Call Tear Down at TPS - No
ISUP
This section takes a closer look at the processing and messaging
completed by the TPS when acting as a gateway between the PSTN
and an IP network.
1. The SIP PH receives and accepts the BYE message from the
OPS. The message informs the TPS the calling party went
on-hook.
2. 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. The SIP terminal process verifies that
encapsulated ISUP is not required. If not required, as in this
example, processing continues and a default ISUP REL is
created.
3. The SIP PH builds the 200 OK (BYE) message in standard,
external SIP format, adds the appropriate SCTP and IP headers,
and forwards it to OPS via the IP signaling network.
4. The SIP terminal process passes the updated call state to the
ISUP terminal process. An ISUP REL message is forwarded to
the ST PH in the SS7 GSM. Finally, the message is sent to the
terminating switch.
Figure 3-27 Call Tear Down at TPS
OIU
SDL
Ethernet
IP Network
OC-3c
IP Network
OC-3c
SONET
Originating
Packet
Switch
(OPS)
Terminating Packet Switch (TPS)
AM
NLI
PSU
DLTU
SM-2000
TSI
SMP
NLI
SM-2000
SMP
PSU
GQPH
SIP-PH
PSUCOM
TSI
NLI
SM-2000
SMP
TSI
OFI-IP
OFI-IP
BRR TP
SIP TP
NLI
DNUS
SM-2000
TSI
SMP
ISUP TP
CM
CMP
Terminating
Switch
PSTN
CCS-SS7
2
1
5
BYE
Message
Message
In a standard, external format
In a compact, internal format
OK BYE
3
4
ISUP REL
ISUP REL
4
4
BYE
SIP without Encapsulated ISUP - Detailed
Call Scenario
Call Flow
....................................................................................................................................................................................................................................
235-200-118
Issue 3.02B, March 2007
Lucent Technologies
3-63
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