Audio/Video Transport Working Group G. Hunt Internet-Draft Unaffiliated Intended status: Standards Track A. Clark Expires: October 20, 2012 Telchemy G. Zorn Network Zen Q. Wu Huawei April 18, 2012 RTCP XR Report Block for Discard metric Reporting draft-ietf-xrblock-rtcp-xr-discard-02.txt Abstract This document defines an RTCP XR Report Block that allows the reporting of a simple discard count metric for use in a range of RTP applications. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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 20, 2012. Copyright Notice Copyright (c) 2012 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 Hunt, et al. Expires October 20, 2012 [Page 1] Internet-Draft RTCP XR Discard April 2012 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 1.1. Discard Report Block . . . . . . . . . . . . . . . . . . . 3 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 4 3. Discard Metric Report Block . . . . . . . . . . . . . . . . . 5 3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 5 3.2. Definition of Fields in Discard Metric Report Block . . . 5 4. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 5.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 8 5.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 8 5.3. Contact information for registrations . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 10 8. Changes from previous version . . . . . . . . . . . . . . . . 11 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.1. Normative References . . . . . . . . . . . . . . . . . . . 12 9.2. Informative References . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Hunt, et al. Expires October 20, 2012 [Page 2] Internet-Draft RTCP XR Discard April 2012 1. Introduction 1.1. Discard Report Block This draft defines a new block type to augment those defined in [RFC3611] for use in a range of RTP applications. The new block type supports the reporting of the number of packets which are received correctly but are never played out, typically because they arrive too late to be played out (buffer underflow) or too early (buffer overflow). The metric is applicable both to systems which use packet loss repair techniques (such as forward error correction [RFC5109] or retransmission [RFC4588]) and to those which do not. This metric is useful for identifying the existence, and characterising the severity, of a packet transport problem which may affect users' perception of a service delivered over RTP. The metric belongs to the class of transport-related terminal metrics defined in [MONARCH] (work in progress). 1.2. RTCP and RTCP XR Reports The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] defined an extensible structure for reporting using an RTCP Extended Report (XR). This draft defines a new Extended Report block that MUST be used as defined in [RFC3550] and [RFC3611]. 1.3. Performance Metrics Framework The Performance Metrics Framework [RFC6390] provides guidance on the definition and specification of performance metrics. Metrics described in this draft either reference external definitions or define metrics generally in accordance with the guidelines in [RFC6390]. 1.4. Applicability This metric is believed to be applicable to a large class of RTP applications which use a jitter buffer. Hunt, et al. Expires October 20, 2012 [Page 3] Internet-Draft RTCP XR Discard April 2012 2. Terminology 2.1. Standards Language 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 RFC 2119 [RFC2119]. In addition, the following terms are defined: Received, Lost and Discarded A packet shall be regarded as lost if it fails to arrive within an implementation-specific time window. A packet that arrives within this time window but is too early or late to be played out shall be regarded as discarded. A packet shall be classified as one of received (or OK), discarded or lost. The Discard Metric counts only discarded packets. The metric "cumulative number of packets lost" defined in [RFC3550] reports a count of packets lost from the media stream (single SSRC within single RTP session). Similarly the metric "number of packets discarded" reports a count of packets discarded from the media stream (single SSRC within single RTP session) arriving at the receiver. Another metric defined in [RFC5725] is available to report on packets which are not recovered by any repair techniques which may be in use. Hunt, et al. Expires October 20, 2012 [Page 4] Internet-Draft RTCP XR Discard April 2012 3. Discard Metric Report Block 3.1. Report Block Structure 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=NBGD | I |DT | resv.| block length = 2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC of Source | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | number of packets discarded | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Report Block Structure 3.2. Definition of Fields in Discard Metric Report Block Block type (BT): 8 bits A Discard Metric Report Block is identified by the constant ND. [Note to RFC Editor: please replace ND with the IANA provided RTCP XR block type for this block.] Interval Metric flag (I): 2 bits This field is used to indicate whether the Discard metric is an sampled,Interval or Cumulative metric, that is, whether the reported values applies to the most recent measurement interval duration between successive metrics reports (I=10) (the Interval Duration) or to the accumulation period characteristic of cumulative measurements (I=11) (the Cumulative Duration) or to the value of a continuously measured or calculated that has been sampled at end of the interval (I=01) (Sampled Value). Discard Type (DT): 2bits This field is used to identify the discard type used in this report block. The discard type is defined as follows: 01: packets are discarded due to too early arrival. Hunt, et al. Expires October 20, 2012 [Page 5] Internet-Draft RTCP XR Discard April 2012 10: packets are discarded due to too late arrival. 11: packets are discarded due to both early arrival and late arrival. Reserved (resv): 5 bits These bits are reserved. They SHOULD be set to zero by senders and MUST be ignored by receivers. block length: 16 bits The length of this report block in 32-bit words, minus one. For the Delay block, the block length is equal to 2. SSRC of source: 32 bits As defined in Section 4.1 of [RFC3611]. number of packets discarded: 32 bits Number of packets discarded over the period (Interval or Cumulative) covered by this report. If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE SHOULD be reported to indicate an over-range measurement. If the measurement is unavailable, the value 0xFFFFFFFF SHOULD be reported. Note that the number of packets expected in the period covered by the metric (whether interval or cumulative) is available from the difference between a pair of extended sequence numbers in the Measurement Identity block, so need not be repeated in this block. Hunt, et al. Expires October 20, 2012 [Page 6] Internet-Draft RTCP XR Discard April 2012 4. SDP Signaling [RFC3611] defines the use of SDP (Session Description Protocol) [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used without prior signaling. This section augments the SDP [RFC4566] attribute "rtcp-xr" defined in [RFC3611] by providing an additional value of "xr-format" to signal the use of the report block defined in this document. rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF (defined in [RFC3611]) xr-format =/ xr-pd-block xr-pd-block = "pkt-dscrd" Hunt, et al. Expires October 20, 2012 [Page 7] Internet-Draft RTCP XR Discard April 2012 5. 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]. 5.1. New RTCP XR Block Type value This document assigns the block type value ND in the IANA "RTCP XR Block Type Registry" to the "Discard Metrics Block". [Note to RFC Editor: please replace ND with the IANA provided RTCP XR block type for this block.] 5.2. New RTCP XR SDP Parameter This document also registers a new parameter "pkt-dscrd" in the "RTCP XR SDP Parameters Registry". 5.3. Contact information for registrations The contact information for the registrations is: Geoff Hunt (r.geoff.hunt@gmail.com) Orion 2 PP3, Adastral Park, Martlesham Heath, Ipswich IP5 3RE, United Kingdom Hunt, et al. Expires October 20, 2012 [Page 8] Internet-Draft RTCP XR Discard April 2012 6. Security Considerations It is believed that this proposed RTCP XR report block introduces no new security considerations beyond those described in [RFC3611]. This block does not provide per-packet statistics so the risk to confidentiality documented in Section 7, paragraph 3 of [RFC3611] does not apply. Hunt, et al. Expires October 20, 2012 [Page 9] Internet-Draft RTCP XR Discard April 2012 7. Contributors The authors gratefully acknowledge the comments and contributions made by Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin Connor, Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert Higashi, Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith Lantz, Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, Ravi Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada. Hunt, et al. Expires October 20, 2012 [Page 10] Internet-Draft RTCP XR Discard April 2012 8. Changes from previous version Changed BNF for SDP following Christian Groves' and Tom Taylor's comments (4th and 5th May 2009), now aligned with RFC 5234 section 3.3 "Incremental Alternatives". Updated references. Allocate 1 bit to distinguish early discard from later discard. Expand Interval Metric flag to 2 bit to allow using sampled metric. Hunt, et al. Expires October 20, 2012 [Page 11] Internet-Draft RTCP XR Discard April 2012 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", March 1997. [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time Applications", RFC 3550, July 2003. [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control Protocol Extended Reports (RTCP XR)", November 2003. [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", July 2006. 9.2. Informative References [MONARCH] Wu, Q., "Monitoring Architectures for RTP", ID draft-ietf-avtcore-monarch-12, April 2012. [RFC4588] Rey, J., "RTP Retransmission Payload Format", RFC 4588, July 2006. [RFC5109] Li, A., "RTP Payload Format for Generic Forward Error Correction", RFC 5109, July 2006. [RFC5725] Begen, A., "RTCP XR Report Block for Post-Repair Loss metric Reporting", RFC 5725, February 2010. [RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric Development", RFC 6390, October 2011. Hunt, et al. Expires October 20, 2012 [Page 12] Internet-Draft RTCP XR Discard April 2012 Authors' Addresses Geoff Hunt Unaffiliated Email: r.geoff.hunt@gmail.com Alan Clark Telchemy Incorporated 2905 Premiere Parkway, Suite 280 Duluth, GA 30097 USA Email: alan.d.clark@telchemy.com Glen Zorn Network Zen 77/440 Soi Phoomjit, Rama IV Road Phra Khanong, Khlong Toie Bangkok 10110 Thailand Phone: +66 (0) 87 502 4274 Email: gwz@net-zen.net Qin Wu Huawei 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: sunseawq@huawei.com Hunt, et al. Expires October 20, 2012 [Page 13]