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SIP Trunks Explained for SMEs

A SIP trunk is a logical bundle of voice sessions from your PBX to the public network over IP. Instead of ISDN channels, you size concurrent calls, choose codecs and point trunks at a carrier SBC — on-prem or hosted.

Next step: Match SIP capacity to peak inbound + outbound. Contact us with your current channel count and DDI range.

Channels vs burstable concurrency

Retail peaks (Monday 9am) need headroom. Some carriers sell fixed channels; others meter. Model marketing campaigns and seasonal lines so you do not hit 486 Busy during a radio ad.

Codecs and bandwidth

G.711 is predictable; compressed codecs save bandwidth but complicate transcoding. Align with handset firmware and any hosted PBX defaults.

Emergency services and location

VoIP emergency calling requires accurate address data per site and per outbound CLI. Hybrid homeworkers complicate policy — document who may present which DDI.

Network readiness

Use QoS, monitor jitter and prefer static IPs for SBC pinning when your firewall rules depend on it.

Related guides

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