tcp bbr v3(一)

目前google 发布了tcp bbrv2+fixbug===tcp bbrv3

目前说是 BBRv3 的数据包重传率降低了 12%，延迟也略有改善

Impact of BBRv3 vs BBRv1 on Google.com and YouTube TCP public Internet traffic:

○ Lower retransmit rate (12% reduction)

○ Slight latency improvement (0.2% reduction) for:

　　■ Google.com web search

　　■ Starting YouTube video playback

○ Latency wins seem to be from lower loss rate (less/faster loss recovery)

• https://github.com/google/bbr/blob/v3/README.md
• https://datatracker.ietf.org/meeting/117/materials/slides-117-ccwg-bbrv3-algorithm-bug-fixes-and-public-internet-deployment-00

New: a version increment for BBR, from v2 to v3

○ Recent bug fixes change the bandwidth/fairness convergence properties of BBR ○ So most test results for BBRv2 will not apply to BBRv3

○ So we are incrementing the version number for BBR from v2 to v3

● A summary of BBR versions:

○ BBRv1: [obsolete/deprecated]

    ■ Bandwidth, RTT as signals primary signals; loss used over short time scales

○ BBRv2: [obsolete/deprecated]

  ■ BBRv1 + using ECN, loss as signals (with bugs mentioned previously at IETF)

○ BBRv3:

  ■ BBRv2 + bug fixes and performance tuning

○ BBR.Swift: [discussed at IETF 109: slide link]

  ■ BBRv3 + using network_RTT (excluding receiver delay) as primary CC signal