[Bloat] [bbr-dev] Re: Are we heading towards a BBR-dominant Internet?

Mon Aug 29 18:16:50 EDT 2022

Sure thing. Defining some multivariate signals using "non-bulk flow" or
"realistic" traffic scenarios that could be automated (and a proxy for
user QoE) would be very useful for L2 driver, MAC/PHY, and AP scheduling
engineers allowing them to provide the best quality packet forwarding plane
products possible for the transport layers and those engineering teams.

Bob

On Mon, Aug 29, 2022, 1:07 PM Neal Cardwell <ncardwell at google.com> wrote:

> Thanks for the pointers,  Bob.
>
> best regards,
> neal
>
>
> On Mon, Aug 29, 2022 at 12:47 PM 'Bob McMahon' via BBR Development <
> bbr-dev at googlegroups.com> wrote:
>
>> Thanks Neal. You might want to check out the flows released as iperf 2.
>> <https://sourceforge.net/p/iperf2/code/ci/master/tree/flows/> Basically
>> instantiate flows and run them. There typically is a controller running
>> python3 (v 3.10 or better) that uses ssh pipes to DUTs. The design is event
>> driven <https://en.wikipedia.org/wiki/Event-driven_programming> and
>> utilizes python's asyncio
>> <https://docs.python.org/3/library/asyncio.html> which is quite
>> powerful. The DUTs just need iperf2 and ssh.
>>
>> The code is at an alpha level and we're looking for broader industry
>> support and contributions. Both in realtime plotting but also in things
>> like multivariate regression detection using statistical process controls
>> (SPC) e.g. Hoteling
>> <https://www.itl.nist.gov/div898/handbook/pmc/section3/pmc341.htm>.
>> There is some crude clustering code around latency too which uses
>> Kolmogorov-Smirnov
>> <https://en.wikipedia.org/wiki/Kolmogorov%E2%80%93Smirnov_test>distance
>> matrices per the histograms.
>>
>> A suggestion is that those in developer and control test roles
>> synchronize their device clocks with PTP. Iperf 2 supports one way delay
>> (OWD) calculations but these only work if the clocks are sync'd.  These in
>> turn can be used per Little's law
>> <https://en.wikipedia.org/wiki/Little%27s_law> to calculate effective
>> average queue depth, though this typically assumes a steady state
>> measurement.
>>
>> Bob
>>
>> On Sun, Aug 28, 2022 at 4:54 PM Neal Cardwell <ncardwell at google.com>
>> wrote:
>>
>>> If you are talking about the screenshot of the UI at
>>> https://github.com/google/transperf, yes, that particular test is a
>>> simple bulk flow test to show a simple case to give a sense of what the UI
>>> looks like. :-)
>>>
>>> We use a few different approaches that can examine dynamic flows causing
>>> packet loss:
>>>
>>> (1) The test configuration language is Python, so you can construct
>>> arbitrarily fancy dynamic flow scenarios with arbitrary numbers of flows
>>> starting and stopping at arbitrary times.
>>>
>>> (2) The tests can also use netperf command line options to run periodic
>>> short transfers. (And we welcome patches to integrate support for other
>>> tools.)
>>>
>>> (3) We also run a fair number of tests for robustness to loss just using
>>> randomly injected packet loss (using netem).
>>>
>>> These are just some of the approaches we have used, and I don't claim
>>> that these are the only or best approaches to look at this. :-)
>>>
>>> cheers,
>>> neal
>>>
>>>
>>> On Sun, Aug 28, 2022 at 6:39 PM Bob McMahon <bob.mcmahon at broadcom.com>
>>> wrote:
>>>
>>>> Hi Neal,
>>>>
>>>> These look like steady-state bulk flow tests unless I'm missing
>>>> something.
>>>>
>>>> Bob
>>>>
>>>> On Sun, Aug 28, 2022 at 11:43 AM Neal Cardwell <ncardwell at google.com>
>>>> wrote:
>>>>
>>>>> Sure. For testing these kinds of properties of the BBR algorithm we
>>>>> use various transperf test cases. The transperf tool is something Soheil
>>>>> Hassas Yeganeh and our team cooked up and open-sourced here:
>>>>>
>>>>>   https://github.com/google/transperf
>>>>>
>>>>> Best regards,
>>>>> neal
>>>>>
>>>>> On Sat, Aug 27, 2022, 4:43 PM Bob McMahon <bob.mcmahon at broadcom.com>
>>>>> wrote:
>>>>>
>>>>>> Curious to what you're doing during development, if you can share?
>>>>>>
>>>>>> Thanks,
>>>>>> Bob
>>>>>>
>>>>>> On Sat, Aug 27, 2022 at 7:44 AM Neal Cardwell <ncardwell at google.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Hi Bob,
>>>>>>>
>>>>>>> Good question. I can imagine a number of different techniques to
>>>>>>> generate and measure the traffic flows for this kind of study, and don't
>>>>>>> have any particular suggestions.
>>>>>>>
>>>>>>> neal
>>>>>>>
>>>>>>>
>>>>>>> On Fri, Aug 26, 2022 at 4:54 PM Bob McMahon <
>>>>>>> bob.mcmahon at broadcom.com> wrote:
>>>>>>>
>>>>>>>> Hi Neal,
>>>>>>>>
>>>>>>>> Any thoughts on tooling to generate and measure the traffic flows
>>>>>>>> BBR is designed to optimize? I've been adding some low duty cycle support
>>>>>>>> in iperf 2 <https://sourceforge.net/projects/iperf2/> with things
>>>>>>>> like --bounceback and --burst-period and --burst-period
>>>>>>>> <https://iperf2.sourceforge.io/iperf-manpage.html>. We could pull
>>>>>>>> the size and period from a known distribution or distributions though not
>>>>>>>> sure what to pick.
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> Bob
>>>>>>>>
>>>>>>>> Bob
>>>>>>>>
>>>>>>>> On Fri, Aug 26, 2022 at 6:36 AM 'Neal Cardwell' via BBR Development
>>>>>>>> <bbr-dev at googlegroups.com> wrote:
>>>>>>>>
>>>>>>>>> Yes, I agree the assumptions are key here. One key aspect of this
>>>>>>>>> paper is that it focuses on the steady-state behavior of bulk flows.
>>>>>>>>>
>>>>>>>>> Once you allow for short flows (like web pages, RPCs, etc) to
>>>>>>>>> dynamically enter and leave a bottleneck, the considerations become
>>>>>>>>> different. As is well-known, Reno/CUBIC will starve themselves if new flows
>>>>>>>>> enter and cause loss too frequently. For CUBIC, for a somewhat typical 30ms
>>>>>>>>> broadband path with a flow fair share of 25 Mbit/sec, if new flows enter
>>>>>>>>> and cause loss more frequently than roughly every 2 seconds then CUBIC will
>>>>>>>>> not be able to utilize its fair share. For a high-speed WAN path, with
>>>>>>>>> 100ms RTT and fair share of 10 Gbit/sec,  if new flows enter and cause loss
>>>>>>>>> more frequently than roughly every 40 seconds then CUBIC will not be able
>>>>>>>>> to utilize its fair share. Basically, loss-based CC can starve itself in
>>>>>>>>> some very typical kinds of dynamic scenarios that happen in the real world.
>>>>>>>>>
>>>>>>>>> BBR is not trying to maintain a higher throughput than CUBIC in
>>>>>>>>> these kinds of scenarios with steady-state bulk flows. BBR is trying to be
>>>>>>>>> robust to the kinds of random packet loss that happen in the real world
>>>>>>>>> when there are flows dynamically entering/leaving a bottleneck.
>>>>>>>>>
>>>>>>>>> cheers,
>>>>>>>>> neal
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Thu, Aug 25, 2022 at 8:01 PM Dave Taht via Bloat <
>>>>>>>>> bloat at lists.bufferbloat.net> wrote:
>>>>>>>>>
>>>>>>>>>> I rather enjoyed this one. I can't help but wonder what would
>>>>>>>>>> happen
>>>>>>>>>> if we plugged some different assumptions into their model.
>>>>>>>>>>
>>>>>>>>>> https://www.comp.nus.edu.sg/~bleong/publications/imc2022-nash.pdf
>>>>>>>>>>
>>>>>>>>>> --
>>>>>>>>>> FQ World Domination pending:
>>>>>>>>>> https://blog.cerowrt.org/post/state_of_fq_codel/
>>>>>>>>>> Dave Täht CEO, TekLibre, LLC
>>>>>>>>>> _______________________________________________
>>>>>>>>>> Bloat mailing list
>>>>>>>>>> Bloat at lists.bufferbloat.net
>>>>>>>>>> https://lists.bufferbloat.net/listinfo/bloat
>>>>>>>>>>
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>>>>>>>>> .
>>>>>>>>>
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