A SIP trunk is the connection that carries voice calls between a call center's systems, such as a ViciDial server, and the public telephone network over the internet. The carrier providing the trunk sets how many calls can run at once, how fast new calls can start, and which caller IDs may be used.
For an offshore floor dialing the US, the trunk provider is also the carrier that signs calls for STIR/SHAKEN, so it affects connect rates as well as cost.
How a SIP trunk works on a floor
A dialer in Noida sends a call request to the carrier's SIP server, the carrier places the call on the US network, and audio flows back over the internet. Trunks are sized by channels, meaning concurrent calls, and by calls per second, the rate at which new calls can be started. A predictive dialer at a high dial level can hit either limit quickly.
What to watch
Call quality depends on the internet path between the floor and the carrier. Latency, jitter and packet loss show up as delay, clipped words and robotic audio. Callers in the US hang up faster on a bad line. Track failed call attempts, audio complaints and per-minute cost by carrier, and keep a second trunk ready in case the first one fails during a shift.
Common mistakes
Sizing the trunk for the number of agents instead of the number of simultaneous dials.
Choosing a carrier on price alone without asking about attestation and spam handling.
Ignoring codec settings, which affect both bandwidth and audio quality.
Trunks for voice bots
Voice bots use the same trunk as human agents when they log in through the dialer, so the floor's carrier, caller IDs and number reputation stay its own. Low, steady latency matters even more for bots, because a slow reply sounds like hesitation to the caller.