Wholesale SIP Trunking
A wholesale SIP trunk is the pipe. Termination is what happens at the far end of it. You need both, and the trunk is where concurrency, authentication and failover get decided.
Wholesale trunks are not business trunks
A business SIP trunk is sold in channels — ten, thirty, a hundred — with a monthly fee per channel and a bundle of minutes.
A wholesale trunk is sold on capacity and rate. You are not counting channels against a seat plan; you are negotiating how much concurrency you can burst to and what each minute costs by destination. If a supplier quotes you a per-channel monthly fee, you are being sold a business product with a wholesale label.
Trunks for diallers
Predictive and power diallers produce a traffic shape that breaks assumptions built for conversational calling: concurrency spikes hard at campaign start, attempt-to-answer ratios are poor by design, and average duration is short.
What that demands is burstable concurrency rather than a fixed ceiling, a supplier who has sized their SBC for your attempt rate, and honesty about the pattern up front. A trunk provisioned for 500 concurrent conversational calls is not the same as one provisioned for 500 concurrent dialler attempts.
Authentication and interconnect
IP authentication is the norm for wholesale: you give us your signalling IPs, we allowlist them, and there is no registration to drop. It is simpler and more robust at volume.
Registration-based trunking exists for dynamic-IP scenarios but adds a failure mode you do not want carrying production traffic. For sustained volume the right answer is usually a direct SIP interconnect with allowlisted IPs at both ends. [HUMAN: confirm SBC IPs, supported ports and whether TLS/SRTP is available.]
Failover
Point at more than one SBC. A single signalling destination is a single point of failure, and it will find you at the worst moment.
Configure a secondary and test the cutover deliberately rather than discovering it during an incident. This is basic, it is cheap, and a surprising number of operators only do it after they have already had the outage.
Frequently asked
Frequently Asked Questions
Business SIP trunking is sold per channel with a monthly fee and often a minute bundle, sized for an office phone system. Wholesale SIP trunking is sold on capacity and per-destination rate, sized for carriers, resellers and dialling operations. If you are being quoted a per-channel monthly fee, that is a business product regardless of what it is called. Wholesale pricing lives in the rate deck, not in a channel count.
Yes, but the trunk has to be provisioned for it. Diallers generate concurrency spikes at campaign start, a high ratio of unanswered attempts and short average durations — a pattern that can trip carrier-side controls and overwhelm an SBC sized for conversational traffic. Tell your supplier your peak concurrency and expected ACD before contracting, and ask specifically whether the route tolerates dialler traffic.
IP authentication is standard for wholesale traffic — you supply your signalling IPs, they are allowlisted, and there is no registration state to expire or drop. Registration-based trunking is available where a dynamic IP makes allowlisting impractical, but it introduces a failure mode that is best avoided on production volume. [HUMAN: confirm which authentication methods are offered.]
This is a commercial and capacity question rather than a fixed product limit, and it depends on your traffic shape as much as the number. Burstable concurrency matters more than a headline ceiling for dialler traffic, since campaign starts spike well above the average. [HUMAN: confirm default concurrency limits and burst policy.]
Configure at least two signalling destinations and test failover deliberately before you need it. A single SIP endpoint is a single point of failure, and the time to discover your failover configuration does not work is not during an outage. [HUMAN: confirm SBC redundancy, geographic distribution and published failover targets.]
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