Re: [Bloat] [tsvwg] how much of a problem is buffer bloat today?

[Jim Gettys <jg@freedesktop.org>]

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Also, Windows XP is still significantly in use in the Internet
(unfortunately).



On Thu, Mar 21, 2013 at 3:25 PM, Mikael Abrahamsson <swmike@swm.pp.se>wrote:

> On Thu, 21 Mar 2013, Oliver Hohlfeld wrote:
>
>  In summary, the question on how much of a problem buffer bloat currently
>> is cannot be fully answered and still requires further research.
>>
>
> Buffer bloat is a problem on basically all access forms apart from ETTH.
> Usually ETTH is produced using L2 or L3 switches with very small buffers (5
> ms or so), and policing is used instead of buffering for limiting service
> rate. This means high speed TCP flows will sawtooth their performance over
> time because of large amount of consecutive drops, meaning low bw
> interactive flows are less impacted.
>
> So it's my belief that your measurements means most people don't actually
> put congestion pressure on their accesses, thus the large buffers are
> seldom used and you're not seeing buffering.



Due to the fact TCP window scaling is off by default in Windows XP, the
most a single TCP connection will have in flight on Windows XP is 64K bytes.

This both limits the ability of a Windows XP system to saturate a link in
the first place (thereby sometimes avoiding filling buffers at the
bottleneck at all), and limits the amount of latency a single TCP
connection will inflict.

Every more modern TCP can easily fill any sized buffer given time with a
single TCP connection.
                                   - Jim

>
>
> --
> Mikael Abrahamsson    email: swmike@swm.pp.se
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