RTP Control Protocol (RTCP) Feedback for Congestion Control in Interactive Multimedia Conferences
draft-ietf-rmcat-rtp-cc-feedback-05
Network Working Group C. Perkins
Internet-Draft University of Glasgow
Intended status: Informational November 4, 2019
Expires: May 7, 2020
RTP Control Protocol (RTCP) Feedback for Congestion Control in
Interactive Multimedia Conferences
draft-ietf-rmcat-rtp-cc-feedback-05
Abstract
This memo discusses the types of congestion control feedback that it
is possible to send using the RTP Control Protocol (RTCP), and their
suitability of use in implementing congestion control for unicast
multimedia applications.
Status of This Memo
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This Internet-Draft will expire on May 7, 2020.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Possible Models for RTCP Feedback . . . . . . . . . . . . . . 2
3. What Feedback is Achievable With RTCP? . . . . . . . . . . . 4
3.1. Scenario 1: Voice Telephony . . . . . . . . . . . . . . . 4
3.2. Scenario 2: Point-to-Point Video Conference . . . . . . . 6
3.3. Scenario 3: Group Video Conference . . . . . . . . . . . 10
3.4. Scenario 4: Screen Sharing . . . . . . . . . . . . . . . 10
4. Discussion and Conclusions . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
8. Informative References . . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
The coming deployment of WebRTC systems raises the prospect that high
quality video conferencing will see extremely wide use. To ensure
the stability of the network in the face of this use, WebRTC systems
will need to use some form of congestion control for their RTP-based
media traffic. To develop such congestion control, it is necessary
to understand the sort of congestion feedback that can be provided
within the framework of RTP [RFC3550] and the RTP Control Protocol
(RTCP). It then becomes possible to determine if this is sufficient
for congestion control, or if some form of RTP extension is needed.
This memo considers the congestion feedback that can be sent using
RTCP under the RTP/SAVPF profile [RFC5124] (the secure version of the
RTP/AVPF profile [RFC4585]). This profile was chosen as it forms the
basis for media transport in WebRTC [I-D.ietf-rtcweb-rtp-usage]
systems. Nothing in this memo is specific to the secure version of
the profile, or to WebRTC, however.
2. Possible Models for RTCP Feedback
Several questions need to be answered when providing RTCP reception
quality feedback for congestion control purposes. These include:
o How often is feedback needed?
o How much overhead is acceptable?
o How much, and what, data does each report contain?
The key question is how often does the receiver need to send feedback
on the reception quality it is experiencing, and hence the congestion
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state of the network? Traditional congestion control protocols, such
as TCP, send acknowledgements with every packet (or, at least, every
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