What CONGESTION means in VICIdial and how to stop it

When VICIdial logs CONGESTION, it is telling you the calls you handed off were not placed by your carrier. The dialer did its job, sent the call toward the network, and the carrier came back unable to complete it. That is a carrier-side capacity or routing problem — or a sign you are pushing more calls than the route can take.

This is where CONGESTION gets confused with a local line shortage. The two look similar on the surface but live on opposite sides of the handoff. Congestion is downstream of your box; the call left and the carrier choked on it.

Where the call gets stuck

Your dialer sends the call out over a Trunk to your Carrier. The carrier then tries to route it onto the public network. If the carrier's own capacity is full, or the destination route is saturated, it returns a congestion signal and the call never completes.

flowchart TD
  A[Dialer places call] --> B[Sent over trunk to carrier]
  B --> C{Carrier has capacity}
  C -->|Yes| D[Call routes to network]
  C -->|No| E[Carrier returns congestion]
  E --> F[Logged as CONGESTION]
  F --> G{You over-dialed}
  G -->|Yes| H[Lower dial ratio]
  G -->|No| I[Carrier or route issue]

Two things drive it. Either your Dial level is set so high that you are firing more simultaneous calls than the carrier's channels can absorb, or the carrier itself has a capacity or routing fault on the destinations you are hitting.

The two have different fingerprints. Over-dialing congestion rises and falls with your own pacing — push harder, more congestion; ease off, it clears. A carrier-side fault ignores your pacing entirely and tends to stick to certain destinations or certain hours. Watching how the count moves when you change your dial ratio is the cleanest way to tell them apart before you pick up the phone to the carrier.

How to confirm and fix it

1. Plot the CONGESTION count against time of day. If it spikes when your dial ratio is highest, you are over-dialing the route.
2. Lower the dial ratio a notch and re-run a slice. If congestion drops in step, the carrier capacity was the ceiling and you found it.
3. If congestion stays flat regardless of how hard you dial, it is on the carrier. Open a ticket with sample call timestamps and the destinations affected.
4. Check whether it concentrates on specific area codes. A regional route problem at the carrier shows up as congestion only on those destinations.
5. Confirm the calls really left the box. If they never reached the carrier, you are looking at a line shortage instead — that is CHANUNAVAILABLE, a different problem entirely.

Confirm which side of the handoff the call died on first. That one check decides whether you tune your own dialing or take it to the carrier.

For how congestion fits with the other carrier-side codes, see the troubleshooting playbook. For the local-capacity twin of this problem, read what CHANUNAVAILABLE means. If you would rather not tune dial ratios against carrier capacity by hand, VICIfast runs the box and the trunk wiring for you → see plans and pricing.