RTP Topologies
RFC 5117
| Document | Type |
RFC - Informational
(January 2008; Errata)
Obsoleted by RFC 7667
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Replaces | draft-wenger-avt-topologies | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Reviews | |||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 5117 (Informational) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Cullen Jennings | ||
| Send notices to | (None) | ||
Network Working Group M. Westerlund
Request for Comments: 5117 Ericsson
Category: Informational S. Wenger
Nokia
January 2008
RTP Topologies
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Abstract
This document discusses multi-endpoint topologies used in Real-time
Transport Protocol (RTP)-based environments. In particular,
centralized topologies commonly employed in the video conferencing
industry are mapped to the RTP terminology.
Westerlund & Wenger Informational [Page 1]
RFC 5117 RTP Topologies January 2008
Table of Contents
1. Introduction ....................................................2
2. Definitions .....................................................3
2.1. Glossary ...................................................3
2.2. Indicating Requirement Levels ..............................3
3. Topologies ......................................................3
3.1. Point to Point .............................................4
3.2. Point to Multipoint Using Multicast ........................5
3.3. Point to Multipoint Using the RFC 3550 Translator ..........6
3.4. Point to Multipoint Using the RFC 3550 Mixer Model .........9
3.5. Point to Multipoint Using Video Switching MCUs ............11
3.6. Point to Multipoint Using RTCP-Terminating MCU ............12
3.7. Non-Symmetric Mixer/Translators ...........................13
3.8. Combining Topologies ......................................14
4. Comparing Topologies ...........................................15
4.1. Topology Properties .......................................15
4.1.1. All to All Media Transmission ......................15
4.1.2. Transport or Media Interoperability ................16
4.1.3. Per Domain Bit-Rate Adaptation .....................16
4.1.4. Aggregation of Media ...............................16
4.1.5. View of All Session Participants ...................16
4.1.6. Loop Detection .....................................17
4.2. Comparison of Topologies ..................................17
5. Security Considerations ........................................17
6. Acknowledgements ...............................................19
7. References .....................................................19
7.1. Normative References ......................................19
7.2. Informative References ....................................20
1. Introduction
When working on the Codec Control Messages [CCM], considerable
confusion was noticed in the community with respect to terms such as
Multipoint Control Unit (MCU), Mixer, and Translator, and their usage
in various topologies. This document tries to address this confusion
by providing a common information basis for future discussion and
specification work. It attempts to clarify and explain sections of
the Real-time Transport Protocol (RTP) spec [RFC3550] in an informal
way. It is not intended to update or change what is normatively
specified within RFC 3550.
When the Audio-Visual Profile with Feedback (AVPF) [RFC4585] was
developed the main emphasis lay in the efficient support of point to
point and small multipoint scenarios without centralized multipoint
control. However, in practice, many small multipoint conferences
operate utilizing devices known as Multipoint Control Units (MCUs).
MCUs may implement Mixer or Translator (in RTP [RFC3550] terminology)
Westerlund & Wenger Informational [Page 2]
RFC 5117 RTP Topologies January 2008
functionality and signalling support. They may also contain
additional application functionality. This document focuses on the
media transport aspects of the MCU that can be realized using RTP, as
discussed below. Further considered are the properties of Mixers and
Translators, and how some types of deployed MCUs deviate from these
properties.
2. Definitions
2.1. Glossary
ASM - Any Source Multicast
AVPF - The Extended RTP Profile for RTCP-based Feedback
CSRC - Contributing Source
Link - The data transport to the next IP hop
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