Note: All SIP messages have the common mandatory SIP headers
used to identify and route SIP messages and associate them with
particular transactions within calls, e.g.: either Request URI or
response status line, To, From, Call-ID, CSeq, Via, Length,
Max-Forwards, etc. The following message flow description does not
explicitly list these. For more detailed examples, refer to the Session
Initiation Protocol (SIP) - Interface Specification, 235-900-344,
document.
The following steps provide a description of the messages between the
Originating IP TAS, 5ESS
®
switch PSTN Gateway and Terminating
PSTN switch.
1. The SIP INVITE includes:
• SDP offer with bearer session description for originating IP
subscriber,
• SIP Allow header indicating support for at least these
methods: INVITE, ACK, BYE, CANCEL, UPDATE, INFO,
OPTIONS, PRACK,
• SIP Supported header indicating support for reliable
provisional responses (indicated by ″100rel″ parameter), and
• SIP P-Asserted-Identity header, with calling party
information.
If the call was forwarded one or more times within the IP
network, before ultimately being forwarded to a PSTN
subscriber, the SIP INVITE from the TAS OPS may also include
a SIP Diversion header for each instance of call forwarding.
If there are presentation restrictions on the calling party
information, the INVITE may include a Privacy header.
The TAS OPS may include Originating Line Information (OLI),
Message Flows
Call Flow
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3-22
Lucent Technologies 235-200-118
Issue 3.02B, March 2007
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