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WLAN Visualization Meets GIS Mapping
martin dodge writes "The Wireless Ntwork Visualization Project (Univ. of Kansas)
has an interesting alternative to just dot maps of wlan base stations. These guys are mapping out the zone of availability using gis. nice maps using aerial photographs backdrops as well.
If you are interested, check out other ways of mapping 802.11b network infrastructure.
"
I have a question about the specific mechanics of this: What is the behaviour of 802.11b cards passing multiple nodes at high speed?
If you're driving down a highway with continuous 802.11b coverage and all the APs are set up to allow external access using some common agreed upon collection of settings (no WEP, a standard network name, etc), how well would a card support switching from AP to AP within seconds of each other?
Useful but check out the dynamically generated node map from http://www.pdxwireless.org It's updated as the nodes go on and off.
Last year i took my laptop & gps & a few perl scripts and mapped out the wireless access at my campus (UCSD). I made some maps too. Pretty fun!
http://www.cs.ucsd.edu/~ghamerly/wireless.html
hand-over is what you want, i.e. the ability to have a permanent session when you switch from one transmitter to another.
It is embedded in cellular networks (PCS, GSM, 3G, etc.) but is not (I think) a 802.11b feature, which was built for home, soho networks, not wireless internet coverage.
Besides, even if you could negotiate a transaction fast enough to keep the overhead low, the lack of a persistent ip address and connection scheme (firewalls) would make it difficult to work.
OTOH, a telecom-carrier operated wireless network is easy to standardize, and made for this type of thing (I remember having an half hour phone call on a 180mph train in France).
The real issue here is cost :
802.11b works because it's cheap and can be built by geeks, but hasn't got the features of a telecom network that's expensive to install, operate, and that nobody is really willing to pay for. (the market just isn't here yet : Metricom, anyone)
Besides, most features were supposed to come with 3G networks, but with fear of bankruptcy in the telecom sector, there is little chance we see this working before two years.
just my 0.02 euros
"The obvious mathematical breakthrough would be development of an easy way to factor large prime numbers." Bill Gates,
Can anybody comment on the following:
.11b network has 128wep, MAC list restriction, and SSID broadcast turned off. I realise that someone can sniff the traffic and decrypt the packets by cracking WEP, but this would otherwise prevent them from doing something ON the network, right?
Linksys (and other folks) have a flag that disables the SSID broadcast 'feature' of their basestations.
According to netstumbler.com:
"Linksys' latest firmware update for WAP11 includes closed network support. It disables the SSID beacon broadcast and as a result no longer shows up on either the Boingo or CyberPixie roaming clients, nor on Apsniff or NetStumbler network discovery tools. "
Is this REALLY a security 'adder' or can folks discover the network in other ways?
Our
We're investigating adding our VPN to the mix, but it's a non-trivial network topology change for a group that really doesn't have sensitive data.
"Draco dormiens nunquam titillandus."
I have actually done seamless roaming while streaming video at 75mph with the breezecom equipment. I believe that technically very high roaming speeds are possible with more dense configurations of AP's.
The first problem is that the breezecom stuff is FHSS which is a little bit easier to "roam" than DSSS, simply because you can hear neighboring AP's without having to switch channels as you do with DSSS, thus you know more about neighboring AP's.
The next problem is that the network has to be specially designed to support roaming clients. It has to have intelligence on the ethernet side of the AP's to teach the network about roaming client routing, so that packets always get to where they need. In large WLAN's, AP's are all rarely connected via a 100mbps backbone or the like. They are often connected with layer 3 switches, or worse -- routers, such that roaming is near impossible anyway without using special client software that implements MobileIP (or even ipv6)
The final problem with the way that breezecom does it is that their roaming is proprietary. The AP's preauthenticate clients before they show up, saving time after switching. It's not compatible with 802.11, though "regualr" 802.11 FHSS cards can indeed roam on breezecom equipment.
The fast roaming modes do not work on the breezecom direct sequence 802.11b equipment. You must be going 5mph or practically 10mph to roam seamlessly (ie without a data stream interruption) on this equipment.
When I worked for Sprint and other Clients we had mapping similar to this made using software such as Planet made by MSI. Planet was cool, it would help map out coverage for a given area. However it was still needed to go out and drive the network. I worked a project in Tijuana using some equipment made by DTI that had 8 scanners in it and would record about a thousand channels of data to be later displayed on a map. It was cool when you would look at the map and actualy see the coverage of each cell tower based on the driving that had been done.
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