Example 4. IMS-terminal-to-IMS-terminal message switch routing

The following figure shows a terminal T connected to IMSA effecting a message switch to terminal T2, which is connected to IMSB.

Figure 1. ISC example for IMS-terminal-to-IMS-terminal message switch routing

1. The terminal T enters the following data stream:

   LTISC1 | T2 | Data...

   LTISC1 is an LTERM name that IMSA has associated with an ISC session to IMSB. The terminal operator (T) must know this ISC LTERM name as well as the LTERM name of the destination terminal (T2) attached to IMSB.

2. ISC message switch support removes the LTERM name (LTISC1) before sending the balance of the message on the ISC session to IMSB. Therefore, the data stream that is sent on the ISC session looks like:

   FMH: DPN=SCHEDULER

   FMH: DPN=ISCE,PRN=,RDPN=,RPRN=T | T2 | Data...

   1. DPN=ISCE is specified, because IMS ISC support supplies this value as a default if IMS does not supply a DPN when output is sent to another subsystem.
   2. PRN= is not required, because the destination, terminal T2, is part of the data stream, but could be supplied or modified by MFS.
   3. RDPN= is not supplied and is also not required for this example. This value could have been supplied by MFS.
   4. RPRN=T, as in Example 1, is automatically inserted by IMSA as a default function of the message switching capability of IMS ISC. Because no reply is returned, this parameter is discarded by IMSB. MFS can be used in IMSB to make this parameter available to the operator of terminal T2.
3. Before the data stream is placed on IMSB's message queues, it is edited by ISC edit. In IMSB, ISC edit examines the data (because no PRN is available in the input FMH) to determine the destination. T2 is found to be the destination and the input message is placed on the message queues with a destination T2.
4. On output from IMSB to terminal T2, the data stream now looks like this:

   T2 | Data...

5. A default system MOD would be used for output if T2 were a required MFS device.