What HUC statuses (enhanced disconnect logging) tell you about failed calls

When you see statuses like HUC18 or HUC34 in your reports, they look cryptic, but they are some of the most useful failure codes VICIdial produces. An HUC status is the dialer telling you exactly how the carrier disconnected a failed call, with the carrier's own reason baked into the code itself.

How to read an HUC code

HUCXXX is an enhanced disconnect-logging level 3 record for a failed call, where the XXX part is the disconnect code that ended it. The code is not random. For example, HUC18 maps to cause 18, which is the SIP 408 request timeout. So the Status (lead status) is not just saying the call failed, it is carrying the carrier's verdict inside the label.

The point of enhanced disconnect logging is to stop you guessing. A plain failed-call status tells you a call did not work. An HUC status tells you precisely how it did not work, in the carrier's own terms, without you having to dig into raw logs. That is a real time saver when you are trying to decide whether a batch of failures is your problem or your provider's, because the cause code usually settles the argument on its own.

What the number maps to

The digits are standard telephony disconnect causes. A few you will meet often:

• HUC18 is cause 18, the SIP 408 request timeout. The far end never responded in time. This is a Hangup cause you can map straight to a SIP response code.
• Causes in the 19, 21, 34, and 38 range cover busy, rejected, no-circuit, and network-out-of-order conditions, the same family the dialer treats as carrier CONGESTION.
• Whatever the number, an HUC status means the call reached enhanced logging because it failed in a way worth recording in detail.

From status to root cause

flowchart TD
  A[Status starts with HUC] --> B[Read the number after HUC]
  B --> C{Which cause?}
  C -->|18| D[SIP 408 timeout no response]
  C -->|19 21 34 38| E[Busy rejected or congestion family]
  C -->|other| F[Look up the carrier cause]
  D --> G[Check carrier latency and routing]
  E --> H[Check trunk capacity and number quality]
  F --> I[Match against the hangup cause report]

How to use them

• Group your failures by HUC number, not just by the HUC prefix. One dominant cause is a single root problem.
• Tie a spike of one code to the Carrier and Trunk that carried those calls. Most HUC spikes are upstream, not in your config.
• Use the code as evidence with your carrier. A wall of HUC18 means timeouts they can investigate on their side.

One word of caution before you act. A small number of HUC records on a busy day is normal. Calls time out, networks hiccup, and individual numbers misbehave. What you are watching for is concentration. If one HUC code suddenly owns a large share of your failures, or if the HUC count climbs at a steady rate across the day, that is a pattern worth investigating rather than a handful of unrelated bad calls.

Because HUC18 is cause 18, the deeper write-up in what cause 18 means is the natural next stop for that specific code. For the broader first-response checklist, start with the VICIdial troubleshooting playbook.

Logging that pays off

Enhanced disconnect logging only helps if it is turned on and the reports are easy to read. VICIfast runs a managed, hardened VICIdial box, live in under 40 seconds, with detailed disconnect logging configured out of the box. See our plans and pricing.