
BBR v2: Model-based Congestion Control Performance Optimizations [slides] - Sami_Lehtinen
https://datatracker.ietf.org/meeting/106/materials/slides-106-iccrg-update-on-bbrv2
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eadan
Dropbox have a good real-world comparison [1] between BBRv1 and BBRv2. They
found the retransmission rate to be 4x lower for v2. It's on their edge
network, so would be interesting to see how v2 performs on connections with a
high bandwidth delay product.

[1] [https://dropbox.tech/infrastructure/evaluating-bbrv2-on-
the-...](https://dropbox.tech/infrastructure/evaluating-bbrv2-on-the-dropbox-
edge-network)

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Item_Boring
For those interested these are the changes to v1:

[https://datatracker.ietf.org/meeting/104/materials/slides-10...](https://datatracker.ietf.org/meeting/104/materials/slides-104-iccrg-
an-update-on-bbr-00)

So v2 now also uses packet loss as a congestion indicator and supports ECN.

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londons_explore
Network congestion really is game theory...

When should I send my packets to maximize my throughput while not unfairly
affecting everyone else's packets?

And the best strategy in such a game with the whole intermediate network hard
to model and with plenty of unknowns, tends to be some kind of adversarial
neural net.

Clearly running that for every packet is impractical, but it could at least be
used to make a set of strategies to choose from.

~~~
wmf
Some work in this area:

[https://web.mit.edu/remy/](https://web.mit.edu/remy/)

[https://www.usenix.org/conference/nsdi18/presentation/dong](https://www.usenix.org/conference/nsdi18/presentation/dong)

[https://dl.acm.org/doi/10.1145/3229543.3229550](https://dl.acm.org/doi/10.1145/3229543.3229550)

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ajrw
It's been a while since I caught up on the BBR work, are there any ways to
tweak the algorithm for cases where you want 'increased fairness' – ie.
deferring to other data streams because the current one is a lower priority?
This would probably mean approximating LEDBAT, which is often used in large
backgrounded file downloads like system updates.

