Alan Johnson wrote:
I had forgotten to mention that we had eliminated all the 11b we could in that 200 users network. That definitely helped a lot.On Sat, Feb 28, 2009 at 3:29 PM, Dan Jenkins <d...@rastech.com> wrote:I have successfully used Linksys WRT54GL with DDWRT or HyperWRT Thibor (the latter is deprecated I gather) firmware for about 40 concurrent users in three different settings: teachers in a training session, kids in a mobile lab setting, and a small cube farm with mixed engineers & biz folk. I had no problems with simultaneous connections. The teachers and kids all were making Internet connections simultaneously for their training and testing (25-35 of them).I have also used Belkin (don't recollect the model) with stock firmware for a school with about 200 users. I have eight scattered around, plus two with stock WRT54G firmware. We used to have a lot of problems when we had older Linksys units, but most of the problem likely came from them moving the access points around, rather than from the equipment itself. They didn't have enough APs for the physical space and did not understand how to deal with wireless. (Several times we found three or four access points stacked on top of each other to, in the words of someone, "boost the signal.") Once we got the units evenly distributed and secured and configured the laptops properly, things have been running well. We did do some basic testing to ensure reasonable signal strength throughout the space when we positioned the units. Based on your physical dimensions, I would go with two, on non-overlapping channels, one at each end of the spaceLooking only at the wireless network layer, 802.11b is bad at handling multiple active clients and will only get you 5Mbps of application throughput when you have an 11Mbps connection over the air. It should handle 10-20 active clients on a ~1Mbps back haul fairly nicely since that leaves 4Mbps to be wasted on collisions and retransmits. I've definitely seen problems with 2.4GHz cordless phones taking out 11g. Never noticed microwaves doing it though.11a/g starts with a bigger pipe of ~14Mbps of application throughput on a 36Mbps+ connection over the air and is better at sharing it. If every one has full signal and with 54Mbps of on-the-air speed, that gives you 18Mbps to waste on collisions. You should easily be able to serve 40 clients (as mentioned by Dan) sharing a 12Mbps connection. You might not want to play Doom on it, but if you are mostly talking about web browsing and email, that kind of bursty, not-so-latency-sensitivity traffic should be fine. In fact, I would think you could get 100 or more users sharing such a connection. If you are limited to 6Mbps back-haul, and disable 11b, then I'd bet on a pretty smooth ride all 100+. 11n varies widely in application throughput by device (did that ever come out of draft?), but I have not heard anything less than 100Mbps. I don't know for sure, but I am pretty sure it uses the same sharing as 11a/g. I would be shocked if it is worse. At a max of 200 simultaneous routed connections (a la Bruce Dawson's link) you are going to hit that before you max out 11n clients. So, my suggestion is that 1 11g router on a clean channel should more than meet your needs if the guts behind the radio can handle the connections. Go for 11n if you expect that kind of client, but remember that 2.4Ghz 11n traffic will crush any 11b/g traffic competing for the same bandwidth on a nearby access point. Same goes for 5Ghz 11n vs 11a. Not really your problem, but we Linux geeks are all about play-nice, right? Also, 11n uses twice the bandwidth per channel, so you need 2 of the 3 non-overlapping channels of 11b/g to run 11n at 2.4Ghz. This means you will aways be using some of channel 6, the middle of which is the resonant frequency of H2O used by microwave ovens. (This is why the 2.4Ghz band is unlicensed.) I have not heard of microwave ovens causing noticeable problems with 11n at 2.4Ghz, but they sure can screw up 11g and they crush any 11b within range. My experience with 11n at 2.4 GHz is limited. It works nicely at 5 GHz.As for picking a clean channel and playing nice, run net stumbler before you buy anything just to see the situation, unless you are sure you are clean in this location. It is free, so it does not hurt to check anyway. Kind of a fun tool to play with. It even cracks WEP keys for you! Or is that Air Snort... It has been a while since I played with either. In a perfect world, everyone runs 5Ghz 11n and leaves 2.4 for other technologies, but unless you are in a corporate setup with bucks to blow on new client WNICs, then I'm guessing that won't happen. =) I was (operative word, "was") in a situation where we could have switched everyone at our client to 11n, but then the economy happened and that project is shelved now. While I agree in principle with Ben that commercial grade is better than consumer grade, I have had pretty good experience with consumer grade.Oh, and it is worth mentioning that Linksys hardware runs on open-source Linux based software. Maybe others too, but they have been doing it the longest. Oh, Buffalo Technologies did at one point, but I have not checked in a while. I'm planning to be at the next DLSLUG, Ted (or anyone), if you want to dig into this deeper with me. =) The 200 user client was quoted $25,000 for a commercial-grade wireless solution from someone whose name escapes me at the moment. We used eight $50 Belkin APs, disabling 11b in the environment, retiring any 11b wireless adapters, and proper configuration of existing wireless clients and are happy with this $400 solution, which the $25,000 vendor said would not work. I do not doubt that the other solution would have been better technically, but it was not affordable. |
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