Type of BICC calls

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BICC Bearer establishment procedures:

Four variants of BICC IP bearer set-up procedures are defined:
-            Fast Forward
-            Delayed Forward
-            Fast Backward
-            Delayed Backward 

Those procedures differ on the way the bearer control information are exchanged, and on whether an APM (Connected) message shall be sent by the originating BICC node once the bearer is ready for use.


-            Bearer control information exchanges :
-            In Fast bearer setup (forward or backward) and in delayed forward bearer establishment procedures, the IP bearer establishment is done in the forward direction, i.e. the IPBCP request is sent from the originating towards the terminating MGWs ; the bearer establishment request is sent in the IAM message in fast (forward or backward) procedures, while it is sent in subsequent APM message, after a first IAM/APM exchange, in case of delayed forward bearer establishment.
-            In reverse, in the Delayed backward bearer establishment procedure, the IP bearer establishment is done in the direction reverse to the call establishment direction, i.e. the IPBCP request is sent from the terminating towards the originating MGWs, through a backward APM message.
-            APM (Connected) exchange :
-            In Forward bearer setup procedures, the terminating BICC node decides by its own whether it requires or not the originating BICC node to send an APM (Connected) message once the bearer is ready for use at the originating side.
-            In Delayed backward bearer setup procedure, APM(Connected) is never sent (BICC protocol).
-            In Fast backward bearer setup procedure, an APM(Connected) message shall always be sent (BICC protocol).





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