5. The bearer terminal process selects an OFI and a port for the
call. The corresponding IP address and port number are
forwarded to the SIP terminal process.
6. The SIP terminal process develops an INVITE message. This
message is in a compact, internal SIP format. An INVITE
message requests that the TPS allocate resources for the call.
This message includes:
• IP address and port number for the OPS OFI-IP
• Encapsulated ISUP IAM message
• A description of the requested session.
The formulated message is forwarded to the SIP PH in the SIP
GSM. Additionally, an INVITE transaction timer is started.
7. The SIP PH expands the INVITE message to standard, external
SIP format, adds the appropriate SCTP and IP headers, and
forwards it to TPS via the IP signaling network.
8. The OPS waits for the TPS to respond.
9. The SIP PH receives a 183 SESSION PROGRESS message from
the TPS. The message includes the IP address and port number of
the TPS bearer resource.
Detailed Call Scenarios - SIP Base
Call Flow
....................................................................................................................................................................................................................................
3-28
Lucent Technologies 235-200-118
Issue 3.02B, March 2007
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