SIP trunk
A virtual connection that carries voice calls over the internet instead of physical phone lines.
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A virtual connection that carries voice calls over the internet instead of physical phone lines.
A SIP trunk is a virtual link that connects a business phone system to the public telephone network over an internet connection, using the Session Initiation Protocol. It replaces the physical circuits that used to perform the same job.
Because capacity is a matter of configuration rather than physical installation, SIP trunks scale far more easily than traditional lines and generally cost less, which is why most business telephony has moved to them.
Numbers delivered over SIP trunks are typically classified as VOIP in a line-type lookup. That classification is worth knowing before an SMS campaign, since SMS support on VOIP numbers depends entirely on the provider.
Related terms
- DID (Direct Inward Dialing) — A phone number that routes directly to a specific extension or user, bypassing a receptionist.
- PSTN — The Public Switched Telephone Network — the traditional circuit-switched phone system.
- Line type — The classification of a phone number as mobile, landline, VOIP, or invalid.