An SBC (Session Border Controller) is a device deployed in VoIP networks to control the signaling and media streams involved in setting up, conducting, and tearing down telephone calls and other interactive media communications. SBCs have traditionally come as hardware appliances, but are now also available as software that runs in a virtualized environment.

They provide enterprises and contact centers secure and reliable connectivity to SIP trunks and hosted services, supporting multiple concurrent sessions per device. In hosted environments, SBCs provide local survivability in case of WAN failure or a service outage. Enterprises benefit from seamless interconnection between their own IP-PBXs, unified communications systems, or contact centers and multiple SIP trunking providers, while maintaining high VoIP quality and protecting their network from malicious or fraudulent security threats. AudioCodes and Sonus are two of the leading manufacturers of SBCs.

SBCs provide an array of tools that are useful when migrating from a legacy PBX to a UC platform with enterprise voice. This includes:

• The ability to “fork” calls to multiple destinations; for example, both a legacy PBX and Skype for Business
• Routing calls based on an active directory lookup
• Transcoding between audio codecs like G.711 and G.729