Call Setup at Originating
Packet Switch (ISUP to
SIP)
This section takes a closer look at the processing and messaging
performed by the OPS when acting as a gateway between the PSTN
and an IP network.
1. An ISUP IAM message arrives at the OPS on a signaling data
link (SDL). The message is sent from the trunk peripheral
terminating the SDL to the ST PH in the SS7 GSM via nailed up
timeslots.
2. The ST PH in the PSU2 examine the message and forward it to
the ISUP terminal process.
3. The ISUP terminal process performs digit analysis to determine if
the call should be routed to a line or a trunk. Digit analysis
determines that the call should be routed to a SIP packet group
and requests that the CMP select a SIP packet group for the call.
4. The CMP:
• determines the call is routed to a SIP packet group,
• selects a switching module for the SIP terminal process, and
• selects a switching module for the bearer terminal process.
The determined information is then forwarded to the SIP terminal
process and then the bearer terminal process.
Detailed Call Scenarios - SIP Base
Call Flow
....................................................................................................................................................................................................................................
235-200-118
Issue 3.02B, March 2007
Lucent Technologies
3-27
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