Session border controller or SBC is a dedicated network element. Its main function is to secure and control real-time communication calls or sessions over SIP-based VoIP infrastructures. Session border controller (SBC) plays a major role in security, interoperability, and transcoding. The main function of the Session Border Controller is to secure and control the real-time communication calls or sessions over SIP-based VoIP infrastructures. It is deployed to protect SIP-based voice over Internet Protocol networks.

Monitor Real-time Performances
Securing the Real-time Network
Network and Protocol Interconnection
Session admission control

Read more: https://revesystem.wordpress.com/2020/01/08/role-of-session-border-controller-in-real-time-communication-network/