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Load Balancing - Wireless

Hi

If I'm reading correctly Load Balancing is not advisable if using voice of wifi.

On a conroler with 70.220 - Wireless - Advanced - Load balancing

          Load balancing - client windows is default 5, max denial 3

But on the wlan, the load balancing isn't enabled..

Which one is the master setting?

We're boardcasting several SSIDs, one of them is a guest SSID, which is open, so we get the Apple devices autmaticaly associating to them.

So if we dont set the load balancing on each wlan, this means there is a msximum of 5 devices to 1 AP, doesn't matter which wlan it's on?

Is there a best practice guide for load balancing?

Clarrifaction would be great

Cheers


Craig

Everyone's tags (2)
7 REPLIES

Load Balancing - Wireless

Craig,

Do not use load balancing for latency-sensitive WLANs, especially voice WLANs. Rejecting voice clients extends their roaming delay and can drop calls.

The setting on the WLAN Advanced tab determines whether or not clients associating to that WLAN will be denied if the load balancing algorithm determines the AP to which the client wants to associate is too loaded (determined by the global LB settings). If you have the box unchecked, then LB is not in effect for that WLAN and clients on that WLAN will never be rejected.

The load balancing algorithm is run against clients for an AP. The count of clients is cumulative for all WLANs, i.e., the load balancing numbers are not set and comared on a per-WLAN basis. This wouldn't make a lot of sense as the LB algorithm is attempting to keep clients physically spread across infrastructure radio resources, regardless of whether you have 1 WLAN or 5 WLANs active on the radio.

I don't know of a best practices guidefor load balancing other than don't use it on WLANs that have low-latency applications such as voice or live-streaming (unbuffered) video. The controller configuration guide is a good place to start and does a pretty good job of explaining how it works.

One other thing I would recommend is to make the algorithm less aggressive. I think max 3 denials is too high and would drop to 1 or 2. I'd also open up the LB window size to about 8 or 10 instead of the default 5.

I think some folks on the forums here have found some issues with LB, although I haven't run into too many so far. I think the AP sends a message type 17 and some clients have trouble processing it (or something like that). You might want to search the forums here and check the bug toolkit to see if there's anything that comes up.

Justin

Re: Load Balancing - Wireless

Reason code 17 is sent from an ap that is at the limit of associations (a set condition). A client who honors this will ignore this access point and not consider it as an optional ap to roam to. Some clients ignore this code and will continue to send probe request and eventually, the WLC will let it on.

I dont know if anything has changed in code to change this behavior on the wlc's. But this was the case back when I tested.

__________________________________________________________________________________________ "Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin ___________________________________________________________
Silver

Load Balancing - Wireless

That's still the case and we should avoid load balancing like the plague!

Re: Load Balancing - Wireless

Blake,

Can you explain?

Justin

Silver

Re: Load Balancing - Wireless

It's just not a good idea when you think about, you are denying access to a client that feels it has a good reason to roam. Clients make the decision on what AP to connect to, when you are denying them access you could cause a lot more harm than good. I personally have never once had Cisco recommend that setting be enabled. Pretty much any connection (other than guest) could be considered a latency sensitive network these days. Plus with todays APs we are talking client counts in the 30's with acceptable connections, do we really need to load balance with todays designs?

Re: Load Balancing - Wireless

+5 Blake

__________________________________________________________________________________________ "Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin ___________________________________________________________
Hall of Fame Super Silver

Re: Load Balancing - Wireless

I agree!

Thanks,

Scott Fella

Sent from my iPhone

-Scott
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