What Is Ping, and What Does It Say About Call Quality?

What ping actually is

Ping is the name of a long-standing test tool found on almost every computer, phone and router. The computer sends a short message to a particular server that says, roughly, "are you there?", and the server answers right away. The tool measures how much time passed from sending to the reply coming back.

That time is called RTT (Round Trip Time) and it is measured in milliseconds (ms). A ping of 20 ms means the packet left, reached the server and came back within a fifth of a tenth of a second.

The name comes from the sound of sonar on a submarine: you send out a "ping," wait for the echo, and from the timing you know the distance. In a network it is the same idea — only the distance is measured in time rather than in meters.

What ping measures — and what it doesn't

Ping measures latency: how long it takes a packet to travel the route. It does not measure download or upload speed, or the amount of data the line can carry. A 1,000 Mbps line can have a high ping, and a modest line can have a low, stable ping.

Ping is affected by several things: the physical distance to the server, the number of routers along the way, the quality of the internal network (Wi-Fi or cable), and the load on the line at that moment. When someone in the office uploads a large file, ping jumps — because the small packets have to wait in line behind the big ones.

That is why a single test doesn't tell the whole story. It is important to check ping continuously over time, and to look not only at the average but also at the spikes and at packets that didn't come back at all.

How to check ping on a computer

On a Windows computer, open the "Command Prompt" (type cmd in the Start menu) and type ping followed by a server name or address. By default it sends only four packets, which is too short for diagnosis.

A continuous test uses the -t option, for example ping -t 8.8.8.8. The test runs until you stop it with Ctrl+C, and then a summary appears: how many packets were sent, how many were lost, and the minimum, maximum and average times. It is worth leaving it running for a few minutes, preferably during a busy hour at the office.

On a Mac or Linux computer the test is continuous on its own (ping followed by the address), and you also stop it with Ctrl+C. On mobile phones there are simple apps that do the same thing.

Field tip: test twice — once against the router in the office (its address, usually something like 192.168.1.1) and once against a server on the internet. If there are spikes even against the router, the problem is in the internal network — a cable, a switch or Wi-Fi. If everything is smooth against the router and the problem appears only against the internet, the problem is in the line or at the internet provider.

tracert — seeing the whole route

When ping is high, you ask "where along the way does it get stuck?" For that there is another tool: tracert on Windows (and traceroute on Mac and Linux). It shows a list of all the stops — the routers — that a packet passes on the way to the server, and how long it takes to reach each one.

You read the list from top to bottom. The first stop is your router, followed by your internet provider's stops, and then stops around the world. If the time jumps suddenly at a certain stop and stays high until the end, that is where the bottleneck is.

Two notes: asterisks (*) at a single stop are usually not a fault — some routers simply don't answer such tests. And a single stop with a high time, after which the times return to normal, is also usually not a problem.

What the numbers mean for calls

In telephony we talk about one-way latency — how much time passes from the moment you say a word until the other side hears it. The international standard ITU-T G.114 says that up to about 150 ms in each direction, a call sounds natural. Above that, rhythm problems begin: both sides start talking at the same moment and "step on" each other.

Ping measures there and back, so as a rough approximation one-way latency is half the ping, plus processing time in the phone and the server. A rule of thumb for reading a ping result for a PBX:

Just as important: stability. A constant ping of 80 is far better than a ping that jumps between 20 and 400. These jumps are called jitter, and they are the common reason for a "robotic" voice and swallowed words.

"My ping is 50 — how many phones can I connect?"

This is one of the questions we hear most, and the short answer is surprising: ping does not determine the number of phones. A ping of 50 ms is a very good result, and it means calls will sound natural — but it doesn't say how many calls the line can carry at once.

Think of a road: ping is how long it takes to drive from home to work when the road is empty. The number of lanes is the bandwidth. A short road with one lane gets you there quickly — until there are ten cars on it at once. The number of simultaneous calls is determined by bandwidth, and mainly by the upload speed, which is usually the narrow side of internet plans.

One small correction to the question itself: the right thing to ask is how many simultaneous calls, not how many phones. A phone sitting on a desk and not talking uses almost nothing — just a tiny "I'm here" message every few dozen seconds. An office with 30 phones that handles 8 calls at once at peak needs a line for 8 calls, not 30.

How many simultaneous calls — by upload speed

A call using the common G.711 codec uses about 100 kilobits per second in each direction, including network overhead. Because an office also has computers, email and backups, we calculate a safe margin of 50%: only half the upload is dedicated to calls. The table shows a conservative estimate:

These numbers assume that the line itself is stable and that there are no other heavy consumers on it, such as cameras streaming to the cloud or video calls. The full calculation, including computers, cameras and switches, is in the article How many phones can my network carry.

What raises ping

• Load on the line — a large download or upload (a cloud backup, computer updates, a video) fills the queue in the router, and the call's packets wait.
• Wi-Fi — a wireless network adds latency and spikes, especially when there are many devices or thick walls.
• A weak or old router — a router that can't handle the number of connections starts delaying packets.
• VPN — every packet goes first through another server, sometimes abroad, and that lengthens the route.
• Distance to the server — every thousand kilometers adds a few milliseconds. It is less noticeable than everything else.

Most problems that look like they are "in the line" are actually in the internal network. Before contacting the internet provider, check ping against the router from a computer connected by cable.

Ping that doesn't come back

Sometimes instead of a time you see the message "Request timed out" — the packet went out and did not come back. This is called packet loss, and in a call it sounds like a word that disappears or a moment of silence.

A single lost packet out of hundreds of tests is not worrying. But if more than one percent is lost in a test of a few minutes, calls will be affected. The summary at the end of the continuous test shows the percentage exactly (Lost = 3 (1% loss)).

Note: some servers and routers deliberately block ping tests. If no packet comes back, try another address before concluding that there is a fault.

Example from the field: the audio "cuts out" in the afternoon

At the office of an accountant named Moshe (a made-up name) they complained that calls were excellent in the morning and started cutting out after two in the afternoon. A speed test showed a healthy line, and a single ping showed 25 ms.

Only a continuous ping, left running for a full hour, revealed the picture: every day at two, computer backups to the cloud begin, and the ping jumped to 300–600 ms intermittently. The solution was not a faster line, but moving the backups to the night hours and setting call priority in the router (QoS).

The conclusion: ping should be tested over time and under real conditions. A ten-second test at a quiet moment won't reveal the problem.

How to improve ping

1. Connect important phones and computers by cable, not Wi-Fi.
2. Turn on QoS in the router so that calls go ahead of downloads and backups.
3. Move heavy tasks (backups, updates) to hours when there are no calls.
4. Replace an old or home-grade router in an office with many devices.
5. Check that there is no open VPN routing calls through a distant server.
6. If the problem is in the line itself — contact the internet provider with tracert and continuous ping results in hand.