Audio/Video Transport Core Maintenance S. Dawkins
Internet-Draft Wonder Hamster Internetworking LLC
Intended status: Experimental V. Pascual
Expires: 14 August 2025 Nokia
10 February 2025
SDP Offer/Answer for RTP over QUIC (RoQ)
draft-dawkins-avtcore-sdp-roq-00
Abstract
This document describes several new SDP "proto" and "attribute-name"
attribute values in the "Session Description Protocol (SDP)
Parameters" IANA registry that can be used to describe QUIC transport
for RTP and RTCP packets, and describes how SDP Offer/Answer can be
used to set up an RTP connection using QUIC as a transport protocol.
These new values are necessary to allow the use of QUIC as an
underlying transport protocol for RTP applications that commonly use
SDP as a session signaling protocol to set up RTP connections, such
as SIP and WebRTC.
This document also contains non-normative guidance for implementers.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at https://github.com/
ietf-wg-avtcore/sdp-roq/draft-dawkins-avtcore-sdp-roq.html. Status
information for this document may be found at
https://datatracker.ietf.org/doc/draft-dawkins-avtcore-sdp-roq/.
Discussion of this document takes place on the Audio/Video Transport
Core Maintenance Working Group mailing list (mailto:avt@ietf.org),
which is archived at https://mailarchive.ietf.org/arch/browse/avt/.
Subscribe at https://www.ietf.org/mailman/listinfo/avt/.
Source for this draft and an issue tracker can be found at
https://github.com/ietf-wg-avtcore/sdp-roq.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notes for Readers . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 4
3. New SDP Protocol identifiers . . . . . . . . . . . . . . . . 4
3.1. The QUIC proto . . . . . . . . . . . . . . . . . . . . . 4
3.2. RoQ RTP Protos . . . . . . . . . . . . . . . . . . . . . 5
3.2.1. The QUIC/RTP/AVP proto . . . . . . . . . . . . . . . 5
3.2.2. The QUIC/RTP/AVPF proto . . . . . . . . . . . . . . . 5
3.2.3. The QUIC/RTP/SAVP proto . . . . . . . . . . . . . . . 6
3.2.4. The QUIC/RTP/SAVPF proto . . . . . . . . . . . . . . 6
4. New SDP Attribute-Names for RoQ . . . . . . . . . . . . . . . 6
4.1. RoQ QUIC-DATAGRAMs Attribute . . . . . . . . . . . . . . 6
4.2. RoQ Flow Identifiers . . . . . . . . . . . . . . . . . . 8
5. Special Considerations for Selected SDP Attributes When Using
RoQ Transport . . . . . . . . . . . . . . . . . . . . . . 9
5.1. The SDP "setup" Attribute . . . . . . . . . . . . . . . . 10
5.2. The SDP "connection" Attribute . . . . . . . . . . . . . 10
5.3. The SDP "fingerprint" Attribute . . . . . . . . . . . . . 10
5.4. The SDP "rtcp-mux" Attribute . . . . . . . . . . . . . . 10
6. A QUIC/RTP/AVPF Offer Example . . . . . . . . . . . . . . . . 10
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7. Implementation Topics . . . . . . . . . . . . . . . . . . . . 12
7.1. Bundling Considerations . . . . . . . . . . . . . . . . . 13
7.2. Implications of Replacing RTCP Feedback with QUIC
Feedback . . . . . . . . . . . . . . . . . . . . . . . . 13
7.3. Implications of Congestion Control . . . . . . . . . . . 14
7.4. Implications of using ICE with RoQ . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15
8.1. AV Profile-related Security Considerations . . . . . . . 15
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
9.1. quic-datagrams . . . . . . . . . . . . . . . . . . . . . 16
9.2. roq-flow-id . . . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . 16
10.2. Informative References . . . . . . . . . . . . . . . . . 19
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction
This document describes several new SDP "proto" and "attribute-name"
attribute values in the "Session Description Protocol (SDP)
Parameters" IANA registry ([SDP-protos] and [SDP-attribute-name])
that can be used to describe QUIC transport for RTP and RTCP packets
(hereafter abbreviated as "RoQ"), and describes how SDP Offer/Answer
([RFC3264]) can be used to set up an ([RFC3550]) connection using
QUIC ([RFC9000] and related specifications), as defined in
[I-D.ietf-avtcore-rtp-over-quic]. These new values are necessary to
allow the use of QUIC as an underlying transport protocol for RTP
applications that commonly use SDP as a session signaling protocol to
set up RTP connections, such as SIP ([RFC3261]) and WebRTC
([RFC8825]).
The normative descriptions and requirements for RoQ SDP appear in
Section 3, Section 4, and Section 5.
A sample SDP offer appears in Section 6.
Non-normative guidance for implementers appears in Section 7.
1.1. Notes for Readers
(Note to RFC Editor - if this document ever reaches you, please
remove this section)
This document has not yet been adopted by any IETF working group, so
does not carry any special status within the IETF.
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2. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Because the use of SDP to describe RTP over QUIC transport relies
heavily on terminology introduced in
[I-D.ietf-avtcore-rtp-over-quic], the definitions in that document
are prerequisite for understanding this document, and those terms are
included here by reference.
3. New SDP Protocol identifiers
This document reuses the following AVP profiles from [SDP-protos], in
order to allow existing SIP and RTCWEB RTP applications to migrate
more easily to RTP over QUIC:
* RTP/AVP ("RTP Profile for Audio and Video Conferences with Minimal
Control"), as defined in [RFC3551].
* RTP/AVPF ("Extended RTP Profile for Real-time Transport Control
Protocol (RTCP)-Based Feedback (RTP/AVPF)"), as defined in
[RFC4585].
* RTP/SAVP ("The Secure Real-time Transport Protocol (SRTP)"), as
defined in [RFC3711].
* RTP/SAVPF ("Extended Secure RTP Profile for Real-time Transport
Control Protocol (RTCP)-Based Feedback (RTP/SAVPF)"), as defined
in [RFC5124].
3.1. The QUIC proto
The 'QUIC' protocol identifier is similar to the 'UDP' and 'TCP'
protocol identifiers in that it only describes the transport
protocol, and not the upper-layer protocol.
An 'm' line that specifies 'QUIC' MUST further qualify the
application-layer protocol using an fmt identifier, such as
"QUIC/RTP/AVPF".
Media described using an 'm' line containing the 'QUIC' protocol
identifier are carried using QUIC streams, as defined in [RFC9000],
or in QUIC DATAGRAMs, as defined in [RFC9221].
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The following is an update to the ABNF for an 'm' line, as specified
by [RFC8866], that defines a new value for the QUIC protocol.
media-field = %s"m" "=" media SP port \["/" integer\]
SP proto 1*(SP fmt) CRLF
m= line parameter parameter value(s)
------------------------------------------------------------------
<media>: (unchanged from RFC8866)
<proto>: 'QUIC'
<port>: UDP port number
<fmt>: (unchanged from RFC8866)
3.2. RoQ RTP Protos
As much as possible, attributes used in this section are reused from
other specifications, with references to the original definitions.
3.2.1. The QUIC/RTP/AVP proto
The following is an update to the ABNF for an 'm' line, as specified
by [RFC8866], that defines a new value for the QUIC/RTP/AVP protocol.
media-field = %s"m" "=" media SP port \["/" integer\]
SP proto 1*(SP fmt) CRLF
m= line parameter parameter value(s)
------------------------------------------------------------------
<media>: (unchanged from RFC8866)
<proto>: 'QUIC/RTP/AVP'
<port>: UDP port number
<fmt>: (unchanged from RFC8866)
3.2.2. The QUIC/RTP/AVPF proto
The following is an update to the ABNF for an 'm' line, as specified
by [RFC8866], that defines a new value for the QUIC/RTP/AVPF
protocol.
media-field = %s"m" "=" media SP port \["/" integer\]
SP proto 1*(SP fmt) CRLF
m= line parameter parameter value(s)
------------------------------------------------------------------
<media>: (unchanged from RFC8866)
<proto>: 'QUIC/RTP/AVPF'
<port>: UDP port number
<fmt>: (unchanged from RFC8866)
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3.2.3. The QUIC/RTP/SAVP proto
The following is an update to the ABNF for an 'm' line, as specified
by [RFC8866], that defines a new value for the QUIC/RTP/SAVP
protocol.
media-field = %s"m" "=" media SP port \["/" integer\]
SP proto 1*(SP fmt) CRLF
m= line parameter parameter value(s)
------------------------------------------------------------------
<media>: (unchanged from RFC8866)
<proto>: 'QUIC/RTP/SAVP'
<port>: UDP port number
<fmt>: (unchanged from RFC8866)
3.2.4. The QUIC/RTP/SAVPF proto
The following is an update to the ABNF for an 'm' line, as specified
by [RFC8866], that defines a new value for the QUIC/RTP/SAVPF
protocol.
media-field = %s"m" "=" media SP port \["/" integer\]
SP proto 1*(SP fmt) CRLF
m= line parameter parameter value(s)
------------------------------------------------------------------
<media>: (unchanged from RFC8866)
<proto>: 'QUIC/RTP/SAVPF'
<port>: UDP port number
<fmt>: (unchanged from RFC8866)
4. New SDP Attribute-Names for RoQ
This section describes new SDP attributes that are created for use
with RoQ.
4.1. RoQ QUIC-DATAGRAMs Attribute
As noted in [I-D.ietf-avtcore-rtp-over-quic], the RoQ specification
only assumes a baseline QUIC implementation as defined in [RFC8999],
[RFC9000], [RFC9001], and [RFC9002], and this baseline does not
provide unreliable datagrams, which are defined in [RFC9221].
It is very likely that RoQ implementers will wish to use QUIC
DATAGRAMs, for a variety of reasons too large to list in this
specification.
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In order to support this capability, this section defines a new SDP
media-level attribute, "quic-datagrams". The attribute can be
associated with an SDP media description ("m=" line) with any of the
QUIC proto values defined in Section 3.1.
Actual support for QUIC DATAGRAMs is negotiated between two QUIC
endpoints, as described in Section 3 of [RFC9221], and nothing
specified in SDP will cause a QUIC endpoint that does not advertise
support for QUIC DATAGRAMs to suddenly begin to support them.
However, it may be useful to tell a RoQ receiver that the RoQ sender
plans to send QUIC DATAGRAMs, and to allow a RoQ receiver to tell the
SDP sender that the RoQ receiver does not plan to support receiving
QUIC DATAGRAMs for that media flow.
If the quic-datagrams attribute is present, the RoQ sender indicates
its intention to use QUIC DATAGRAMs for the associated media flow,
and the RoQ receiver indicates its willingness to accept QUIC
DATAGRAMs for that media flow.
The quic-datagrams attribute is OPTIONAL for RoQ applications, even
when the sender intends to use QUIC DATAGRAMs. Omitting the quic-
datagrams attribute merely complicates the sender's decision whether
to send specific media using QUIC DATAGRAMs.
If the attribute is not present in SDP, the sender sends its QUIC
Initial packet with a non-zero max_datagram_frame_size QUIC transport
parameter, and the receiver with a non-zero max_datagram_frame_size
QUIC transport parameter, all will proceed normally. If the sender
attempts to send DATAGRAMs before it receives a non-zero
name=max_datagram_frame_size QUIC transport parameter in the initial
handshake, this is a QUIC PROTOCOL_VIOLATION, as described in
Section 3 of [RFC9221].
The definition of the SDP "quic-datagrams" attribute is:
Attribute name: quic-datagrams
Type of attribute: media
Mux category: IDENTICAL
*NOTE:* This specification sets the mux category (as discussed in
Section 4 of [RFC8859]) as IDENTICAL, as an RTP mixer which is
multiplexing several incoming streams onto one connection needs to
provide the same quidance to a RoQ receiver for all multiplexed
media flows.
Subject to charset: No
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Purpose: This attribute provides a hint as to whether the media
associated with the SDP media description is likely to arrive via
QUIC DATAGRAMs. It is a property attribute, which does not take a
value.
Contact name: Spencer Dawkins
Contact e-mail: spencerdawkins.ietf@gmail.com
Reference: [I-D.dawkins-avtcore-sdp-roq] (This document)
Syntax:
quic-datagrams
4.2. RoQ Flow Identifiers
Section 5.1 of [I-D.ietf-avtcore-rtp-over-quic] introduces a
multiplexing identifier for RTP flows carried over a QUIC connection
called "Flow Identifiers". This section defines a new SDP media-
level attribute, "roq-flow-id". The attribute can be associated with
an SDP media description ("m=" line) with any of the QUIC proto
values defined in Section 3.1. In that case, the "m=" line port
value indicates the port of the underlying QUIC transport UDP port,
and the "roq-flow-id" value indicates the RoQ Flow Identifier.
No default value is defined for the SDP "roq-flow-id" attribute.
Therefore, if the attribute is not present, the associated "m=" line
MUST be considered invalid.
The definition of the SDP "roq-flow-id" attribute is:
Attribute name: roq-flow-id
Type of attribute: media
Mux category: CAUTION
*NOTE:* This specification sets the mux category (as discussed in
Section 4 of [RFC8859]) as CAUTION, as an RTP mixer which is
multiplexing several incoming streams onto one connection needs to
ensure that RoQ Flow Identifiers do not overlap, and might need to
rewrite the Flow Identifiers in received streams when further
multiplexing them.
Subject to charset: No
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Purpose: This attribute indicates the RoQ Flow Idenfitier associated
with the SDP media description.
Contact name: Spencer Dawkins
Contact e-mail: spencerdawkins.ietf@gmail.com
Reference: [I-D.dawkins-avtcore-sdp-roq] (This document)
Syntax:
roq-flow-id = 1*19(DIGIT) ; DIGIT defined in RFC 4566
The RoQ flow identifier range is between 0 and 4611686018427387903
(2^62 - 1) (both included). Leading zeroes MUST NOT be used.
5. Special Considerations for Selected SDP Attributes When Using RoQ
Transport
This section does not introduce new SDP attribute extensions, but
describes how some existing SDP attribute extensions are reused to
describe RoQ media flows.
We have two goals for this section:
* To describe how existing SDP attributes are used differently in
order to support RoQ, and
* To be able to make the statement that other existing SDP attribute
extensions can be reused with RoQ, with no special considerations.
*What other considerations have we missed, that need to be mentioned
here?*
This document assumes that an authenticated QUIC connection will be
opened using a "roq" ALPN or some other ALPN, as described in
Section 4.1 of [I-D.ietf-avtcore-rtp-over-quic].
*Editor's Note:* Do we need to mention the SDP "tls-id" attribute,
defined in [RFC8842]? That spec is DTLS-specific, but whether it
would also apply to TLS/QUIC connections changing five-tuples isn't
clear to Spencer. This may require some conversations about QUIC
connection migration (and, of course, Multipath QUIC, when
[I-D.draft-ietf-quic-multipath] leaves the QUIC working group).
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5.1. The SDP "setup" Attribute
The SDP "setup" attribute, defined for media over TCP in [RFC4145],
is reused to indicate which endpoint initiates a QUIC connection
(whether the endpoint actively opens a QUIC connection, or accepts an
incoming QUIC connection. This attribute MUST be present in SDP
offers and answers for RoQ.
5.2. The SDP "connection" Attribute
The SDP "connection" attribute, defined for TCP in [RFC4145], is
reused to indicate whether the endpoint will open a new QUIC
connection, or reuse an existing QUIC connection. This attribute
MUST be present in SDP offers and answers for RoQ.
5.3. The SDP "fingerprint" Attribute
Because QUIC itself uses the TLS handshake as described in [RFC9001],
the parties to a RoQ session MUST also provide authentication
certificates as part of the TLS handshake procedure, as described in
Section 5 of [RFC8122]. When self-signed certificates are used,
certificate fingerprint is represented in SDP using the fingerprint
SDP attribute, as illustrated in Section 3.4 of [RFC8122], in order
to provide assurance that two endpoints with no prior relationship
are not being subjected to a man-in-the-middle attack.
5.4. The SDP "rtcp-mux" Attribute
[I-D.ietf-avtcore-rtp-over-quic] defines how RTP and RTCP can be
multiplexed onto a single QUIC connection. An application that will
perform this multiplexing MUST include the "rtcp-mux" attribute
defined in [RFC5761] in its SDP signaling.
6. A QUIC/RTP/AVPF Offer Example
*Editor's Note:* Spencer has been updating this example while working
on the document, but we will need to review it carefully, before
requesting Working Group Last Call.
A complete example of an SDP offer using QUIC/RTP/AVPF might look
like:
+===========================================================+==========================+
|SDP line |Notes |
+===========================================================+==========================+
|v=0 |Same as Section 5 of |
| |[RFC8866] |
+-----------------------------------------------------------+--------------------------+
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|o=jdoe 3724394400 3724394405 IN IP4 198.51.100.1 |Same as Section 5 of |
| |[RFC8866] |
+-----------------------------------------------------------+--------------------------+
|s=Call to John Smith |Same as Section 5 of |
| |[RFC8866] |
+-----------------------------------------------------------+--------------------------+
|i=SDP Offer #1 |Same as Section 5 of |
| |[RFC8866] |
+-----------------------------------------------------------+--------------------------+
|u=http://www.jdoe.example.com/home.html |Same as Section 5 of |
| |[RFC8866] |
+-----------------------------------------------------------+--------------------------+
|e=Jane Doe jane@jdoe.example.com |Same as Section 5 of |
|(mailto:jane@jdoe.example.com) |[RFC8866] |
+-----------------------------------------------------------+--------------------------+
|p=+1 617 555-6011 |Same as Section 5 of |
| |[RFC8866] |
+-----------------------------------------------------------+--------------------------+
|c=IN IP4 198.51.100.1 |Same as Section 5 of |
| |[RFC8866] |
+-----------------------------------------------------------+--------------------------+
|t=0 0 |Same as Section 5 of |
| |[RFC8866] |
+-----------------------------------------------------------+--------------------------+
|fingerprint:sha-1 |Section 5 of [RFC8122] |
|47:5D:A9:48:E4:BA:44:D9:B5:BC:31:AB:4B:80:06:11:3F:D5:F5:38| |
+-----------------------------------------------------------+--------------------------+
|m=audio 49170 QUIC/RTP/AVP 0 |As defined in |
| |Section 3.2.1 |
+-----------------------------------------------------------+--------------------------+
|a=quic-datagrams |Expects to use QUIC |
| |DATAGRAMs for this audio |
| |media stream, as defined |
| |in this specification |
+-----------------------------------------------------------+--------------------------+
|a=rtcp-mux |Will multiplex RTP and |
| |RTCP on the same port |
| |[RFC5761] |
+-----------------------------------------------------------+--------------------------+
|m=audio 49180 QUIC/RTP/AVP 0 |As defined in |
| |Section 3.2.1 |
+-----------------------------------------------------------+--------------------------+
|a=quic-datagrams |Expects to use QUIC |
| |DATAGRAMs for this audio |
| |media stream, as defined |
| |in this specification |
+-----------------------------------------------------------+--------------------------+
|m=video 51372 QUIC/RTP/AVPF 99 |As defined in |
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| |Section 3.2.2 |
+-----------------------------------------------------------+--------------------------+
|a=setup:passive |Will wait for QUIC |
| |handshake (setup attribute|
| |from [RFC4145]) |
+-----------------------------------------------------------+--------------------------+
|a=connection:new |don't want to reuse an |
| |existing QUIC connection |
| |(connection attribute from|
| |[RFC4145]) |
+-----------------------------------------------------------+--------------------------+
|a=roq-flow-id:2 |RoQ Flow Identifier shall |
| |be 2 for streams described|
| |by this SDP media |
| |description |
+-----------------------------------------------------------+--------------------------+
|c=IN IP6 2001:db8::2 |Same as Section 5 of |
| |[RFC8866] |
+-----------------------------------------------------------+--------------------------+
|a=rtpmap:99 h266/90000 |H.266 VVC codec |
| |[I-D.ietf-avtcore-rtp-vvc]|
+-----------------------------------------------------------+--------------------------+
Table 1
This example is largely based on an example appearing in [RFC8866],
Section 5, but includes the necessary protos and attribute-names for
RoQ SDP.
This SDP offer might be included in a SIP INVITE, for example.
7. Implementation Topics
*Editors' Question:* Section 7 contains (ought to contain) no
normative requirements.
Section 3 and Section 4 of this document provide normative
requirements for RoQ endpoints that use SDP for signaling.
Beyond those normative requirements, there are topics that are worth
considering as part of implementation work. These topics are not
part of "SDP for RoQ", but are gathered here for ease of reference.
These topics might be moved into an appendix or a separate "SDP for
RoQ Implementation Guide", or even included in the GitHub repository
Wiki for this document.
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*Editors' Question:* We've been asked about interaction with UDP-
Connect to open pinholes in corporate proxies. What is there to say
about that, in this specification?
7.1. Bundling Considerations
[RFC8843] describes a Session Description Protocol (SDP) Grouping
Framework extension called 'BUNDLE'. The extension can be used with
the SDP offer/answer mechanism to negotiate the usage of a single
transport (5-tuple) for sending and receiving media described by
multiple SDP media descriptions ("m=" sections).
The authors believe that no special considerations apply when using
BUNDLE with a single QUIC connection carrying RoQ.
If an application uses multiple 5-tuples in order to allow QUIC
Connection Migration as described in Section 9 of [RFC9000], it is
assumed that only one QUIC path will be active at any given time.
If an application uses multiple 5-tuples in order to make use of the
Multipath Extension for QUIC as described in
[I-D.draft-ietf-quic-multipath], this would allow multiple QUIC paths
to be active simultaneously, and this assumption will need revisiting
when [I-D.draft-ietf-quic-multipath] is approved.
7.2. Implications of Replacing RTCP Feedback with QUIC Feedback
Section 10.4 of [I-D.ietf-avtcore-rtp-over-quic] describes how some
RTCP feedback can be replaced by equivalent statistics that are
already collected by QUIC. The exact RTCP feedback that can be
replaced depends on the QUIC statistics exposed by the underlying
QUIC implementation, and these QUIC statistics might depend in turn
on QUIC extensions supported in the underlying QUIC implementation.
The set of possible relevant QUIC extensions is not fixed, but some
discussion appears in Section 11 of [I-D.ietf-avtcore-rtp-over-quic].
For these reasons, decisions about what RTCP feedback can be replaced
will always be media-dependent and implementation-dependent.
It is assumed that an implementer will review the application
requirements, the RTP proto in use, the available RTCP feedback for
the media types being transferred, and available QUIC statistics, and
will do the right thing.
More information about what RTCP feedback might be replaced by QUIC
statistics, and what is possible, appears in Appendix B of
[I-D.ietf-avtcore-rtp-over-quic].
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*Editors' Question:* The API between QUIC and RoQ is, of course, a
private matter, but in at least some cases, it might be useful to
specify specific QUIC feedback substitutions so that the other RoQ
endpoint does not provide RTCP feedback that this RoQ endpoint does
not need and does not plan to use. *We almost certainly need
implementation and deployment experience before we can do more than
offer a strawman proposal.* Spencer suggests that we include any
IETF-specified QUIC feedback substitutions in separate documents, as
we do with RTCP extensions today, or even include them in the GitHub
repository Wiki for this document.
7.3. Implications of Congestion Control
A significant distinction between QUIC transport and UDP transport is
that QUIC transport is always congestion-controlled at the QUIC
layer. For RTP media, this ought to be a difference without a
difference. Any RTP application ought to perform flow control and
congestion control using a control mechanism that is appropriate for
the media being transferred, and this applies to RoQ applications as
well.
Having said this, it is worth saying that RoQ applications can use
any RTCP mechanisms such as Codec Control Messages [RFC5104] that can
affect variables such as the Maximum Media Stream Bit Rate, as long
as the RTP application respects the relevant congestion control
considerations (in the case of Codec Control Messages, these
considerations appear in Section 5 of [RFC5104]).
RoQ applications can also use RTP Control Protocol (RTCP) Feedback
for Congestion Control, as described in [RFC8888].
Because RoQ applications are always congestion controlled at the QUIC
connection level, QUIC congestion control also acts as an RTP Circuit
Breaker [RFC8083], with no special considerations for RoQ.
7.4. Implications of using ICE with RoQ
Because a peer address is validated during QUIC connection
establishment as described in Section 8.1 of [RFC9000], when a RoQ
endpoint uses ICE [RFC8445] to communicate with another RoQ endpoint,
an ICE agent will have already performed ICE candidate pair
connectivity checking before a QUIC connection can be opened for use
with RoQ.
An implementer should be aware that it is possible for a RoQ
connection to be subject to "ping"/liveness checks at several
different levels:
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* QUIC PING frames, as described in Section 10.1.2 of [RFC9000]
* ICE keepalives, as described in Section 10 of [RFC5245] and in
[RFC6263]
* ICE consent freshness, as described in [RFC7675]
* RTCP packets, as described in Section 6.2 of [RFC3550]
The following considerations are worth reviewing for implementers.
* QUIC PING frames are entirely under the control of an
implementation. If a QUIC connection carries RTP/RTCP traffic,
the RTCP transmission interval is likely to suffice for RTP
liveness detection, but a wise implementer will look at this in
their environment and proceed accordingly.
* ICE consent freshness, as described in Section 4 of [RFC7675],
also serves the ICE keepalive function, so ICE keepalives are no
longer necessary.
* At least some RTCP feedback might be unnecessary, as described in
Section 7.2, so a wise implementer will look at what RTCP feedback
can be replaced with QUIC feedback.
8. Security Considerations
The security considerations sections of the Normative References used
in this document are incorporated by reference.
8.1. AV Profile-related Security Considerations
This document currently defines the QUIC/RTP/SAVP and QUIC/RTP/SAVPF
secure profiles, although this might seem unnecessary, because RoQ
already uses QUIC security mechanisms. That choice is made for two
reasons:
* If an implementer wishes to use an existing RTP application over
RoQ, continuing to support existing legacy secure profiles
minimizes the changes required to the implementations at each end.
* If a RoQ RTP endpoint is communicating with a non-RoQ RTP endpoint
using an Top-PtP-Translator RTP middlebox (as described in
Section 3.2.1 of [RFC7667], the RoQ endpoint might reasonably use
a secure AVP profile over QUIC when sending to the middlebox,
because the sending endpoint doesn't have any way to control or
even discover whether the RTP middlebox used a secure profile when
forwarding RTP to a non-RoQ endpoint.
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If this is not a good plan, there are two alternatives.
* We can REQUIRE conformant RoQ middleboxes to bridge between AVP
and AVPF profiles carried over RoQ and SAVP and SAVPF profiles
carried using other transports, so that insecure media flows are
not relayed over insecure transport protocols.
* Alternatively, an implementation can use SFRAME as described in
[RFC9605] to achieve end-to-end media security, at the price of
disallowing some types of translating middleboxes (for example,
Topo-Media-Translator middleboxes, as described in Section 3.2.1.2
of [RFC7667].
*Editors' Question:* We will need discussion within the working group
to determine whether we do need to include QUIC/RTP/SAVP and
QUIC/RTP/SAVPF in this specification.
9. IANA Considerations
This document defines new IANA values in the [SDP-protos] and
[SDP-attribute-name] registries.
9.1. quic-datagrams
This document defines a new SDP media-level attribute, "quic-
datagrams". The details of the attribute are defined in Section 4.1.
9.2. roq-flow-id
This document defines a new SDP media-level attribute, "roq-flow-id".
The details of the attribute are defined in Section 4.2.
10. References
10.1. Normative References
[I-D.dawkins-avtcore-sdp-roq]
"*** BROKEN REFERENCE ***".
[I-D.ietf-avtcore-rtp-over-quic]
Engelbart, M., Ott, J., and S. Dawkins, "RTP over QUIC
(RoQ)", Work in Progress, Internet-Draft, draft-ietf-
avtcore-rtp-over-quic-12, 21 October 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-avtcore-
rtp-over-quic-12>.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
DOI 10.17487/RFC3264, June 2002,
<https://www.rfc-editor.org/rfc/rfc3264>.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <https://www.rfc-editor.org/rfc/rfc3550>.
[RFC3551] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and
Video Conferences with Minimal Control", STD 65, RFC 3551,
DOI 10.17487/RFC3551, July 2003,
<https://www.rfc-editor.org/rfc/rfc3551>.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, DOI 10.17487/RFC3711, March 2004,
<https://www.rfc-editor.org/rfc/rfc3711>.
[RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in
the Session Description Protocol (SDP)", RFC 4145,
DOI 10.17487/RFC4145, September 2005,
<https://www.rfc-editor.org/rfc/rfc4145>.
[RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
"Extended RTP Profile for Real-time Transport Control
Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585,
DOI 10.17487/RFC4585, July 2006,
<https://www.rfc-editor.org/rfc/rfc4585>.
[RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for
Real-time Transport Control Protocol (RTCP)-Based Feedback
(RTP/SAVPF)", RFC 5124, DOI 10.17487/RFC5124, February
2008, <https://www.rfc-editor.org/rfc/rfc5124>.
[RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
Control Packets on a Single Port", RFC 5761,
DOI 10.17487/RFC5761, April 2010,
<https://www.rfc-editor.org/rfc/rfc5761>.
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[RFC7667] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 7667,
DOI 10.17487/RFC7667, November 2015,
<https://www.rfc-editor.org/rfc/rfc7667>.
[RFC8122] Lennox, J. and C. Holmberg, "Connection-Oriented Media
Transport over the Transport Layer Security (TLS) Protocol
in the Session Description Protocol (SDP)", RFC 8122,
DOI 10.17487/RFC8122, March 2017,
<https://www.rfc-editor.org/rfc/rfc8122>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8445] Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive
Connectivity Establishment (ICE): A Protocol for Network
Address Translator (NAT) Traversal", RFC 8445,
DOI 10.17487/RFC8445, July 2018,
<https://www.rfc-editor.org/rfc/rfc8445>.
[RFC8866] Begen, A., Kyzivat, P., Perkins, C., and M. Handley, "SDP:
Session Description Protocol", RFC 8866,
DOI 10.17487/RFC8866, January 2021,
<https://www.rfc-editor.org/rfc/rfc8866>.
[RFC8999] Thomson, M., "Version-Independent Properties of QUIC",
RFC 8999, DOI 10.17487/RFC8999, May 2021,
<https://www.rfc-editor.org/rfc/rfc8999>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/rfc/rfc9000>.
[RFC9001] Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure
QUIC", RFC 9001, DOI 10.17487/RFC9001, May 2021,
<https://www.rfc-editor.org/rfc/rfc9001>.
[RFC9002] Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection
and Congestion Control", RFC 9002, DOI 10.17487/RFC9002,
May 2021, <https://www.rfc-editor.org/rfc/rfc9002>.
[RFC9221] Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable
Datagram Extension to QUIC", RFC 9221,
DOI 10.17487/RFC9221, March 2022,
<https://www.rfc-editor.org/rfc/rfc9221>.
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[RFC9605] Omara, E., Uberti, J., Murillo, S. G., Barnes, R., Ed.,
and Y. Fablet, "Secure Frame (SFrame): Lightweight
Authenticated Encryption for Real-Time Media", RFC 9605,
DOI 10.17487/RFC9605, August 2024,
<https://www.rfc-editor.org/rfc/rfc9605>.
[SDP-attribute-name]
"SDP Parameters - attribute-name", September 2021,
<https://www.iana.org/assignments/sdp-parameters/sdp-
parameters.xhtml#sdp-att-field>.
[SDP-protos]
"SDP Parameters - Proto", September 2021,
<https://www.iana.org/assignments/sdp-parameters/sdp-
parameters.xhtml#sdp-parameters-2>.
10.2. Informative References
[I-D.draft-ietf-quic-multipath]
Liu, Y., Ma, Y., De Coninck, Q., Bonaventure, O., Huitema,
C., and M. Kühlewind, "Multipath Extension for QUIC", Work
in Progress, Internet-Draft, draft-ietf-quic-multipath-12,
22 January 2025, <https://datatracker.ietf.org/doc/html/
draft-ietf-quic-multipath-12>.
[I-D.ietf-avtcore-rtp-vvc]
Zhao, S., Wenger, S., Sanchez, Y., Wang, Y., and M. M.
Hannuksela, "RTP Payload Format for Versatile Video Coding
(VVC)", Work in Progress, Internet-Draft, draft-ietf-
avtcore-rtp-vvc-18, 4 August 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-avtcore-
rtp-vvc-18>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002,
<https://www.rfc-editor.org/rfc/rfc3261>.
[RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
"Codec Control Messages in the RTP Audio-Visual Profile
with Feedback (AVPF)", RFC 5104, DOI 10.17487/RFC5104,
February 2008, <https://www.rfc-editor.org/rfc/rfc5104>.
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[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,
<https://www.rfc-editor.org/rfc/rfc5245>.
[RFC6263] Marjou, X. and A. Sollaud, "Application Mechanism for
Keeping Alive the NAT Mappings Associated with RTP / RTP
Control Protocol (RTCP) Flows", RFC 6263,
DOI 10.17487/RFC6263, June 2011,
<https://www.rfc-editor.org/rfc/rfc6263>.
[RFC7675] Perumal, M., Wing, D., Ravindranath, R., Reddy, T., and M.
Thomson, "Session Traversal Utilities for NAT (STUN) Usage
for Consent Freshness", RFC 7675, DOI 10.17487/RFC7675,
October 2015, <https://www.rfc-editor.org/rfc/rfc7675>.
[RFC8083] Perkins, C. and V. Singh, "Multimedia Congestion Control:
Circuit Breakers for Unicast RTP Sessions", RFC 8083,
DOI 10.17487/RFC8083, March 2017,
<https://www.rfc-editor.org/rfc/rfc8083>.
[RFC8825] Alvestrand, H., "Overview: Real-Time Protocols for
Browser-Based Applications", RFC 8825,
DOI 10.17487/RFC8825, January 2021,
<https://www.rfc-editor.org/rfc/rfc8825>.
[RFC8842] Holmberg, C. and R. Shpount, "Session Description Protocol
(SDP) Offer/Answer Considerations for Datagram Transport
Layer Security (DTLS) and Transport Layer Security (TLS)",
RFC 8842, DOI 10.17487/RFC8842, January 2021,
<https://www.rfc-editor.org/rfc/rfc8842>.
[RFC8843] Holmberg, C., Alvestrand, H., and C. Jennings,
"Negotiating Media Multiplexing Using the Session
Description Protocol (SDP)", RFC 8843,
DOI 10.17487/RFC8843, January 2021,
<https://www.rfc-editor.org/rfc/rfc8843>.
[RFC8859] Nandakumar, S., "A Framework for Session Description
Protocol (SDP) Attributes When Multiplexing", RFC 8859,
DOI 10.17487/RFC8859, January 2021,
<https://www.rfc-editor.org/rfc/rfc8859>.
[RFC8888] Sarker, Z., Perkins, C., Singh, V., and M. Ramalho, "RTP
Control Protocol (RTCP) Feedback for Congestion Control",
RFC 8888, DOI 10.17487/RFC8888, January 2021,
<https://www.rfc-editor.org/rfc/rfc8888>.
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Acknowledgments
The authors thank Sam Hurst for sharing his thoughts about the
challenges of developing SDP for RoQ, and for providing specific
comments and draft text.
The authors thank Bernard Aboba and Mathis Westerlund for comments on
various previous versions of this specification, under a variety of
draft names.
*Editors' Question:* Who else should we name in this paragraph? I
should look through the minutes from previous AVTCORE meetings, to
see who I missed.
The authors thank Mathis Engelbart for helping to keep this draft
aligned with [I-D.ietf-avtcore-rtp-over-quic].
A significant amount of work on this draft happened while Spencer was
affiliated with Tencent America LLC. Spencer appreciates that
support.
Authors' Addresses
Spencer Dawkins
Wonder Hamster Internetworking LLC
United States of America
Email: spencerdawkins.ietf@gmail.com
Victor Pascual
Nokia
Barcelona
Spain
Email: victor.pascual_avila@nokia.com
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