--- 1/draft-ietf-rmcat-eval-criteria-03.txt 2015-10-19 17:15:14.438544689 -0700 +++ 2/draft-ietf-rmcat-eval-criteria-04.txt 2015-10-19 17:15:14.470545452 -0700 @@ -1,18 +1,19 @@ RMCAT WG V. Singh -Internet-Draft J. Ott -Intended status: Informational Aalto University -Expires: September 11, 2015 March 10, 2015 +Internet-Draft callstats.io +Intended status: Informational J. Ott +Expires: April 22, 2016 Aalto University + October 20, 2015 Evaluating Congestion Control for Interactive Real-time Media - draft-ietf-rmcat-eval-criteria-03 + draft-ietf-rmcat-eval-criteria-04 Abstract The Real-time Transport Protocol (RTP) is used to transmit media in telephony and video conferencing applications. This document describes the guidelines to evaluate new congestion control algorithms for interactive point-to-point real-time media. Status of This Memo @@ -22,85 +23,76 @@ 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 September 11, 2015. + This Internet-Draft will expire on April 22, 2016. Copyright Notice Copyright (c) 2015 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 3.1. RTP Log Format . . . . . . . . . . . . . . . . . . . . . 5 - 4. Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 4.1. Avoiding Congestion Collapse . . . . . . . . . . . . . . 5 - 4.2. Stability . . . . . . . . . . . . . . . . . . . . . . . . 5 - 4.3. Media Traffic . . . . . . . . . . . . . . . . . . . . . . 5 - 4.4. Start-up Behaviour . . . . . . . . . . . . . . . . . . . 6 - 4.5. Diverse Environments . . . . . . . . . . . . . . . . . . 6 - 4.6. Varying Path Characteristics . . . . . . . . . . . . . . 6 - 4.7. Reacting to Transient Events or Interruptions . . . . . . 7 - 4.8. Fairness With Similar Cross-Traffic . . . . . . . . . . . 7 - 4.9. Impact on Cross-Traffic . . . . . . . . . . . . . . . . . 7 - 4.10. Extensions to RTP/RTCP . . . . . . . . . . . . . . . . . 7 - 5. List of Network Parameters . . . . . . . . . . . . . . . . . 7 - 5.1. One-way Propagation Delay . . . . . . . . . . . . . . . . 7 - 5.2. End-to-end Loss . . . . . . . . . . . . . . . . . . . . . 8 - 5.3. DropTail Router Queue Length . . . . . . . . . . . . . . 8 - 5.4. Loss generation model . . . . . . . . . . . . . . . . . . 8 - 5.5. Jitter models . . . . . . . . . . . . . . . . . . . . . . 9 - 5.5.1. Random Bounded PDV (RBPDV) . . . . . . . . . . . . . 9 - 5.5.2. Approximately Random Subject to No-Reordering Bounded - PDV (NR-RPVD) . . . . . . . . . . . . . . . . 10 - 6. Traffic Models . . . . . . . . . . . . . . . . . . . . . . . 11 - 6.1. TCP taffic model . . . . . . . . . . . . . . . . . . . . 11 - 6.2. RTP Video model . . . . . . . . . . . . . . . . . . . . . 12 - 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 - 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 12 - 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 11.1. Normative References . . . . . . . . . . . . . . . . . . 12 - 11.2. Informative References . . . . . . . . . . . . . . . . . 13 - Appendix A. Application Trade-off . . . . . . . . . . . . . . . 14 - A.1. Measuring Quality . . . . . . . . . . . . . . . . . . . . 14 - Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 14 - B.1. Changes in draft-ietf-rmcat-eval-criteria-02 . . . . . . 14 - B.2. Changes in draft-ietf-rmcat-eval-criteria-02 . . . . . . 14 - B.3. Changes in draft-ietf-rmcat-eval-criteria-01 . . . . . . 14 - B.4. Changes in draft-ietf-rmcat-eval-criteria-00 . . . . . . 15 - B.5. Changes in draft-singh-rmcat-cc-eval-04 . . . . . . . . . 15 - B.6. Changes in draft-singh-rmcat-cc-eval-03 . . . . . . . . . 15 - B.7. Changes in draft-singh-rmcat-cc-eval-02 . . . . . . . . . 15 - B.8. Changes in draft-singh-rmcat-cc-eval-01 . . . . . . . . . 15 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 + 3.1. RTP Log Format . . . . . . . . . . . . . . . . . . . . . 4 + 4. List of Network Parameters . . . . . . . . . . . . . . . . . 5 + 4.1. One-way Propagation Delay . . . . . . . . . . . . . . . . 5 + 4.2. End-to-end Loss . . . . . . . . . . . . . . . . . . . . . 5 + 4.3. DropTail Router Queue Length . . . . . . . . . . . . . . 6 + 4.4. Loss generation model . . . . . . . . . . . . . . . . . . 6 + 4.5. Jitter models . . . . . . . . . . . . . . . . . . . . . . 6 + 4.5.1. Random Bounded PDV (RBPDV) . . . . . . . . . . . . . 7 + 4.5.2. Approximately Random Subject to No-Reordering Bounded + PDV (NR-RPVD) . . . . . . . . . . . . . . . . 8 + 5. WiFi or Cellular Links . . . . . . . . . . . . . . . . . . . 9 + 6. Traffic Models . . . . . . . . . . . . . . . . . . . . . . . 9 + 6.1. TCP taffic model . . . . . . . . . . . . . . . . . . . . 9 + 6.2. RTP Video model . . . . . . . . . . . . . . . . . . . . . 9 + 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 + 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 + 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 10 + 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 + 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 + 11.1. Normative References . . . . . . . . . . . . . . . . . . 10 + 11.2. Informative References . . . . . . . . . . . . . . . . . 11 + Appendix A. Application Trade-off . . . . . . . . . . . . . . . 12 + A.1. Measuring Quality . . . . . . . . . . . . . . . . . . . . 12 + Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 12 + B.1. Changes in draft-ietf-rmcat-eval-criteria-04 . . . . . . 12 + B.2. Changes in draft-ietf-rmcat-eval-criteria-03 . . . . . . 12 + B.3. Changes in draft-ietf-rmcat-eval-criteria-02 . . . . . . 12 + B.4. Changes in draft-ietf-rmcat-eval-criteria-01 . . . . . . 13 + B.5. Changes in draft-ietf-rmcat-eval-criteria-00 . . . . . . 13 + B.6. Changes in draft-singh-rmcat-cc-eval-04 . . . . . . . . . 13 + B.7. Changes in draft-singh-rmcat-cc-eval-03 . . . . . . . . . 13 + B.8. Changes in draft-singh-rmcat-cc-eval-02 . . . . . . . . . 13 + B.9. Changes in draft-singh-rmcat-cc-eval-01 . . . . . . . . . 14 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 1. Introduction This memo describes the guidelines to help with evaluating new congestion control algorithms for interactive point-to-point real time media. The requirements for the congestion control algorithm are outlined in [I-D.ietf-rmcat-cc-requirements]). This document builds upon previous work at the IETF: Specifying New Congestion Control Algorithms [RFC5033] and Metrics for the Evaluation of Congestion Control Algorithms [RFC5166]. @@ -200,194 +193,83 @@ RTP sequence no RTP timestamp marker bit payload size If the congestion control implements, retransmissions or FEC, the evaluation should report both packet loss (before applying error- resilience) and residual packet loss (after applying error- resilience). -4. Guidelines - - A congestion control algorithm should be tested in simulation or a - testbed environment, and the experiments should be repeated multiple - times to infer statistical significance. The following guidelines - are considered for evaluation: - -4.1. Avoiding Congestion Collapse - - The congestion control algorithm is expected to take an action, such - as reducing the sending rate, when it detects congestion. Typically, - it should intervene before the circuit breaker - [I-D.ietf-avtcore-rtp-circuit-breakers] is engaged. - - Does the congestion control propose any changes to (or diverge from) - the circuit breaker conditions defined in - [I-D.ietf-avtcore-rtp-circuit-breakers]. - -4.2. Stability - - The congestion control should be assessed for its stability when the - path characteristics do not change over time. Changing the media - encoding rate estimate too often or by too much may adversely affect - the application layer performance. - -4.3. Media Traffic - - The congestion control algorithm should be assessed with different - types of media behavior, i.e., the media should contain idle and - data-limited periods. For example, periods of silence for audio, - varying amount of motion for video, or bursty nature of I-frames. - - The evaluation may be done in two stages. In the first stage, the - endpoint generates traffic at the rate calculated by the congestion - controller. In the second stage, real codecs or models of video - codecs are used to mimic application-limited data periods and varying - video frame sizes. - -4.4. Start-up Behaviour - - The congestion control algorithm should be assessed with different - start-rates. The main reason is to observe the behavior of the - congestion control in different test scenarios, such as when - competing with varying amount of cross-traffic or how quickly does - the congestion control algorithm achieve a stable sending rate. - -4.5. Diverse Environments - - The congestion control algorithm should be assessed in heterogeneous - environments, containing both wired and wireless paths. Examples of - wireless access technologies are: 802.11, GPRS, HSPA, or LTE. One of - the main challenges of the wireless environments for the congestion - control algorithm is to distinguish between congestion induced loss - and transmission (bit-error) loss. Congestion control algorithms may - incorrectly identify transmission loss as congestion loss and reduce - the media encoding rate by too much, which may cause oscillatory - behavior and deteriorate the users' quality of experience. - Furthermore, packet loss may induce additional delay in networks with - wireless paths due to link-layer retransmissions. - -4.6. Varying Path Characteristics - - The congestion control algorithm should be evaluated for a range of - path characteristics such as, different end-to-end capacity and - latency, varying amount of cross traffic on a bottleneck link and a - router's queue length. For the moment, only DropTail queues are - used. However, if new Active Queue Management (AQM) schemes become - available, the performance of the congestion control algorithm should - be again evaluated. - - In an experiment, if the media only flows in a single direction, the - feedback path should also be tested with varying amounts of - impairments. - - The main motivation for the previous and current criteria is to - identify situations in which the proposed congestion control is less - performant. - -4.7. Reacting to Transient Events or Interruptions - - The congestion control algorithm should be able to handle changes in - end-to-end capacity and latency. Latency may change due to route - updates, link failures, handovers etc. In mobile environment the - end-to-end capacity may vary due to the interference, fading, - handovers, etc. In wired networks the end-to-end capacity may vary - due to changes in resource reservation. - -4.8. Fairness With Similar Cross-Traffic - - The congestion control algorithm should be evaluated when competing - with other RTP flows using the same or another candidate congestion - control algorithm. The proposal should highlight the bottleneck - capacity share of each RTP flow. - -4.9. Impact on Cross-Traffic - - The congestion control algorithm should be evaluated when competing - with standard TCP. Short TCP flows may be considered as transient - events and the RTP flow may give way to the short TCP flow to - complete quickly. However, long-lived TCP flows may starve out the - RTP flow depending on router queue length. - - The proposal should also measure the impact on varied number of - cross-traffic sources, i.e., few and many competing flows, or mixing - various amounts of TCP and similar cross-traffic. - -4.10. Extensions to RTP/RTCP - - The congestion control algorithm should indicate if any protocol - extensions are required to implement it and should carefully describe - the impact of the extension. - -5. List of Network Parameters +4. List of Network Parameters The implementors initially are encouraged to choose evaluation settings from the following values: -5.1. One-way Propagation Delay +4.1. One-way Propagation Delay Experiments are expected to verify that the congestion control is able to work in challenging situations, for example over trans- continental and/or satellite links. Typical values are: 1. Very low latency: 0-1ms 2. Low latency: 50ms + 3. High latency: 150ms 4. Extreme latency: 300ms -5.2. End-to-end Loss +4.2. End-to-end Loss To model lossy links, the experiments can choose one of the following loss rates, the fractional loss is the ratio of packets lost and packets sent. 1. no loss: 0% 2. 1% 3. 5% 4. 10% 5. 20% -5.3. DropTail Router Queue Length +4.3. DropTail Router Queue Length The router queue length is measured as the time taken to drain the FIFO queue. It has been noted in various discussions that the queue length in the current deployed Internet varies significantly. While the core backbone network has very short queue length, the home gateways usually have larger queue length. Those various queue lengths can be categorized in the following way: 1. QoS-aware (or short): 70ms 2. Nominal: 300-500ms 3. Buffer-bloated: 1000-2000ms Here the size of the queue is measured in bytes or packets and to convert the queue length measured in seconds to queue length in bytes: QueueSize (in bytes) = QueueSize (in sec) x Throughput (in bps)/8 -5.4. Loss generation model +4.4. Loss generation model [Editor's note : Describes the model for generating packet losses, for example, losses can be generated using traces, or using the Gilbert-Elliot model, or randomly (uncorrelated loss).] -5.5. Jitter models +4.5. Jitter models This section defines jitter model for the purposes of this document. When jitter is to be applied to both the RMCAT flow and any competing flow (such as a TCP competing flow), the competing flow will use the jitter definition below that does not allow for re-ordering of packets on the competing flow (see NR-RBPDV definition below). Jitter is an overloaded term in communications. Its meaning is typically associated with the variation of a metric (e.g., delay) with respect to some reference metric (e.g., average delay or minimum @@ -411,21 +293,21 @@ minimum delay, and then a minority of the packets transits the network with delays higher than the median or average transit time (these are outliers). Although infrequent, outliers can cause significant deleterious operation in adaptive systems and should be considered in RMCAT adaptation designs. In this section we define two different bounded PDV characteristics, 1) Random Bounded PDV and 2) Approximately Random Subject to No- Reordering Bounded PDV. -5.5.1. Random Bounded PDV (RBPDV) +4.5.1. Random Bounded PDV (RBPDV) The RBPDV probability distribution function (pdf) is specified to be of some mathematically describable function which includes some practical minimum and maximum discrete values suitable for testing. For example, the minimum value, x_min, might be specified as the minimum transit time packet and the maximum value, x_max, might be idefined to be two standard deviations higher than the mean. Since we are typically interested in the distribution relative to the mean delay packet, we define the zero mean PVD sample, z(n), to be @@ -447,21 +329,21 @@ become re-ordered such as in load balancing topologies and during route changes. However, for the vast majority of cases there is no packet re-ordering because most of the time packets follow the same path. Due to this, if a packet becomes overly delayed, the packets after it on that flow are also delayed. This is especially true for mobile wireless links where there are per-flow queues prior to base station scheduling. Owing to this important use case, we define another PDV profile similar to the above, but one that does not allow for re-ordering within a flow. -5.5.2. Approximately Random Subject to No-Reordering Bounded PDV (NR- +4.5.2. Approximately Random Subject to No-Reordering Bounded PDV (NR- RPVD) No Reordering RPDV, NR-RPVD, is defined similarly to the above with one important exception. Let serial(n) be defined as the serialization delay of packet n at the lowest bottleneck link rate (or other appropriate rate) in a given test. Then we produce all the post-jitter values for j(n) for n = 1, 2, ... N, where N is the length of the source sequence s to be offset-ed. The exception can be stated as follows: We revisit all j(n) beginning from index n=2, and if j(n) is determined to be less than [j(n-1)+serial(n-1)], we @@ -486,45 +368,56 @@ development for RMCAT. [Editor's Note: It may require to define test distributions as well. Example test distribution may include- 1 - Two-sided: Uniform PDV Distribution. Two quantities to define: x_min and x_max. 2 - Two-sided: Truncated Gaussian PDV Distribution. Four quantities to define: the appropriate x_min and x_max for test (e.g., +/- two - sigma values), the standard deviation and the mean. + sigma values), the standard deviation, and the mean. - 3 - One Sided: TBD] + 3 - One Sided: Truncated Gaussian PDV Distribution. Quantities to + define: three sigma value, the standard deviation, and the mean] + +5. WiFi or Cellular Links + + [I-D.fu-rmcat-wifi-test-case] describes methods to evaluate the + congestion control in WiFi network, alternatively + [I-D.ietf-rmcat-wireless-tests] describes mechanisms to emulate and + simulate cellular networks. 6. Traffic Models 6.1. TCP taffic model Long-lived TCP flows will download data throughout the session and - are expected to have infinite amount of data to send or receive. + are expected to have infinite amount of data to send or receive. For + example, to Each short TCP flow is modeled as a sequence of file downloads interleaved with idle periods. Not all short TCPs start at the same time, i.e., some start in the ON state while others start in the OFF state. - The short TCP flows can be modelled in two ways, 1) 100s of flows - fetching small (5-20 KB) amounts of data, or 2) 10s of flows fetching - slightly larger (100-1000KB) amounts of data. + The short TCP flows can be modelled as follows: 30 connections start + simultaneously fetching small (30-50 KB) amounts of data. This + covers the case where the short TCP flows are not fetching a video + file. - The idle period is typically derived from an exponential distribution - with the mean value of 10 seconds. + The idle period between bursts of starting a group of TCP flows is + typically derived from an exponential distribution with the mean + value of 10 seconds. - [Open issue: short-lived/bursty TCP cross-traffic parameters are - still to be agreed upon]. + [These values were picked based on the data available at + http://httparchive.org/interesting.php as of October 2015]. 6.2. RTP Video model [I-D.zhu-rmcat-video-traffic-source] describes two types of video traffic models for evaluating RMCAT candidate algorithms. The first model statistically characterizes the behavior of a video encoder. Whereas the second model uses video traces. 7. Security Considerations @@ -584,20 +477,32 @@ Jesup, R. and Z. Sarker, "Congestion Control Requirements for Interactive Real-Time Media", draft-ietf-rmcat-cc- requirements-09 (work in progress), December 2014. [I-D.ietf-avtcore-rtp-circuit-breakers] Perkins, C. and V. Singh, "Multimedia Congestion Control: Circuit Breakers for Unicast RTP Sessions", draft-ietf- avtcore-rtp-circuit-breakers-09 (work in progress), March 2015. + [I-D.ietf-rmcat-wireless-tests] + Sarker, Z. and I. Johansson, "Evaluation Test Cases for + Interactive Real-Time Media over Wireless Networks", + draft-ietf-rmcat-wireless-tests-00 (work in progress), + June 2015. + + [I-D.fu-rmcat-wifi-test-case] + Fu, J., Zhu, X., Ramalho, M., and W. Tan, "Evaluation Test + Cases for Interactive Real-Time Media over Wi-Fi + Networks", draft-fu-rmcat-wifi-test-case-01 (work in + progress), July 2015. + 11.2. Informative References [RFC5033] Floyd, S. and M. Allman, "Specifying New Congestion Control Algorithms", BCP 133, RFC 5033, August 2007. [RFC5166] Floyd, S., "Metrics for the Evaluation of Congestion Control Mechanisms", RFC 5166, March 2008. [RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion Control", RFC 5681, September 2009. @@ -637,100 +542,107 @@ currently an open issue. However, there is consensus that congestion control algorithm should be able to show that it is useful for interactive video by performing analysis using a real codec and video sequences. Appendix B. Change Log Note to the RFC-Editor: please remove this section prior to publication as an RFC. -B.1. Changes in draft-ietf-rmcat-eval-criteria-02 +B.1. Changes in draft-ietf-rmcat-eval-criteria-04 + + o Removed the guidelines section, as most of the sections are now + covered: wireless tests, video model, etc. + + o Improved Short TCP model based on the suggestion to use + httparchive.org. + +B.2. Changes in draft-ietf-rmcat-eval-criteria-03 o Keep-alive version. o Moved link parameters and traffic models from eval-test -B.2. Changes in draft-ietf-rmcat-eval-criteria-02 +B.3. Changes in draft-ietf-rmcat-eval-criteria-02 o Incorporated fairness test as a working test. o Updated text on mimimum evaluation requirements. -B.3. Changes in draft-ietf-rmcat-eval-criteria-01 +B.4. Changes in draft-ietf-rmcat-eval-criteria-01 o Removed Appendix B. o Removed Section on Evaluation Parameters. -B.4. Changes in draft-ietf-rmcat-eval-criteria-00 +B.5. Changes in draft-ietf-rmcat-eval-criteria-00 o Updated references. o Resubmitted as WG draft. -B.5. Changes in draft-singh-rmcat-cc-eval-04 +B.6. Changes in draft-singh-rmcat-cc-eval-04 o Incorporate feedback from IETF 87, Berlin. o Clarified metrics: convergence time, bandwidth utilization. o Changed fairness criteria to fairness test. o Added measuring pre- and post-repair loss. o Added open issue of measuring video quality to appendix. o clarified use of DropTail and AQM. o Updated text in "Minimum Requirements for Evaluation" -B.6. Changes in draft-singh-rmcat-cc-eval-03 +B.7. Changes in draft-singh-rmcat-cc-eval-03 o Incorporate the discussion within the design team. o Added a section on evaluation parameters, it describes the flow and network characteristics. o Added Appendix with self-fairness experiment. o Changed bottleneck parameters from a proposal to an example set. o -B.7. Changes in draft-singh-rmcat-cc-eval-02 +B.8. Changes in draft-singh-rmcat-cc-eval-02 o Added scenario descriptions. -B.8. Changes in draft-singh-rmcat-cc-eval-01 +B.9. Changes in draft-singh-rmcat-cc-eval-01 o Removed QoE metrics. o Changed stability to steady-state. o Added measuring impact against few and many flows. o Added guideline for idle and data-limited periods. o Added reference to TCP evaluation suite in example evaluation scenarios. Authors' Addresses Varun Singh - Aalto University - School of Electrical Engineering - Otakaari 5 A - Espoo, FIN 02150 + Nemu Dialogue Systems Oy + Runeberginkatu 4c A 4 + Helsinki 00100 Finland - Email: varun@comnet.tkk.fi - URI: http://www.netlab.tkk.fi/~varun/ + Email: varun@callstats.io + URI: http://www.callstats.io/ Joerg Ott Aalto University School of Electrical Engineering Otakaari 5 A Espoo, FIN 02150 Finland Email: jo@comnet.tkk.fi