Session border controllers

Rooms

1. RFC 5853 is requirements, not a protocol

   RFC 5853 collects requirements from SBC deployments. It does not define an SBC wire protocol.

2. An SBC is commonly a B2BUA

   RFC 7092 taxonomizes B2BUAs. An SBC is commonly a UAS on one side and a UAC on the other, not a pure proxy.

3. Topology hiding rewrites the addresses you leak

   Topology hiding replaces caller addresses in signaling and, when media is anchored, in SDP.

4. Anchor, bypass, transcode, and DTMF

   Anchoring terminates RTP on the SBC. Bypass lets endpoints exchange media. Transcoding and DTMF interworking need the media path.

5. OPTIONS keepalives

   SBCs probe a peer with OPTIONS. A 200 OK means the peer answered. The interval is product configuration.

6. Call admission stays on the datasheet

   An SBC can refuse a new INVITE when its configured budget is exhausted. The number itself is platform-specific.

7. Active and standby, without a made-up timer

   Active/standby is a product behavior. One unit owns the work and the other is ready. Timers belong in that product’s HA guide.

Ecosystem

SIP does not replace workforce management, quality monitoring, CRM, emergency policy, or a messaging registry. It is the session seam those systems hang from. Compliance notes on this page are educational and are not legal advice.

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