[sdnog] manage my wifi

Nishal Goburdhan nishal at controlfreak.co.za
Fri Sep 9 12:20:10 SAST 2016

On 29 Aug 2016, at 21:57, ghazi ebnof wrote:

> hi people
> - i want know how i can manage my channel in my wifi professionally 
> and the
> best tool to do that .

hi there,

that depends on what your setup is really;  are you able to explain what 
you have setup, and what you need to do.  and perhaps also, what you 
have access too.

first, understand that there is *no* silver bullet.  there’s no 
“tool” that will fix this for you.  you can, in a lot of cases, use, 
a proprietary controller to get a lot of these things done but, even 
then, it’s hardly going to be a plug-n-play setup.

let’s assume you want to setup something like the sdnog meeting;  the 
first thing that you’d want to do, is to do a site survey to check the 
radio (RF) usage.  normally, you can get this done with a laptop/modern 
smartphone which is good enough to check the general wifi-band usage.  
if you want to be more thorough though, you probably want to use a 
proper spectrum analyser - wispy+chanalyzer work well, and will fill in 
the gaps for what’s eating up your airwaves.

remember that wifi isn’t the only radio that’s using 2.4ghz (which 
is likely where you’ll find the most interference).
there’s cordless phones, microwaves, etc.  that all share the same 
spectrum, so, if you want to do it properly, you’ll want to spend time 
and effort to find and minimise interference.  at this years afnog, we 
had a crazy dutch guy :-)  walking around the conference hotel, 
unplugging the hotel APs, so that they would not be interfering with the 
conference network wireless that we’d setup.  made a huge difference 
to user experience!

khansa already mentioned the three channel usage (1,6,11) for 2.4ghz, so 
use these to separate out your different APs. when you’re building a 
large are wifi network, it’s tempting to think that you should aim to 
maximise range;  in truth, that’s not how you’d want to do it.  
instead, you want to have lots of small, tightly controlled (ie. how far 
can your transmit) coverage.  more APs, with the range/transmit power 
turned down, to cover a small area, is a Good Thing.  you’ll minimise 
interference, and maximise your throughput;  even though it might cost 
you more time in setup.  oh, and be nice, when you play in 2.4ghz;  it 
might sound cool to use 40mhz channels (and some silly wireless vendors 
let you do this) but you’re greatly impacting other people’s use of 
the same airspace.  some devices will even refuse to connect to 40mhz 
channels in 2.4, so just don’t do it!

if you can help it, using quality APs makes a huge difference;  your 
standard TP-LINK or linksys or home-grade equipment, might claim to 
support 30-50 associations, but, they really won’t.  and when an AP 
starts to suffer, it’ll affect all users connected to that.  cisco 
make great gear, but this is pricey. for sdnog, we use the ubiquiti 
unifi series, and that’s also very good, and at a fraction of the 
price.  they “software” controller that they provide is also very 
useful to use, and, for sdnog, the controller is run off a raspberry 
pi2.  if you’re interested in how this works, ask a member of next 
year’s noc team to show you the setup (or volunteer to help setup!)

of course, it’s nicer to use 5ghz if you can, since there’s 
traditionally a lot less interference here;  the ubiquiti gear that we 
use for sdnog can actually signal to clients to prefer 5ghz.  however, 
with 802.11ac becoming more common, it’ll be interesting to see how 
long this lasts.  i was at a data-centre earlier this week, where there 
were already too many overlaps in 5ghz, simply because the operator just 
plugged stuff in, and expected it all to auto-configure itself.  heh!  
if you’re seriously planning to use 802.11.ac gear (and use the high 
bandwidth that’s available here) i would start at the UNII-3 range, 
and work downwards.

personally, i still find it useful to use a hand-drawn map during setup, 
and little markers that i can move around.  of course that depends on 
your setup - if you’re going to run into a very large (hundreds) this 
won’t scale :-)

there’s lot to consider, and really, it depends on what you’re 
designing for, and what you want to achieve.
good luck, and do let us know what you end up doing.


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