Smh

The SMH function routes SS7 messages during normal conditions. SMH identifies whether the destination address is the receiving endpoint or whether the message needs to be routed. If the destination address is the receiving endpoint, SMH also identifies the user application (SCCP, ISUP, TUP, or TCAP). If the message needs to be forwarded, SMH identifies the link to which the message is to be forwarded.

The SMH is divided into three processes:

• SMH Message Discrimination—Determines the SS7 message's destination endpoint address. Message discrimination reads the DPC from the routing label in the SIF of the MSU. If it is addressed to the receiving node, message discrimination passes the message to the message distribution function. If it is not addressed to the receiving node, message discrimination passes the message to the message routing function.

• SMH Message Distribution—Identifies the user and delivers the user information (SCCP, TUP, ISUP, TCAP, or network management) in the SS7 message to the upper-level protocol. As previously mentioned, the message distribution process is invoked only when the message is addressed to the receiving endpoint or to itself. The Service Indicator value in the Service Indicator octet field of the MSU determines the user of the message.

If the user of the message is unavailable for processing, the User Part Unavailable (UPU) message is sent back to the transmitting endpoint. UPU messages sent by the network management process include a cause code that identifies one of the following problems:

o User part function is not provisioned.

o User part function is out of service.

o User part function is unavailable for unknown reasons.

• SMH Message Routing—Interfaces with MTP2 to route messages over the network. The SMH routing process routes messages to the appropriate signaling links. The SMH routing process receives messages from the message discrimination and L4 applications. Message discrimination passes messages to the routing process when the message is destined for another signaling point. Higherlevel applications pass messages to the routing process to transport the outgoing messages.

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