MSC security and the TM and MSC message routing and control exit routine

The TM and MSC Message Routing and Control exit routine (DFSMSCE0) is concerned primarily with the routing of messages for TM and MSC; however, you can also use this exit to specify which user ID will be used for security checking.

The specifications you can make with DFSMSCE0 regarding user IDs are the same as those specified by the second positional parameter of the MSCSEC= keyword in the DFSDCxxx PROCLIB member.

When IMS calls DFSMSCE0 for MSC link-receive routing, IMS passes to DFSMSCE0 the second security specification defined in the DFSDCxxx MSCSEC= parameter. If the security specification in DFSMSCE0 differs from the one received from IMS for a given transaction, DFSMSCE0 can override the specification received from IMS for that transaction. DFSMSCE0 can also reroute or cancel the transaction.

IMS calls DFSMSCE0 through one of four entry points when transactions are received from an MSC link, but only the following two entry points are used for security checking:

LRTRAN for non-direct-routed transaction messages local to the receiving IMS system
LRDIR for direct-routed transaction messages local to the receiving IMS system

Related reading: For more information about the TM and MSC Message Routing and Control exit routine (DFSMSCE0), see IMS Version 15.5 Exit Routines.