WAP Questions

2 Questions if I may:

1. How many computers can realistically use a single WAP before you notice a slow down? My WAP (Linksys WAP54G) is suppose to be able to handle 32 computers. That sounds like an awful lot for one WAP.

2. Can you set up two WAPs in the same area...WAP A on channel 1 and WAP B on channel 2....split the computers in that area between channel 1 and channel 2...and they work?

I apologize if these are beginner questions. Thanks in advance.

 

How many computers? It's more a question of how much simultaneous data transfer. I suspect that 32 PCs all running 802.11g and screaming along transferring data at their full rated 54Mbps would give you problems. Not sure though but I'd bet it would.

32 PCs connected and most running 802.11b and not doing much and I would not expect any problems whatever.

Between those two extremes, I'd say you would just have to play with it.

As to your second question, no clue. Not wireless-literate yet.

 

A wireless network is basically a shared connection. Only one communication at a time. So as Newt says, if everyone is quiet 32 may be possible, but in reality the limit is much less (around half I would suggest). The main protocols used by Microsoft systems (NetBIOS over TCP/IP) is fairly noisy and I bet they did their limit test using something much quieter like straight TCP/IP.

I haven't messed about with a large 802.11g network, so this may be a little out of date: with a 802.11b network there are about 12 channels available, but because there is a large overlap between channels you have to leave spare channels between each channel you use within an area. I forget the exact numbers, but the effect is that you can only have three operating wireless channels in one area if you are to avoid Access Points intefering.

It's quite a good gotcha. If you see someone design a wireless solution that involves flooding an area with APs, you know they don't have a good grasp of the technology.

And don't forget that wireless goes through floors. That can cause surprises when you carefully arrange your APs on a floor plan and forget that ther could be interference from the APs on the floor above and the one below.

 

Thanks for the info Newt and Reggie.

A little more info. We have approximately 650 computers in the school on a wired network. I have 4 labs one of which is a "mobile" lab. We are wanting to make those laptops into a permanent lab....basically Microsoft Office and internet. Instead of hard wiring the new lab I was looking into making it a wireless lab. The computers all have a wireless card (802.11b). There will be 31 computers total...30 students and 1 teacher. I was looking for the best way to accomondate this. I was thinking 16 on one channel of WAP A. 15 on a different channel on WAP B. 31 with just the internet may work?? I have been told we will be going totally wireless shortly but in the schools...shortly could mean 5 years...who knows around here!

Reggie do you feel this is doable? Or should I look into just having the lab wired? Not sure how network intensive the internet would be. At home I run 4 computers over a WAP with no noticable slow down on my internet.

Thanks again.

 

To compliment the above info, with 802.11b you have 3 non-overlapping channels you can use (US specs) #1, #6, and #11 using all 3 you would have an aggregate of 33Mbps (3AP's sep channels) depending also on distance/reception, 33 would be best case scenario. With 802.11g you still only have 3 non-overlapping channels, but would have 162Mbps aggregate (best case). I'm not a Wi-Fi expert but believe the .b if used by all 31 machines at one time would be taxed, think the .g might be do-able. Will look for more info that might help ya.

Do you have a comparable "wired" network that you could measure the bandwidth being used? .b might work depending?

 

I'd suggest using two APs to give the 30 odd laptops access. You shouldn't have to assign particular laptops to particular APs; they should be able to dynamically detect the least busy AP in their area and use that. Try two and add a third if you need to boost the performance. If most of the access is internet and occasional file download that should be fine. If access is to a shared application, directly to a database, or streaming media, I'd suggest you tread carefully - you may be better sticking with a wired solution.

The next piece of advice is base on a personal opinion: Wireless is a great addition to a wired network, but with the current technology it should not be considered as a replacement for a wired network (unless the network is very small - Small Office/Home Office for example). Comments such as "we will be going totally wireless shortly" raise alarm bells in my head.

Speed is an issue because each connection is shared. So your 54Mb bandwidth is shared with everyone using that signal. So, as with a hub, with 15 users each user has about 3Mb of bandwidth (it's not quite that simple but this gives you the idea). Looked at in that way, a 54Mb wireless system suddenly does not make such a good comparison with a 100Mb switch.

However, the overlapping AP issue is the real killer. If you flood an area with too many APs you get interference and all sorts of related problems, which will only further reduce the performance of your network.

Last and perhaps least there is the compatibility issue. Are you sure that the wireless kit you buy now will be compatible with the kit you can buy in five years time? I don't think I would be. When wireless is only used in part of the network that isn't too much of a problem, but when it comprises the whole network it is a problem.

If you do end up going for as much wireless as you can get, I would strongly recommend bridging between AP via cable (in other words keeping a wired backbone). If you wireless birdge between APs you loose bandwitch with each jump. There is also a limit to the number of wireless jumps you can make.

So lastly I would repeat that wireless is a great addition to a network. It has got me out of a couple of sticky problems trying to connect to remote places, and providing network access to roaming users. But it has it's limits, and wires aren't dead yet!

 

Reggie....Thank you so much for your insight. I will keep it all in mind.

I currently have 4 drops in the class room we will be using. I was planning on bridging the APs with wires. So if I understand you correctly, just set the two APs up using the same SSID and channels....and the laptops themselves will select which AP is best?

Kids will do internet searchs and use that info in Word and PowerPoint for class projects. Other than the internet, the only time the kids would be hitting the network would be to save their projects. (Currently we have a "Student Drive ". Hopefully, this coming year each kid will have his own log in and small personal drive area.)

"Totally" was a bad choice of words. The Executive Tech Director is looking at adding APs throughout the school so you would have wireless access in most parts of the school. The wired network would still be the main network. Tech people and teachers (all have a laptop eqquiped with 802.11b) would have network access without having to "plug in ".

Thanks to all of you again for your time and info. I'll let you know how it all works out.

 

You may find this of some help, it's a webcast dealing with what you want to do, it's about 45 mins long, but think it would be quite helpfull to you. Good Luck.

http://searchnetworking.techtarget.com/webcast/0,295011,sid7_gci929536,00.html

 

You need to set the two APs on different channels. Put one on the highest channel and the other on the lowest. That will leave you with plenty of room to put one in the middle if needs be.

"Executive Tech Director is looking at adding APs throughout the school" - that's more sensible.

To get best coverage there is no substitution for try it and see. I've had many happy hours wondering around schools with an AP and a laptop, finding best locations. Sometimes a wall will make a big difference, sometimes not. I've even seen instances of signal droping when the kids get up! But for what you are trying to achieve, I believe wireless is a good solution and worth the effort.