XR Block Working GroupInternet Engineering Task Force (IETF) J. OttInternet-DraftRequest for Comments: 7097 V. Singh, Ed.Intended status:Category: Standards Track Aalto UniversityExpires: May 16, 2014ISSN: 2070-1721 I. Curcio Nokia Research CenterNovember 12, 2013January 2014 RTP Control Protocol (RTCP) Extended Report (XR) forRun Length Encoding (RLE)RLE of Discarded Packetsdraft-ietf-xrblock-rtcp-xr-discard-rle-metrics-09Abstract The RTP Control Protocol (RTCP) is used in conjunction with the Real- time Transport Protocol (RTP) in order to provide a variety ofshort-termshort- term and long-term reception statistics. The available reporting may include aggregate information across longer periods of time as well as individual packet reporting. This document specifies a per-packet report metric capturing individual packets discarded from the de- jitter buffer after successful reception. Status of This Memo ThisInternet-Draftissubmitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documentsan Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF).Note that other groups may also distribute working documents as Internet-Drafts. The listIt represents the consensus ofcurrent Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents validthe IETF community. It has received public review and has been approved fora maximumpublication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741. Information about the current status ofsix monthsthis document, any errata, and how to provide feedback on it may beupdated, replaced, or obsoleted by other documentsobtained atany 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 May 16, 2014.http://www.rfc-editor.org/info/rfc7097. Copyright Notice Copyright (c)20132014 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....................................................3 2. Terminology. . . . . . . . . . . . . . . . . . . . . . . . . 4.....................................................4 3. RTCP XR Discard RLE Report Block. . . . . . . . . . . . . . . . . 4................................4 4. Protocol Operation. . . . . . . . . . . . . . . . . . . . . 5..............................................5 4.1. Reporting Node (Receiver). . . . . . . . . . . . . . . . 6..................................6 4.2. Media Sender. . . . . . . . . . . . . . . . . . . . . . 6...............................................6 5. SDPsignaling . . . . . . . . . . . . . . . . . . . . . . . . 6Signaling ...................................................6 6. Security Considerations. . . . . . . . . . . . . . . . . . . 7.........................................7 7. IANA Considerations. . . . . . . . . . . . . . . . . . . . . 7.............................................7 7.1. XR Report Block Registration. . . . . . . . . . . . . . 7...............................7 7.2. SDP Parameter Registration. . . . . . . . . . . . . . . 8.................................7 7.3. ContactinformationInformation for IANAregistrations . . . . . . . 8Registrations .................8 8. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . 8.................................................8 9. References. . . . . . . . . . . . . . . . . . . . . . . . . 8......................................................8 9.1. Normative References. . . . . . . . . . . . . . . . . . 8.......................................8 9.2. Informative References. . . . . . . . . . . . . . . . . 8.....................................8 Appendix A. Metricsrepresented using RFC6390Represented Using the Template. . . . . 9 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 10 B.1. changes in draft-ietf-xrblock-rtcp-xr-discard-rle- metrics-00 . . . . . . . . . . . . . . . . . . . . . . . 10 B.2. changes in draft-ietf-xrblock-rtcp-xr-discard-rle- metrics-01 . . . . . . . . . . . . . . . . . . . . . . . 10 B.3. changes in draft-ietf-xrblock-rtcp-xr-discard-rle- metrics-02 . . . . . . . . . . . . . . . . . . . . . . . 10 B.4. changes in draft-ietf-xrblock-rtcp-xr-discard-rle- metrics-03 . . . . . . . . . . . . . . . . . . . . . . . 10 B.5. changes in draft-ietf-xrblock-rtcp-xr-discard-rle- metrics-04 . . . . . . . . . . . . . . . . . . . . . . . 11 B.6. changes in draft-ietf-xrblock-rtcp-xr-discard-rle- metrics-05 . . . . . . . . . . . . . . . . . . . . . . . 11 B.7. changes in draft-ietf-xrblock-rtcp-xr-discard-rle- metrics-06 . . . . . . . . . . . . . . . . . . . . . . . 11 B.8. changes in draft-ietf-xrblock-rtcp-xr-discard-rle- metrics-07 . . . . . . . . . . . . . . . . . . . . . . . 11 B.9. changes in draft-ietf-xrblock-rtcp-xr-discard-rle- metrics-08 . . . . . . . . . . . . . . . . . . . . . . . 11 B.10. changes in draft-ietf-xrblock-rtcp-xr-discard-rle- metrics-09 . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11from RFC 6390 ...9 1. Introduction RTP [RFC3550] provides a transport for real-time media flows such as audio and video together with the RTPcontrol protocol (RTCP)Control Protocol (RTCP), which provides periodic feedback about the media streams received in a specific duration. In addition, RTCP can be used for timely feedback about individual events to report (e.g., packet loss) [RFC4585]. Both long-term and short-term feedback enable a media sender to adapt its media transmission and/or encoding dynamically to the observed path characteristics.RFC3611RFC 3611 [RFC3611] defines RTCP Extended Reports as a detailed reporting framework to provide more than just the coarse Receiver Report (RR) statistics. The detailed reporting may enable a media sender to react more appropriately to the observed networking conditions as these can be characterized better, although at the expense of extra overhead. Among many other report blocks,RFC3611RFC 3611 specifies the Loss Run Length Encoding (RLE)blockblock, which reports runs of packets received and lost with the granularity of individual packets. This can help both error recovery and path loss characterization. In addition to lost packets,RFC3611RFC 3611 defines the notion of "discarded" packets: packets that were received but dropped from the de-jitter buffer because they were either too early (for buffering) or too late (for playout). The "discard rate" metric is part of theVoIPVoice over IP (VoIP) metrics report block even though it is not just applicable to audio: it is specified as the fraction of discarded packets since the beginning of thesession. See sectionsession (see Section 4.7.1 ofRFC3611 [RFC3611].RFC 3611 [RFC3611]). The discard metric is believed to be applicable to a large class of RTP applicationswhichthat use a de-jitter bufferRFC5481[RFC5481]. Recently proposed extensions to the Extended Reports(XR)(XRs) reporting suggest enhancing this discard metric: o Reporting the number of discarded packets in a measurement interval, i.e.,duringeither during the last reporting interval or since the beginning of the session, as indicated by a flag in the suggested XRreport[RFC7002]. If an endpoint needs to report packet discard due tootherreasons other thanearly-early andlate-arrivallate arrival (for example, discard due to duplication, redundancy,etc.)etc.), then it should consider using the Discarded PacketsReport Blockreport block [RFC7002]. o Reporting gaps and bursts of discarded packets during a measurement interval, i.e., the last reporting interval or the duration of the session [RFC7003]. o Reporting the sum of payload bytes discarded during a measurement interval, i.e., the last reporting interval or the duration of the session[I-D.ietf-xrblock-rtcp-xr-bytes-discarded-metric].[DISCARD-METRIC]. However, none of these metrics allow a receiver to report precisely which packets were discarded. While this information could in theory be derived from high-frequency reporting on the number of discarded packets [RFC7002] or from the gap/burst report [RFC7003], these two mechanisms do not appear feasible:Thethe former would require an unduly high amount ofreportingreporting, which still might not be sufficient due to the non-deterministic scheduling of RTCP packets. The latterincurincurs significant complexity and reporting overhead and might still not deliver the desired accuracy. This document defines a discard report block following the idea of the run-length encoding applied for lost and received packets in [RFC3611]. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119 [RFC2119]. The terminology defined in RTP [RFC3550] and in the extensions for XR reporting [RFC3611] applies. 3. RTCP XR Discard RLE Report Block The RTCP XR Discard RLE report block uses the same format as specified for the loss and duplicate report blocks in RFC 3611 [RFC3611]. Figure 1 describes the packet format. The fields "BT", "T", "block length", "SSRC of source", "begin_seq", and "end_seq" have the same semantics and representation as defined in [RFC3611], with the addition of the "E" flag to indicate the reason for discard. The "chunks" encoding the run length have the same representation as inRFC3611,RFC 3611, but encode discarded packets. A definition of a discarded packet is given in RFC 7002 [RFC7002]. 0 1 2 3 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |BT=DRLEBT=25 |rsvd |E| T | block length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC of source | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | begin_seq | end_seq | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | chunk 1 | chunk 2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : ... : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | chunk n-1 | chunk n | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: RTCP XR Discard RLE Report Block Block Type (BT, 8 bits): ARun-length encoded Discarded Packets Report BlockDiscard RLE report block is identified by the constantDRLE. [Note to RFC Editor: please replace DRLE with the IANA provided RTCP XR block type for this block. Please remove this note prior to publication as an RFC.]25. rsvd (3 bits): This field is reserved for future definition. In the absence of such definition, the bits in this field MUST be set to zero and MUST be ignored by the receiver. The 'E' bit is introduced to distinguish between packets discarded due to early arrival and those discarded due to late arrival. The 'E' bit is set to '1' if the chunks represent packets discarded due to arriving too earlyarrivaland is set to '0' otherwise. In case both early and late discarded packets shall be reported, two Discard RLE report blocks MUST be included; their sequence number range MAY overlap, but individual packets MUST only be reported as either early or late and not appear marked in both. If packets appear in both report blocks, the conflicting packetsarewill be ignored. Packets not reported inneithereither block are considered to be properly received and not discarded. Discard RLEReport Blocksreport blocks SHOULD be sent in conjunction with an RTCP RR as a compound RTCP packet. 4. Protocol Operation This section describes the behavior of the reporting node (= media receiver) and the media sender. 4.1. Reporting Node (Receiver) Transmission of RTCP XR Discard RLEReportsreport blocks is up to the discretion of the media receiver, as is the reporting granularity. However, it is RECOMMENDED that the media receiversignalssignal all discarded packets using the method defined in this document. If all packets over a reporting periodwereare discarded, the media receiver MAY use the Discard Report Block [RFC7002] instead. In case of limited available reporting bandwidth, it is up to the receiver whether or not to include RTCP XR Discard RLEreports.report blocks. The media receiver MAY send the Discard RLEReportsreport blocks as part of the regularly scheduled RTCPpacketspackets, as perRFC3550.RFC 3550. It MAY also include Discard RLEReportsreport blocks in immediate or early feedbackpacketspackets, as perRFC4585.RFC 4585. 4.2. Media Sender The media sender MUST be prepared to operate without receiving any Discard RLEreports.report blocks. If Discard RLEreportsreport blocks are generated by the media receiver, the media sender cannot rely on all these reports being received, nor can the media sender rely on a regular generation pattern from the media receiver. However, if the media sender receivesanyRTCP XR reports but the reports contain no Discard RLE report blocks and is aware that the media receiver supports Discard RLE report blocks, it MAY assume that no packets were discarded at the media receiver. 5. SDPsignalingSignaling A participant of a media session MAY use SDP to signal its support for the report block specified in this document or use them without any prior signaling (seesectionSection 5 of RFC 3611 [RFC3611]). For signaling in SDP, the RTCP XR attribute as defined in RFC 3611 [RFC3611] MUST be used. The SDP [RFC4566] attribute 'xr-format' defined inRFC3611RFC 3611 is augmented as described in the following to indicate the the discard RLE metric. rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF ; defined in [RFC3611] xr-format =/ xr-discard-rle xr-discard-rle = "discard-rle" The parameter 'discard-rle' is used to indicate support for the Discard RLEReport Blockreport block defined in Section 3. When SDP is used in Offer/Answer context, the mechanism defined in RFC 3611 [RFC3611] for unilateral "rtcp-xr" attribute parameters applies (seesectionSection 5.2 of RFC 3611 [RFC3611]). 6. Security Considerations The Discard RLE report block provides per-packet statistics so the risk to confidentiality documented in Section 7,paragraph 3Paragraph 3, of RFC 3611 [RFC3611] applies. In some situations, returning very detailed error information (e.g., over-range measurement or measurement unavailable) using this report block can provide an attacker with insight into the security processing. Implementers should consider the guidance in[I-D.ietf-avt-srtp-not-mandatory][NO-SRTP] for using appropriate security mechanisms, i.e., where security is a concern, the implementation should apply encryption and authentication to the report block. Forexampleexample, this can be achieved by using the AVPF profile together with the Secure RTP profile as defined in RFC 3711 [RFC3711]; an appropriate combination of the two profiles (an "SAVPF") is specified in RFC 5124 [RFC5124]. However, other mechanisms also exist(documented in [I-D.ietf-avtcore-rtp-security-options])[SRTP-OPTIONS] and might be more suitable. Additionally, The security considerations of RFC 3550 [RFC3550], RFC 3611 [RFC3611], and RFC 4585 [RFC4585] apply. 7. IANA Considerations New block types for RTCP XR are subject to IANA registration. For general guidelines on IANA considerations for RTCP XR, refer to[RFC3611].RFC 3611. 7.1. XR Report Block Registration This document extends the IANA "RTP Control Protocol Extended Reports (RTCP XR) Block Type Registry" bya new value:assigning value 25 to DRLE (Discard RLE Report).[Note to RFC Editor: please replace DRLE with the IANA provided RTCP XR block type for this block here and in the diagrams above. Please remove this note prior to publication as an RFC.]7.2. SDP Parameter Registration This document registersa new parameters for the Session Description Protocol (SDP), "discard-rle"'discard-rle' in the"RTP Control Protocol Extended Reports (RTCP XR) Session Description Protocol (SDP) Parameters Registry"."RTCP XR SDP Parameters". 7.3. ContactinformationInformation for IANAregistrationsRegistrations Joerg Ott (jo@comnet.tkk.fi) Aalto University Comnet, Otakaari 5A, 02150 Espoo, Finland. 8. Acknowledgments The authors would like to thank Alan Clark, Roni Even, Sam Hartman, Colin Perkins, Dan Romascanu, Dan Wing, and Qin Wu for providing valuable feedback on earlier draft versions of thisdraft.document. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003. [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control Protocol Extended Reports (RTCP XR)", RFC 3611, November 2003. [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, "Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July 2006. [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, July 2006. [RFC7002] Clark, A., Zorn, G., and Q. Wu, "RTP Control Protocol (RTCP) Extended Report (XR) Block for Discard Count Metric Reporting", RFC 7002, September 2013. 9.2. Informative References [RFC7003] Clark, A., Huang, R., and Q. Wu, "RTP Control Protocol (RTCP) Extended Report (XR) Block for Burst/Gap Discard Metric Reporting", RFC 7003, September 2013. [RFC5481] Morton, A. and B. Claise, "Packet Delay Variation Applicability Statement", RFC 5481, March 2009. [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, "The Secure Real-time Transport Protocol (SRTP)", RFC 3711, March 2004. [RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/SAVPF)", RFC 5124, February 2008.[I-D.ietf-avt-srtp-not-mandatory][NO-SRTP] Perkins, C. and M. Westerlund, "Securing the RTP Protocol Framework: Why RTP Does Not Mandate a Single Media Security Solution",draft-ietf-avt-srtp-not-mandatory-13 (workWork inprogress), MayProgress, October 2013.[I-D.ietf-avtcore-rtp-security-options][SRTP-OPTIONS] Westerlund, M. and C. Perkins, "Options for Securing RTP Sessions",draft-ietf-avtcore-rtp-security-options-04 (workWork inprogress), JulyProgress, November 2013.[I-D.ietf-xrblock-rtcp-xr-bytes-discarded-metric][DISCARD-METRIC] Singh, V., Ott, J., and I. Curcio, "RTP Control Protocol (RTCP) Extended Report (XR) for Bytes Discarded Metric",draft-ietf-xrblock-rtcp-xr-bytes-discarded-metric-00 (workWork inprogress), OctoberProgress, November 2013. Appendix A. Metricsrepresented using RFC6390 Template RFC EDITOR NOTE: please change XXXX in [RFCXXXX] byRepresented Using thenewTemplate from RFCnumber, when assigned.6390 a.Run-length encodingRLE of Discarded RTP Packets Metric * Metric Name: RLE - Run-length encoding of Discarded RTP Packets Metric. * Metric Description: Instances of RTP packets discarded over the period covered by this report. * Method of Measurement or Calculation: SeesectionSection 3, for the definition of Discardrun-length encoding [RFCXXXX]RLE [RFC7097] andsectionSection 4.1 ofRFC3611RFC 3611 forRun-length encoding.RLE. * Units of Measurement: Every RTP packet in the interval is reported as discarded or not. SeesectionSection 3 of RFC 7097 [RFC7097] for thedefinition of [RFCXXXX].definition. * Measurement Point(s) with Potential Measurement Domain: The measurement of these metrics is made at the receiving end of the RTP stream. * Measurement Timing: Each RTP packet between a beginning sequence number (begin_seq) and ending sequence number (end_seq)areis reported as discarded or not. SeesectionSection 3 of RFC 7097 [RFC7097] for the definition of Discardrun-length encoding [RFCXXXX].RLE. * Use and applications: SeesectionSection 1, Paragraph 1,paragraph 1of[RFCXXXX].[RFC7097]. * Reporting model: SeeRFC3611. 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-xrblock-rtcp-xr-discard-rle-metrics-00 o Changed the interval flag from 1 to 2 bits in the discarded bytes report. Also added the measurement identification tag to the block. o Added this section. B.2. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-01 o Removed the measurement identification tag in the bytes discarded block. B.3. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-02 o Removed the extra Tag bits from the Discarded bytes XR block. o Clarified use of measurement identity block in Section 4 and 5.2 B.4. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-03 o Added explanation for block length in bytes discarded block. o Added an acknowledgement section. B.5. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-04 o Added Block Type definition to each XRBlock. o Made changes requested in WGLC. B.6. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-05 o Made changes requested by SDP directorate. B.7. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-06 o Editorial fixes based on review from Gen-art and IESG review. B.8. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-07 o Editorial fixes based on review from IESG. o Editorial fixes based on Security and PM directorate. o Split bytes discarded from this draft to another. o Updated Security Considerations Section. o This draft now normatively cites the definition of discards in 'packets discarded' draft. B.9. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-08 o Editorial fixes: Updated references from drafts to RFCs. o Updated RFC6390 template with RTP keyword. B.10. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-09 o Removed (RLE) from RFC6390 template.RFC 3611. Authors' Addresses Joerg Ott Aalto University School of Electrical Engineering Otakaari 5 A Espoo, FIN 02150 FinlandEmail:EMail: jo@comnet.tkk.fi Varun Singh (editor) Aalto University School of Electrical Engineering Otakaari 5 A Espoo, FIN 02150 FinlandEmail:EMail: varun@comnet.tkk.fi URI: http://www.netlab.tkk.fi/~varun/ Igor D.D. Curcio Nokia Research Center P.O. Box 1000 (Visiokatu 3) Tampere, FIN 33721 FinlandEmail:EMail: igor.curcio@nokia.com