Re: The 'Wi-Fi At Conferences' Problem

[David Farber <dave () farber net>]

Begin forwarded message:

From: Brett Glass <brett () lariat net>
Date: October 9, 2009 7:54:44 PM EDT
To: dave () farber net, "ip" <ip () v2 listbox com>
Subject: Re: [IP] The 'Wi-Fi At Conferences' Problem

Dave, for IP if you will.

Because our ISP has developed BSD UNIX-based traffic shaping and anti- 
bandwidth hogging software for its own networks, we have also deployed  
it for conferences. It does a good job of keeping each user's  
bandwidth use to a sane level, and is capable of administratively  
blocking activities that have no place on a shared conference LAN.

We also use RF tricks. One of the best is to use 802.11a, which has  
lots of non-overlapping channels. (You can even use alternate  
channels, especially if you use the lower, indoor-only ones.) Also,  
when they process 802.11a, the chipsets also tend to be better at  
filtering out unwanted signals on nearby frequencies. 5 GHz signals  
also penetrate walls poorly, which is a good thing; it allows  
frequency reuse and helps to avoid interference from sources outside  
the building or in other parts of the venue.

It also helps to know your equipment and use quality gear. When I  
attended David Isenberg's conference a couple of years back, the folks  
who were running the network use Linksys routers, but with the  
upstream network cables plugged into the 4 port switch rather than  
into the upstream port of the NAT router.

I believe they did this -- in a spirit of extreme "network purism" --  
so that they could avoid doing NAT and give every client a public,  
static IP. (You can't turn NAT off on the Linksys routers, so they  
couldn't just give each router a subnet.)

An interesting idea in theory, but a bad one in practice. Not only did  
this architecture fail to prevent broadcast packets from being relayed  
between the APs, jamming the network; it also triggered a known bug in  
the Linksys routers that caused packets to be reflected back from the  
access points.

At that conference, as at many others, I fell back to EV-DO when the  
network fell apart.

--Brett Glass





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