Audio/Video Transport Working Group G. Hunt Internet-Draft Unaffiliated Intended status: Standards Track A. Clark Expires: July 23, 2012 Telchemy R. Huang Q. Wu, Ed. Huawei January 20, 2012 RTCP XR Report Block for Burst/Gap Discard metric Reporting draft-ietf-xrblock-rtcp-xr-burst-gap-discard-02.txt Abstract This document defines an RTCP XR Report Block that allows the reporting of Burst and Gap Discard metrics 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 July 23, 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 include Simplified BSD License text as described in Section 4.e of Hunt, et al. Expires July 23, 2012 [Page 1] Internet-Draft RTCP XR Burst/Gap Discard January 2012 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Burst and Gap Discard Report Block . . . . . . . . . . . . 3 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 5 3. Burst/Gap Discard Block . . . . . . . . . . . . . . . . . . . 6 3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 6 3.2. Definition of Fields in Burst/Gap Loss Report Block . . . 6 3.3. Derived metrics based on reported metrics . . . . . . . . 8 4. Considerations for Voice-over-IP applications . . . . . . . . 9 5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 10 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 6.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 11 6.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 11 6.3. Contact information for registrations . . . . . . . . . . 11 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 13 9. Changes from previous version . . . . . . . . . . . . . . . . 14 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 10.1. Normative References . . . . . . . . . . . . . . . . . . . 15 10.2. Informative References . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 Hunt, et al. Expires July 23, 2012 [Page 2] Internet-Draft RTCP XR Burst/Gap Discard January 2012 1. Introduction 1.1. Burst and Gap 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 proportion of packets discarded by the receiver due to jitter. The discards during discard bursts are reported, together with the number of bursts and additional data allowing the calculation of statistical parameters (mean and variance) of the distribution of burst lengths. This block is intended to be used in conjunction with [DISCARD] which provides the total packets discarded, and on which this block therefore depends. However the metric in [DISCARD] may be used independently of the metrics in this block. This block provides information on transient IP problems. Burst/Gap metrics are typically used in Cumulative reports however MAY be used in Interval reports. The burstiness of packet discard affects user experience, may influence any sender strategies to mitigate the problem, and may also have diagnostic value. The metric belongs to the class of transport-related terminal metrics defined in [MONARCH] (work in progress). The definitions of Burst, Gap, Loss and Discard are consistent with definitions in [RFC3611]. To accommodate the range of jitter buffer algorithms and packet discard logic that may be used by implementors, the method used to distinguish between bursts and gaps may be an equivalent method to that defined in[RFC3611] . 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]. Hunt, et al. Expires July 23, 2012 [Page 3] Internet-Draft RTCP XR Burst/Gap Discard January 2012 1.4. Applicability These metrics are applicable to a range of RTP applications. Hunt, et al. Expires July 23, 2012 [Page 4] Internet-Draft RTCP XR Burst/Gap Discard January 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. Bursts and Gaps The terms Burst and Gap are used in a manner consistent with that of RTCP XR [RFC3611]. RTCP XR views a RTP stream as being divided into bursts, which are periods during which the loss rate is high enough to cause noticeable quality degradation (generally over 5 percent loss rate), and gaps, which are periods during which lost packets are infrequent and hence quality is generally acceptable. Hunt, et al. Expires July 23, 2012 [Page 5] Internet-Draft RTCP XR Burst/Gap Discard January 2012 3. Burst/Gap Discard Block Metrics in this block report on Burst/Gap Discard in the stream arriving at the RTP system. 3.1. Report Block Structure Burst/Gap Discard metrics block 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| resv. | block length = 3 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC of Source | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Threshold | Packets Discarded in Bursts | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Total Packets expected in bursts | Reserved. | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Report Block Structure 3.2. Definition of Fields in Burst/Gap Loss Report Block Block type (BT): 8 bits A Burst/Gap Discard Report Block is identified by the constant NBGD. [Note to RFC Editor: please replace NBGD with the IANA provided RTCP XR block type for this block.] Interval Metric flag (I): 1 bit This field is used to indicate whether the Packet Delay Variation metrics block is an Interval or a Cumulative report, that is, whether the reported values apply to the most recent measurement interval duration between successive metrics reports (I=1) (the Interval Duration) or to the accumulation period characteristic of cumulative measurements (I=0) (the Cumulative Duration). Reserved (resv): 7 bits These bits are reserved. They SHOULD be set to zero by senders and MUST be ignored by receivers. Hunt, et al. Expires July 23, 2012 [Page 6] Internet-Draft RTCP XR Burst/Gap Discard January 2012 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 3. SSRC of source: 32 bits As defined in Section 4.1 of [RFC3611]. Threshold: 8 bits The Threshold is equivalent to Gmin in [RFC3611], i.e. the number of successive packets that must be received prior to and following a lost packet in order for this lost packet to be regarded as part of a gap. Packets lost in bursts: 24 bits The total number of packets lost during loss bursts. If the measured value exceeds 0xFFFFFD, the value 0xFFFFFE SHOULD be reported to indicate an over-range measurement. If the measurement is unavailable, the value 0xFFFFFF SHOULD be reported. Total packets expected in bursts: 24 bits The total number of packets expected during loss bursts (that is, the sum of received packets and lost packets). If the measured value exceeds 0xFFFFFD, the value 0xFFFFFE SHOULD be reported to indicate an over-range measurement. If the measurement is unavailable, the value 0xFFFFFF SHOULD be reported. Reserved (resv): 8 bits These bits are reserved. They SHOULD be set to zero by senders and MUST be ignored by receivers. Hunt, et al. Expires July 23, 2012 [Page 7] Internet-Draft RTCP XR Burst/Gap Discard January 2012 3.3. Derived metrics based on reported metrics The metrics described here are intended to be used as described in this section, in conjunction with information from the Measurement Information block [MEASID], discard block [DISCARD] (which MUST be present in the same RTCP packet as the Burst/Gap Discard block). These metrics provides the following information relevant to statistical parameters, including: o The fraction of packets discarded during bursts (burst discard rate in [SUMSTAT]) o The fraction of packets discarded during gaps (gap discard rate in [SUMSTAT]) The details on calculation these parameters in the metrics are described in [SUMSTAT]. Hunt, et al. Expires July 23, 2012 [Page 8] Internet-Draft RTCP XR Burst/Gap Discard January 2012 4. Considerations for Voice-over-IP applications This metric block is applicable to a broad range of RTP applications. Where the metric is used with a Voice-overIP (VoIP) application, the following considerations apply. RTCP XR views a call as being divided into bursts, which are periods during which the loss rate is high enough to cause noticeable call quality degradation (generally over 5 percent loss rate), and gaps, which are periods during which lost packets are infrequent and hence call quality is generally acceptable. If Voice Activity Detection is used the Burst and Gap Duration shall be determined as if silence frames had been sent, i.e. a period of silence in excess of Gmin frames MUST terminate a burst condition. The recommended value for the threshold Gmin in [RFC3611] results in a Burst being a period of time during which the call quality is degraded to a similar extent to a typical PCM Severely Errored Second [PSES]. Hunt, et al. Expires July 23, 2012 [Page 9] Internet-Draft RTCP XR Burst/Gap Discard January 2012 5. 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-bgd-block xr-bgd-block = "brst-gap-dscrd" Hunt, et al. Expires July 23, 2012 [Page 10] Internet-Draft RTCP XR Burst/Gap Discard January 2012 6. 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]. 6.1. New RTCP XR Block Type value This document assigns the block type value NDEL in the IANA "RTCP XR Block Type Registry" to the "Burst/Gap Discard Metrics Block". [Note to RFC Editor: please replace NBGD with the IANA provided RTCP XR block type for this block.] 6.2. New RTCP XR SDP Parameter This document also registers a new parameter "brst-gap-dscrd" in the "RTCP XR SDP Parameters Registry". 6.3. 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 July 23, 2012 [Page 11] Internet-Draft RTCP XR Burst/Gap Discard January 2012 7. 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 July 23, 2012 [Page 12] Internet-Draft RTCP XR Burst/Gap Discard January 2012 8. 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 July 23, 2012 [Page 13] Internet-Draft RTCP XR Burst/Gap Discard January 2012 9. 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. Hunt, et al. Expires July 23, 2012 [Page 14] Internet-Draft RTCP XR Burst/Gap Discard January 2012 10. References 10.1. 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. 10.2. Informative References [DISCARD] Hunt, G., "RTCP XR Report Block for Discard metric Reporting", ID draft-ietf-xrblock-rtcp-xr-discard-01, December 2011. [MEASID] Wu, Q., "Measurement Identity and information Reporting using SDES item and XR Block", ID draft-ietf-xrblock-rtcp-xr-meas-identity-01, October 2011. [MONARCH] Hunt, G., "Monitoring Architectures for RTP", ID draft-ietf-avtcore-monarch-04, August 2011. [PSES] "URL", http://www.its.bldrdoc.gov/projects/devglossary/ _severely_errored_second.html, October 2011. [RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric Development", RFC 6390, October 2011. [SUMSTAT] Zorn, G., "RTCP XR for Summary Statistics Metrics Reporting", ID draft-zorn-xrblock-rtcp-xr-al-stat-03, October 2011. Hunt, et al. Expires July 23, 2012 [Page 15] Internet-Draft RTCP XR Burst/Gap Discard January 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 Rachel Huang Huawei Technologies Co., Ltd. 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: Rachel@huawei.com Qin Wu (editor) Huawei 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: sunseawq@huawei.com Hunt, et al. Expires July 23, 2012 [Page 16]