Call quality

"The phones were bad this morning" is hard to act on without knowing whether the line was at fault. Tenvara works out how calls would sound over each site's line, minute by minute, and where a connected phone system reports the quality of its calls, sets each poor call against the line at that moment.

The estimated MOS#

MOS (mean opinion score) is the standard 1 to 5 scale for how a call sounds. Around 4.4 is the best a normal call can score; under 3.6 many people are unhappy with it.

Tenvara estimates the MOS for every site with a site probe, with no phone system needed:

• It takes the probe's measurements to the internet anchors: latency, jitter and packet loss. That is the path a call to a hosted phone system or a SIP trunk crosses. The site's own gateway is left out.
• It applies the ITU-T G.107 E-model, the telecoms industry's standard calculation for call quality from network measurements.
• It assumes the codec set for the customer. G.711 with loss concealment is the default, which suits most desk phones and softphones; G.711 without it, G.729A and G.723.1 can be chosen instead.

Where a site has two lines, the line carrying the traffic at that moment is the one that counts. A minute in which half the pings or more are lost is the line being down, so it shows as down and is left out of the averages: that is an outage, not a quality problem.

The estimate is worked out from the measurements each time you look, and the measurements are kept for 400 days. Changing the codec or the poor threshold therefore applies to the past as well.

Note: The estimate describes the line. It says how a call would sound if nothing else were wrong. A poor call on a good line points at the handset, its cable, the Wi-Fi or the far end.

The customer's VoIP block#

Open a customer's Connectivity tab and scroll to VoIP. It brings the customer's telephony together:

• Phone systems: each one with its problems, or No problems. One with no connection says that only what was entered by hand is known.
• Estimated MOS now: the figure for the worst site, with a word for how good it is.
• Calls in the last 7 days, and how many came with quality information.
• Call spend this month, from rated call records. See Call rating.
• Estimated call quality (MOS): a chart per site over 24 hours, 7 days or 30 days, with the poor threshold drawn as a line.
• Last outages: the five most recent, with their cause.
• Call quality: the table of calls, described below.

All phone systems opens Infrastructure > Phone systems, where each system's row has Line MOS now for its site, or Line down.

Poor calls against the line#

When a customer's 3CX, Yeastar or Teams Phone is connected with your own account for it, and that system reports the quality of its calls, they are listed in the Call quality table. What a phone system reports depends on the system, its version and its plan, and the table says so plainly when a connected system reports none.

Each row shows when the call started, the direction, the extension or user, the other party, the talk time, the MOS, jitter and loss, and The line then. The MOS is either as the phone system reported it or estimated from the call's own jitter, loss and round trip; hover to see which.

Use the filters to switch between All calls and Poor calls, and between 24 hours, 7 days and 30 days. Search by number or extension.

Open a call for the detail:

• Why it was poor: a low MOS, or the phone system's own flag such as packet loss.
• The site's line then: the line's MOS, worst MOS, jitter and loss during the call, or that it was down for part of it.
• The site's line around the call: a chart from half an hour before the call to half an hour after, with the call highlighted.
• Each side of the call: the codec, jitter, loss and round trip of each leg.

The verdict is one of four:

This is what turns a vague complaint into a decision: raise a fault with the supplier, or send someone to look at the desk phone.

Reading per-call quality can be switched off for a customer in Settings > Telephony; the VoIP block says so when it is.

Thresholds in Settings > Telephony#

Under Call quality in Settings > Telephony:

• The poor MOS (3.6 by default). It is the line on the charts, what marks a call as poor, and what the poor call quality alert uses.
• The codec assumed for the estimate.
• How many days before a licence or certificate runs out it counts as a warning (30 by default).
• How old the last phone system backup may be before it is a warning (7 days by default).
• How long per-call quality is kept (400 days by default).

Each can be set per customer. The screens and the alerts read the same numbers, so a site that shows as poor on the chart is the same site that alerts. See Telephony alerts.

Related problems on the phone system#

The VoIP block and the Phone systems page list a phone system's problems worst first. Critical: the phone service is down, the connection has an error, a trunk is not registered, or a licence or certificate has run out. Warning: extensions that should stay registered not registered, a licence or certificate running out soon, an old backup, a failed firewall check, or the site's estimated MOS under the poor threshold now. An available update is shown as a note.