58 • Web Server Integration
[ S N O M 4S NAT FI L T E R ]
ter, the From-header will be set to the value that you pass here.
Please note that requests may loop through several SBC. This
will typically happen in data centres that use a SBC server farm. In this
environment, the application server must be able to handle several call
initiation requests for the same call as the SBC do not exchange informa-
tion about web requests. A simple implementation just passes an empty
response. The subsequent SBC will then just route that call without any
other change of the request.
When the uri parameter is present, the SBC does not use the out-
bound proxies to route the request. You must make sure in the application
logic that an appropriate request URI is inserted.
5.5 Call Termination
When the SBC calls the destructor for the call object, it first sends
out web request that informs the applications server that the call has fin-
ished. In contrast to the other web requests the answer to that request
does not matter — the call is finished anyway.
The SBC provides the following arguments to the request:
• The parameter “action” is set to “end”.
• If the id parameter was set in the response to the start request, the
SBC will put that argument in the parameter “id”. The application
server may use this information to match the call.
• The parameter “callid” is set to the Call-ID of the call.
• The parameters “from_uri” and “to_uri” are set to the same values
as they had during the action=start call.
• The parameter “reason” is set to the message that describes why
the desructor was called (see below).
• There are several time values available. All these times are mea-
sured in seconds since Jan 1st, 1970. The parameter “time_invite”
indicates when the initial INVITE was received. The parameter
“time_180” indicates when a 18x request was received (if there was
such a response), the parameter “time_200” indicates when the
first 2xx code was received. The “time_bye” parameter (if present)
shows when a BYE request was received (this parameter is only
present when a 2xx was received).
5.