June 16, 2006

Conference Wifi

Last year at the reboot conference I set up the network with organic network. I have heard later that it had been one of the most stable wifi networks people had experienced at conferences. The conference had 400 visitors of which 60%(242) had a laptop online at some point during the conference. This years reboot conference had 500 visitors of which 75%(375) had a laptop online during the conference. We clearly did not expect this increase in laptops and usage so the network was not really scaled to handle the load. This post will summarize some thoughts on networks for conferences that should make the network quality better next year.

The network:

Internet------router------switch-------M0n0wall-------wifi APs
                                       \------------speaker network

You may grab the config file for the M0n0wall if you want to use it, but you need to change the interface names and the admin password.

The wireless network:
You will need approximately 1 access point for every 40 laptops on the network (This ratio should be recalculated to match the bandwidth usage in the "The bandwidth:" paragraph). I think you can assume that almost all attendants will bring laptops next year, so that will be 1 access point for every 40 attendants at the conference. The access points should be configured for bridging with no encryption or authentication. If you need authentication or encryption you can do it on the monowall. It is much better at handling such things. Access points that are installed physically close should be configured with some gap between the channels so they won't conflict (e.g. channel 3 and 6 ). Areas with many users should be convered with access points according to the 1AP/40 users quota.

The bandwidth:
Last year we had 1,8 Mbits for 242 laptops in total (avarage 7,6 Kbits pr. laptop). That was sufficient. This year we had 3 Mbits for 375 laptops in totalt which was not sufficient in any way. In general I would recommend to get an internet connection which can be boosted to more bandwidth during the conference if needed. I think the need for bandwidth will increase by a factor of 2 every year. So the bandwidth this year should have been 15-16 Kbits pr. laptop ~ 5,7 Mbits in total to be sufficient. In short 7,6 Kbits pr. laptop last year, 15-16 Kbits pr. laptop this year, and 31 Kbits pr. laptop next year. This will probably not hold true after two or three years, but it's better than nothing.
Also remember to get your own bandwidth. This should be easy now when you can order WiMAX connections really fast. Remember to shape the bandwidth usage on the monowall, to leave some dedicated bandwidth for the speaker network.

Posted by simon at June 16, 2006 12:19 PM

Great observations.

Posted by: Thomas Madsen-Mygdal at June 16, 2006 9:22 PM

If the channel thing is a real problem and the 40 users/ap is real as well you basically can't reliably serve more than 200 people in the same room.
So if possible one should actually restrict the radio range of the AP's to reduce conflicts so that more AP's can be fitted into a room.

Posted by: Claus at June 19, 2006 2:01 PM
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