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Glossary · Voice technology

What is Dropped call?

  • Also called: call drop, drop call, call disconnected

Reviewed by Sujan ThapaliyaLast updated

Definition

A dropped call is one that ends unexpectedly after connecting, without either party hanging up. On IP telephony the usual causes are network interruption, a session timer expiring, or an intermediate device forgetting the call exists.
The three STIR/SHAKEN attestation levels, which underpin how dropped call behaves in practice: A asserts both that the carrier knows the customer and that the customer may use the calling number, B asserts the customer only, and C asserts neither. A shared number pool can reach B at best, which is why number ownership keeps recurring in these definitions.
Attestation is the backdrop to most caller-ID and deliverability terms, dropped call included.

In practice

How dropped call actually works

The most common cause on business systems is a firewall or router with a short idle timeout, closing the path mid-call when the network sees no traffic it recognises. Calls that drop consistently at a similar duration are almost always this.

Consistent drops at a round interval point to a session timer misconfiguration between two systems that disagree on refresh intervals.

Random drops are more often the access network: wifi handover, congestion, or a mobile device moving between cells.

Drops are also worth separating from calls that never connected. A drop after two minutes of conversation is a network or timer problem; a call that fails at setup is signalling, routing or capacity. Reporting them together produces a figure that trends without ever pointing at a cause.

Worked example

Calls ending at almost exactly fifteen or thirty minutes is a timer or timeout problem, not a coverage one — the clock is the clue.

Dropped call: common questions

Why do my VoIP calls drop after a set time?
A session timer or firewall idle timeout. If drops cluster near the same duration, something is expiring on a clock rather than failing on the network.
Is a dropped call the same as an abandoned call?
No. A dropped call ends unexpectedly after connecting. An abandoned call, in outbound dialing, is one the dialer deliberately disconnects because no agent was free.
How do I diagnose random drops?
Check whether they correlate with wifi, with a specific site, or with a duration. Duration points to timers, location points to the access network, and neither points to the phone system itself.

Sources

  1. Combating Spoofed Robocalls with Caller ID Authentication — Federal Communications CommissionThe STIR/SHAKEN framework, the attestation levels carriers sign calls with, and the mandate requiring providers to authenticate caller ID.
  2. 47 U.S.C. § 227 — Restrictions on the use of telephone equipment — Cornell Legal Information InstituteThe Telephone Consumer Protection Act itself — the consent requirements, calling-hours limits, and private right of action.
  3. ITU-T Recommendation E.164 — The international public telecommunication numbering plan — International Telecommunication UnionThe international number format, the 15-digit maximum, and how country codes and national numbers compose.

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