draft-ietf-dccp-rtp-04.txt   draft-ietf-dccp-rtp-05.txt 
Network Working Group C. Perkins Network Working Group C. Perkins
Internet-Draft University of Glasgow Internet-Draft University of Glasgow
Intended status: Standards Track March 4, 2007 Intended status: Standards Track March 26, 2007
Expires: September 5, 2007 Expires: September 27, 2007
RTP and the Datagram Congestion Control Protocol (DCCP) RTP and the Datagram Congestion Control Protocol (DCCP)
draft-ietf-dccp-rtp-04.txt draft-ietf-dccp-rtp-05.txt
Status of this Memo Status of this Memo
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This Internet-Draft will expire on September 5, 2007. This Internet-Draft will expire on September 27, 2007.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
Abstract Abstract
The Real-time Transport Protocol (RTP) is a widely used transport for The Real-time Transport Protocol (RTP) is a widely used transport for
real-time multimedia on IP networks. The Datagram Congestion Control real-time multimedia on IP networks. The Datagram Congestion Control
Protocol (DCCP) is a newly defined transport protocol that provides Protocol (DCCP) is a newly defined transport protocol that provides
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note that the semantics of the RTP sequence number and the DCCP note that the semantics of the RTP sequence number and the DCCP
sequence number are not compatible, and the value of one cannot be sequence number are not compatible, and the value of one cannot be
inferred from the other). inferred from the other).
A DCCP connection is opened when an end system joins an RTP session, A DCCP connection is opened when an end system joins an RTP session,
and it remains open for the duration of the session. To ensure NAT and it remains open for the duration of the session. To ensure NAT
bindings are kept open, an end system SHOULD send a zero length DCCP- bindings are kept open, an end system SHOULD send a zero length DCCP-
Data packet once every 15 seconds during periods when it has no other Data packet once every 15 seconds during periods when it has no other
data to send. This removes the need for RTP no-op packets [18], and data to send. This removes the need for RTP no-op packets [18], and
similar application level keep-alives, when using RTP over DCCP. similar application level keep-alives, when using RTP over DCCP.
This application level keepalive does not need to be sent if it is
known that the DCCP CCID in use provides a transport level keepalive.
RTP data packets MUST obey the dictates of DCCP congestion control. RTP data packets MUST obey the dictates of DCCP congestion control.
In some cases, the congestion control will require a sender to send In some cases, the congestion control will require a sender to send
at a rate below that which the payload format would otherwise use. at a rate below that which the payload format would otherwise use.
To support this, an application should use either a rate adaptive To support this, an application should use either a rate adaptive
payload format, or a range of payload formats (allowing it to switch payload format, or a range of payload formats (allowing it to switch
to a lower rate format if necessary). Details of the rate adaptation to a lower rate format if necessary). Details of the rate adaptation
policy for particular payload formats are outside the scope of this policy for particular payload formats are outside the scope of this
memo (but see [19] and [20] for guidance). memo (but see [19] and [20] for guidance).
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DCCP ports 5004 ("DCCP RTP") and 5005 ("DCCP RTCP") are registered DCCP ports 5004 ("DCCP RTP") and 5005 ("DCCP RTCP") are registered
for use as default RTP/RTCP ports (see Section 5.1 of this memo). for use as default RTP/RTCP ports (see Section 5.1 of this memo).
The four services codes listed above are to be associated with these The four services codes listed above are to be associated with these
ports. ports.
8. Acknowledgements 8. Acknowledgements
This work was supported in part by the UK Engineering and Physical This work was supported in part by the UK Engineering and Physical
Sciences Research Council. Thanks are due to to Philippe Gentric, Sciences Research Council. Thanks are due to to Philippe Gentric,
Magnus Westerlund, Sally Floyd, Dan Wing, Gorry Fairhurst, Stephane Magnus Westerlund, Sally Floyd, Dan Wing, Gorry Fairhurst, Stephane
Bortzmeyer and the other members of the DCCP working group for their Bortzmeyer, Arjuna Sathiaseelan, and the other members of the DCCP
comments. working group for their comments.
9. References 9. References
9.1. Normative References 9.1. Normative References
[1] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, [1] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", STD 64, "RTP: A Transport Protocol for Real-Time Applications", STD 64,
RFC 3550, July 2003. RFC 3550, July 2003.
[2] Kohler, E., Handley, M., and S. Floyd, "Datagram Congestion [2] Kohler, E., Handley, M., and S. Floyd, "Datagram Congestion
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