Google 發表的 TCP BBR 塞車演算法

這是舊文了,但之前沒看到覺得很有趣,也是在公司讀書會提到的 Google 在 2017 年發表 TCP BBR (“Bottleneck Bandwidth and Round-trip propagation time”) 塞車演算法,簡單說就是可以很平均的吃滿頻寬,而且達到更低的 Latency,是個純 sender-side 的演算法,可以直接用在現有的 internet

文中還引述 WordPress CTO 稱讚 TCP BBR

BBR allows the 500,000 WordPress sites on our digital experience platform to load at lightning speed. 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. Network innovations like BBR are just one of the many reasons we partner with GCP.” — Jason Cohen, Founder and CTO, WP Engine


不用說 GCP 本身就有使用 TCP BBR 演算法,這算是對整個 internel 有很大的幫助

In a nutshell, BBR creates an explicit model of the network pipe by sequentially probing the bottleneck bandwidth and RTT. On the arrival of each ACK, BBR derives the current delivery rate of the last round trip, and feeds it through a windowed max-filter to estimate the bottleneck bandwidth. Conversely it uses a windowed min-filter to estimate the round trip propagation delay. The max-filtered bandwidth and min-filtered RTT estimates form BBR’s model of the network pipe.


另外還特別提到 QUIC protocol 要應用在 Chrome 瀏覽器的訊息


Google 正在改變世界 ..

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