A not uncommon source of frustration is poor wifi access in public spaces such as hotels, airports, etc., and by extension, poor wifi at events. We’ve all seen the issues – very slow downloads, congestion, dropped connections.
One of the things I do is regularly attend Internet industry events, and by nature of what they are, they are full of geeks, nerds and other types of “heavy user”, and they need their own significant wifi capability to support the event. Yet even those events, which don’t rely on the in-house wifi provision, still run into problems – for instance, the most recent NANOG meeting had some significant wifi issues on the first day, though they did have the challenge of serving over 800 users in a relatively tight space.
I’ve also been involved in setting up connectivity at meetings, so I know from experience that it’s not that difficult to provide good quality wifi. You just need to make a little bit of effort.
This is probably the first of a short series of posts, where I’ll share nuggets of wisdom I’ve picked up along the years. I’m going to assume that if you’re reading this, you know a bit about wifi.
1) Band steering does not work reliably enough
Wi-fi operates on two bands, 5GHz and 2.4GHz. The 2.4GHz spectrum is congested. Most modern clients support both bands. Band steering is an attempt to force clients that can use the 5GHz spectrum off the 2.4GHz spectrum. It works by having a base station “ignore” 2.4GHz association attempts from a client that can associate on 5GHz.
However, experience shows that this is not reliable for all clients, and many clients which could be associated with a 5GHz base station end up associated not only with a 2.4GHz base station, but one which is suboptimal (e.g. further away).
Band steering seems especially problematic when enabled on autonomous base stations. At least on a centrally orchestrated controller-based network, the controller can simultaneously tell all base stations to band steer a particular client.
Which leads me on to…
2) Run separate SSIDs for 5GHz and 2.4GHz bands
If band steering is unreliable, then you need some other way of getting clients on the “right” wifi band. Running separate SSIDs is the best way of doing this.
The majority of modern clients support 5GHz (802.11a). I would therefore recommend that your main/primary SSID is actually 5GHz only. All the clients will ordinarily connect to that.
You can then set up a second SSID which could end in “-2.4” or “-g” or “-legacy” for the non-5GHz clients to connect to. The 2.4GHz clients will only see this SSID and not the 5GHz one. There are significantly fewer 2.4GHz clients around these days.
At the end of the day, both the 5GHz and 2.4GHz wifi SSIDs should then still be bridged to the same backend network so that the network services are the same for the 5GHz and 2.4GHz clients.
3) Turn off 802.11b
Are there any 802.11b only devices still around in regular use?
Disabling 802.11b will restrict your 2.4GHz spectrum to .11g capable devices only, and has the effect of raising the minimum connect speed.
If you know you don’t have to support legacy 802.11b devices, switch off support for it.
4) Restrict the minimum connect speed
The default configuration on some base stations, especially if 802.11b is switched on, is to accept wifi connect speeds as slow as 1Mb/sec.
All you need is one rogue, buggy or distant client to connect at a slow speed and this acts as a “lowest common denominator” to bring your wifi to it’s knees, slowing all clients on that base station to a crawl.
Right. That’s it for today.
Eventually I’ll be showing you how you can run wifi for a 200-300 person meeting out of a suitcase.
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