Sunday, November 19, 2017

network speed: TCP BBR

Google Cloud Platform Blog: TCP BBR congestion control comes to GCP – your Internet just got faster

"BBR powers TCP traffic from google.com and that improved YouTube network throughput by 4 percent on average globally — and by more than 14 percent in some countries.
...
According to Google’s tests, BBR's throughput can reach as much as 2,700x higher than today's best loss-based congestion control; queueing delays can be 25x lower. "


BBR ("Bottleneck Bandwidth and Round-trip propagation time") is a new congestion control algorithm developed at Google. Congestion control algorithms — running inside every computer, phone or tablet connected to a network — that decide how fast to send data.

How does a congestion control algorithm make this decision? The internet has largely used loss-based congestion control since the late 1980s, relying only on indications of lost packets as the signal to slow down. This worked well for many years, because internet switches’ and routers’ small buffers were well-matched to the low bandwidth of internet links. As a result, buffers tended to fill up and drop excess packets right at the moment when senders had really begun sending data too fast.

But loss-based congestion control is problematic in today's diverse networks"


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