Message conversion
between PSTN and IP
protocols
PSTN signaling messages are converted to SIP messages using
translation and encapsulation. For outgoing messages, the SIP protocol
handler (PH) in the 5ESS
®
switch constructs a SIP message in a
standard, external format using information provided by the SIP call
processing SM.
The SIP message contains the following:
• information used to route the message in the IP network,
• information describing the message type and content, and
• data associated with the particular application.
For incoming messages, the SIP PH extracts information from the SIP
message and delivers the data to the SIP call processing SM. The SIP
call processing SM passes the information to the SM that generates
PSTN signaling messages and completes the call using TDM circuits.
The details of how the call signaling messages are converted to and
from SIP are controlled by a number of provisionable parameters on
Figure 3-2 PSTN Gateway
PSTN
5ESS Switch
®
5ESS Switch
PSTN Gateway
®
IP Network
Telephone Application
Server (TAS)
Signaling Path
Bearer Path
POTS Subscriber
ISDN Subscriber
IP Subscriber
Network Architecture
Call Flow
....................................................................................................................................................................................................................................
3-4
Lucent Technologies 235-200-118
Issue 3.02B, March 2007
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