# What is an SBC (Session Border Controller)?

> An SBC (Session Border Controller) is the security and control element that sits at the edge of a VoIP network, policing SIP signaling and RTP media as they cross between networks. It handles NAT and firewall traversal, hides internal topology, enforces call admission and rate limits, transcodes codecs when two sides differ, and defends against SIP-based attacks and toll fraud. Every serious SIP trunking and voice-API deployment sits behind one. See /answers/what-is-sip, /answers/what-is-nat-traversal, and /answers/voice-api-sip-trunking.

- Canonical URL: https://www.broadnet.me/answers/what-is-sbc
- Language: en
- Last reviewed: 2026-07-22
- Publisher: BroadNet (https://www.broadnet.me)

## Related

- [All answers](https://www.broadnet.me/answers)
- [Glossary](https://www.broadnet.me/answers)
- [What is SIP (Session Initiation Protocol)?](https://www.broadnet.me/answers/what-is-sip)
- [What is NAT traversal in VoIP?](https://www.broadnet.me/answers/what-is-nat-traversal)
- [How does a voice API and SIP trunking work?](https://www.broadnet.me/answers/voice-api-sip-trunking)
- [What are voice codecs (G.711, Opus)?](https://www.broadnet.me/answers/what-is-voice-codec)
- [Voice](https://www.broadnet.me/products/voice)
- [Voice integration](https://www.broadnet.me/products/voice)