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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