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Strategy to improve wireless or prevent my network from crashing.

Posted on 2008-10-02
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Last Modified: 2013-11-12
I have a problem with the wireless (or i think that is where the problem is) network in school.  I have a wrt54g router with ~50 clients.  Yes, i know that is bad, but i cannot do anything about it :( .
At my disposal i also have 2 wap54g access points.
Problem is, when there are many active laptops the wrt54g crashes and i have to reset it a number of times every day to get it back on.  Thing is, before i switched most of the school on cable and got some new computers, switches, servers, ISA wrt54 was serving the entire school (over 100) all by itself and the users said it worked just fine back then.
BTW, it is acting as a router between "foreign" laptops and school's own network, that is it does not connect directly to internet itself.  Just routes between wireless and local (i did this for some security reasons, and ISA 2006 connects the whole thing to interenet).
I am not sure where the problem is: what exactly contributes to the overload, the wireless part of the wrt54g or the router.  If i add more access points i am sure it will help with the load on the wireless part of the wrt54g, but will it stop it from overloading?

Hope this was not very confusing.
Thanks for any comments.
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Question by:AlexanderR
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by:rionroc
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Hello

Change beacon interval to 256 or to 384.



Great is our GOD.
:)
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by:Johnjces
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I respectfully disagree with rionroc regarding the beacon interval helping out your crashing AP.

"By increasing the beacon interval, you can reduce the number of beacons and associated overhead, but that will likely delay the association and roaming process because stations scanning for available access points may miss the beacons. You can decrease the beacon interval, which increases the rate of beacons. This will make the association and roaming process very responsive; however, the network will incur additional overhead and throughput will go down. In addition, stations using power save mode will need to consume more power because they'll need to awaken more often, which reduces power saving mode benefits."

But, it might be just that "nudge" you need...

However, the AP may have worked fine on a 100 users possibly because the throughput was not taxed or exceeded. Most LinkSys items are for homes and small offices. I all 100 users were hammering it, like continuous surfing, etc., I feel certain that it would have crashed them.

On an experience isue, I had a home type NetGear DSL router that would do the same thing and I finally determined it was the load, the amount of data/throughput that it was trying to handle just simply hosed it up. I replaced it with D-Link unit and have had no problems.

Remember too that some of the electronic components when installed inside the unit might not have been 100% and after time, heat and use, are worse off. An actual component failure could be the root cause as well.

Hope this may help a bit.

John
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by:AlexanderR
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Thank you for the input.

Since i am a real novice in networking, (i prefer programming) and this is a matter of collecting data this will take some time to investigate.

I will see what this "beacon" thing does.
I never thought about bad components.  Come to think of it, out of 4 ports, only 2 are working.  I will try to replace it with a newer one as an experiment (i just like this old one because it is v3 and has more memory than newer v6) as well.

What about having extra APs? Should i bother trying them as well?
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by:rionroc
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Hello

OK, if you don't believe me.

Beacon Interval is the amount of time where data from ap/router to client wlan transmit, enable not to crash the ap/router.   You must change it.

Just Test it.
Off ap/router for 5 seconds after changing.



and you'll know soon.
http://wwr.wirelessroot.com



Great is our GOD.
:)
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by:Johnjces
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I do concur with rionroc.. try it. I did mention that, even though I disagree, it may work and be the nudge you need.

Anything trying in a unique wireless network is worth trying anything as one learns a lot be such experimentation, even though time is used, but also one may find a perfect solution to their unique problem.

John
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Johnjces earned 250 total points
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I don't know how that got scrambled...

Experimenting on one's unique wireless network, as long as changes can be undone, are worth doing. Trying extra APs, keeping channels separated by at least 5, i.e. one on channel 1 another on channel 6 the next on 11, may work. In your environment you may stumble upon that perfect solution and you learn!

I think that is better than what came out above!

John
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by:rionroc
rionroc earned 250 total points
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Hello

I assume you already channeled them to: 1, 4, 7, 10, (and if you have more than four channels to use),  to the far location of channel 1 to 10, loop it again and use channel 2, 5, 8, 11.

And for close area connections that uses 1 AP for so many WLAN Clients/Routers/AP Clients, apply my first comment, so that your AP will not crash.


Believed me or not, I'm the wireless system/network engineer in our area, up to this time our network are good and fine.
http://wwr.wirelessroot.com


Sorry if I got it wrong, but I'm just trying to reveal some wireless secrets, here for EE.


Great is our GOD.
:)
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by:AlexanderR
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Update:
Change beacon from 100 to 384.
Will attempt to install the other WAP this saturday.  So i gather each WAP should be on different channel and the clients will be able to select the closes ones without any conflicts?


Will see how this works throughout next week.
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by:Johnjces
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Yes. Keep the same SSID on all WAPs. Keep same channels as far apart physically as possible and try to separate channel spacings, by 5 chanels, I.E. 1,5, 11. The spacing that rionroc states would be just fine too.

John
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by:rionroc
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Hello

No!, not from 100 to 384, 256 to 384, or just stay at 256.

Yes, if you have small network using less channels, it would be good to use 1,5,11, just like Johnjces said.

If same problem arises again with the solutions provided, we'll think another.



Good Luck.

Great is our GOD.
:)
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by:Johnjces
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My apologies rionroc and AlexanderR!

My yes was to, "So each wap should be on a different channel..." Not about the beacon..

I am so sorry! Need to make certain that it is impossible for someone to read my mind!!!

John
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by:AlexanderR
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@rionroc
Sorry for being a little dense, but i do not understand the difference between changing
from 100 to 384 or 256 to 384.

There is only one text box in the advanced wireless tab labeled "beacon interval".  Default value is 100 so i changed it to 384 as suggested.  How is that a problem?
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by:rionroc
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Hello

I suggest to put 256, and its up to you to test until 384.


Great is our GOD.
:)
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by:Johnjces
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AlexanderR

Any results from your Saturday tests/changes?

John
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by:AlexanderR
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Sorry. Not yet.  due to the way i have it set up i could not just add another access point.  Technically i need to run another cable for the other locations, but i cannot due to some physical limitations (one going there now serving the wired clients, but not really an option to do another one for an AP).  I was thinking of splitting it (orange green for regular clients, blue brown for this AP) but thought against going through such an adventure until i know for sure.  For the time being i am going to merge wireless and cable networks again, so i can plug in the APs anywhere i want.

So that change of mind was a slow down.
I changed beacon interval and i THINK it drops out less but still does.  Somewhat hard to do statistics of this kind.

I also noticed a very strange phenomenon.  I just fixed my laptop and after it tries to connect to wireless, the whole wireless network drops out.  After i turn laptop off, network appears again after a while.

Another strange thing, is that there many, what appears to be ad-hock, networks flowing around with names like CJ-PC.  No clue where they are coming from.

Anyway, i will soon proceed into really putting in those APs (i started today, but ran out of time).
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by:rionroc
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Hello again AlexanderR


Possible link why wireless network drops are: using same ip address/mac address.

Possible link why many ad-hock networks coming because some other wireless clients connect as ad-hock to your pc/laptop.   Maybe your pc/laptop Soft-AP was enabled and that's one of the possible reason your network begins to drop.



Great is our GOD.
:)
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by:rionroc
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Ops!

Another reason why wireless network drops: using same SSID was configured.

:)
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by:Johnjces
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rionroc,

"Another reason why wireless network drops: using same SSID was configured."

For seamless roaming of a wireless clients, I believe that best practices are to keep the same SSID. Can you point me to some document somewhere regarding the same SSID and disconnects or arguments, pr or con?

John

(I love this forum. One can certainly learn a lot)!
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by:rionroc
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Hello John

I do believed of what your trying to say, but for the problem of alexanderR, he have to troubleshoot it basically step by step with different SSID first.  And if no trouble comes he may configure it the same if he want it to be.  But in my opinion I would not.

There are lot of ways to overcome the problem, enable to solve it, we must take a step basically in order to know where the problem starts and end.



Great is our GOD.
:)
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by:AlexanderR
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Just an update.
Managed to find some time today to merge wireless and cable on the same network (really didn't want to do that, but the only way i can plug the other APs anywhere i need).  I spaced the channels as far away as i could (4 APs total), same SSID on all to enable seemless roaming, and forgot to adjust beacon level on all of them to the same value. Will do that tomorrow.

Sorry for the wait, but i will need another few working days to collect info on any "changes" the members of the network experienced.   Unfortunatly this is not a problem that can be said "it works" or "it does not" on the spot.

Thank you for continuous responses.
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by:AlexanderR
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OK.
Experiment worked :D.
There have been NO wireless interuptions the entire week.  Compare that to having to reboot the router at least 4 times a day every day and hear everyone complain and we can call this case solved.

The only "problem" i have is that these linksys AP are so low end, that even if anyone of them knocks out, there is no way to tell, because of the redundancy of the others.  Actually thats a good thing, but i am a bit blind this way.  But thats OK.  I can just do a scheduled power cycle few times a week to make sure they are at their best.
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by:AlexanderR
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Thanks for sticking with this one.
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by:AlexanderR
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Actually the assist/accept was suppose to be reversed.  Wonder how it got scrambled.

But thank you both anyway!
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by:rionroc
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Hello

It's OK, the important thing is we've help you.



Great is our GOD.
:)
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