AudioCodes Mediant 3000, User Manual

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Version 6.6 421 Mediant 3000
User's Manual 28. SBC Overview
user agent to send the INVITE to the device.

Adds a special prefix ("T~&R_") to the Contact user part – to identify the new INVITE
as a 3xx resultant INVITE.
The SBC handling for the 3xx resultant INVITE is as follows:
1. The incoming INVITE is identified as a 3xx resultant INVITE according to the special
prefix.
2. The device automatically replaces the SBC host part (in the Request-URI) with the
host from the 3xx Contact.
3. The prefix ("T~&R_") remains in the user part for the classification, manipulation, and
routing mechanisms.
4. The classification, manipulation, and routing processes are done exactly like any other
INVITE handling. The special prefix can be used for specific routing rules for 3xx
resultant INVITEs.
5. The prefix is removed before the resultant INVITE is sent to the destination.
Figure 28-6: SIP 3xx Response Handling
The process of this feature is described using an example:
1. The device receives the Redirect server's SIP 3xx response (e.g., Contact:
<sip:User@IPPBX:5060;transport=tcp;param=a>;q=0.5).
2. The device replaces the Contact header value with the special prefix and database
key value as user part, and with the device's URL as host part (e.g., Contact:
<sip:Prefix_Key_User@SBC:5070;transport=udp>;q=0.5).
3. The device sends this manipulated SIP 3xx response to the Far-End User (FEU).
4. The FEU sends a new request with the Request-URI set to the value of the received
3xx response's Contact header (e.g., RequestURI:
sip:Prefix_Key_User@SBC:5070;transport=udp).
5. Upon receipt of the new request from the FEU, the device replaces the Request-URI
with the new destination address (e.g., RequestURI:
sip:Prefix_User@IPPBX:5070;transport=tcp;param=a).
6. The device removes the user prefix from the Request-URI, and then sends this
Request-URI to the new destination (e.g., RequestURI:
sip:User@IPPBX:5070;transport=tcp;param=a).