Audio/Video Transport (avt)

NOTE: This charter is a snapshot of that in effect at the time of the 38th IETF Meeting in Memphis, Tennessee. It may now be out-of-date.


Stephen Casner <>

Transport Area Director(s): 

Allison Mankin <>
Allyn Romanow <>

Mailing Lists: 

To Subscribe:

Description of Working Group: 

The Audio/Video Transport Working Group was formed to specify experimental protocols for real-time transmission of audio and video over UDP and IP multicast. The focus of this group is near-term and its purpose is to integrate and coordinate the current AVT efforts of existing research activities. No standards-track protocols are expected to be produced because UDP transmission of audio and video is only sufficient for small-scale experiments over fast portions of the Internet. However, the transport protocols produced by this working group should be useful on a larger scale in the future in conjunction with additional protocols to access network-level resource management mechanisms. Those mechanisms, research efforts now, will provide low-delay service and guard against unfair consumption of bandwidth by audio/video traffic. 

Similarly, initial experiments can work without any connection establishment procedure so long as a priori agreements on port numbers and coding types have been made. To go beyond that, we will need to address simple control protocols as well. Since IP multicast traffic may be received by anyone, the control protocols must handle authentication and key exchange so that the audio/video data can be encrypted. More sophisticated connection management is also the subject of current research. It is expected that standards-track protocols integrating transport, resource management, and connection management will be the result of later working group efforts. 

The AVT Working Group may design independent protocols specific to each medium, or a common, lightweight, real-time transport protocol may be extracted. Sequencing of packets and synchronization among streams are important functions, so one issue is the form of timestamps and/or sequence numbers to be used. The working group will not focus on compression or coding algorithms that are domain of higher layers.

Goals and Milestones:


Define the scope of the working group, and who might contribute. The first step will be to solicit contributions of potential protocols from projects that have already developed packet audio and video. From these contributions the group will distill the appropriate protocol features.


Conduct a teleconference working group meeting using a combination of packet audio and telephone. The topic will be a discussion of issues to be resolved in the process of synthesizing a new protocol.


Review contributions of existing protocols, and discuss which features should be included and tradeoffs of different methods. Make writing assignments for first-draft documents.


Post an Internet-Draft of the lightweight audio/video transport protocol.


Post a revision of the AVT protocol addressing new work and security options as an Internet-Draft.

Jun 93 

Submit the AVT protocol to the IESG for consideration as an Experimental Protocol.


· RTP Payload Format for H.263 Video Streams 

· Compressing IP/UDP/RTP Headers for Low-Speed Serial Links 

· Real-Time Transport Protocol Management Information Base 

· RTP Profile for Audio and Video Conferences with Minimal Control

Request For Comments:






RTP: A Transport Protocol for Real-Time Applications



RTP Profile for Audio and Video Conferences with Minimal Control



RTP Payload Format for MPEG1/MPEG2 Video



RTP payload format for H.261 video streams



RTP Payload Format for JPEG-compressed Video



RTP Payload Format of Sun's CellB Video Encoding

Current Meeting Report

None Received 


None Received endees List

Attendees List