Back-to-Back Gateway
When the Oracle® Enterprise Session Border Controller is functioning as a back-to-back gateway (B2BGW), it appears as multiple H.323 gateways to multiple networks. Each Oracle® Enterprise Session Border Controller virtual gateway discovers and registers with a gatekeeper in its respective domain. Each gateway relies on its gatekeeper for admission and location services through the ARQ/ACF exchange. H.225 call control and H.245 messages are exchanged directly with the terminating gateway or gatekeeper. Routing policies are used to associate one virtual gateway with another.
The following diagram illustrates the back-to-back gateway.
![](img/GUID-4EF28CE8-5514-43F1-9A33-8C63285E222A-default.jpg)