--- 1/draft-ietf-rmcat-coupled-cc-02.txt 2016-07-29 18:31:04.008760610 -0700 +++ 2/draft-ietf-rmcat-coupled-cc-03.txt 2016-07-29 18:31:04.052761726 -0700 @@ -1,19 +1,19 @@ RTP Media Congestion Avoidance Techniques (rmcat) S. Islam Internet-Draft M. Welzl Intended status: Experimental S. Gjessing -Expires: October 16, 2016 University of Oslo - April 14, 2016 +Expires: January 29, 2017 University of Oslo + July 28, 2016 Coupled congestion control for RTP media - draft-ietf-rmcat-coupled-cc-02 + draft-ietf-rmcat-coupled-cc-03 Abstract When multiple congestion controlled RTP sessions traverse the same network bottleneck, it can be beneficial to combine their controls such that the total on-the-wire behavior is improved. This document describes such a method for flows that have the same sender, in a way that is as flexible and simple as possible while minimizing the amount of changes needed to existing RTP applications. It specifies how to apply the method for both the NADA and Google congestion @@ -27,74 +27,76 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on October 16, 2016. + This Internet-Draft will expire on January 29, 2017. Copyright Notice Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Limitations . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Architectural overview . . . . . . . . . . . . . . . . . . . 4 5. Roles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 5.1. SBD . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 + 5.1. SBD . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.2. FSE . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.3. Flows . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.3.1. Example algorithm 1 - Active FSE . . . . . . . . . . 7 5.3.2. Example algorithm 2 - Conservative Active FSE . . . . 8 - 6. Application . . . . . . . . . . . . . . . . . . . . . . . . . 9 + 6. Application . . . . . . . . . . . . . . . . . . . . . . . . . 10 6.1. NADA . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6.2. GCC . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6.3. General recommendations . . . . . . . . . . . . . . . . . 10 - 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 - 9. Security Considerations . . . . . . . . . . . . . . . . . . . 11 - 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 10.1. Normative References . . . . . . . . . . . . . . . . . . 11 - 10.2. Informative References . . . . . . . . . . . . . . . . . 12 - Appendix A. Scheduling . . . . . . . . . . . . . . . . . . . . . 13 - Appendix B. Example algorithm - Passive FSE . . . . . . . . . . 13 - B.1. Example operation (passive) . . . . . . . . . . . . . . . 16 - Appendix C. Change log . . . . . . . . . . . . . . . . . . . . . 20 - C.1. draft-welzl-rmcat-coupled-cc . . . . . . . . . . . . . . 20 - C.1.1. Changes from -00 to -01 . . . . . . . . . . . . . . . 20 - C.1.2. Changes from -01 to -02 . . . . . . . . . . . . . . . 20 - C.1.3. Changes from -02 to -03 . . . . . . . . . . . . . . . 20 - C.1.4. Changes from -03 to -04 . . . . . . . . . . . . . . . 21 - C.1.5. Changes from -04 to -05 . . . . . . . . . . . . . . . 21 - C.2. draft-ietf-rmcat-coupled-cc . . . . . . . . . . . . . . . 21 - C.2.1. Changes from draft-welzl-rmcat-coupled-cc-05 . . . . 21 - C.2.2. Changes from -00 to -01 . . . . . . . . . . . . . . . 21 - C.2.3. Changes from -01 to -02 . . . . . . . . . . . . . . . 21 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 + 7. Expected feedback from experiments . . . . . . . . . . . . . 11 + 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 + 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 + 10. Security Considerations . . . . . . . . . . . . . . . . . . . 11 + 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 + 11.1. Normative References . . . . . . . . . . . . . . . . . . 12 + 11.2. Informative References . . . . . . . . . . . . . . . . . 12 + Appendix A. Scheduling . . . . . . . . . . . . . . . . . . . . . 14 + Appendix B. Example algorithm - Passive FSE . . . . . . . . . . 14 + B.1. Example operation (passive) . . . . . . . . . . . . . . . 17 + Appendix C. Change log . . . . . . . . . . . . . . . . . . . . . 21 + C.1. draft-welzl-rmcat-coupled-cc . . . . . . . . . . . . . . 21 + C.1.1. Changes from -00 to -01 . . . . . . . . . . . . . . . 21 + C.1.2. Changes from -01 to -02 . . . . . . . . . . . . . . . 21 + C.1.3. Changes from -02 to -03 . . . . . . . . . . . . . . . 21 + C.1.4. Changes from -03 to -04 . . . . . . . . . . . . . . . 22 + C.1.5. Changes from -04 to -05 . . . . . . . . . . . . . . . 22 + C.2. draft-ietf-rmcat-coupled-cc . . . . . . . . . . . . . . . 22 + C.2.1. Changes from draft-welzl-rmcat-coupled-cc-05 . . . . 22 + C.2.2. Changes from -00 to -01 . . . . . . . . . . . . . . . 22 + C.2.3. Changes from -01 to -02 . . . . . . . . . . . . . . . 22 + C.2.4. Changes from -02 to -03 . . . . . . . . . . . . . . . 22 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 1. Introduction When there is enough data to send, a congestion controller must increase its sending rate until the path's capacity has been reached; depending on the controller, sometimes the rate is increased further, until packets are ECN-marked or dropped. This process inevitably creates undesirable queuing delay -- an effect that is amplified when multiple congestion controlled connections traverse the same network bottleneck. @@ -286,25 +287,20 @@ o The rate used by the flow in bits per second, FSE_R. Note that the priority does not need to be a floating point value and its value range does not matter for this algorithm: the algorithm works with a flow's priority portion of the sum of all priority values. Priorities can therefore be mapped to the "very-low", "low", "medium" or "high" priority levels described in [I-D.ietf-rtcweb-transports] using the values 1, 2, 4 and 8, respectively. - The FSE can operate on window-based as well as rate-based congestion - controllers. In case of a window-based controller, FSE_R is a - window, and all the text below should be considered to refer to - window, not rates. - In the FSE, each FG contains one static variable S_CR which is the sum of the calculated rates of all flows in the same FG. This value is used to calculate the sending rate. The information listed here is enough to implement the sample flow algorithm given below. FSE implementations could easily be extended to store, e.g., a flow's current sending rate for statistics gathering or future potential optimizations. 5.3. Flows @@ -326,21 +322,22 @@ This algorithm was designed to be the simplest possible method to assign rates according to the priorities of flows. Simulations results in [fse] indicate that it does however not significantly reduce queuing delay and packet loss. (1) When a flow f starts, it registers itself with SBD and the FSE. FSE_R is initialized with the congestion controller's initial rate. SBD will assign the correct FGI. When a flow is assigned an FGI, it adds its FSE_R to S_CR. - (2) When a flow f stops, its entry is removed from the list. + (2) When a flow f stops or pauses, its entry is removed from the + list. (3) Every time the congestion controller of the flow f determines a new sending rate CC_R, the flow calls UPDATE, which carries out the tasks listed below to derive the new sending rates for all the flows in the FG. A flow's UPDATE function uses a local (i.e. per-flow) temporary variable S_P, which is the sum of all the priorities. (a) It updates S_CR. @@ -366,21 +363,22 @@ This algorithm extends algorithm 1 to conservatively emulate the behavior of a single flow by proportionally reducing the aggregate rate on congestion. Simulations results in [fse] indicate that it can significantly reduce queuing delay and packet loss. (1) When a flow f starts, it registers itself with SBD and the FSE. FSE_R is initialized with the congestion controller's initial rate. SBD will assign the correct FGI. When a flow is assigned an FGI, it adds its FSE_R to S_CR. - (2) When a flow f stops, its entry is removed from the list. + (2) When a flow f stops or pauses, its entry is removed from the + list. (3) Every time the congestion controller of the flow f determines a new sending rate CC_R, the flow calls UPDATE, which carries out the tasks listed below to derive the new sending rates for all the flows in the FG. A flow's UPDATE function uses a local (i.e. per-flow) temporary variable S_P, which is the sum of all the priorities, and a local variable DELTA, which is used to calculate the difference between CC_R and the previously stored FSE_R. To prevent flows from either ignoring congestion or overreacting, a timer keeps them from changing their rates @@ -460,37 +458,51 @@ congestion control mechanisms. Receiver-side calculations: When receiver-side calculations make assumptions about the rate of the sender, the calculations need to be synchronized or the receiver needs to be updated accordingly. This applies to TFRC [RFC5348], for example, where simulations showed somewhat less favorable results when using the FSE without a receiver-side change [fse]. -7. Acknowledgements +7. Expected feedback from experiments + + The algorithm described in this memo has so far been evaluated using + simulations covering all the tests for more than one flow from + [I-D.ietf-rmcat-eval-test] (see [IETF-93], [IETF-94]). Experiments + should confirm these results using at least one of the same + congestion control algorithms (GCC or NADA) with real-life code + (e.g., browsers communicating over an emulated network covering the + conditions in [I-D.ietf-rmcat-eval-test]. The tests with real-life + code should be repeated afterwards in real network environments and + monitored. Implementers and testers are invited to document their + findings in an Internet draft. + +8. Acknowledgements This document has benefitted from discussions with and feedback from David Hayes, Mirja Kuehlewind, Karen Nielsen, Andreas Petlund, David Ros (who also gave the FSE its name), Zaheduzzaman Sarker, Varun - Singh and Kristian Hiorth. The authors would like to thank Xiaoqing - Zhu and Stefan Holmer for helping with NADA and GCC. + Singh, Anna Brunstrom, Martin Stiemerling, and Kristian Hiorth. The + authors would like to thank Xiaoqing Zhu and Stefan Holmer for + helping with NADA and GCC. This work was partially funded by the European Community under its Seventh Framework Programme through the Reducing Internet Transport Latency (RITE) project (ICT-317700). -8. IANA Considerations +9. IANA Considerations This memo includes no request to IANA. -9. Security Considerations +10. Security Considerations In scenarios where the architecture described in this document is applied across applications, various cheating possibilities arise: e.g., supporting wrong values for the calculated rate, the desired rate, or the priority of a flow. In the worst case, such cheating could either prevent other flows from sending or make them send at a rate that is unreasonably large. The end result would be unfair behavior at the network bottleneck, akin to what could be achieved with any UDP based application. Hence, since this is no worse than UDP in general, there seems to be no significant harm in using this @@ -499,75 +511,90 @@ In the case of a single-user system, it should also be in the interest of any application programmer to give the user the best possible experience by using reasonable flow priorities or even letting the user choose them. In a multi-user system, this interest may not be given, and one could imagine the worst case of an "arms race" situation, where applications end up setting their priorities to the maximum value. If all applications do this, the end result is a fair allocation in which the priority mechanism is implicitly eliminated, and no major harm is done. -10. References +11. References -10.1. Normative References +11.1. Normative References [I-D.ietf-rmcat-gcc] Holmer, S., Lundin, H., Carlucci, G., Cicco, L., and S. Mascolo, "A Google Congestion Control Algorithm for Real- - Time Communication", draft-ietf-rmcat-gcc-01 (work in - progress), October 2015. + Time Communication", draft-ietf-rmcat-gcc-02 (work in + progress), July 2016. [I-D.ietf-rmcat-nada] - Zhu, X., Pan, R., Ramalho, M., Cruz, S., Jones, P., Fu, + Zhu, X., Pan, R., Ramalho, D., Cruz, S., Jones, P., Fu, J., D'Aronco, S., and C. Ganzhorn, "NADA: A Unified Congestion Control Scheme for Real-Time Media", draft- ietf-rmcat-nada-02 (work in progress), March 2016. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ - RFC2119, March 1997, + Requirement Levels", BCP 14, RFC 2119, + DOI 10.17487/RFC2119, March 1997, . [RFC3124] Balakrishnan, H. and S. Seshan, "The Congestion Manager", RFC 3124, DOI 10.17487/RFC3124, June 2001, . [RFC5348] Floyd, S., Handley, M., Padhye, J., and J. Widmer, "TCP - Friendly Rate Control (TFRC): Protocol Specification", RFC - 5348, DOI 10.17487/RFC5348, September 2008, + Friendly Rate Control (TFRC): Protocol Specification", + RFC 5348, DOI 10.17487/RFC5348, September 2008, . -10.2. Informative References +11.2. Informative References [fse] Islam, S., Welzl, M., Gjessing, S., and N. Khademi, "Coupled Congestion Control for RTP Media", ACM SIGCOMM Capacity Sharing Workshop (CSWS 2014) and ACM SIGCOMM CCR 44(4) 2014; extended version available as a technical report from http://safiquli.at.ifi.uio.no/paper/fse-tech-report.pdf , 2014. [fse-noms] Islam, S., Welzl, M., Hayes, D., and S. Gjessing, "Managing Real-Time Media Flows through a Flow State Exchange", IEEE NOMS 2016, Istanbul, Turkey , 2016. + [I-D.ietf-rmcat-eval-test] + Sarker, Z., Singh, V., Zhu, X., and D. Ramalho, "Test + Cases for Evaluating RMCAT Proposals", draft-ietf-rmcat- + eval-test-03 (work in progress), March 2016. + [I-D.ietf-rmcat-sbd] Hayes, D., Ferlin, S., Welzl, M., and K. Hiorth, "Shared Bottleneck Detection for Coupled Congestion Control for RTP Media.", draft-ietf-rmcat-sbd-04 (work in progress), March 2016. [I-D.ietf-rtcweb-transports] Alvestrand, H., "Transports for WebRTC", Internet-draft draft-ietf-rtcweb-transports-11.txt, January 2016. + [IETF-93] Islam, S., Welzl, M., and S. Gjessing, "Updates on Coupled + Congestion Control for RTP Media", July 2015, + . + + [IETF-94] Islam, S., Welzl, M., and S. Gjessing, "Updates on Coupled + Congestion Control for RTP Media", November 2015, + . + [RFC7478] Holmberg, C., Hakansson, S., and G. Eriksson, "Web Real- Time Communication Use Cases and Requirements", RFC 7478, DOI 10.17487/RFC7478, March 2015, . [rtcweb-rtp-usage] Perkins, C., Westerlund, M., and J. Ott, "Web Real-Time Communication (WebRTC): Media Transport and Use of RTP", Internet-draft draft-ietf-rtcweb-rtp-usage-26.txt, March 2016. @@ -619,21 +646,22 @@ bandwidth from application-limited or terminated flows) which is initialized to 0. For the passive version, S_CR is limited to increase or decrease as conservatively as a flow's congestion controller decides in order to prohibit sudden rate jumps. (1) When a flow f starts, it registers itself with SBD and the FSE. FSE_R and DR are initialized with the congestion controller's initial rate. SBD will assign the correct FGI. When a flow is assigned an FGI, it adds its FSE_R to S_CR. - (2) When a flow f stops, it sets its DR to 0 and sets P to -1. + (2) When a flow f stops or pauses, it sets its DR to 0 and sets P to + -1. (3) Every time the congestion controller of the flow f determines a new sending rate CC_R, assuming the flow's new desired rate new_DR to be "infinity" in case of a bulk data transfer with an unknown maximum rate, the flow calls UPDATE, which carries out the tasks listed below to derive the flow's new sending rate, Rate. A flow's UPDATE function uses a few local (i.e. per-flow) temporary variables, which are all initialized to 0: DELTA, new_S_CR and S_P. @@ -927,30 +955,36 @@ connection to the prioritization text there. C.2.3. Changes from -01 to -02 o Minor changes. o Moved references of NADA and GCC from informative to normative. o Added a reference for the passive variant of the algorithm. -Authors' Addresses +C.2.4. Changes from -02 to -03 + + o Minor changes. + o Added a section about expected feedback from experiments. + +Authors' Addresses Safiqul Islam University of Oslo PO Box 1080 Blindern Oslo N-0316 Norway Phone: +47 22 84 08 37 Email: safiquli@ifi.uio.no + Michael Welzl University of Oslo PO Box 1080 Blindern Oslo N-0316 Norway Phone: +47 22 85 24 20 Email: michawe@ifi.uio.no Stein Gjessing