Managing Bufferbloat

All Puffed Up

Testing Bufferbloat

Some speed measurement websites only determine the delay when the respective connection is idle and no data transfer is active. To determine bufferbloat accurately, you should start a ping (e.g., to Google). As a result, you will receive a series of ping responses that typically have times in the range of 20-100ms (Listing 1).

Listing 1

Google.com Ping

ping google.com
PING google.com (172,217,16,206): 56 data bytes
64 Bytes from 172.217.16.206: icmp_seq=0 ttl=54 time=26.587 ms
64 Bytes from 172.217.16.206: icmp_seq=1 ttl=54 time=24.823 ms
64 Bytes from 172.217.16.206: icmp_seq=2 ttl=54 time=25.474 ms
64 Bytes from 172.217.16.206: icmp_seq=3 ttl=54 time=24.450 ms
64 Bytes from 172.217.16.206: icmp_seq=4 ttl=54 time=23.802 ms
64 Bytes from 172.217.16.206: icmp_seq=5 ttl=54 time=29.555 ms
64 Bytes from 172.217.16.206: icmp_seq=6 ttl=54 time=34.759 ms

In the next step, select a speed test [2]-[5] for the Internet connection and monitor the ping times while the speed test is running. If the upload or download times increase dramatically, your router is probably suffering from bufferbloat.

Conclusions

Because bufferbloat misleads the TCP congestion avoidance algorithm in terms of effective line size, modern networks are prone to congestion-driven collapse caused by saturated buffers, leading to unexpectedly high packet delays. If a congestion collapse occurs on a large network, only a complete shutdown and careful restart of the entire network will help restore network stability. If such a breakdown occurs, you will need to contact the manufacturers of the linking components as soon as possible. Sometimes the suppliers provide appropriate patches.

Moving around the Internet is like being in a high-speed plane while constantly changing the wings, the engines, and the fuselage. Most of the cockpit instruments have also been removed and replaced by a few new instruments. The Internet has crashed several times over the past 30 years and will crash again. For this reason, you should always install the latest firmware versions and patches on your network components to steer clear of avoidable problems.

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