From 4bfd864f10b68b71482b35c818559068ef8d5797 Mon Sep 17 00:00:00 2001 From: Thomas Voss Date: Wed, 27 Nov 2024 20:54:24 +0100 Subject: doc: Add RFC documents --- doc/rfc/rfc6128.txt | 339 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 339 insertions(+) create mode 100644 doc/rfc/rfc6128.txt (limited to 'doc/rfc/rfc6128.txt') diff --git a/doc/rfc/rfc6128.txt b/doc/rfc/rfc6128.txt new file mode 100644 index 0000000..d904bc2 --- /dev/null +++ b/doc/rfc/rfc6128.txt @@ -0,0 +1,339 @@ + + + + + + +Internet Engineering Task Force (IETF) A. Begen +Request for Comments: 6128 Cisco +Updates: 5760 February 2011 +Category: Standards Track +ISSN: 2070-1721 + + + RTP Control Protocol (RTCP) Port for + Source-Specific Multicast (SSM) Sessions + +Abstract + + The Session Description Protocol (SDP) has an attribute that allows + RTP applications to specify an address and a port associated with the + RTP Control Protocol (RTCP) traffic. In RTP-based source-specific + multicast (SSM) sessions, the same attribute is used to designate the + address and the RTCP port of the Feedback Target in the SDP + description. However, the RTCP port associated with the SSM session + itself cannot be specified by the same attribute to avoid ambiguity, + and thus, is required to be derived from the "m=" line of the media + description. Deriving the RTCP port from the "m=" line imposes an + unnecessary restriction. This document removes this restriction by + introducing a new SDP attribute. + +Status of This Memo + + This is an Internet Standards Track document. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication 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 of this document, any errata, + and how to provide feedback on it may be obtained at + http://www.rfc-editor.org/info/rfc6128. + + + + + + + + + + + + + + +Begen Standards Track [Page 1] + +RFC 6128 RTCP Port for Multicast Sessions February 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. + +Table of Contents + + 1. Introduction ....................................................2 + 2. The 'multicast-rtcp' Attribute ..................................3 + 3. SDP Example .....................................................3 + 4. Security Considerations .........................................4 + 5. IANA Considerations .............................................4 + 5.1. Registration of SDP Attributes .............................5 + 6. Acknowledgments .................................................5 + 7. References ......................................................5 + 7.1. Normative References .......................................5 + 7.2. Informative References .....................................5 + +1. Introduction + + The Session Description Protocol (SDP) [RFC4566] has an attribute + that allows RTP applications [RFC3550] to specify an address and a + port associated with the RTP Control Protocol (RTCP) traffic + [RFC3605]. This attribute is called 'rtcp'. + + Now consider a network where one or more media senders send RTP + packets to a distribution source, which then multicasts these RTP + packets to multicast receivers using a source-specific multicast + (SSM) arrangement [RFC5760]. The distribution source also multicasts + the forward RTCP traffic (i.e., RTCP sender reports and receiver + reports or their summaries) to the receivers in the same SSM session. + + In RTP-based SSM sessions, the 'rtcp' attribute is used to designate + the address and the RTCP port of the Feedback Target in the SDP + description [RFC5760]. However, the RTCP port associated with the + SSM session itself cannot be specified by the same attribute since it + could potentially cause ambiguity. Thus, the multicast RTCP port is + required to be derived from the "m=" line of the media description + + + +Begen Standards Track [Page 2] + +RFC 6128 RTCP Port for Multicast Sessions February 2011 + + + (see Section 10.2 of [RFC5760]) by following the +1 rule (see Section + 11 of [RFC3550]). However, [RFC3550] lifted the requirement for the + +1 rule since it imposed an unnecessary restriction on RTCP port + selection. + + In this specification, we introduce a new SDP attribute to remove + this restriction. The new attribute allows the multicast sender to + use its desired port in the RTCP session. This document updates + [RFC5760]. + +2. The 'multicast-rtcp' Attribute + + In RTP-based SSM sessions, the distribution source can use different + multicast RTP and RTCP ports to send the RTP and RTCP packets, + respectively. Alternatively, the distribution source can use RTP/ + RTCP port muxing [RFC5761], in which case the RTP and RTCP packets + are sent to the same destination port in the SSM session. + + For the cases when the distribution source does not want to use the + one higher port for the RTCP traffic, this document defines a new SDP + attribute, called 'multicast-rtcp'. By using this attribute, the + distribution source uses a desired port for the SSM RTCP session. In + the absence of the 'multicast-rtcp' attribute, the +1 rule applies + following [RFC5760]. + + The following ABNF [RFC5234] syntax formally describes the + 'multicast-rtcp' attribute: + + rtcp-attribute = "a=multicast-rtcp:" port CRLF + + Figure 1: ABNF syntax for the 'multicast-rtcp' attribute + + Here, the 'port' token is defined as specified in Section 9 of + [RFC4566]. + + The 'multicast-rtcp' attribute is defined as both a media-level and + session-level attribute. Except where stated otherwise in this + document, the rules of [RFC3550] apply. + +3. SDP Example + + In the session description shown in Figure 2, a source stream is + multicast from a distribution source (with a source IP address of + 198.51.100.1) to the multicast destination address of 233.252.0.2 and + port 41000. The forward RTCP traffic is multicast in the same + multicast group but to port 42000 as specified by the "a=multicast- + rtcp:42000" line. A feedback target with an address of 192.0.2.1 and + port of 43000 is specified by the 'rtcp' attribute. + + + +Begen Standards Track [Page 3] + +RFC 6128 RTCP Port for Multicast Sessions February 2011 + + + v=0 + o=ali 1122334455 1122334466 IN IP4 ssm.example.com + s='multicast-rtcp' Example + t=0 0 + a=rtcp-unicast:rsi + m=video 41000 RTP/AVPF 98 + i=Multicast Stream + c=IN IP4 233.252.0.2/255 + a=source-filter:incl IN IP4 233.252.0.2 198.51.100.1 + a=rtpmap:98 MP2T/90000 + a=multicast-rtcp:42000 + a=rtcp:43000 IN IP4 192.0.2.1 + a=mid:1 + + Figure 2: Example SDP showing the use of the 'multicast-rtcp' + attribute + +4. Security Considerations + + The 'multicast-rtcp' attribute is not believed to introduce any + significant security risk to multimedia applications. A malevolent + third party could use this attribute to redirect the RTCP traffic, + but this requires intercepting and rewriting the packets carrying the + SDP description; and if an interceptor can do that, many more attacks + are possible, including a wholesale change of the addresses and port + numbers at which the media will be sent. + + In order to avoid attacks of this sort, the SDP description needs to + be integrity protected and provided with source authentication. This + can, for example, be achieved on an end-to-end basis using S/MIME + [RFC5652] [RFC5751] when SDP is used in a signaling packet using MIME + types (application/sdp). Alternatively, HTTPS [RFC2818] or the + authentication method in the Session Announcement Protocol (SAP) + [RFC2974] could be used as well. + +5. IANA Considerations + + The following contact information shall be used for all registrations + in this document: + + Ali Begen + abegen@cisco.com + + + + + + + + + +Begen Standards Track [Page 4] + +RFC 6128 RTCP Port for Multicast Sessions February 2011 + + +5.1. Registration of SDP Attributes + + This document registers a new attribute name in SDP. + + SDP Attribute ("att-field"): + Attribute name: multicast-rtcp + Long form: Port in the multicast RTCP session + Type of name: att-field + Type of attribute: Media or session level + Subject to charset: No + Purpose: Specifies the port for the SSM RTCP session + Reference: [RFC6128] + Values: See [RFC6128] + +6. Acknowledgments + + Thanks to Colin Perkins and Magnus Westerlund for suggesting the name + for the 'multicast-rtcp' attribute and providing text for portions of + this specification. Some parts of this specification are based on + [RFC3605] and [RFC5760]. So, also thanks to those who contributed to + those specifications. + +7. References + +7.1. Normative References + + [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. + Jacobson, "RTP: A Transport Protocol for Real-Time + Applications", STD 64, RFC 3550, July 2003. + + [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session + Description Protocol", RFC 4566, July 2006. + + [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control + Protocol (RTCP) Extensions for Single-Source Multicast + Sessions with Unicast Feedback", RFC 5760, February 2010. + + [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax + Specifications: ABNF", STD 68, RFC 5234, January 2008. + +7.2. Informative References + + [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute + in Session Description Protocol (SDP)", RFC 3605, + October 2003. + + [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and + Control Packets on a Single Port", RFC 5761, April 2010. + + + +Begen Standards Track [Page 5] + +RFC 6128 RTCP Port for Multicast Sessions February 2011 + + + [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, + RFC 5652, September 2009. + + [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. + + [RFC2974] Handley, M., Perkins, C., and E. Whelan, "Session + Announcement Protocol", RFC 2974, October 2000. + + [RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet + Mail Extensions (S/MIME) Version 3.2 Message + Specification", RFC 5751, January 2010. + +Author's Address + + Ali Begen + Cisco + 181 Bay Street + Toronto, ON M5J 2T3 + Canada + + EMail: abegen@cisco.com + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Begen Standards Track [Page 6] + -- cgit v1.2.3