draft-ietf-rmcat-rtp-cc-feedback-04.txt   draft-ietf-rmcat-rtp-cc-feedback-05.txt 
Network Working Group C. Perkins Network Working Group C. Perkins
Internet-Draft University of Glasgow Internet-Draft University of Glasgow
Intended status: Informational July 1, 2018 Intended status: Informational November 4, 2019
Expires: January 2, 2019 Expires: May 7, 2020
RTP Control Protocol (RTCP) Feedback for Congestion Control in RTP Control Protocol (RTCP) Feedback for Congestion Control in
Interactive Multimedia Conferences Interactive Multimedia Conferences
draft-ietf-rmcat-rtp-cc-feedback-04 draft-ietf-rmcat-rtp-cc-feedback-05
Abstract Abstract
This memo discusses the types of congestion control feedback that it This memo discusses the types of congestion control feedback that it
is possible to send using the RTP Control Protocol (RTCP), and their is possible to send using the RTP Control Protocol (RTCP), and their
suitability of use in implementing congestion control for unicast suitability of use in implementing congestion control for unicast
multimedia applications. multimedia applications.
Status of This Memo Status of This Memo
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Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
skipping to change at page 8, line 32 skipping to change at page 8, line 32
with video frames. This gives the following, assuming Nr =1 and Nnc with video frames. This gives the following, assuming Nr =1 and Nnc
= 0 (i.e., send a compound RTCP packet for each video frame, and no = 0 (i.e., send a compound RTCP packet for each video frame, and no
non-compound packets), and using the calculation from Scenario 1: non-compound packets), and using the calculation from Scenario 1:
Brtcp = (n * (Sc + Nnc * Snc))/(Nr * Tf * (1 + Nnc)) Brtcp = (n * (Sc + Nnc * Snc))/(Nr * Tf * (1 + Nnc))
+---------+---------+--------------+--------------+-----------------+ +---------+---------+--------------+--------------+-----------------+
| Data | Video | Video | Audio | Required RTCP | | Data | Video | Video | Audio | Required RTCP |
| Rate | Frame | Packets per | Packets per | bandwidth: | | Rate | Frame | Packets per | Packets per | bandwidth: |
| (kbps) | Rate | Report: Nv | Report: Na | Brtcp (kbps) | | (kbps) | Rate | Report: Nv | Report: Na | Brtcp (kbps) |
+---------+---------+--------------+--------------+-----------------+ +---------+---------+--------------+--------------+-----------------+
| 100 | 8 | 1 | 6 | 33.2 (33%) | | 100 | 8 | 1 | 6 | 32.8 (32%) |
| 200 | 16 | 1 | 3 | 65.0 (32%) | | 200 | 16 | 1 | 3 | 64.0 (32%) |
| 350 | 30 | 1 | 2 | 120.9 (34%) | | 350 | 30 | 1 | 2 | 119.1 (34%) |
| 700 | 30 | 2 | 2 | 121.9 (17%) | | 700 | 30 | 2 | 2 | 120.0 (17%) |
| 700 | 60 | 1 | 1 | 240.0 (34%) | | 700 | 60 | 1 | 1 | 236.2 (33%) |
| 1024 | 30 | 3 | 2 | 122.8 (11%) | | 1024 | 30 | 3 | 2 | 120.9 (11%) |
| 1400 | 60 | 2 | 1 | 241.9 (17%) | | 1400 | 60 | 2 | 1 | 238.1 (17%) |
| 2048 | 30 | 6 | 2 | 125.6 ( 6%) | | 2048 | 30 | 6 | 2 | 123.8 ( 6%) |
| 2048 | 60 | 3 | 1 | 243.8 (11%) | | 2048 | 60 | 3 | 1 | 240.0 (11%) |
| 4096 | 30 | 12 | 2 | 131.2 ( 3%) | | 4096 | 30 | 12 | 2 | 129.4 ( 3%) |
| 4096 | 60 | 6 | 1 | 249.4 ( 6%) | | 4096 | 60 | 6 | 1 | 245.6 ( 5%) |
+---------+---------+--------------+--------------+-----------------+ +---------+---------+--------------+--------------+-----------------+
Table 3: Required RTCP bandwidth, reporting on every frame Table 3: Required RTCP bandwidth, reporting on every frame
The RTCP bandwidth needed scales inversely with Nr. That is, it is The RTCP bandwidth needed scales inversely with Nr. That is, it is
halved if Nr=2 (report on every second packet), is reduced to one- halved if Nr=2 (report on every second packet), is reduced to one-
third if Nr=3 (report on every third packet), and so on. third if Nr=3 (report on every third packet), and so on.
The needed RTCP bandwidth scales as a percentage of the data rate The needed RTCP bandwidth scales as a percentage of the data rate
following the ratio of the frame rate to the data rate. As can be following the ratio of the frame rate to the data rate. As can be
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reporting SSRC. This will be 12 + 28 + 12 + 8 + 2*Nv + 8 + 2*Na reporting SSRC. This will be 12 + 28 + 12 + 8 + 2*Nv + 8 + 2*Na
octets, plus UDP/IP header. That is, Snc = (96 + 2*Nv + 2*Na)/2. octets, plus UDP/IP header. That is, Snc = (96 + 2*Nv + 2*Na)/2.
Repeating the analysis above, but alternating compound and non- Repeating the analysis above, but alternating compound and non-
compound reports, i.e., setting Nnc = 1, gives: compound reports, i.e., setting Nnc = 1, gives:
+---------+---------+--------------+--------------+-----------------+ +---------+---------+--------------+--------------+-----------------+
| Data | Video | Video | Audio | Required RTCP | | Data | Video | Video | Audio | Required RTCP |
| Rate | Frame | Packets per | Packets per | bandwidth: | | Rate | Frame | Packets per | Packets per | bandwidth: |
| (kbps) | Rate | Report: Nv | Report: Na | Brtcp (kbps) | | (kbps) | Rate | Report: Nv | Report: Na | Brtcp (kbps) |
+---------+---------+--------------+--------------+-----------------+ +---------+---------+--------------+--------------+-----------------+
| 100 | 8 | 1 | 6 | 23.5 (23%) | | 100 | 8 | 1 | 6 | 23.2 (23%) |
| 200 | 16 | 1 | 3 | 45.5 (22%) | | 200 | 16 | 1 | 3 | 45.0 (22%) |
| 350 | 30 | 1 | 2 | 84.4 (24%) | | 350 | 30 | 1 | 2 | 83.4 (23%) |
| 700 | 30 | 2 | 2 | 85.3 (12%) | | 700 | 30 | 2 | 2 | 84.4 (12%) |
| 700 | 60 | 1 | 1 | 166.9 (23%) | | 700 | 60 | 1 | 1 | 165.0 (23%) |
| 1024 | 30 | 3 | 2 | 86.2 ( 8%) | | 1024 | 30 | 3 | 2 | 85.3 ( 8%) |
| 1400 | 60 | 2 | 1 | 168.8 (12%) | | 1400 | 60 | 2 | 1 | 166.9 (11%) |
| 2048 | 30 | 6 | 2 | 89.1 ( 4%) | | 2048 | 30 | 6 | 2 | 88.1 ( 4%) |
| 2048 | 60 | 3 | 1 | 170.6 ( 8%) | | 2048 | 60 | 3 | 1 | 168.8 ( 8%) |
| 4096 | 30 | 12 | 2 | 94.7 ( 2%) | | 4096 | 30 | 12 | 2 | 93.8 ( 2%) |
| 4096 | 60 | 6 | 1 | 176.2 ( 4%) | | 4096 | 60 | 6 | 1 | 174.4 ( 4%) |
+---------+---------+--------------+--------------+-----------------+ +---------+---------+--------------+--------------+-----------------+
Table 4: Required RTCP bandwidth, reporting on every frame, with Table 4: Required RTCP bandwidth, reporting on every frame, with
reduced-size reports reduced-size reports
The use of reduced-size RTCP gives a noticeable reduction in the The use of reduced-size RTCP gives a noticeable reduction in the
needed RTCP bandwidth, and can be combined with reporting every few needed RTCP bandwidth, and can be combined with reporting every few
frames rather than every frames. Overall, it is clear that the RTCP frames rather than every frames. Overall, it is clear that the RTCP
overhead can be reasonable across the range of data and frame rates, overhead can be reasonable across the range of data and frame rates,
if RTCP is configured carefully. if RTCP is configured carefully.
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7. Acknowledgements 7. Acknowledgements
Thanks to Magnus Westerlund and the members of the RMCAT feedback Thanks to Magnus Westerlund and the members of the RMCAT feedback
design team for their feedback. design team for their feedback.
8. Informative References 8. Informative References
[I-D.ietf-avtcore-cc-feedback-message] [I-D.ietf-avtcore-cc-feedback-message]
Sarker, Z., Perkins, C., Singh, V., and M. Ramalho, "RTP Sarker, Z., Perkins, C., Singh, V., and M. Ramalho, "RTP
Control Protocol (RTCP) Feedback for Congestion Control", Control Protocol (RTCP) Feedback for Congestion Control",
draft-ietf-avtcore-cc-feedback-message-01 (work in draft-ietf-avtcore-cc-feedback-message-04 (work in
progress), March 2018. progress), July 2019.
[I-D.ietf-avtcore-rtp-multi-stream-optimisation] [I-D.ietf-avtcore-rtp-multi-stream-optimisation]
Lennox, J., Westerlund, M., Wu, Q., and C. Perkins, Lennox, J., Westerlund, M., Wu, Q., and C. Perkins,
"Sending Multiple RTP Streams in a Single RTP Session: "Sending Multiple RTP Streams in a Single RTP Session:
Grouping RTCP Reception Statistics and Other Feedback", Grouping RTCP Reception Statistics and Other Feedback",
draft-ietf-avtcore-rtp-multi-stream-optimisation-12 (work draft-ietf-avtcore-rtp-multi-stream-optimisation-12 (work
in progress), March 2016. in progress), March 2016.
[I-D.ietf-rtcweb-rtp-usage] [I-D.ietf-rtcweb-rtp-usage]
Perkins, C., Westerlund, M., and J. Ott, "Web Real-Time Perkins, C., Westerlund, M., and J. Ott, "Web Real-Time
skipping to change at page 12, line 8 skipping to change at page 12, line 8
<https://www.rfc-editor.org/info/rfc3611>. <https://www.rfc-editor.org/info/rfc3611>.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)", Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, DOI 10.17487/RFC3711, March 2004, RFC 3711, DOI 10.17487/RFC3711, March 2004,
<https://www.rfc-editor.org/info/rfc3711>. <https://www.rfc-editor.org/info/rfc3711>.
[RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
"Extended RTP Profile for Real-time Transport Control "Extended RTP Profile for Real-time Transport Control
Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585,
DOI 10.17487/RFC4585, July 2006, <https://www.rfc- DOI 10.17487/RFC4585, July 2006,
editor.org/info/rfc4585>. <https://www.rfc-editor.org/info/rfc4585>.
[RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for [RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for
Real-time Transport Control Protocol (RTCP)-Based Feedback Real-time Transport Control Protocol (RTCP)-Based Feedback
(RTP/SAVPF)", RFC 5124, DOI 10.17487/RFC5124, February (RTP/SAVPF)", RFC 5124, DOI 10.17487/RFC5124, February
2008, <https://www.rfc-editor.org/info/rfc5124>. 2008, <https://www.rfc-editor.org/info/rfc5124>.
[RFC5506] Johansson, I. and M. Westerlund, "Support for Reduced-Size [RFC5506] Johansson, I. and M. Westerlund, "Support for Reduced-Size
Real-Time Transport Control Protocol (RTCP): Opportunities Real-Time Transport Control Protocol (RTCP): Opportunities
and Consequences", RFC 5506, DOI 10.17487/RFC5506, April and Consequences", RFC 5506, DOI 10.17487/RFC5506, April
2009, <https://www.rfc-editor.org/info/rfc5506>. 2009, <https://www.rfc-editor.org/info/rfc5506>.
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