Table of Contents
Advertisement
Table 6-1
Mapping of PRI and ISUP messages
Message type
Call takedown
Call takedown
Note 1: ACM can be mapped to ALERT or PROG depending on the value of the
backward call indicator (BCI). If the BCI indicates interworking with PTS trunks,
ACM is mapped to a PROG message; otherwise, it is mapped to an ALERT
message.
Note 2: REL can be mapped to a DISC or REL message depending on the state
of the call. When an active call is cleared, REL is mapped to a DISC; otherwise, it
is mapped to a REL.
The following PRI/ISUP messages are not interworked because they have
local significance only. Any PRI/ISUP message that is not in the following
list is not interworked by this feature.
CALL PROCeeding (PRI)
CONNect ACKnowledge (PRI)
RELease COMplete (PRI)
ReLease Complete (ISUP)
The diagrams that follow illustrate the interworking between PRI and ISUP
protocol messages for call establishment and takedown. The mapping of the
messages used in Figures 6-1 through 6-7 are detailed in Table 6-1 given
earlier in this chapter.
This list of notes applies to all of the interworking diagrams:
The Q.931 messages CALL PROC, CONN ACK, and RLC are of local
significance only and are not mapped.
The ISUP message RLC is of local significance only and is not mapped.
The PRI interfaces cut through pulse code modulation (PCM) in both
directions upon receipt of the call proceeding message.
The CCS7 network cuts through PCM in both directions upon
propagation of the Address Complete Message.
The terminating exchange (either ISDN or non-ISDN) provides the
ringback tone.
Digital Switching Systems DMS-250 ISDN Reference Manual MWC14 (CSP14)
(continued)
PRI message
ISUP message
DISC
Release (REL) (Note 2)
REL
REL (Note 2)
—end—
PRI interworking 6-3
Advertisement
Table of Contents
