Friday, April 4, 2014

Lessons learnt after setting up Wifi for Abacus Hackathon

Abacus is a Computer Science symposium conducted by the students of CEG.

The Hacakathon for this year was sponsored by Freshdesk and was called Save The Hacker

Here are some of the lessons that I learnt

Lesson 1:
Have an access point per 10 attendees

Turns out that people at a Hackathon have more that two devices that connect to the wifi network per person.

We had three access points for ~60 people while the wifi worked fine for most of the time, it fell to pieces when people started to torrent(will get to that later)


Lesson 2
Have both channels with access points that have band steering

I used ubiquiti nano stations as my access points,these are single channel 2.4 GHz radios, while the three access points were in different channels, there are only three non overlapping 2.4Ghz channels.

I wish, I had dual channel radios in my access points that would allow me to steer the clients to the less congested 5Ghz band where there are over ten non over lapping channels to use

Lesson 3
Have a local transparent proxy and a local DNS cache
I think that the INTERNET would have felt faster if there was a local transparent proxy on the network

The Internet also felt slow as the DNS server that was on the university network was taking in the order of 2000ms for a DNS request, this caused the network to seem super slow, even though the available bandwidth was over 100 megabits per second 

Lesson 4
Have monitoring  on the network(relegated to no 5)
The ubituiti gear is not supported my NAGIOS properly, I made a mistake by not having any kind of monitoring on the network except for inbound/outbound bandwidth. This ended up being a huge mistake because the network becaume very slow at one point through the hackathon and I could not figure out what was wrong .


Lesson 5
Throttle/ enforce qos on P2P downloads like torrents
All the ports were open on the network, this caused the participants to start downloading torrents over the network. This causes the network to slow down to a complete crawl and at one point causing wifi clients to deauth( could also be due to no 6)

Lesson 6
Discourage use of personal hotspots like connectifi
A lot of the participants were using personal hotspots that were causing the spectrum to be fully utilized, this can also be mitigated by moving to 5 GHz radios on the access points

Lesson 7
Have RF monitoring tools
I recommend any one attempting to have a large wifi network to have a rf monitoring tool, that allows you see spectrum utilization and take action based on that


I will put up another blog post on all the gear used for the hackathon

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