BBR Development

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BBR Congestion Control Development

BBR is a new congestion control algorithm developed at Google.

There is a blog post on the launch of BBR for Google.com, YouTube, and Google Cloud Platform
There is a paper describing BBR in the February 2017 issue of CACM (the same content is in the ACM Queue BBR article from Oct 2016).
There are Internet Drafts specifying the BBR algorithm and the delivery rate estimation algorithm used by BBRv1.
BBR code from the BBR team at Google:
- BBRv1:
  - BBRv1 for Linux TCP (added in Linux v4.9: main commit)
  - BBRv1 for QUIC: .cc | .h
- BBRv2 (alpha):
  - BBRv2 alpha for Linux TCP
  - BBRv2 alpha for QUIC: .cc | .h
Quick start: a guide for getting started with the Linux TCP BBR implementation
BBR FAQ: frequently asked questions related to BBR and its implementations
[YouTube] [slides] for a BBR talk at the Linux netdev 1.2 conference (Oct 2016)
[YouTube] [slides] for a BBR talk in the ICCRG session at IETF 97 (Nov 2016)
[YouTube] [slides] for a talk covering policers and BBR's handling of policers, in the MAPRG session at IETF 97 (Nov 2016)
[YouTube] [slides] BBR talk at the ICCRG session at IETF 98 (Mar 2017)
[YouTube] [slides] BBR talk at the ICCRG session at IETF 99 (Jul 2017)
[YouTube] [slides] BBR talk at the ICCRG session at IETF 100 (Nov 2017)
[YouTube] [slides] BBR talk at the ICCRG session at IETF 101 (Mar 2018)
[YouTube] [slides] BBR Congestion Control Work at Google: IETF 102 Update (Jul 2018)
[YouTube] [slides] BBR Congestion Control: IETF 102 Update: BBR Startup (Jul 2018)
[YouTube] [slides] BBR v2: A Model-based Congestion Control - ICCRG at IETF 104 (Mar 2019)
[YouTube] [slides] BBR v2: A Model-based Congestion Control: IETF 105 Update - ICCRG (Jul 2019)
[YouTube] [slides] BBR v2: A Model-based Congestion Control: Performance Optimizations - IETF 106 - ICCRG (Nov 2019)
[YouTube] BBR: A Model-based Congestion Control - High-Speed Networking Workshop (May 2020)
[YouTube] [slides] BBR Update: 1: BBR.Swift; 2: Scalable Loss Handling - IETF 109 - ICCRG (Nov 2020)
[YouTube] [slides] BBR Internal Deployment, Code, Draft Plans - IETF 110 - ICCRG (Mar 2021)

0 selected

mingkun bian, ians...@google.com2

Jan 13

why does not quic bbr use undo mechanism

Undo logic is relatively complex, and with BBR relying on bandwidth more than loss, I'd expect

unread,

why does not quic bbr use undo mechanism

Undo logic is relatively complex, and with BBR relying on bandwidth more than loss, I'd expect

Jan 13

Jan 5

BBRv2 - output bbr2 variables using ss

Hello dear BBR community ! First of all, happy new year ! Secondly, I was wondering how one can,

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BBRv2 - output bbr2 variables using ss

Hello dear BBR community ! First of all, happy new year ! Secondly, I was wondering how one can,

Jan 5

李锤子, ians...@google.com2

12/28/21

Question about bytes_in_flight & prior_bytes_inlight in OnPacketSent & OnCongestionEvent

bytes_in_fight in OnPacketSent() is bytes_in_flight prior to the packet being sent. If you look at

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Question about bytes_in_flight & prior_bytes_inlight in OnPacketSent & OnCongestionEvent

bytes_in_fight in OnPacketSent() is bytes_in_flight prior to the packet being sent. If you look at

12/28/21

12/17/21

flash tcp paper

There's a lot to like about this paper, https://www.sci-hub.se/10.1109/ACCESS.2021.3077612 Not

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flash tcp paper

There's a lot to like about this paper, https://www.sci-hub.se/10.1109/ACCESS.2021.3077612 Not

12/17/21

Dhvit Mehta, … Neal Cardwell3

12/11/21

Specify the BBR Congestion Control Algorithm for each connection

You can use a BPF program to do that sort of thing. Here's an example BPF program to set the

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Specify the BBR Congestion Control Algorithm for each connection

You can use a BPF program to do that sort of thing. Here's an example BPF program to set the

12/11/21

Holger Hoffstätte, Neal Cardwell2

12/11/21

Re: [bbr-dev] How to specify the BBR Congestion Control Algorithm for each port

You can use a BPF program to do that sort of thing. Here's an example BPF program to set the

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Re: [bbr-dev] How to specify the BBR Congestion Control Algorithm for each port

You can use a BPF program to do that sort of thing. Here's an example BPF program to set the

12/11/21

Adrian Z, Neal Cardwell3

11/18/21

Comments on new BBRv2 draft (draft-cardwell-iccrg-bbr-congestion-control-01)

Hi Neal, >Thanks for the careful reading and excellent comments/questions! I will add your name to

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Comments on new BBRv2 draft (draft-cardwell-iccrg-bbr-congestion-control-01)

Hi Neal, >Thanks for the careful reading and excellent comments/questions! I will add your name to

11/18/21

11/8/21

Fwd: New Version Notification for draft-cheng-iccrg-delivery-rate-estimation-01.txt

Posting this for discussion at today's ICCRG session and beyond. Feedback welcome! Thanks! neal -

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Fwd: New Version Notification for draft-cheng-iccrg-delivery-rate-estimation-01.txt

Posting this for discussion at today's ICCRG session and beyond. Feedback welcome! Thanks! neal -

11/8/21

11/8/21

Fwd: New Version Notification for draft-cardwell-iccrg-bbr-congestion-control-01.txt

Posting this for discussion at today's ICCRG session and beyond. Feedback welcome! Thanks! neal -

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Fwd: New Version Notification for draft-cardwell-iccrg-bbr-congestion-control-01.txt

Posting this for discussion at today's ICCRG session and beyond. Feedback welcome! Thanks! neal -

11/8/21

Adrian Z, Neal Cardwell2

10/22/21

Some questions about BBRv2's behavior

On Fri, Oct 22, 2021 at 4:53 AM Adrian Z <adrianzap24@gmail.com> wrote: Hi Neal, I've been

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Some questions about BBRv2's behavior

On Fri, Oct 22, 2021 at 4:53 AM Adrian Z <adrianzap24@gmail.com> wrote: Hi Neal, I've been

10/22/21

Brian Tierney, Neal Cardwell4

10/7/21

bbr2 on 100G LANs

Hi Brian, Thanks for pinging us about this. You have not missed any patches. :-) This is still on our

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bbr2 on 100G LANs

Hi Brian, Thanks for pinging us about this. You have not missed any patches. :-) This is still on our

10/7/21

Mahdi, Neal Cardwell2

9/29/21

BBRv2 parameters

On Tue, Sep 28, 2021 at 10:46 PM 'Mahdi' via BBR Development <bbr-dev@googlegroups.com>

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BBRv2 parameters

On Tue, Sep 28, 2021 at 10:46 PM 'Mahdi' via BBR Development <bbr-dev@googlegroups.com>

9/29/21

赵亚, Neal Cardwell3

9/27/21

Why BBR in probebw state use min_rtt round instead of packet-timed round

For what it's worth, the motivation for using wall clock time rather than packet-timed round

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Why BBR in probebw state use min_rtt round instead of packet-timed round

For what it's worth, the motivation for using wall clock time rather than packet-timed round

9/27/21

9/22/21

added to BBR FAQ: where does the value of the BBR Drain pacing_gain come from?

Hi, We have just posted to the BBR FAQ an analytic derivation explaining the pacing gain used in

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added to BBR FAQ: where does the value of the BBR Drain pacing_gain come from?

Hi, We have just posted to the BBR FAQ an analytic derivation explaining the pacing gain used in

9/22/21

Anton Maier, … MUHAMMAD AHSAN3

9/21/21

TSQ part in this paper has many flaws , not accurate. Regards, Muhammad Ahsan Assistant Professor

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TSQ part in this paper has many flaws , not accurate. Regards, Muhammad Ahsan Assistant Professor

9/21/21

Anton Maier, Neal Cardwell2

9/12/21

Enduserquestions.

On Sun, Sep 12, 2021 at 6:58 AM Anton Maier <anton.maier@gmail.com> wrote: Some information is

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Enduserquestions.

On Sun, Sep 12, 2021 at 6:58 AM Anton Maier <anton.maier@gmail.com> wrote: Some information is

9/12/21

Mahdi, … rwj...@gmail.com5

9/11/21

BBR friendliness with other CCAs

Let's assume that a new CCA called X has been developed and it is better than all the current

unread,

BBR friendliness with other CCAs

Let's assume that a new CCA called X has been developed and it is better than all the current

9/11/21

MUHAMMAD AHSAN, Neal Cardwell2

8/26/21

Simulation script ( startup.c ) compilation help needed.

Hi, The startup.c program builds in our environment, so I believe we will need more information in

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Simulation script ( startup.c ) compilation help needed.

Hi, The startup.c program builds in our environment, so I believe we will need more information in

8/26/21

marywan...@gmail.com, … MUHAMMAD AHSAN17

8/26/21

Why did the gain in the STARTUP phase be 2/ln(2)?

kindly read this. https://github.com/google/bbr/blob/master/Documentation/startup/gain/analysis/

unread,

Why did the gain in the STARTUP phase be 2/ln(2)?

kindly read this. https://github.com/google/bbr/blob/master/Documentation/startup/gain/analysis/

8/26/21

Eric xu, … Neal Cardwell4

8/23/21

about the meaning of cwnd_gain in bbr

On Mon, Aug 23, 2021 at 10:02 AM MUHAMMAD AHSAN <muhammadahsan@umt.edu.pk> wrote: this is

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about the meaning of cwnd_gain in bbr

On Mon, Aug 23, 2021 at 10:02 AM MUHAMMAD AHSAN <muhammadahsan@umt.edu.pk> wrote: this is

8/23/21

Neal Cardwell, MUHAMMAD AHSAN5

8/23/21

BBRv2 v2alpha branch rebased from 5.10 to 5.13.12

Also, please note that many systems, including Ubuntu, in my experience, are configured to not let

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BBRv2 v2alpha branch rebased from 5.10 to 5.13.12

Also, please note that many systems, including Ubuntu, in my experience, are configured to not let

8/23/21

MUHAMMAD AHSAN, Neal Cardwell3

8/21/21

error while running ./gce-install.sh -m ${HOST}

Hi, Thanks for the details! I was able to reproduce the build problem you described on Ubuntu 21.04.

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error while running ./gce-install.sh -m ${HOST}

Hi, Thanks for the details! I was able to reproduce the build problem you described on Ubuntu 21.04.

8/21/21

MUHAMMAD AHSAN, Neal Cardwell2

8/21/21

BBR v1 flows and cubic flows.

Hi, Please note that with TCP and most other standard transport protocols (QUIC, etc.) the congestion

unread,

BBR v1 flows and cubic flows.

Hi, Please note that with TCP and most other standard transport protocols (QUIC, etc.) the congestion

8/21/21

8/21/21

BBR and "Toward Formally Verifying Congestion Control Behavior" (SIGCOMM 2021 paper)

Hi, I was interested to read your SIGCOMM 2021 paper, "Toward Formally Verifying Congestion

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BBR and "Toward Formally Verifying Congestion Control Behavior" (SIGCOMM 2021 paper)

Hi, I was interested to read your SIGCOMM 2021 paper, "Toward Formally Verifying Congestion

8/21/21

MUHAMMAD AHSAN, Neal Cardwell2

8/20/21

changing pacing gain in TCP BBR

Yes, it's possible to run experiments modifying the pacing gain. For BBRv1 you can modify

unread,

changing pacing gain in TCP BBR

Yes, it's possible to run experiments modifying the pacing gain. For BBRv1 you can modify

8/20/21

Tergel Munkhbat, … Bob McMahon4

8/12/21

BBRv2 throughput behavior in the real-world environment

forgot to mention, use the -Z option to set the TCP congestion control algorithm [rjmcmahon@ryzen3950

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BBRv2 throughput behavior in the real-world environment

forgot to mention, use the -Z option to set the TCP congestion control algorithm [rjmcmahon@ryzen3950

8/12/21

7/28/21

Talk about the new CCA: Elastic-TCP

Hi, I'm not sure it is suitable to discuss another CCA here. The paper: https://ieeexplore.ieee.

unread,

Talk about the new CCA: Elastic-TCP

Hi, I'm not sure it is suitable to discuss another CCA here. The paper: https://ieeexplore.ieee.

7/28/21

7/19/21

Fwd: [tsvwg] BBR based CCID5 for (MP-)DCCP - ANRW paper

---------- Forwarded message --------- From: <Markus.Amend@telekom.de> Date: Mon, Jul 19, 2021

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Fwd: [tsvwg] BBR based CCID5 for (MP-)DCCP - ANRW paper

---------- Forwarded message --------- From: <Markus.Amend@telekom.de> Date: Mon, Jul 19, 2021

7/19/21

Eric xu, … Fernando Xavier10

7/15/21

BBR performance and optimization in cellular wireless network with high delay jitter

Hi guys If anyone is interested, I've contacted the author to get ABC code, and got this: Hi

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BBR performance and optimization in cellular wireless network with high delay jitter

Hi guys If anyone is interested, I've contacted the author to get ABC code, and got this: Hi

7/15/21

Fejes Ferenc, … Neal Cardwell11

7/7/21

Question about BBR2 ECN mode

Hi! Neal Cardwell <ncardwell@google.com> ezt írta (időpont: 2021. júl. 7., Sze, 16:56): >

unread,

Question about BBR2 ECN mode

Hi! Neal Cardwell <ncardwell@google.com> ezt írta (időpont: 2021. júl. 7., Sze, 16:56): >

7/7/21

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