We have a mesh network consisting of Linksys WRT54GL routers that we want to test/play around with. A big problem that we forsee is controlling the radio signals. Ideally, we'd like to be able to determine which router communicates with which other router even if all the routers were in the same room.
Does anyone have any ideas on how we might accomplish this?
Sure. If your WRT54GL routers have alternative firmware (i.e. DD-WRT or OpenWRT) which support SNMP, you can dump the connecting MAC addresses and lots of other goodies using a MIB browser or any other SNMP tool. SNMP details and examples on request (time permitting).
For Windoze, find a copy of SNMPUTIL.EXE and run: snmputil walk 192.168.1.1 public .1.3. which dumps the entire MIB table. You should see (I haven't checked) the connecting MAC addresses listed by physical port number/name. Duh... you'll have to first enable SNMP in the router configuration.
If you want connecting IP's instead of MAC's (becuase I'm too lazy to figure out who belongs to which MAC address), try: snmputil walk 192.168.1.1 public .184.108.40.206.220.127.116.11.18.104.22.168
Variable = at.atTable.atEntry.atNetAddress.22.214.171.124.85.1 Value = IpAddress 126.96.36.199
WRT54GL routers have alternative firmware (i.e. DD-WRT
Jeff, thanks a lot for the information, opinions and joke. This is really good stuff & it's going to take me a while to digest it. Using the MAC addresses to control the routing will be helpful.
I understand when you say putting all the routers in the same room is a worst case scenario. I hope this doesn't sound too silly but I don't have much experience in this area so I can't judge for myself. Would it be possible to 'pipe' the radio signals from one router to another using some sort of physical device so that the radio signal doesn't escape into the ether? I am thinking something along the lines of some sort of metal tubing that wraps around the antenna stubs. This would keep the routers from interfering with each other when they're trying to set up the network.
The basics. *ALL* and I do mean *ALL* 802.11 wireless is bridging. There's no routing involved until it this a router. Therefore, all transmission control, encryption, authentication, and connections are made at the Layer 2 (MAC) layer.
Yes. There are RF proof test chambers. Most 802.11 test bench setups use these because the measurements would be ruined from all the 2.4GHz crud floating around in the air. You can build your own, or simply embalm the routers in aluminum foil. Leave some aluminum mesh (window screening) around the vent holes to prevent meltdown. This is what I used to do in order to get sane and repeatable measurements.
That won't work. Pretend it's all setup and configured. You have an unspecified number of mesh access points (or wireless routers) in the same room. All are on the same RF channel. Only one can transmit at a time or you have a collision. For fun, try to send some packets through as many mesh routers as you can. You'll find that things slow down to 1/2 through one (store and forward) hop, by 1/4 through two, by 1/8th through three hops, and so on. However, this is under ideal conditions, which means the end points and intermediate routers can only hear the adjacent radios. That's not going to happen in a closed environment. You'll get considerable interference from your own radios, and I predict your thruput will suffer accordingly.
Grab IPerf and setup two computers for benchmarking TCP thruput. Get some real numbers. As you add WDS or mesh repeaters in the path, watch the thruput go down, down, down, etc.
I would be interested in seeing your results (because I'm too lazy to do the same test myself).