Query about reducing pacing rate by 1%

Mohit P. Tahiliani

unread,

May 28, 2024, 11:40:55 PMMay 28

to BBR Development

Hello!

In the Internet Draft, `BBR.pacing_rate` is reduced by 1% (`BBRPacingMarginPercent`) only on `BBRSetPacingRateWithGain`, not on `BBRInitPacingRate` [1].

However, in the Linux implementation, both the methods `bbr_init_pacing_rate_from_rtt` and `bbr_set_pacing_rate` use a common method `bbr_bw_to_pacing_rate` which internally calls `bbr_rate_bytes_per_sec` and the reduction of pacingRate is actually implemented here [2], due to which the `pacing_rate` is being reduced by 1% on both.

Our understanding is that the Linux implementation is different from what the Internet Draft mentions. Is that correct?

If so, which approach should be followed?

Thanks and Regards,

Mohit P. Tahiliani

[1] https://datatracker.ietf.org/doc/html/draft-cardwell-iccrg-bbr-congestion-control#name-pacing-rate-bbrpacing_rate

[2] https://github.com/torvalds/linux/blob/56fb6f92854f29dcb6c3dc3ba92eeda1b615e88c/net/ipv4/tcp_bbr.c#L251

Michael Davis

unread,

May 30, 2024, 1:09:42 PMMay 30

to BBR Development

AFAIK, you should check the draft v1, since the current linux implementation is v1.

Mohit P. Tahiliani

unread,

May 31, 2024, 1:30:50 PMMay 31

to Michael Davis, BBR Development

Thanks, Michael.

I see that draft v1 and v2 are similar in this aspect [1].

Regards,

Mohit P. Tahiliani

[1] https://datatracker.ietf.org/doc/html/draft-cardwell-iccrg-bbr-congestion-control-01#name-pacing-rate-bbrpacing_rate

--
You received this message because you are subscribed to the Google Groups "BBR Development" group.
To unsubscribe from this group and stop receiving emails from it, send an email to bbr-dev+u...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/bbr-dev/2f0e99a4-7246-4c86-a4d3-a3c0f47ac08cn%40googlegroups.com.

MUHAMMAD AHSAN

unread,

May 31, 2024, 1:33:07 PMMay 31

to Mohit P. Tahiliani, Michael Davis, BBR Development

Sept 2022 is the latest draft and it is based on bbr v2 , there is no draft yet for bbr v3.

In linux mainline we have bbr v1 and in windows 11 we have bbr v2.

I hope this helps.

Regards,
Ahsan

To view this discussion on the web visit https://groups.google.com/d/msgid/bbr-dev/CA%2B4FxsgVf6%3DtVta9cHNo%3DpqzXNKGwu81mG%3DCYJTZcUgoBGGB8w%40mail.gmail.com.

Reply all

Reply to author

Forward