AVT A. Begen Internet-Draft Cisco Systems Intended status: Standards Track March 3, 2009 Expires: September 4, 2009 Rapid Multicast Synchronization Report Block Type for RTCP XR draft-begen-avt-rapid-sync-rtcp-xr-00 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on September 4, 2009. Copyright Notice Copyright (c) 2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Begen Expires September 4, 2009 [Page 1] Internet-Draft Rapid Multicast Synch Report Block Type March 2009 Abstract In most RTP-based multicast applications, the RTP source sends inter- related data. Due to the dependency in the multicast data, randomly joining RTP receivers may not be able to start usefully consuming the data upon joining the multicast session, thus, they often experience a random synchronization delay. In order to reduce this delay, an auxiliary unicast RTP session that facilitates rapid synchronization with the multicast session may be used between a retransmission server and RTP receivers. Yet, due to various random components pertaining to the RTP data and networking infrastructure, the performance of rapid synchronization may vary. For quality reporting and diagnostics, it is important to collect detailed information from the RTP receivers about their rapid synchronization experiences. This document addresses this issue by defining a new report block type, called Rapid Multicast Synchronization Report Block, within the framework of RTP Control Protocol (RTCP) Extended Reports (XR). This document also defines the necessary signaling of the new report block type in the Session Description Protocol (SDP). Begen Expires September 4, 2009 [Page 2] Internet-Draft Rapid Multicast Synch Report Block Type March 2009 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 5 3. Rapid Multicast Synchronization Report Block . . . . . . . . . 6 4. Session Description Protocol Signaling . . . . . . . . . . . . 8 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . . 12 8.2. Informative References . . . . . . . . . . . . . . . . . . 12 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13 Begen Expires September 4, 2009 [Page 3] Internet-Draft Rapid Multicast Synch Report Block Type March 2009 1. Introduction RTP Control Protocol (RTCP) is the out-of-band control protocol for the applications that are using the Real-time Transport Protocol (RTP) for media transport [RFC3550]. In addition to providing minimal control functionality to RTP entities via sender and receiver reports, RTCP also enables a basic level monitoring of RTP sessions. More statistically detailed monitoring as well as application- specific monitoring is usually achieved through the RTCP Extended Reports (XR) [RFC3611]. In most RTP-based multicast applications such as the ones carrying video content, the RTP source sends inter-related data. That is, the RTP application may not be able to decode and present the data in an RTP packet before decoding one or more earlier RTP packets and/or before acquiring some certain information about the content itself. Thus, RTP receivers that are randomly joining the multicast session often experience a random synchronization delay. In order to reduce this delay, [I-D.versteeg-avt-rapid-synchronization-for-rtp] proposes an approach where an auxiliary unicast RTP session is established between a retransmission server and the joining RTP receiver. Over this unicast RTP session, the retransmission server provides all the information the RTP receiver needs to rapidly synchronize with the multicast session. However, depending on the variability in the IGMP processing times [RFC3376], availability of network resources for rapid synchronization and nature of the RTP data itself, not all RTP receivers synchronize with the multicast session in the same amount of time. The performance of rapid synchronization may vary not only for different RTP receivers but also over time. To increase the visibility of the service provider into its network, to diagnose slow multicast synchronization issues and to collect the synchronization experiences of the RTP receivers, this document defines a new report block type, which is called Rapid Multicast Synchronization Report Block, within the framework of RTCP XR. RTP receivers that are benefiting from the rapid synchronization method described in [I-D.versteeg-avt-rapid-synchronization-for-rtp] may use this report every time they join a new multicast RTP session. Begen Expires September 4, 2009 [Page 4] Internet-Draft Rapid Multicast Synch Report Block Type March 2009 2. Requirements Notation 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 [RFC2119]. Begen Expires September 4, 2009 [Page 5] Internet-Draft Rapid Multicast Synch Report Block Type March 2009 3. Rapid Multicast Synchronization Report Block The report format is shown in Figure 1. 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 | rsvd. | Status| Block Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC of the Multicast Session | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RTP Extended Seqnum of the First Received Multicast Packet | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IGMP Join Time | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Format for the Rapid Multicast Synchronization Report Block BT (8 bits): Block type that identifies the block format. Rapid Multicast Synchronization Report Block is identified by the constant TBD. rsvd. (4 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 RTP receiver. Status (4 bits): TBD. Block Length (16 bits): The length of this report block, including the header, in 32-bit words minus one. It MUST be set to 3. SSRC of the Multicast Session (32 bits): The SSRC of the multicast RTP session that the RTP receiver has joined. RTP Extended Seqnum of the First Received Multicast Packet (32 bits): The RTP extended sequence number of the first packet received from the multicast session. IGMP Join Time (32 bits): Greater of zero or the time difference (in ms) between the instant IGMP Join message has been sent and the instant the first RTP packet was received from the multicast session. The semantics of this report block is independent of the payload type of the multicast RTP session. Begen Expires September 4, 2009 [Page 6] Internet-Draft Rapid Multicast Synch Report Block Type March 2009 Editor's note: More fields can be defined in this XR report to give more details about rapid synchronization such as: o Delta time between the rapid synchronization request and the arrival of the first unicast packet o Delta time between the rapid synchronization request and the arrival of the first multicast packet o Duplicate packet information (duplication due to receiving the same packet from both unicast and multicast session) Details are TBD. Begen Expires September 4, 2009 [Page 7] Internet-Draft Rapid Multicast Synch Report Block Type March 2009 4. Session Description Protocol Signaling A new parameter is defined for the Rapid Multicast Synchronization Report Block to be used with Session Description Protocol (SDP) [RFC4566]. It has the following syntax within the 'rtcp-xr' attribute: rtcp-xr-attrib = "a=rtcp-xr:" [xr-format *(SP xr-format)] CRLF xr-format = "multicast-join" CRLF = %d13.10 Figure 2 Refer to Section 5.1 of [RFC3611] for a detailed description and the full syntax of the "rtcp-xr" attribute. Begen Expires September 4, 2009 [Page 8] Internet-Draft Rapid Multicast Synch Report Block Type March 2009 5. Security Considerations The security considerations of [RFC3611] apply in this document as well. Additional security considerations are TBD. If desired, similar to other RTCP XR reports, the rapid multicast synchronization reports MAY be protected by using SRTP and SRTCP [RFC3711]. Begen Expires September 4, 2009 [Page 9] Internet-Draft Rapid Multicast Synch Report Block Type March 2009 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]. This document (provisionally) assigns the block type value TBD in the RTCP XR Block Type Registry to "Rapid Multicast Synchronization Report Block." This document also registers the SDP [RFC4566] parameter 'multicast-join' for the 'rtcp-xr' attribute in the RTCP XR SDP Parameters Registry. The contact information for the registrations is: Ali Begen abegen@cisco.com 170 West Tasman Drive San Jose, CA 95134 USA Begen Expires September 4, 2009 [Page 10] Internet-Draft Rapid Multicast Synch Report Block Type March 2009 7. Acknowledgments TBC. Begen Expires September 4, 2009 [Page 11] Internet-Draft Rapid Multicast Synch Report Block Type March 2009 8. References 8.1. 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. [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. Thyagarajan, "Internet Group Management Protocol, Version 3", RFC 3376, October 2002. [I-D.versteeg-avt-rapid-synchronization-for-rtp] Steeg, B., Begen, A., and T. Caenegem, "Unicast-Based Rapid Synchronization with RTP Multicast Sessions", draft-versteeg-avt-rapid-synchronization-for-rtp-01 (work in progress), November 2008. [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, July 2006. 8.2. Informative References [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, "The Secure Real-time Transport Protocol (SRTP)", RFC 3711, March 2004. Begen Expires September 4, 2009 [Page 12] Internet-Draft Rapid Multicast Synch Report Block Type March 2009 Author's Address Ali Begen Cisco Systems 170 West Tasman Drive San Jose, CA 95134 USA Email: abegen@cisco.com Begen Expires September 4, 2009 [Page 13]