Latency vs bandwidth

Latency targets by activity

Note the difference between one-way and round-trip figures. A speed test's ping is a round trip. ITU-T G.114 talks about one-way delay, so on a typical path, where both directions take about the same time, a 150 ms one-way limit is roughly a 300 ms round trip. Calls are more forgiving than games; the harder limits are for gaming.

Why more Mbps doesn’t lower your ping

Bandwidth decides how quickly a large amount of data arrives. Latency decides how quickly anything arrives at all. Game updates and call audio are small packets, so the time spent pushing each one onto the line is tiny whatever the plan:

transmit time = packet bits ÷ line rate
1,500-byte packet at 100 Mbps  = 12,000 ÷ 100,000,000   = 0.12 ms
1,500-byte packet at 1000 Mbps = 12,000 ÷ 1,000,000,000 = 0.012 ms

Upgrading from 100 Mbps to gigabit saves about a tenth of a millisecond per packet. A game with 40 ms ping still has close to 40 ms of ping. The rest of the delay comes from elsewhere:

• Distance. Signals take time to travel, so a server in another region adds delay no plan can remove.
• Routing. The path your provider takes to the game or call server can be longer than the straight-line distance.
• Connection type. Different access technologies add different amounts of delay before traffic even leaves your area.
• Your home network. Wi-Fi and a busy router add delay and variation.
• Queues. When the line is full, packets wait. This is bufferbloat, below.

That is why a 50 Mbps connection with 15 ms ping can feel better in a shooter than a gigabit connection with 120 ms. To measure what your line actually carries, the network throughput calculator turns any transfer into Mbps.

Jitter: when ping won’t stay still

Jitter is how much latency varies from one packet to the next. A steady 60 ms is often easier to live with than a ping that swings between 20 and 150. Call apps hold audio in a small jitter buffer to smooth it out, which adds delay; when variation exceeds the buffer you hear robotic or clipped speech. In games, jitter shows up as rubber-banding and hits that don't register. Wi-Fi interference and a saturated line are the usual causes.

Bufferbloat: why ping spikes during uploads

Routers and modems queue packets when more data arrives than the line can send. If those queues are large, a busy link can add a lot of delay: someone starts a cloud backup, the upload fills, and everyone's ping jumps while it runs. Upload is the usual culprit because it is the smaller of the two directions on most plans.

To check for it, compare ping when the line is idle with ping during a speed test. Many speed tests now show latency under load as well as idle latency. If the loaded figure is far higher, try:

• turning on smart queue management (SQM) or a similar quality-of-service feature, if your router has one;
• capping the upload rate of backup and sync apps, or scheduling them overnight;
• checking the upload side of your plan against what the household sends at once, for example with the internet speed calculator.

Wired vs Wi-Fi

Wi-Fi shares the air between every device and neighboring network, retries lost frames, and slows down with distance and walls. All of that adds latency and, more noticeably, jitter. An Ethernet cable avoids it. For a gaming PC or console, or a desk used for calls all day, a cable is the most reliable fix. If a cable is impossible, keep the device close to the router or access point and on the 5 GHz or 6 GHz band where available.

How to test your latency

1. Run a speed test such as Fast.com or Speedtest on a wired device, then again on Wi-Fi in the room where you play or work.
2. Note idle ping and ping under load if the test shows it.
3. For cloud gaming, use the service's own network test, which measures the path to its data center.
4. Enter the numbers in the speed test checker, which flags ping above 100 ms.