Session Border Controller (SBC)

A "Session Border Controller" (SBC) is a device that generally sits between two administrative domains (e.g., between two service providers) and is responsible for routing VoIP calls between the two domains.

An SBC may route only call signaling or it may route both the call signaling and the media between the administrative domains. Most will route both.

The SBC may also serve as a protocol interworking function to interwork between various VoIP protocols, including H.323 and SIP.

Probably the most important function of the SBC is to provide control. This device will generally perform functions to ensure that QoS is maintained or ensured, that call detail records are properly recorded, and provide some level of security to prevent unauthorized calls into or out of an administrative domain.

Resources: VoIP Information Site

See Also: H.323, Session Initiation Protocol (SIP)