Breakout Gateway Control Function (BGCF)

The Breakout Gateway Control Function is an IMS element that chooses the network where PSTN breakout happens. If the breakout is to occur in the same network as the BGCF then the BGCF selects a MGCF (Media Gateway Control Function) which will be responsible for the interworking with the PSTN. The MGCF then receives the SIP signalling from the BGCF.  If the breakout is in another network, the BGCF will forward this session signalling to another BGCF, or an MGCF, depending on the configuration in the selected network.

The functions performed by the BGCF are:

- Receives request from S-CSCF to select appropriate PSTN break out point for the session

- Select the network in which the interworking with the PSTN is to occur.  If the interworking is in another network, then the BGCF will forward the SIP signalling to the BGCF of that network.

- Select the MGCF in the network in which the interworking with PSTN is to occur and forward the SIP signalling to that MGCF. This may not apply if the interworking is a different network.

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