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Packet Scheduling and QoS for Wireless Networks

The frottle project has flown the nest. It can now be found on SourceForge


Here is an extract from a post by Marcus from when frottle got slashdot'd.

Once upon a time, in the mystical land of Oz, there was the quiet city of Perth. Broadband was expensive (cable was only in one suburb), and ADSL was only just beginning to roll out. WiFi has just been released, and a group of enthusiasts saw the potential.

A bunch of people got together, and through many donations, were able to buy their first public WAFreenet Access Point. Now - Perth is fairly flat, with a long ridge running down one side - perfect! The AP was setup on a private property with an incerible view of the city, and we named it HillsHub (we'll call it HH).

By about 5 clients, the hidden node issue started to get noticable. Easy, they turned on RTS, and it made an improvement.

Since it had such good visibility, HH began to get pretty popular. By about 10 clients it was really stuggling, and many of those clients had AP and clients of their own adding to the routed traffic. RTS just wasnt cutting it anymore - the RTS packets are subject to collisions aswell. In a desperate effort to regain some control, rate limiting was implemented, dropping speeds back to 10kB/sec during the day to maintain some reliability. However - during the night, a free for all would occur - some people would get 100's kB/sec, whislt others would be drowned out, near complete packetloss.

By 14 clients, the situation was ridiculous. We HAD to do something. We knew Kalrnet Turbocell (a polled system) would fix it, so we sold our soul (advertising on the e3 website) and negotiated a lower price - even then we needed to fork out A$150 each. We got together and pooled the cash, and just as we were about to buy, realised that the linux support was terrible - old, buggy kernels, binary driver only. We stopped in our tracks, and wondered what to do.

There were plenty of ideas about building our own kalrnet, but none of us were kernel programmers, so it seemed a bit out of reach. That was until one day, when I came up with a plan. I'd read that iptables could send packets to a userspace program, so inspired by some examples (countertrace), I set about building the first version of frottle using perl.

There was nothing new about the concept - polled systems and token rings are common knowledge in communications and networking. It wasnt difficult - it only took me a weekend, and that included the time spent learning perl (it was my first go). It was even operating at the wrong layer - using UDP control messages to schedule IP traffic. Regardless of all it's limitations, it worked, so I got the other WAFreenet members involved with testing and development. Radix picked it up and tried to continue development with C++, but had problems. Then, ChrisK took up the challege, and the result is the dynamic, performance C version we have released.

Halfway through development, WiCCP was released. This was a similar concept, but implemented as an loadable module/interface. We liked the concept better than our userspace app, so we trialled it ourselves. One of the perth guys (Brad) even got involved with development, improving the product. Still, whislt it was an implrovement on no QoS, it didnt seem to perform quite as well as frottle. This was the decider, so ChrisK prepared frottle for release.

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