The 'Wi-Fi At Conferences' Problem

[Dave Farber <dave () farber net>]

Begin forwarded message:

> From: Jim Thompson <jim () netgate com>
> Date: October 9, 2009 18:18:58 EDT
> To: dave () farber net
> Cc: Dewayne Hendricks <dewayne () warpspeed com>
> Subject: Re: [IP] The 'Wi-Fi At Conferences' Problem

> The majority of the problem with Wi-Fi for 2000 people is that the  
> parties who 'install' the Wi-Fi Access Points typically don't know  
> what they're doing.
>
> For instance, one of the *classic* mistakes is that the installers  
> will hear the often-stated, "three non-overlapping channels" (in the  
> 2.4GHz band) and
> assume that this means that they can install access points on  
> channels 1, 6, and 11.
>
> While its true that these channels don't "overlap" in terms of  
> transmit mask, the radios used in the APs *and the clients* don't  
> have enough selectivity
> to "ignore" (if you will) a radio operated on the adjacent "non- 
> overlapping" channel.   The result is many, if not most packets (or  
> frames) end up being
> smashed in the receiver.   Remember that this happens for the  
> clients (iPhones, notebooks, etc) too.   The result: extremely low  
> 'throughput'.  I've witnessed
> Apple make this mistake (using their own staff and their own gear)  
> at events as large as MacWorld.(*)
>
> Another mistake is under-provisioning bandwidth.  A T-1 line can be  
> saturated by the average conference attendee, especially if the  
> conference content
> is boring.   The IETF meetings normally get a DS-3 or better.
>
> Having a DHCP server "run out" of addresses is just rank  
> amateurism.   While the 802.11 (wifi) specification (from IEEE)  
> "allows" 2037 stations (clients) to
> associate with a single AP, I can't think of any commercially- 
> available AP that will support this number of simultaneous "clients".
>
> Jim
> (*) its also the proximate cause of failure on Vivato's first- 
> generation product as well as other "Wi-Fi switches" that used to be  
> marketed by various firms.
>
>
> On Oct 9, 2009, at 11:18 AM, David Farber wrote:
>
> > Begin forwarded message:
> >
> > From: dewayne () warpspeed com (Dewayne Hendricks)
> > Date: October 9, 2009 10:57:17 AM EDT
> > To: Dewayne-Net Technology List <xyzzy () warpspeed com>
> > Subject: [Dewayne-Net] The 'Wi-Fi At Conferences' Problem
> >
> > [Note:  This item comes from friend David Isenberg.  DLH]
> >
> > The “WiFi At Conferences” Problem
> > by Joel Spolsky
> > Thursday, October 08, 2009
> > <http://www.joelonsoftware.com/items/2009/10/08.html>
> >
> > Why does WiFi work so poorly at tech conferences?
> >
> > I assume that WiFi wasn’t really designed to handle a big ballroom 
> >  with 2000 people, all trying to connect with their laptops and ce 
> > ll phones at the same time. Sometimes I feel like I’m lucky if it  
> > works in my apartment. So I never thought it was even possible to  
> > get it to work at a large, technically-savvy conference. At Stack  
> > Overflow DevDays, yesterday in Boston, the bandwidth seemed OK but 
> >  the DHCP server ran out of addresses. This didn’t seem to be some 
> > thing that anyone could fix. The conference organizers (er, me and 
> >  Greg) were incredibly busy trying to, you know, organize the conf 
> > erence, so spending time tracking down the mysterious ISP and maki 
> > ng them fix their router was impossible.
> >
> > It’s almost getting boring to read the conference reports complain 
> > ing about this. Almost every conference, even the ones put on by f 
> > ancy tech companies, has trouble. I never assume WiFi is going to  
> > work whenever I’m in a room with that many techies.
> >
> > [snip]RSS Feed: <http://www.warpspeed.com/wordpress>
> >
> >
> >
> >
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