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Glossary · Voice technology

What is Packet loss?

  • Also called: dropped packets, voice packet loss

Reviewed by Sujan ThapaliyaLast updated

Definition

Packet loss is the share of voice packets that never arrive. Because voice cannot wait for retransmission, lost packets are gone, and each one is a fragment of missing audio — the clipping and dropouts people describe as a call breaking up.
The three STIR/SHAKEN attestation levels, which underpin how packet loss 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, packet loss included.

In practice

How packet loss actually works

Loss under about 1% is generally masked by concealment algorithms that interpolate the gap. Above 2–3% it is clearly audible, and above 5% conversation becomes difficult.

The usual causes are a saturated uplink, wifi interference, and equipment discarding packets under load. Loss is often asymmetric, which is why one party hears a broken call while the other hears it perfectly.

Fixing it is a network exercise: prioritise voice traffic, put fixed positions on ethernet, and check the uplink at the times of day complaints cluster.

Loss is also bursty rather than evenly distributed, which is why averages mislead. A call reported as having 1% loss may have been perfect for nineteen minutes and unusable for one, and the caller remembers the minute. Per-call distribution tells you more than a network-wide average ever will.

Loss is often asymmetric, which is why one side hears a broken call and the other does not.
LossWhat the caller hearsVerdict
Under 1%Nothing — concealment covers itFine
1–3%Occasional clipped wordsNoticeable
3–5%Words missingPeople ask to move to another line
Over 5%Conversation breaks downStop and fix the network

Worked example

Two per cent loss on a 20-minute call is roughly 1,400 lost packets — audible as clipped words throughout, even though every other measurement looks healthy.

Packet loss: common questions

How much packet loss is acceptable on a call?
Under 1% is usually inaudible. Between 1% and 3% is noticeable, and above 3% most people ask to move to another line.
Why can only one side hear the problem?
Because loss is often asymmetric — the path in one direction is congested while the other is clean. Diagnosing from both ends is what makes that visible.
Does more bandwidth fix packet loss?
Rarely on its own. Loss is usually caused by congestion at a specific moment or by wifi, so traffic prioritisation and wired connections fix more calls than raw capacity does.

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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