

Wi-Fi Overload at High-Tech Meetings - wallflower
http://www.nytimes.com/2010/12/29/technology/29wifi.html?hp

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Rantenki
At Defcon every year, we have ~10k attendees, with literally thousands of DHCP
leases active, using a combination of Aruba wireless gear, and Cisco switches.
We don't generally have a problem.

Good planning is key; we have heatmaps (signal strength predictions) for every
venue in the conference, careful AP placement, and a butt-load of security
backend to keep things running smoothly, combined with some EXTREMELY talented
staff running the configurations and monitoring continuously over the weekend.
The network staff shows up a WEEK in advance, and often does a preflight in
April to check on any changes in the hotel (we are switching hotels this year,
so there is a lot more prep this time around). Not many conferences have a
dozen high pay grade network admins prepping for a full week in advance. But
you cannot argue with results.

The real choke point is probably the 100Mbit link back to the ISP, but we keep
upping it every year ;)

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zdw
See here: <http://www.wired.com/epicenter/2010/12/ruckus-wifi-3g/>

Ruckus set up the access points MacTech Conference in Nov, I was seriously
impressed.

At most conferences I've been at, the wifi tends to die or have performance
problems.

In this case, it was actually usable with effectively no performance/signal
issues even with 200+ people (probably 300+ devices between
laptops/iPads/iPhones) in a large hotel conference room.

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crowsfan85
Joel Spolksy posted about this problem on his blog last year:
<http://www.joelonsoftware.com/items/2009/10/08.html>

Here's the related ServerFault post:
<http://www.joelonsoftware.com/items/2009/10/08.html>

~~~
crowsfan85
Correction: ServerFault discussion here...
[http://serverfault.com/questions/72767/why-is-internet-
acces...](http://serverfault.com/questions/72767/why-is-internet-access-and-
wifi-always-so-terrible-at-large-tech-conferences)

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gonzo
So many people, even people who work @ Apple in the Airport group, don't
understand wifi.

Here is one anti-pattern for WiFi... run the APs co-channel. run them all on,
say, channel 6.

Because in the 2.4GHz ISM band, given OFDM modulation, and the minimum
standards set by the IEEE, there is really only one usable channel.

The adjacent channel interference problem is worse with 802.11n receivers,
btw.

But if you run the APs co-channel, then CCA can work.

~~~
mickdarling
I had to convince a former bosses boss of mine that this was the proper setup.
He had setup the network when the company was tiny and explaining what needed
to be changed when we grew to more than 10 times the users and 20 times the
wifi devices was a lesson in convincing a brick wall. Getting all the best
practices collected was not an easy task.

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andrewljohnson
Ugh, that's a piece of non-news if I ever heard one. NYT: Wi-Fi Slow at
Conferences.

Is there a point to this article, or are they just stating something that no
one cares about?

~~~
sbierwagen
It is most definitely not news, but going so far as to say it's something _no
one cares about_ is going a little far.

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daimyoyo
Perhaps someone more technologically inclined than I am can shed light on this
but when a company like Apple hosts a marquee event like WWDC why can't they
see how many people will be at the event, then deploy enough wifi routers to
meet demand? Especially when Apple makes their own wifi routers. Across wifi
a,b,g,and n there should be plenty of spectrum to go around. If a company can
deploy 10,000 servers in one room, why can't they deploy 100 wifi routers?

~~~
DrStalker
Do you have the manpower and budget to get those 100 wi-fi routers set up and
tested in 1 day? Most convention locations don't allow for a huge amount of
prep time.

~~~
tgvcfgtbvcfgh
It can be done if the people have good equipement and REALLY know what they
are doing.

The trouble is that the venue hire the cheapest people to fit the system and
have no clue how to run it. Since nobody knows how the good the system is
before they do the show you have to trust the venue - when you find out it's
crap it's too late - so there's no incentive to do a good job.

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sbierwagen
Intel wrote a whitepaper[1] on this very subject. One of the more amusingly
counterintuitive findings is that you want each radio to cover not a whole lot
of area. No matter how fast the backhaul is, the spectrum can only handle a
couple dozen clients, which fills up fast when you've got tens of thousands of
attendees.

1: <http://www.intel.com/it/pdf/conference-wifi.pdf>

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iwwr
Could work: a combination of wired connections, asking attendees to bring
their own 3G dongles and providing a local cell base station for areas with
poor mobile coverage.

For people with ethernet ports, you could spread a few wifi routers with wired
ports, so wifi traffic is carried over to the fewer routers than to each
individual client.

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pmorici
This isn't just a wifi problem it is a general wireless problem. Where there
are large gatherings like The Daily Shows Rally to Restore Sanity for example
cell service totally failed in the area around the washington mall.

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pjy04
You can't solve the problem by just increasing the # of routers, It's the
noise and the lack of frequency in the space that causes the issue with so
many nodes.

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phlux
This is a serious problem for a network I am designing. With many many systems
on the wireless network we are ensuring that we have better coverage with WAPs
- but the real problem is because we will have more than 10,000 wifi Aeroscout
tags on the network.

Both Cisco and Aeroscout have no idea what this level of activity will look
like. While Aeroscout's largest client has some 30,000 tags - they are on a
much larger square footage campus.

I am still trying to find the best approach to this problem, but any of the
companies that make the HW are only interested in selling you more hardware -
not developing a solution, as of yet.

The network is more than $15M in HW alone - so, I am sure I will bring them
around.

