CHAPTER30 SBC Overview
Mediant 800 Gateway & E-SBC | User's Manual
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).
Local Handling of SIP 3xx
The device can handle SIP 3xx responses on behalf of the dialog-initiating UA and retry the request
(e.g., INVITE) using one or more alternative URIs included in the 3xx response. The new request
includes SIP headers from the initial request such as Diversion, History-Info, P-Asserted-Id, and
Priority. The source and destination URIs can be manipulated using the regular manipulation
mechanism.
The device sends the new request to the alternative destination according to the IP-to-IP Routing
table rules. (where the 'Call Trigger' field is set to 3xx). It is also possible to specify the IP Group
that sent the 3xx request as matching criteria for the re-routing rule in this table ('ReRoute IP Group
ID' field).
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