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AP cpu vs clients vs bandwidth

Posted: Thu Sep 06, 2012 2:36 am
by tgwtoronto
Hi

Might not be the right subject line but here is my question. We have a fairly large MK install in a small down right now. We have 3 250ft towers around the town and all users have clear LOS. We are using some KP Performance 5GHz sectors and RB411AH with R52Hn cards in a dual chain setup. Most cpe are about between 1 to 3 miles of a tower and 95% are SEXTANT 5GHz dual chain cpe. Almost all are sitting around 90% ccq or better and speeds of 117 to 130Mbps over the air.

Everything is running NV2 and works really well, my question is we are seeing slower speeds on AP with say 40 cpe on them, actual bandwidth is not right maybe 10-15Mbps but we can only pull 4-5mbps at a customer site. The cpu usage is not high maybe 50% tops. My question is this, if we upgrade to say rb800 boards do you think we will see some improvement or is this just a cpe limit type situation we are seeing. Seems much above 20 or so we see these slow downs. I was wondering if RAM would help.

Thoughts?

Thanks

Re: AP cpu vs clients vs bandwidth

Posted: Thu Sep 06, 2012 4:49 am
by mahnet
rb800 should help OR even a 433ah will. 411ah has too little ram to handle that much bandwidth. hence u see only 4-5mbps.

Re: AP cpu vs clients vs bandwidth

Posted: Thu Sep 06, 2012 9:33 am
by Tbird
How would RAM impact on throughput?! For sure CPU would, if it was I limiting factor - but memory…?

TB

Re: AP cpu vs clients vs bandwidth

Posted: Thu Sep 06, 2012 5:32 pm
by mahnet
The cpu needs RAM for...??? the more the better...

Re: AP cpu vs clients vs bandwidth

Posted: Thu Sep 06, 2012 6:55 pm
by 0ldman
Maybe I'm missing something here, but Crossroads with a 180MHz CPU and 32MB of RAM can move 10Mb with all of my mangle and queue rules, 16Mb without the rules.

I've got a 411AR, 300MHz w64MB, with an R52n that saturates my 100Mb ethernet.

I don't think RAM or CPU is the limiting factor here.

Re: AP cpu vs clients vs bandwidth

Posted: Thu Sep 06, 2012 7:25 pm
by Tbird
Totally agree, so instead of the “..RAM solves everything –approach”, let’s see if we can help tgwtoronto somehow. If you want to serve 40+ CPEs consider;

* Make sure no CPE have poor signal levels – as that will totally mess up the performance. In my experience – you should aim for better than -75dBm - on all of them.

* Also consider unchecking the highest MCSs on AP and CPEs – as they will not be needed for PtMP, and tends to “calm down” the network a lot (due to a lot less rate negotiating).

* The NV2 is quite sensitive to interference in my experience – so make sure you have channel spacing and best frequency selected.

Maybe post the AP registration list and result of a snooper scan…

TB

Re: AP cpu vs clients vs bandwidth

Posted: Thu Sep 06, 2012 8:43 pm
by mahnet
the only thing that differs in a 411ah and a 433ah apparently when used as an AP is it's RAM, particularly when it is being used with a single mini PCI. I have had quite a few 411ah links where the clients will face youtube buffering when the bandwidth on radio reaches around 12-13mbps. the same link works better with 433ah and the same amount of bandwidth.

Re: AP cpu vs clients vs bandwidth

Posted: Fri Sep 07, 2012 8:12 am
by 0ldman
I can't argue with experience. I haven't run across that issue yet.

Most of my AP's are 600, 433 and 711 with the majority being 64MB MipsBE @ 400MHz. As a matter of fact I am still running on my backup link with a 411a feeding the backhaul. Handles my 10Mb fiber all day long.

Mahnet, I'll keep that in mind when we upgrade the fiber in the near future.

Re: AP cpu vs clients vs bandwidth

Posted: Sat Sep 08, 2012 3:05 am
by tgwtoronto
Thanks for the feedback everyone. I am going to try a few tests with configuration adjustments and then also try an rb800 as I happen to have one and see how things go. I will post some results.

Cheers