Re: [LARTC] patch: HTB update for ADSL users

[Ed Wildgoose <lists@wildgooses.com>]

> I still think that you need to throttle back on down rates - when 
> really full you may find that new/bursty connections mean that you 
> loose control of the queue. Of course having twice as much bandwidth 
> always helps.


Agree that it might be best in practice, but baring the initial surge 
you can now really crank everything up to the limit.  Actually, just 
starting one or two connections (wget), I didn't notice more than a 
slight blip on ping speeds on startup - for single users you could 
probably leave it quite close to the max (as long as you can tolerate 
very brief increases in latency)


> I am only testing uploads - looking at some more pings, it does appear 
> that they are not quite as random as they were - but apart from the 
> odd double dequeue (in a way I think you can expect this with HTB 
> using quanta/DRR rather than per byte), the max is right. I suspect 
> this is nothing to do with ISP/Teleco end. I could actually do 
> slightly better on my latency, but I am running at 100Hz - and I can 
> tell with pings - they slowly rise then snap down by 10ms. This is 
> nothing to do with TC, I normally run 500 but forgot to set it for 
> this kernel.


Aha, I switched off the HTB_HYSTERIS option and now my pings are nailed 
to the floor.  I'm also on a 2.6 kernel which I *think* means 1000Hz 
scheduling by default? 

> My downlink is clear, I am using 1478 MTU (so I don't waste half a 
> cell per packet). Just did another hundred to my first hop -


Hmm, quick question.  I'm using Nildram as ISP, and I can't ping at more 
than 1430 packet sizes and non-fragment bit set.  However, according to 
iptraf on the bridge (behind adsl router), I am receiving 1492 byte 
packets quite regularly...  Since the ADSL router is doing NAT, does 
this likely imply that it is doing packet reassembly before the bridge 
sees each packet?

I just changed the MTU on the router, but I don't see any difference in 
the size of packets.  Shouldn't the router MTU be enough to trigger the 
initial connection to drop to a smaller MTU?  Do I need to apply MTU 
changes to all host machines here..? (My understanding is not)


> Been going for 7 hours now - I started a couple of games and 60 small 
> pps didn't cause any problems.


Perhaps a small perl script to do something like contact your local SMTP 
server, setup the connection to start the body of the message, then feed 
the message in 1 byte pieces (perhaps a random message with crlf every 
100 chars or so).  This should give lots of mostly empty packets.  
Perhaps this can be done with the ping flood option as well...?


>> Basically, HTB in both directions.  RED on the incoming stream (works 
>> nicely).  Outgoing classifies into 10 buckets, and ACK + ping are 
>> definitely going out ok in the top prio bucket, and the rest is going 
>> out in the prio 10 bucket....  But still these high pings...  Hmm
>>
>
> I did find in the worst case I could do better than RED (not much 
> though) and now I do per IP for bulk so Its harder to get the right 
> settings with more than one RED, that may have different bandwidths at 
> any given time. I also reduced the number of classes so each could 
> have a higher rate.


Can you describe a little more about how you are improving on RED? 

I would quite like to tweak the incoming to have 3 buckets.  One for 
ACK's etc, the second for normal incoming and the last for bulk 
incoming.  The idea would be to drop the bulk in preference to the 
normal incoming.  I appreciate this won't work all that well, but it 
would be nice to say that my web browsing takes slight preference over a 
bulk ftp download. Or perhaps that incoming connections to a server 
machine take big preference over downloads to a local client machine 
(think office environment).

I would be interested on your ideas to achieve that.

Thanks Andy.

Ed W


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