carriers-sip
Least-cost routing
A way of automatically sending each call out through whichever carrier is cheapest for that destination, lowering your total call costs without manual work.
Least-cost routing, often shortened to LCR, is the practice of sending each call out through whichever Carrier charges the least for that particular destination. Different carriers have different rates for different places — one might be cheap for mobile numbers, another for a certain country — so routing by cost can meaningfully lower your phone bill without anyone choosing a route by hand.
To do this you connect more than one Trunk, usually from different providers. When a call goes out, the system looks at the destination and picks the trunk with the best rate for it. In VICIdial this is set up through your Dialplan and the use of a Dial prefix that steers calls to the right route based on the number being dialed.
A side benefit: redundancy
Running several carriers for cost reasons also gives you Failover. If your cheapest provider has an outage or starts rejecting calls, you can route through the next-cheapest one and keep dialing. So least-cost routing often pays off twice: lower bills day to day, and a backup path when one carrier has a bad day.
LCR is most worthwhile for high-volume floors or campaigns that dial many destinations, where small per-minute differences add up. For a single domestic campaign with one SIP trunk, the savings may not justify the extra setup. Weigh the management overhead against your call volume, and revisit your routing whenever a carrier changes its rates. The cost picture in choosing a SIP carrier is a good companion read here.
Related terms
Carrier
A carrier is the phone company that actually carries your calls onto the public phone network — VICIdial dials, the carrier delivers.
Dialplan
The set of rules in Asterisk that decides what happens to each call, matching the dialed number and sending it to the right place step by step.
Dial prefix
A short string VICIdial adds to the front of every number a campaign dials, used to route the call out a specific carrier or trunk.
Failover
Failover is an automatic switch to a backup route, server, or carrier when the primary one stops responding, so calls keep flowing instead of dropping.
SIP trunk
A virtual phone line over the internet that connects your dialer to a carrier, letting you place and receive many calls at once without physical wires.
Trunk
The connection between your VICIdial server and your phone carrier that actually carries calls in and out of the system.