Summary

This Recommendation defines a package to allow H.248 controlled media gateways to support explicit congestion notification (ECN). ECN is a mechanism to provide indications of incipient congestion affecting an RTP stream to a receiver and, usually, to a sender.  ECN when used with an RTP stream over UDP uses the RTP Control Protocol to provide feedback of ECN congestion markings to an RTP sender. The mechanism allows senders and/or receivers to react in order to reduce congestion in real-time communications. This Recommendation only describes the use of ECN in RTP over UDP streams.