# Call Drops

**Call Drops** is a fleet-wide anomaly report. It surfaces the NAPs dropping more calls than usual, compared against each NAP's own history.

Open from **TB Nodes > Call Drops**.

<figure><img src="/files/kz3I3EtU0Tr2sggp1dKI" alt=""><figcaption><p>Call Drops — top-N tables per drop type and window</p></figcaption></figure>

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## Layout

The page is a grid of top-N tables — one table per **drop type** × **time window**:

| Drop Type  | What it means                                                            |
| ---------- | ------------------------------------------------------------------------ |
| **Local**  | The NAP dropped the call locally.                                        |
| **Remote** | The remote peer dropped it.                                              |
| **System** | Dropped by the unit itself (resource exhaustion, routing failure, etc.). |

| Time Window | Purpose                                     |
| ----------- | ------------------------------------------- |
| **15m**     | Spot something happening right now.         |
| **1h**      | Catch issues that started in the last hour. |
| **24h**     | Daily rollup.                               |
| **7d**      | Weekly pattern.                             |

Each table lists the top NAPs by drop count over that window, with how unusual the volume is compared to normal.

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## Baseline & Anomaly Detection

Each NAP is compared against its own **12-week time-of-week baseline**. "Monday at 2pm" is compared to previous Mondays at 2pm — so an evening maintenance window doesn't look like an anomaly just because traffic was light.

A **z-score** flags statistically elevated drops:

* High z-score = dropping much more than this NAP normally does at this hour.
* Low or zero z-score = within normal range for the NAP's usual pattern.

### Confidence Flags

* **Limited confidence** — the baseline has too few samples (new NAP, recently added host). The value is shown but trust it less.
* **Insufficient data** — not enough history to compute a z-score at all. The score is omitted.

***

## Drill-Through

Click a NAP name in any table to open its NAP Detail page — all 27 metrics for that NAP on that device, plus a configurable chart to investigate the drop pattern over time.

<figure><img src="/files/WNWbigBGlgPrvSjAYLl1" alt=""><figcaption><p>NAP Detail drill-through view</p></figcaption></figure>


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