[Bloat] An interesting, and probably erroneous, article on 5G and TCP buffering

[Dave Collier-Brown]

In "the morning paper", https://blog.acolyer.org/2020/10/05/understanding-operational-5g/, reviewing http://xyzhang.ucsd.edu/papers/DXu_SIGCOMM20_5Gmeasure.pdf

With TCP the story is less compelling, with common congestion control algorithms not suiting 5G characteristics

Traditional loss/delay based TPC algorithms suffer from extremely low bandwidth utilization – only 21.1%, 31.9%, 12.1%, 14.3% for Reno, Cubic, Vegas, and Veno, respectively!

Only being able to use 20% of the bandwidth is clearly not good (on 4G the same algorithms achieve 50-70%). BBR<https://blog.acolyer.org/2017/03/31/bbr-congestion-based-congestion-control/> does much better with 5G, achieving 82.5% utilization. An investigation reveals the problem to be caused by buffer sizes. In the radio portion of the network, 5G buffer sizes are 5x 4G, but within the wired portion of the network only about 2.5x (this is with a 1000 Mbps provisioned cloud server). At the same time the download capacity of 5G is about 5x greater: "i.e., the capacity growth is incommensurate with the buffer size expansion in the wireline network." Doubling the wireline buffer size would alleviate the problem. BBR does better because it is less sensitive to packet loss/delay.

--
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
dave.collier-brown at indexexchange.com<mailto:dave.collier-brown at indexexchange.com> |              -- Mark Twain



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