HP-UX C SIP Stack Programmer's Guide (Novembery 2007)

Working with Call-legs (Dialogs) 85

Call-leg Forking Support

The application can supply the Forked-1xx-Timer timeout value in the SIP Stack

configuration. This value will apply to all forked call-legs. The application can

also change the timer value for each call-leg using the call-leg API. The

application may also disable this timer by setting its value to 0.

A non-2xx final response should also terminate all call-legs created by the same

initial request. Again, it is recommended that application will terminate all these

call-legs when the non-2xx response is received. However, here again the

application can relay on the forked-1xx-timer that will terminate all call-legs on

its expiration.

SENDING CANCEL

Only the original call-leg may cancel the initial request, since the original call-

leg holds the initial invite transaction. Calling the Cancel() function on a forked

call-leg returns an illegal-action error.

CALL-LEG FORKING

SUPPORT EVENTS

The Call-leg API includes the following event for forking-support

implementation.

RvSipCallLegCreatedDueToForkingEv()

A provisional or final response that is received for an initial INVITE may create

a forked call-leg. This event informs the application of the creation of a new

forked call-leg, and exchanges handle with the application.

If the application does not wish to handle this forked call-leg, it can indicate that

the SIP Stack should terminate the new forked call-leg. In this case, the new

call-leg will be destructed immediately. Otherwise the new forked call-leg will

handle the new response message, update its state machine, send the ACK

response if needed, and call to all the regular call-leg callback functions.

CALL-LEG FORKING

UPPORT API

The Call-leg API includes a set of functions dedicated to forking-support

implementation.

RvSipCallLegGetOriginalCallLeg()

Returns the handle to the original call-leg related to a given forked call-leg. If

the given call-leg is an original call-leg, the call-leg will return its own handle.