draft-ietf-avtcore-rtp-circuit-breakers
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions, Internet Engineering Task Force, RFC 8083, March 2017. DOI:10.17487/RFC8083
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, August 2016, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-18.txt).
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Editorial clarification in the first paragraph of Section 4.5 ("Ceasing Transmission").
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, July 2016, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-17.txt).
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This version replaces the discussion of ECN in Section 7 with a statement that there's no consensus on on how the receipt of ECN feedback will impact the congestion circuit breaker, or indeed whether the congestion circuit breaker ought to take ECN feedback into account.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, June 2016, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-16.txt).
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This version contains three sets of changes:
- Editorial changes to the Abstract and Introduction, to address Stephen Farrell's comment by clarifying what it means to "operate within the envelope defined by this memo".
- Update Section 4.5 ("Ceasing Transmission") to address Alissa Cooper's DISCUSS, clarifying that it is the RTP flows sharing a 5-tuple that are stopped when the circuit breaker triggers, rather than the entire call.
- Update Section 7 to address Mirja Kuehlewind's DISCUSS, expanding the discussion of how the RTP circuit breaker should react to ECN-CE marks. This changes "ECN-CE marked packets SHOULD be treated as if they were lost when calculating if the congestion-based RTP circuit breaker" into a more nuanced recommendation, based on likely future evolution of ECN response.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, April 2016, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-15.txt).
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This is a minor update, to address Spencer Dawkins' Area Director review comments. There are two changes: in Section 4.5, clarify the end of the first paragraph, about when an implementation might reasonably expect congestion to have dissipated; and in Section 7, clarify why ECN-CE marked packets SHOULD be treated as lost, rather than MUST be treated as lost, due to the unreliability of ECN marking on some paths.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, March 2016, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-14.txt).
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This version is intended to address Area Director and Operations Directorate review comments. The changes are:
- Rewrite the Abstract, and update Section 1 to clarify what is meant by a circuit breaker.
- In Section 4, clarify that the RTP circuit breaker SHOULD NOT be disabled on networks that might be subject to congestion, even if the peer doesn't support RTCP, unless there is some other way of detecting congestion.
- In Section 4.3, clarify what information is recorded when RTCP SR/RR report blocks are received.
- In Section 4.4, clarify that the time period that is considered significant is on the order of seconds, of 10s of seconds.
- In Section 4.5, add a paragraph to suggest that implementations might monitor RTCP reception reports, to warn that problems are occurring, before the RTP circuit breaker triggers.
- In Section 8, expand discussion of grouping when different DSCP values are used in a bundled group.
- Move RFC6679 to be a normative reference, rather than informative
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, February 2016, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-13.txt).
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This version adds a reference to ConEx based on feedback from Meral Shirazipour.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, February 2016, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-12.txt).
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This version addresses working group last call comments from Gorry Fairhurst and Meral Shirazipour. There are no protocol changes, but a number of editorial fixes and clarifications have been made.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, October 2015, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-11.txt).
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This version of the draft is a major update, that makes the following changes:
- Update the media timeout circuit breaker to address the over- and under-sampling issues raised by Magnus Westerlund, by taking into account the RTT and RTP framing interval in the calculation, as well as the RTCP reporting interval.
- Update the congestion circuit breaker to address the over- and under-sampling issues raised by Magnus Westerlund, and to account for codecs that cannot change their rate on each frame, by modifying the definition of CB_INTERVAL to include the RTP framing interval, the frame group size, and the RTT in the calculation, as well as the RTCP reporting interval.
- Collect definitions and clarify terminology.
- Clarify behaviour when interworking with systems that don't implement RTCP.
- Remove discussion on Impact of RTCP Reporting Groups, that seemed to confuse rather than clarify.
- Various editorial fixes to address review comments by Simon Perreault.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, March 2015, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-10.txt).
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This version fixes the table in Section 4.5, changes the CB_INTERVAL definition for RTP/AVPF to be max(T_rr_interval, Td), and adds a reference to the TSVWG generic transport circuit breaker draft.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, March 2015, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-09.txt).
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This version adjusts the number of RTCP reporting intervals required to trigger the media timeout and congestion circuit breakers based on the RTCP reporting interval, and adds a new Section 4.5 explaining the choice of the number of intervals needed to trigger. For the RTCP timeout circuit breaker, it clarifies that Tmin = 5 seconds MUST be used for the timeout interval (T_rr_interval = 4 seconds if RTP/AVPF is used), and gives recommendations for the upper bound on Td. Finally behaviour with RTP/AVPF and RTP/SAVPF, and the T_rr_interval parameter, is clarified.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, December 2014, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-08.txt).
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The changes in this version of the draft include:
- In section 4.3, attempt to clarify behaviour of the congestion circuit breaker, especially around the factor-of-ten reduction.
- In section 9, clarify behaviour regarding layered flows and bundled media within a single RTP session.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, October 2014, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-07.txt).
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The changes in this version of the draft include:
- update Section 4.1 to consistently require three consecutive reports before triggering the circuit breaker;
- in Section 4.2, in the discussion of large sessions that round-robin SR/RR reports, strengthen the requirement to treat receipt of any SR/RR packet on the 5-tuple as an indication that the path is working from MAY to SHOULD;
- in Section 4.3, wait for three consecutive reporting intervals before triggering the circuit breaker, to match Sections 4.1 and 4.2;
- update Section 4.3: when sending at a low rate (loss than 1 packet per RTT), a sender MAY ignore a single instance of the congestion circuit breaker, but SHOULD cease transmission if it triggers again immediately, addressing the case where the packet loss rate estimate is inaccurate, due to being derived from too few packets;
- in Section 4.4, clarify that receivers should monitor media quality and terminate the session if it is unusable, not just senders;
- in section 5, clarify when non-compound packets should be ignored;
- add a new section on impact of layered coding;
- add discussion of problem caused by overly long RTCP reporting intervals to the Security Considerations;
- add an Open Issues Section; and
- various minor editorial fixes.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, July 2014, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-06.txt).
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This version addresses review comments from Magnus Westerlund. The changes made are small editorial clarifications; there are no technical changes to the draft.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, February 2014, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-05.txt).
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This version of the draft update the recommendations for choice of TCP throughput equation in Section 4.3, giving references to our measurement results [PV2013], [Infocom2014] to justify the choices. A media usability circuit breaker is also added, recommending that applications cease transmission if the packet loss rate or latency are such that the media will be unusable for the application.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, January 2014, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-04.txt).
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This is a keep-alive version, to prevent the draft expiring. The only changes are to update the references to catch-up with recently published RFCs.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, July 2013, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-03.txt).
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This is a relatively minor update. Changes include:
- In Section 4.3, reorder the text to be clearer that the sender is allowed to reduce it's sending rate by a factor of ten when the congestion circuit breaker fires, to see if this resolves the problem, before it has to cease transmission.
- In Section 4.2 and Section 4.3, add some text about sessions with a large enough number of media streams that the receivers has to generate round-robin RTCP reception reports.
- In Section 4.3, clarify what RTCP reporting interval is used to trigger the circuit breaker
- Add Section 7 on the Impact of RTCP Reporting Groups.
- Colin Perkins and Varun Singh, Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions (.txt|.pdf), Internet Engineering Task Force, February 2013, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-02.txt).
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The significant changes in this version are as follows:
- In the media timeout circuit breaker, disallow reduction in rate by a factor of 10 as a response when circuit breaker triggered. A media timeout (several reporting intervals when media is being set but not received) signals significant path failure, not a transient problem, and so should stop the RTP media flow, not just reduce it's rate.
- Clarify RTCP Timeout circuit breaker: note that the fixed minimum RTCP reporting intervals SHOULD be used when calculating the RTCP timeout. The rationale is in Section 6.2 of RFC 3550; to avoid premature timeouts if not all participants use reduced minimum interval.
- Clarify congestion circuit breaker: use actual RTCP reporting interval, not the fixed minimum interval, when determining if congestion is occurring. The actual interval, when using the reduced minimum interval, scales with the data rate, and so matches the dynamics of the congestion circuit breaker.
- Break out the description of what it means to cease transmission into a separate section, and expand. When deciding when to restart transmission, clarify that the destination 3-tuple (transport, port, IP addr) rather than the full 5-tuple is used when checking if congestion has eased. The Rationale is that it is not okay to simply change the source port, and try again on the same path; need a different IP-layer path
- Clarify behaviour with reduced-size RTCP: reduced-size RTCP packets containing RTCP SR or RR packets MUST be counted towards the circuit breaker conditions, while reduced size RTCP packets that don't contain SR or RR packets are not counted towards the circuit breaker. The intention is to allow use of low-overhead reduced-size RTP/AVPF NACKs for congestion control without risk of triggering circuit breaker, whilst reacting to significant loss events reported by SR/RR packets.
- Expand discussion of how and when ECN-CE marks are counted towards the circuit breaker. RFC 6679 provides RTCP extensions to feedback ECN-CE marks in RTCP XR, and these are counted towards the circuit breaker. ECN-CE marks reported in a reduced size RTCP packets along with SR or RR blocks are processed; if the SR or RR block is not present, they're ignored. These are conceptually the same rules as for packet loss, but adapted for ECN.
- Update title and abstract
- Clarify that multicast is out of scope
- Clarify why unicast RTP sessions might have more than two SSRCs
- Clarify that RTCP support is required
- Clarify that implementations without a circuit breaker, or congestion control algorithm operating within a circuit breaker envelope, ought not be used on networks subject to congestion
- Note that the RTCP RR jitter estimate is not valid for frames split across multiple RTP packets with the same timestamp
- Expand discussion of competition with TCP flows
- Clarify operation of the congestion circuit breaker if the fraction of packets lost is zero
- Clarify that the circuit breaker at a sender only looks at RTCP SR/RR packets that contain reports for the SSRC values it is using to send
- Colin Perkins and Varun Singh, RTP Congestion Control: Circuit Breakers for Unicast Sessions (.txt|.pdf), Internet Engineering Task Force, October 2012, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-01.txt).
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The changes in this version are as follows:
- Clarify that multicast congestion control is outside the scope of this memo.
- Clarify what it means for an implementation to cease transmission when the circuit breaker fires. Specifically, the intention is that the application will stop sending RTP data packets until the user makes an explicit attempt to restart the call. The draft notes that RTP flows halted by the circuit breaker should not be restarted automatically unless the sender has received information that the congestion has dissipated.
- Add an explicit RTCP Timeout circuit breaker in Section 4.2 (this is a revised and extended version of Section 8 of the -00 draft"> Unlike the media timeout in Section 4.1, which fires when returning RTCP RR packets show that media isn't reaching the receiver, this circuit breaker is triggered if RTCP packets are no longer returning to the sender.
- In section 4.3, clarify when high-rate senders can back-off to a lower rate when the circuit breaker is triggered, and when they need to cease transmission.
- Expand and clarify Section 5 about RTP circuit breakers for systems using the RTP/AVPF profile. A sender needs to process early RTCP reports that contain an SR/RR packet as-if they were regular RTCP reports, but ignore early non-compound RTCP packets without an SR/RR. This allows the use of low-overhead early RTP/AVPF feedback without triggering the RTP circuit breaker, and so is suitable for RTP congestion control algorithms that need to quickly report loss events in between regular RTCP reports.
- Expand and clarify Section 6 about the impact of RTCP XR, to note that RTCP XR packets are ignored by the circuit breaker algorithm.
- Expand and clarify Section 7 about the impact of ECN, to note that reports of ECN-CE marks are treated as packet loss for the congestion based circuit breaker, but ignored for the media timeout and RTCP timeout circuit breakers.
- Expand and clarify Section 8 on the security considerations to discuss authentication requirements.
- Colin Perkins and Varun Singh, RTP Congestion Control: Circuit Breakers for Unicast Sessions (.txt|.pdf), Internet Engineering Task Force, October 2012, Work in progress (draft-ietf-avtcore-rtp-circuit-breakers-00.txt).
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Our draft on circuit breakers for RTP congestion control was adopted as an AVTCORE working group draft at IETF 84 in Vancouver. This version is submitted to reflect this change in status. The content is identical to the previous individual submission.
This draft replaces draft-perkins-avtcore-rtp-circuit-breakers