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. "

Is Frottle.. is good

[Radix999]

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 :)

Re:Is Frottle.. is good

[TheZombie187]

Actually, the fact we're all slightly odd helped immensely. *grin*

Most of us connected to this network because we are interested in the technology behind it. 15 "normal" internet users would have undoubtedly leeched the fsck out of the AP and would have seen problems much sooner....

Proud Denizen of the WaFreeNet

Re:They're reinvented Alohanet, circa 1970

[Alan Cox]

Systems like DAMA have taken it somewhat further than Aloha but it is alive and well in a lot of situations. The trick is working out when its a win to use it

Am I new to warring or...

[gerf]

what. Is there some place that the coordinates of all these hotspots are shown? I think it would be helluva cool to be able to see GPS coordinates, or some sort of listing of where there are these hotspots around. It could be helpful in traveling, and the such.

I don't have a wireless card, much less a laptop, but if i wanted to travel, i imagine that having something like this would be quite helpful, rather than roaming around looking for the symbol etched on a roadsign.

What is the state of WAFreeNet these days?

[torpor]

I'm from Perth (born in Subiaco) and have lived outside of Australia since I was a teenager - have visited home a couple of times here and there, and every time I've been impressed with how much progress Perth has made in implementing advanced Internet technologies. Last time I was there - a year ago - I noted teams of wireless-hackers putting up repeater boxes in various neighborhoods at least 4 times - I don't know if it was just by chance, but I kept running into these 3 guys!

One of the things which has kept me from moving back home to Perth and setting up digs has been the state of the Internet down there - the Telecom monopoly, and the distances involved, have been a big factor. Maybe I'm spoiled by American and European bandwidth situations and maybe I ought to just go home and bear with it, but I would be curious to hear from anyone who knows what the scene is like in Perth for cheap, affordable world-class Internet bandwidth?

Fakin' it.

[GoRK]

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.

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 ... 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.

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

Re:TokenRing?

[Anonymous Coward]

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.

Frottle master is a "man in the middle"

[Ungrounded Lightning]

I note that the Frottle master relays traffic when two non-master nodes wish to talk to each other - even if they could talk directly. This both reduces the potential agregate peer-to-peer bandwidth by a factor of two (or more) and sets up the Frottle master as a "man-in-the-middle".

I'd rather see the master simply arbitrating bandwidth in its neighborhood and the peers exchanging data directly. General-casing that to multiple simultaneous masters, while relaying but only when necessary and only by efficient paths, limits out at a mesh network with extreme bandwidth usage efficiency.

But the thing that bugs me is the security implications of having all non-master nodes relay through the master. That lets a hostile node that achieves (or spoofs-up) master-node status perform man-in-the-middle attacks on the security of the communication.

Being man-in-the-middle is probably not a big deal if the master is also the main internet gateway (so it would be man-in-the-middle to most traffic anyhow), operated by a well-known and trusted organization. And it does simplify routing packets from one channel to another. But it bothers me anyhow.

Fortunately, any node that can also hear its peer can check the honesty of the master's forwarding.

Which leads to a potential way to eliminate unnecessary bounces off the master: Clients can inform it that they can hear other particular clients and what the differential delay characteristics are from their site. Then the master can just assign the transmission slot for the packet and drop it on the floor while the receiving peer captures it directly.

Re:Problems with this

[Anonymous Coward]

These problems are all things the product my employer [meshnetworks.com] makes solves. We do RTS/CTS, as well as power control, and full IP routing, all in hardware. RTS/CTS helps the hidden node issue, and power control allows smaller zones of interference, which gives you aggregate throughput close to the theoretical max to an access point.

In fact, we had a similar product that did much of this in a software layer above 802.11, and measured aggregate throughputs of 2-3 times higher than vanilla 802.11. I guess that the concept is similar to what the frottle folks are doing.

Perth, wireless capital of the world

[ttys00]

At one stage (a year go, not sure if its still the case), Perth (capital of Western Australia) had more wireless networks per capita than anywhere else in the world. Yes, that includes San Francisco.

Why? Because it is a spread out, very flat city with piss poor and expensive broadband internet. It's also isolated from the rest of the country, so it's quite often the last Australian city to get infrastructure. There is also an abundance of unused satellite TV antennas from a failed provider, which people let you take off their roof for free (I collected 9 in one afternoon with a mate one day). They make excellent wireless receivers if you mod them right.

I went to Uni in Perth, and in the last 12 months my mates there have put up 3 antennas - they are Comowireless on the node database. I live in Sydney now, and I don't see anywhere near as many wireless antennas here as I did when I lived in Perth.