ITU-T H.248.4 PDF

This Recommendation defines a package that extends the applicability of [ITU-T H.248.1], Gateway control protocol. In particular, this Recommendation defines the transport of ITU-T H.248.1 Gateway Control Protocol messages over the Stream Control Transmission Protocol (SCTP) [IETF RFC 2960].

Protocol messages may be transmitted over the Stream Control Transmission Protocol (SCTP).

In a transaction-oriented protocol like H.248.1, there are still ways for transaction requests or responses to be lost, e.g., caused by entity/component failure. As such, it is recommended that entities using SCTP transport implement application level timers for each request.

Commands should be sent to the default port number, 2944 for text-encoded operation, or 2945 for binary-encoded operation. Responses must be sent to the address and port from which the corresponding commands were sent, except if the response is to a handoff or failover, in which case the procedures of clause 11.5 of [ITU-T H.248.1] apply. SCTP payload protocol identifier shall be 7.

To provide interworking between MTP3B and SCTP, and to allow for flexible implementations of gateways and controllers in order to offer efficient use of SCTP associations, the M3UA layer may be added on top of SCTP.