Communication services utilizing the real-time transport protocol (RTP) as the application level framing protocol normally use a native IP-based transport mechanism [IETF RFC 3550], which results in using two separate user datagram protocol (UDP) ports for the RTP and RTP control protocol (RTCP) traffic components. ITU-T H.248 gateways provide a rich set of gateway services for such types of RTP traffic, as defined by [ITU-T H.248.48], [ITU-T H.248.58], [ITU-T H.248.71], [ITU-T H.248.77], [ITU-T H.248.87] and [ITU-T H.248.88].

In addition, multiple RTP-based traffic flow components could be multiplexed at multiple, different levels (from the perspective of a layered protocol architecture). The purpose of this Recommendation is to clarify how ITU-T H.248 gateways support such "multiplexing structures".

The scope of this Recommendation addresses the following subjects:

– Terminology: clarification of RTP related terms and definitions;

– Multiplexing methods: summary of existing multiplexing schemes in context of RTP-based communication services;

– ITU-T H.248 support: provides information on how dedicated multiplexing methods could be supported by ITU-T H.248 gateways inclusive of references to relevant signalling syntax; and

– Examples: provides some signalling examples as complementary information.

This Recommendation does not define any new ITU-T H.248 protocol extensions.