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Reading a speed test properly: Bandwidth, latency, jitter and packet loss

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tagsglossar, netzwerk, messen

2 min read

Reading a speed test properly: Bandwidth, latency, jitter and packet loss

In short: A speed test measures download, upload and response time; for good internet latency, jitter and packet loss matter too, especially for games and video calls.

In more detail: Many look only at the big number in Mbit/s. The experience depends on four quantities that can be measured with simple tools.

In Depth

The four indicators

  • Bandwidth (download/upload): how much data is transferred per second (Mbit/s). Important for streaming, downloads, large uploads. Example: HD video needs about 5 Mbit/s, 4K about 25 Mbit/s.
  • Latency (ping): round trip of a packet in milliseconds. Important for games, video calls, interactive applications. Under 30 ms good, over 100 ms noticeable.
  • Jitter: variation of latency. High jitter makes speech and video stutter.
  • Packet loss: share of lost packets. Even 1 to 2 % clearly disturb calls and games.

Measuring correctly

  • Measure with a cable (LAN) to exclude Wi-Fi; then compare via Wi-Fi.
  • Pause other devices and downloads.
  • Several measurements at different times (evenings are often slower).
  • Services: speedtest.net, fast.com, measurements by the Federal Network Agency (broadband measurement, important for complaints). In the terminal: ping 1.1.1.1, iperf3 in the home network (shows the link between two devices), mtr for loss per segment.
  • The test shows the route to the test server, not to every site.

Why it is slower than booked

Contracts state “up to” values. Causes: Wi-Fi (distance, walls, interference), overloaded lines at peak times, old devices or cables, weak router, many simultaneous users, VPN, services with their own throttling. With permanent significant shortfall of the contractual performance you have rights (measurement report, price reduction/special termination).

Improving

Place the router centrally, 5 GHz/6 GHz band, change channel, cable (Cat 5e/6) instead of Wi-Fi for fixed devices, mesh/powerline for large houses, update router firmware, limit background downloads (QoS), test DNS. In games latency often matters more than bandwidth.

See also: Ping, Latency, Bandwidth, QoS

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