RFC 3331 (rfc3331) - Page 3 of 94
Signaling System 7 (SS7) Message Transfer Part 2 (MTP2) - User Adaptation Layer
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RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 1.1 Scope There is a need for Switched Circuit Network (SCN) signalling protocol delivery from a Signalling Gateway (SG) to a Media Gateway Controller (MGC) [9]. The delivery mechanism addresses the following objectives: * Support for MTP Level 2 / MTP Level 3 interface boundary * Support for communication between Layer Management modules on SG and MGC * Support for management of SCTP active associations between the SG and MGC The SG will terminate up to MTP Level 2 and the MGC will terminate MTP Level 3 and above. In other words, the SG will transport MTP Level 3 messages over an IP network to a MGC. 1.2 Terminology Application Server (AS) - A logical entity serving a specific application instance. An example of an Application Server is a MGC handling the MTP Level 3 and call processing for SS7 links terminated by the Signalling Gateways. Practically speaking, an AS is modeled at the SG as an ordered list of one or more related Application Server Processes (e.g., primary, secondary, tertiary, ...). Application Server Process (ASP) - A process instance of an Application Server. Examples of Application Server Processes are active or standby MGC instances. Association - An association refers to a SCTP association. The association will provide the transport for the delivery of protocol data units for one or more interfaces. Backhaul - Refers to the transport of signalling from the point of interface for the associated data stream (i.e., SG function in the MGU) back to the point of call processing (i.e., the MGCU), if this is not local [9]. Fail-over - The capability to reroute signalling traffic as required to an alternate Application Server Process within an Application Server in the event of failure or unavailability of a currently used Application Server Process. Fail-back MAY apply upon the return to service of a previously unavailable Application Server Process. Host - The computing platform that the ASP process is running on. Morneault, et. al. Standards Track
