Re: [LARTC] SEPARATING VOIP AND SURFING

[Jason Boxman <jasonb@edseek.com>]

On Tuesday 16 November 2004 09:53, Andy Furniss wrote:
<snip>
> I would do a bit more work to priorotise dns/empty acks/small tcp etc.
> as well as VOIP, then give them a class with plenty of rate spare and
> make bulk borrow. This would mean that each user would notice a bit less
> the fact they have hardly any bandwidth (if that's the case).

Is it really helpful to initially prioritize all TCP handshake packets into 
the highest priority?  After you walk through your list of traffic and 
reclassify flows based on your QoS policy, handshake packets for flows that 
matter ought to be properly accounted for.  Likewise for flows that aren't 
that interesting.  For all other flows only having the handshake prioritized 
and all else going to a default class can't be that beneficial?

> Choosing a queue length should really be related to link speed - but you
> can't do this if you have lots of queues whose rate are variable. What
> to choose depends on typical and I suppose worst case traffic situation
> for your LAN.

I have not noticed in any of the available documentation I have found any 
discussion on how to choose an appropriate queue length.  The shorter the 
queue, the sooner applications become aware of a bandwidth bottleneck?  I 
guess the queue just helps deal with short term busts?  What rate was sfq's 
128p queue originally targeted at?  100Mbps Ethernet?

<snip>
> I think these differences are too small to be representative. One packet
> could add 12kbit to a counter instantaneously and how you measure can
> decieve. For one really low rate class the way HTB uses DRR to even out
> fairness for different sized packets could, I think cause short term
> variations. P2P traffic is mixed packet size and quite variable
> depending on peers - so recreating behavior for tests may be hard. I
> don't think queue length is involved here.

The difference for that leaf with sfq versus pfifo was pretty consistent.  I 
should test with different queue lengths for pfifo.

Thanks.

-- 

Jason Boxman
Perl Programmer / *NIX Systems Administrator
Shimberg Center for Affordable Housing | University of Florida
http://edseek.com/ - Linux and FOSS stuff

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