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frottle: Defeating the Wireless Hidden Node Problem
jasonjordan writes "The West Australian FreeNet Group was the first to go War Flying - and now we've released "frottle" (freenet throttle) - an open source project to control & manage traffic on fixed wireless networks. Such control eliminates the common hidden-node effect even on large scale wireless networks.
frottle works by scheduling client traffic by using a master node to co-ordinate - effectively eliminating collisions!
Developed and tested on the large community wireless network of WaFreeNet, We've found it has given us a significant improvement in network usability and throughput.
"
It really does make a huge difference too. With 15 odd users on an AP we had a nightmare.. someone would start transferring a file and people would drop out, packetloss, etc. The strongest SNR would always dominate, uploads were nigh on impossible (when ANY download was occurring) and the network had no QoS at all.
:)
Thanks to the great work of Frottle, we're now cruising along - we all get a fair go, we have QoS, and bandwidth is shared equally and we're all pretty damn pleased with it.
Is Frottle.. is good
-- Wireless WaFreenet user since March 2002
Well, this idea is good and all (that's why it's a part of the spec!) But the problem with a firewall-based solution is that it is behind the AP and thus the solution of traffic control through client polling is only simulated. Without the AP performing the polling, you don't acutally solve this so called "hidden node" problem.
... about 6 years or so, even the 802.11b ap's! It's like trying to make steel in your fireplace. The consumer-grade equipment is not designed to take the heat. Consumer-grade AP's are going to lack some of the features needed in carrier-grade equipment such as polling. It makes them cheaper - no doubt they are missing features.
802.11b people have a bad habit of thinking that the problems they face are new or unique, so they do a lot of re-inventing the wheel. This, normally is not a bad thing, but quite often "WiFi" supporters produce a crude solution while spewing insane amounts of bullshit radio pseudosience. When did "crosstalk" suddenly mutate into "hidden node problems?" Alvarion (Breezecom) has had polling support in their AP's for
What someone who wants to fix this really ought to do is modify the ihostap drivers to do polling 'on the air' -- If it is possible, at any rate.. I am unaware of the specific implemenation, and it's likely that even toying with the HostAP drivers will not allow one to work with the radio at a low enough level. Still, you know, if it works, it works. Traffic shaping can make things seem faster on congested networks of any kind, so if it throttles the abuser down enough where other radios can get a word in edgewise, then it does a little towards curing a symptom of the real problem. For the freenets and coffee shops, this may be entirely sufficient.
~GoRK
Is your comment designed to infer that token-ring is a less advanced network topology? Token-ring is actually younger then ethernet and has many advantages. It holds up performance wise under load and you can predict the max amout of time a packet will take to travel the network. Thisis something you cannot do on a larger ethernet. Token is widely used with medical and manufacturing eguipment were messaging latency must be garunteed. The only reason speeds of token have not increased is cheaper ethernet is well suited to most but not all situations, wireless A/p like envirormentsthat effectivly are shared medialike a hub is one example where ether falls appart fast with many users. Token would hold perfromance and make best use of the air time. Token scales, ether does not unless you add segments. Token has not increased speed because there has been little demand for it. But it is the more advanced technology and would be the solution for large wireless applications.