Explicit Congestion Notification for RTP
Explicit Congestion Notification for RTP over UDP/IP
19 June 2009
ECN is getting attention as a method to minimise the impact of congestion on real-time multimedia traffic. When ECN is used, the network can signal to applications that congestion is occurring, whether that congestion is due to queuing at a congested link, limited resources and coverage on a radio link, or other reasons. This congestion signal allows applications to reduce their transmission rate in a controlled manner, rather than responding to uncontrolled packet loss, and so improves the user experience while benefiting the network.
The introduction of ECN into the Internet requires changes to both the network and transport layers. At the network layer, IP forwarding has to be updated to allow routers to mark packets, rather than discarding them in times of congestion. In addition, transport protocols have to be modified to inform that sender that ECN marked packets are being received, so it can respond to the congestion. TCP, SCTP, and DCCP have been updated to support ECN, but to date there is no specification how UDP-based transports, such as RTP, can use ECN. The aim of this project is to define such a specification.
This project is a collaboration between Ericsson Research and the University of Glasgow.
Standards Contributions
- Magnus Westerlund, Ingemar Johansson, Colin Perkins, Piers O'Hanlon, and Ken Carlberg, Explicit Congestion Notification (ECN) for RTP over UDP, Internet Engineering Task Force, March 2010, Work in progress (draft-ietf-avt-ecn-for-rtp-01.txt).
- Magnus Westerlund, Ingemar Johansson, Colin Perkins, Piers O'Hanlon, and Ken Carlberg, Explicit Congestion Notification (ECN) for RTP over UDP, Internet Engineering Task Force, February 2010, Work in progress (draft-ietf-avt-ecn-for-rtp-00.txt).
- Magnus Westerlund, Ingemar Johansson, Colin Perkins, Piers O'Hanlon, and Ken Carlberg, Explicit Congestion Notification (ECN) for RTP over UDP, Internet Engineering Task Force, October 2009, Work in progress (draft-westerlund-avt-ecn-for-rtp-02.txt).
- Magnus Westerlund, Ingemar Johansson, Colin Perkins, Piers O'Hanlon, and Ken Carlberg, Explicit Congestion Notification (ECN) for RTP over UDP, Internet Engineering Task Force, October 2009, Work in progress (draft-westerlund-avt-ecn-for-rtp-01.txt).
- Magnus Westerlund, Ingemar Johansson, and Colin Perkins Explicit Congestion Notification (ECN) for RTP over UDP, Internet Engineering Task Force, July 2009, Work in progress (draft-westerlund-avt-ecn-for-rtp-00.txt).