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The CHOKe packet scheduler

The CHOKe packet scheduler

Posted Jan 14, 2011 6:59 UTC (Fri) by marcH (subscriber, #57642)
In reply to: The CHOKe packet scheduler by paulj
Parent article: The CHOKe packet scheduler

> The crux of the problem is that it is not entirely clera what the correct smallest size is. Indeed that optimal size may vary for different deployments. If you make the buffers too small, your router will under-perform - especially in benchmarks in high-bandwidth settings. Making them too large OTOH is unlikely to cost you sales: few people benchmark performance in real-world scenarios, with congestion - except network congestion researchers.

Agreed that the exact *optimal* size is not clear. However this is not an excuse for unreasonable sizes that harm latency with NO throughput benefit.

This research topic is *not* new! This 2004 paper demontrates that just 1ms (!) is enough: http://portal.acm.org/citation.cfm?id=1015499


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The CHOKe packet scheduler

Posted Feb 27, 2011 6:10 UTC (Sun) by gmaxwell (guest, #30048) [Link]

It's absolutely _trivial_ to demonstrate that 1ms is not unconditionally enough.

Take a long pipe with a several ms of delay. Run a single TCP flow across it. Observe that your flow gets nowhere near line rate, but instead it sawtooths against line rate and leaves the link idle for a significant amount of time.

Yes, a single flow is a corner caseĀ— but not not an outrageous one. The behavior also holds true for a small number of flows, especially if they experience identical end to end delays.

So there is the excuse you were missing.


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