Border Controller (SBC)

A Session Border Controller (SBC) is a network security and signalling management device that sits at the border between enterprise telephony networks and external VoIP or SIP-based networks — controlling, protecting, and routing real-time communication sessions. SBCs perform SIP normalisation, security policy enforcement, media transcoding, and NAT traversal. In voice AI deployments, the SBC is typically the entry point through which inbound calls are received from the PSTN or a carrier SIP trunk before routing to the Voice Gateway and AI Agent infrastructure. SBCs may be hardware appliances, software instances, or cloud services.

For enterprise teams, a Session Border Controller (SBC) matters because real-world outcomes depend on how the capability is integrated, governed, and measured — not just on the underlying technology. SBCs may be hardware appliances, software instances, or cloud services.

Key Points

• Sits at the network border to protect and manage SIP/VoIP communication sessions
• Performs SIP normalisation, security enforcement, media transcoding, and NAT traversal
• Entry point for inbound calls before they reach the Voice Gateway and AI Agent
• Protects AI voice infrastructure from toll fraud, DDoS attacks, and unauthorised access
• Can be hardware, software, or cloud-delivered depending on deployment architecture