1. An ISUP REL 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 examines the message and forwards it to the ISUP
terminal process. The message is then forwarded to the SIP
terminal process.
3. Peripheral control in the IP bearer switching module detects
discontinuity and informs the SIP terminal process of the change
of state.
4. The SIP terminal process formulates a BYE message. At the end
of processing, a check is made to determine whether
encapsulated ISUP is allowed. If not, as in this example, the
ISUP REL MIME is discarded. Processing continues and the
message is forwarded to the SIP PH in the SIP GSM. This
message is in a compact, internal SIP format. This message
informs the TPS to tear down the call.
5. The SIP PH expands the BYE message to standard, external SIP
format, without an ISUP MIME or SDP MIME, adds the
appropriate SCTP and IP headers, and forwards it to the TPS via
the IP signaling network.
6. The bearer terminal process takes steps to tear down the call by
closing the port on the OFI and releasing used timeslots.
7. The SIP PH receives a 200 OK (BYE) message from the TPS.
The message informs the OPS that it received the BYE message.
8. The SIP PH strips the SCTP and IP headers, compacts the
message to the internal SIP format, and forwards the message to
the SIP terminal process.
9. The SIP terminal process terminates any remaining processes
dedicated to the call.
10. Call flow is complete.
SIP without Encapsulated ISUP - Detailed
Call Scenario
Call Flow
....................................................................................................................................................................................................................................
3-62
Lucent Technologies 235-200-118
Issue 3.02B, March 2007
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