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zervan
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slow Connection Tracking since 5.8

Fri Dec 09, 2011 12:46 am

One of my friends had a problem with much lower throughput of his main router RB450G (doing NAT) after upgrade to 5.8. He had to return back to 5.7. I've barely believed him, but today I needed to do some transfers between my computer and my NAS and the speed was much lower than it was few weeks before as well. I have RB750G.

Situation: my PC <-> RB750G <-> NAS, router is doing routing only (no NAT). I've disabled all firewall rules. If I turn off conntrack, speed is about 100 Mbps, that's good (maybe speed limit of my NAS). But if I turn conntrack on, speed is decreased to cca 40 Mbps and CPU usage is very low most of the time during data transfers. That is much better in 5.7 - speed with conntrack is about 80 Mbps, but the CPU usage is higher - I've tested downgrade today. Did somebody experience similar problem since 5.8?
Dusan Zervan from Slovakia
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Re: slow Connection Tracking since 5.8

Fri Dec 09, 2011 4:00 am

I also experienced the same problem, but switching to 5.9 solved it.
 
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zervan
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Re: slow Connection Tracking since 5.8

Fri Dec 09, 2011 9:57 am

I also experienced the same problem, but switching to 5.9 solved it.
I've just asked my friend with RB450G and he said the same: 5.9 solved it. Strange. Now I don't have much time but I will try to reset configuration on my RB750G later and test again.
Dusan Zervan from Slovakia
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zervan
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Re: slow Connection Tracking since 5.8

Sat Dec 10, 2011 11:19 pm

Well, I've upgraded to 5.10 and made more accurate tests NAS -> RB750G -> PC. There is a strange behaviour:
  • no firewall rules, no connection tracking: 90-100 Mbps (speed is varying);
  • some firewall rules, no connection tracking: 120 Mbps (why higher??? :shock: )
  • connection tracking: 70 Mbps
So the speeds with 5.10 were: cca 90-100, 120, 70 and the same with 5.9 and 5.8.
There is a little difference with 5.7: cca 90-100, cca 90-110, cca 70-80.

So we can say that Connection Tracking speed is the same as it was in 5.7, but speed without conntrack with firewall rules is a little higher now. I was very surprised that turning on some firewall rules (without conntrack) brought higher speed. Why? Well, processor of RB750G is fast, but firewall shouldn't do it faster.

I've tested it multiple times (oh, my poor RB750G, I'm still re-writing your flash memory!)

Then I tested the opposite direction: PC -> RB750G -> NAS using 5.10 and 5.7 (same results). There is no difference whether firewall rules are on or not - the speed is cca 160 Mbps without conntrack, but it is much lower (cca 30-60 Mbps) with conntrack turned on. Why so big difference?
Dusan Zervan from Slovakia
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Re: slow Connection Tracking since 5.8

Sun Dec 11, 2011 10:51 pm

different port has different speed )) its mikrotik feature :)
 
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Re: slow Connection Tracking since 5.8

Mon Dec 12, 2011 11:30 am

What kind of traffic are you using - if it is TCP, then take a book about TCP and read it.

in short: to make some reasonable testing for comparison you need ether to forget about TCP or use at least 100 simultaneous TCP connections
With great knowledge comes great responsibility, because of ability to recognize id... incompetent people much faster.
 
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Re: slow Connection Tracking since 5.8

Mon Dec 12, 2011 11:53 am

in short: to make some reasonable testing for comparison you need ether to forget about TCP or use at least 100 simultaneous TCP connections
You are right, I know about it - I don't expect that one connection will use all of capacity. But you can not say that described behavior is good. Mostly I don't care what is the transfer speed using 100 simultaneous connections, because I don't use it (I am talking about "small" routers like RB750G, RB751U, ...), but I and my clients do care about "normal" transfer speed. It is strange if the speed will drop to half after upgrade, isn't it? - It was the reason why I started this thread, now it is (mysteriously) solved. It is strange if turning on any firewall rules (it doesn't matter what kind of) increases speed and if connection tracking reduces speed to 1/4, isn't it? It is strange if other routers have much better speed (see also other thread about low 802.11n performance).
Dusan Zervan from Slovakia
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