Re: HTB at 100+ Mbits/sec

Linux Advanced Routing and Traffic Control

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On Fri, 12 May 2006, Muthukumar S wrote:

<cut>
Also I was wondering what limits (if any) the kernel timer resolution
imposes on HTB.
<cut>

The kernel timer resolution does have an impact on the precision of HTB (the delay jitter).

I have done some detailed studies in my master thesis. Which is located at: http://www.adsl-optimizer.dk/thesis/.

You should look at chapter 7.
 Read section 7.3.2 "Timer Granularity" (page 71)
 and section 7.3.3 "Improving Granularity" (page 73)

Figure 7.8 (page 75), shows how the delay jitter bound is improved when changing the timer from HZ=100 to HZ=1500.


For the discusion about, why the you need to reduce the bandwidth to less that the actual bandwidth, you should look at Chapter 6 "Achieving Queue Control". Especially if you have an ADSL link.

Greeting,
  Jesper Brouer

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MSc. Master of Computer Science
Dept. of Computer Science, University of Copenhagen
Author of http://www.adsl-optimizer.dk
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