Slowness?

[Mark182]

I am placing this in the 'wireless' as it only happening on wireless clients. On site we have cisco aironet 1131 AP's and x 2 Cisco 4400 LAN controllers (I know we need to move on)

 

We are having a strange issue where on a laptops web browsing is really poor, going to youtube buffers really bad. Accessing shares is slow, I coped a 10meg file for a share to the local desktop and it took 2 mins 30 seconds. When I run a speed test on a desktop the speeds are as expected.

 

I've logged into the LAN controllers and everything seems fine, nothing alarming. I am unsure what to look at next, any help would greatly be appreciated.

 

The LAN controllers are plugged into our core (3760's)

[Duke5A]

Oh wow, I feel your pain! That is the backbone of my wireless network right there. With no funding in sight I've taken to purchasing 2960S switches and 1142 access points off of eBay. The 4404 controllers will support those access points and it at least gets you 802.11n at 300Mb.

 

How many devices are associated to your access points when things are mind numbingly slow? Anything over 20 and performance drops like a lead sinker after that. If you haven't done so yet, disable all the 802.11b data rates on the controller. This greatly increased speed for us when it was done.

[RobD]

Just to add to what @Duke5A said what speeds are your clients getting and what can they potentially get i.e. do they have AC cards in and is AC supported on the APs?

 

Also on the 2500 wireless controllers you can set QoS polices, if you can on the 4400s then maybe create a new SSID, set it and compare.

[Mark182]

Thanks for the replies, it's our last day today so I will have a look when we get back.

[Simcfc73]

I've just been rolling out the cumulative update to some laptops and one gets 3mb/s the one next to it gets 45kb/s.... both on the same channels, both on the same hardware and chipset and only 2 connected to the AP.

 

Hate WIFI

[AlanD]

...and it at least gets you 802.11n at 300Mb......... Anything over 20 and performance drops like a lead sinker after that.

 

802.11n gets you a UDP connection rate of 300mb/s (..well with 2 stream....450mb/s with 3 streams...but you would need clients with 3 stream support). This is not the same a wired speed measurement of 300mb/s which is fully duplex..and its the speed to ALL of your clients from the access point not to EACH and every client at the same time. Think more like half that say - 150mb/s in terms of wireless traffic speed for comparison with wired with a single client.

 

So it should be no surprise that large numbers of clients have a pretty detrimental throughput on wireless.. Yes an access point "support" 100 connections - or several hundred - but don't expect to get useful data rates to these clients at the same time - because the collision domain - as you point out - gets to be pretty chaotic when you have over 20 clients. I have seen 60 clients playing video clips (around 2 to 3 mb/s each) but that's about your limit...and for various reasons in most high density school environments it doesn't get much better even with the latest "ac" wave 2 stuff because you won't be able to deploy 80 or 160MHz wide channels in blocks of classrooms. (Great for home use though..)

 

Access points that support 5Ghz of course give you a significant gain - because there are lots more channels - and you can use wider 40Mhz channels.....and can therefore deploy more access points in the same building without worrying about co-channel interference....but you will need access points in the same room - and ceiling mounted because 3 to 4 m or so in unrestricted space is the maximum range before all those higher QAM rates start to fall away. And yes - there are senarios where you might not need an AP in every room - especially if its surrounded by rooms clients can connect to several access points from.

 

I am guessing - that your two neighbouring clients with wildly different data rates - may be because they don't even support "n"....or maybe you have Bluetooth stuff nearby (which uses exactly the same 2.4GHz band)...