Definition
What is SIP trunking?
By Lewis CrookPublished
SIP trunking is the delivery of voice calls between an enterprise and a telephony provider over an IP-based signalling protocol (Session Initiation Protocol). It is the substrate every voice AI deployment rides on, and the layer at which residency, recording, and DTMF capture decisions are made.
SIP trunking is the IP pipe that carries voice into and out of the contact centre.
Why it matters for enterprise CX leaders
- SIP routing is what allows phased IVR replacement — voice AI and the legacy IVR can be addressed from the same number.
- Data residency decisions are often made at the SIP layer first, model layer second.
- DTMF capture for PCI compliance requires SIP-level support; not every voice AI platform handles it cleanly.
Frequently asked questions
- Do I need SIP trunking for voice AI?
- Effectively yes for enterprise inbound deployments. Even cloud contact-centre platforms terminate on SIP somewhere in the path.
- Does SIP affect voice AI latency?
- Yes — codec, region, and trunk configuration each add 20–150 ms. Worth measuring end-to-end during evaluation.
- Is SIP trunking secure?
- When configured with TLS for signalling and SRTP for media, yes. Many legacy deployments still run unencrypted SIP — a common audit finding.
Related terms
- Voice AI latency— Voice AI latency is the gap before the system starts talking back.
- IVR replacement— IVR replacement swaps menus and keypad input for natural conversation and actual resolution.
- DTMF fallback— DTMF fallback uses the keypad to capture digits the model is not allowed to hear.
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