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
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