Network Working Group H. Asaeda Internet-Draft Keio University Intended status: Standards Track R. Huang Expires: December 17, 2011 Q. Wu Huawei June 15, 2011 RTCP XR Blocks for Synchronization Delay and Offset Metrics Reporting draft-asaeda-xrblock-rtcp-xr-synchronization-01 Abstract This document defines an RTCP XR Report Block and associated SDP parameters that allows the reporting of synchronization delay and offset 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 December 17, 2011. Copyright Notice Copyright (c) 2011 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. Asaeda, et al. Expires December 17, 2011 [Page 1] Internet-Draft SDO Report Blocks June 2011 This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 3 3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. RTP Flows Initial Synchronization Delay Report Block . . . . . 4 4.1. Metric Block Structure . . . . . . . . . . . . . . . . . . 4 4.2. Definition of Fields in RTP Flow Initial Synchronization Delay Metrics Block . . . . . . . . . . . . 4 5. RTP Flows General Synchronization Offset Metrics Block . . . . 5 5.1. Metric Block Structure . . . . . . . . . . . . . . . . . . 5 5.2. Definition of Fields in RTP Flow General Synchronization Offset Metrics Block . . . . . . . . . . . 6 6. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . . 6 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . . 8 10.2. Informative References . . . . . . . . . . . . . . . . . . 8 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . . 9 A.1. draft-asaeda-xrblock-rtcp-xr-syncronization-00 . . . . . . 9 A.2. draft-asaeda-xrblock-rtcp-xr-syncronization-01 . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Asaeda, et al. Expires December 17, 2011 [Page 2] Internet-Draft SDO Report Blocks June 2011 1. Introduction This draft defines a new block type to augment those defined in [RFC3611], for use in a range of RTP applications. This new block type supports reporting of Initial synchronization delay. Information is recorded about the difference between the start of RTP sessions and the time the RTP receiver acquires all components of RTP sessions [RFC6051]. It also supports reporting of the general Synchronization offset status of an arbitrary number of streams, with the same RTCP CNAME. Information is recorded about the synchronization offset time of each RTP stream relative to the reference RTP stream with the same CNAME and General Synchronization Offset of zero. The metrics belong to the class of transport level metrics defined in [MONARCH] (work in progress). 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]. 3. Applicability The report blocks defined in this document could be used by dedicated network monitoring applications. When joining a layered video session in such an application, a receiver may not synchronize playout across the multimedia session until RTCP SR packets have been received on all of the component RTP sessions. For unicast session, the delay due to negotiation of NAT pinholes, firewall holes, quality-of-service, and media security keys is contributed to such initial synchronization playout. For multicast session, such initial synchronization delay varies with the session bandwidth and the number of members, the number of senders in the session. The RTP flow synchronization delay block can be used to report the initial synchronization delay of these RTP streams beyond the information carried in the standard RTCP packet format. In the absence of packet loss, the initial synchronization delay equals to the average time taken to receive the first RTCP packet in the RTP session with the longest RTCP reporting interval. In the presence of packet loss, the media synchronization needs to wait until the Asaeda, et al. Expires December 17, 2011 [Page 3] Internet-Draft SDO Report Blocks June 2011 reporting interval has passed, and the next RTCP SR packet is sent. In an RTP multimedia session, there can be an arbitrary number of streams, with the same RTCP CNAME. The RTP Flows General Synchronization Offset block can be used to report the general Synchronization offset status of these RTP streams beyond the information carried in the standard RTCP packet format. For layered session or multimedia session, the first RTP packet can be chosen as the basic packet of reference RTP stream. 4. RTP Flows Initial Synchronization Delay Report Block This block reports Initial synchronization delay beyond the information carried in the standard RTCP packet format. Information is recorded about the the difference between the start of RTP sessions and the time the RTP receiver acquires all components of RTP sessions [RFC6051]. The components of RTP session are referred to as one RTP session for each media type or the media content in each layer contained in RTP Control Protocol (RTCP) sender report (SR) packets [RFC3550]. 4.1. Metric Block Structure The RTP Flows Initial Synchronization Delay Report Block has the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BT=TBD | Reserved | Block length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC of Sender | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Initial Synchronization Delay | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 4.2. Definition of Fields in RTP Flow Initial Synchronization Delay Metrics Block Block type (BT): 8 bits The Statistics Summary Report Block is identified by the constant . Asaeda, et al. Expires December 17, 2011 [Page 4] Internet-Draft SDO Report Blocks June 2011 Block length: 16 bits The constant 2, in accordance with the definition of this field in Section 3 of RFC 3611 [RFC3611]. SSRC of Sender: 32 bits The SSRC of the RTP data packet source being reported upon by this report block. (Section 4.1 of [RFC3611]). Initial Synchronization Delay: 32 bits The average delay, expressed in units of 1/65536 seconds, between the RTCP packets received on all of the components RTP sessions and the beginning of session [RFC6051]. The value is calculated as follows: The average time, expressed in units of 1/65536 seconds, taken to receive the first RTCP packet in the RTP session with the longest RTCP reporting interval [RFC6051]. 5. RTP Flows General Synchronization Offset Metrics Block In an RTP multimedia session, there can be an arbitrary number of streams, with the same RTCP CNAME. This block reports the general Synchronization offset status of these RTP streams beyond the information carried in the standard RTCP packet format. Information is recorded about the synchronization offset time of each RTP stream relative to the reference RTP stream with the same CNAME and General Synchronisation Offset of zero. 5.1. Metric Block Structure The RTP Flow General Synchronization Offset Report Block has the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BT=TBD | Reserved | Block length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC of source | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | General Synchronization Offset | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Asaeda, et al. Expires December 17, 2011 [Page 5] Internet-Draft SDO Report Blocks June 2011 5.2. Definition of Fields in RTP Flow General Synchronization Offset Metrics Block Block type (BT): 8 bits The RTP Flow General Synchronization Offset Report Block is identified by the constant . Block length: 16 bits The constant 3, in accordance with the definition of this field in Section 3 of RFC 3611 [RFC3611]. SSRC of Source: 32 bits The SSRC of the RTP data packet source being reported upon by this report block. (Section 4.1 of [RFC3611]). General synchronization offset: 32 bits This field represents the synchronization offset time of one RTP stream in milliseconds relative to the reference RTP stream with the same CNAME and General Synchronisation Offset of zero [RFC6051] This value is calculated based on the interarrival time between arbitray RTP packet and the reference RTP packet with the same CNAME , and timestamps of this arbitray RTP packet and the reference RTP packet with the same CNAME. 6. SDP Signaling Two new parameters are defined for the two report blocks defined in this document to be used with Session Description Protocol (SDP) [RFC4566] using the Augmented Backus-Naur Form (ABNF) [RFC5234]. They have the following syntax within the "rtcp-xr" attribute [RFC3611]: rtcp-xr-attrib = "a=rtcp-xr:" [xr-format *(SP xr-format)] CRLF xr-format = RTP-flows-init-syn / RTP-flows-general-syn RTP-flows-init-syn = "RTP-flows-init-syn" ["=" max-size] max-size = 1*DIGIT ; maximum block size in octets RTP-flow-general-syn = "RTP-flows-general-syn" ["=" max-size] max-size = 1*DIGIT ; maximum block size in octets Asaeda, et al. Expires December 17, 2011 [Page 6] Internet-Draft SDO Report Blocks June 2011 Refer to Section 5.1 of RFC 3611 [RFC3611] for a detailed description and the full syntax of the "rtcp-xr" attribute. 7. IANA Considerations New report block types for RTCP XR are subject to IANA registration. For general guidelines on IANA allocations for RTCP XR, refer to Section 6.2 of [RFC3611]. This document assigns two new block type values in the RTCP XR Block Type Registry: Name: RFISD Long Name: RTP Flows Initial Synchronization Delay Value Reference: Section 4 Name: RFGSO Long Name: RTP Flows General Synchronization Offset Metrics Block Value Reference: Section 5 This document also registers two new SDP [RFC4566] parameters for the "rtcp-xr" attribute in the RTCP XR SDP Parameters Registry: * "RTP-flows-init-syn" * "RTP-flows-general-syn" The contact information for the registrations is: Qin Wu sunseawq@huawei.com 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012, China 8. Security Considerations The new RTCP XR report blocks proposed in this document introduces no new security considerations beyond those described in [RFC3611]. 9. Acknowledgements The authors would like to thank Bill Ver Steeg, David R Oran, Ali Begen, Colin Perkins, Roni Even, Youqing Yang, Wenxiao Yu and Yinliang Hu for their valuable comments and suggestions on this document. Asaeda, et al. Expires December 17, 2011 [Page 7] Internet-Draft SDO Report Blocks June 2011 10. References 10.1. Normative References [I-D.ietf-avt-rtp-svc] Wenger, S., Wang, Y., Schierl, T., and A. Eleftheriadis, "RTP Payload Format for Scalable Video Coding", draft-ietf-avt-rtp-svc-27 (work in progress), February 2011. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2250] Hoffman, D., Fernando, G., Goyal, V., and M. Civanlar, "RTP Payload Format for MPEG1/MPEG2 Video", RFC 2250, January 1998. [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. [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, July 2006. [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. [RFC6051] Perkins, C. and T. Schierl, "Rapid Synchronisation of RTP Flows", RFC 6051, November 2010. 10.2. Informative References [MEASIDENT] Hunt, G. and A. Clark, "RTCP XR Measurement Identifier Block", ID draft-ietf-avt-rtcp-xr-meas-identity-02, May 2009. [MONARCH] Wu, Q., "Monitoring Architectures for RTP", ID draft-ietf-avtcore-monarch-00, April 2011. [PMOL] Clark, A., "Framework for Performance Metric Development", ID draft-ietf-pmol-metrics-framework-08, January 2011. Asaeda, et al. Expires December 17, 2011 [Page 8] Internet-Draft SDO Report Blocks June 2011 Appendix A. Change Log Note to the RFC-Editor: please remove this section prior to publication as an RFC. A.1. draft-asaeda-xrblock-rtcp-xr-syncronization-00 This document is separated from draft-wu-xrblock-rtcp-xr-quality-monitoring-01 with some editorial changes and focuses on RTP Flow Initial Synchronization Delay and RTP Flows General Synchronization Offset. A.2. draft-asaeda-xrblock-rtcp-xr-syncronization-01 Separate Synchronization Delay and Offset Metrics Block into two independent block based on comments on the list. Authors' Addresses Hitoshi Asaeda Keio University Graduate School of Media and Governance 5322 Endo Fujisawa, Kanagawa 252-0882 Japan Email: asaeda@wide.ad.jp Rachel Huang Huawei Technologies Co., Ltd. 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: Rachel@huawei.com Qin Wu Huawei Technologies Co., Ltd. 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: sunseawq@huawei.com Asaeda, et al. Expires December 17, 2011 [Page 9]