Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive
Connectivity Establishment (ICE): A Protocol for Network
Address Translator (NAT) Traversal", draft-ietf-ice-
rfc5245bis-04 (work in progress), June 2016.
[I-D.ietf-mmusic-ice-sip-sdp]
Petit-Huguenin, M., Keranen, A., and S. Nandakumar, "Using
Interactive Connectivity Establishment (ICE) with Session
Description Protocol (SDP) offer/answer and Session
Initiation Protocol (SIP)", draft-ietf-mmusic-ice-sip-
sdp-10 (work in progress), July 2016.
[I-D.ietf-rtcweb-data-channel] [I-D.ietf-rtcweb-data-channel]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data
Channels", draft-ietf-rtcweb-data-channel-13 (work in Channels", draft-ietf-rtcweb-data-channel-13 (work in
progress), January 2015. progress), January 2015.
[I-D.ietf-mmusic-data-channel-sdpneg] [I-D.ietf-mmusic-data-channel-sdpneg]
Drage, K., Makaraju, M., Stoetzer-Bradler, J., Ejzak, R., Drage, K., Makaraju, M., Stoetzer-Bradler, J., Ejzak, R.,
and (. (Unknown), "SDP-based Data Channel Negotiation", and (. (Unknown), "SDP-based Data Channel Negotiation",
draft-ietf-mmusic-data-channel-sdpneg-10 (work in draft-ietf-mmusic-data-channel-sdpneg-10 (work in
progress), September 2016. progress), September 2016.
 End of changes. 41 change blocks. 
110 lines changed or deleted 92 lines changed or added

This html diff was produced by rfcdiff 1.45. The latest version is available from http://tools.ietf.org/tools/rfcdiff/