Pri-To-Isup-To-Pri - Nortel DMS-250 Reference Manual

Digital switching systems

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6-4 PRI interworking

PRI-to-ISUP-to-PRI

Figure 6-1 illustrates PRI-to-ISUP-to-PRI call setup and takedown with

three-stage call clearing.

PRI-to-ISUP-to-PRI with three-stage call clearing

The call scenario in Figure 6-2 illustrates two-stage call clearing whereby a

Q.931 REL message maps into the ISUP REL message at the interworking

switch initiating call clearing (that is, the calling-access DMS-250 switch)

and an ISUP REL message maps into a Q.931 DISConnect message on the

other interworking switch (the called-access DMS-250 switch).

297-2521-106 Standard 23.01 March 2001

For active call clearing, an ISUP REL message is always mapped to a

Q.931 disconnect message.

Note: Dashed lines indicate optional messages.