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Gents, At present we are having deep & scary conversations in the office ref to .11n APs on a cisco 4402 controller. This has 2gig ports & we are going to be trying to put 12 N aps on it my concern is this creates a bottleneck!!! Am i right? This may become even more relevant when N clients are actually on the network as well.

Any advice welcome

Hehehe, you are "mathing" yourself to death on this one probably. You are taking some numbers, doing some math then doing a comparison which indicates you have a problem.

Rather than 'mathing' yourself to death, do this instead. Find out how much traffic you have aggregrate for the entire wiring closet (uplink). Find out how much wireless traffic you have right now (per AP and uplink). Determine what type of growth you can expect for both wired and wireless. Determine your actually throughput you can expect for your WLAN radio (11n radio) which can vary as you add users, by manufacturer, packet size, etc.

What I think you will find is you never (or rarely) have enough traffic to fill you current pipe(s). So the 'mathing' you are doing is theoretical maximum but isn't a realistic situation for you. Since most wired ports are oversubscribed to some degree, you can do the same with wireless.

I've had WLAN vendors make huge presentations completely built around the fact that their product can handle 11n at wirespeed while no one else can. We had already done some research to indicate our current traffic flow and it turns out we won't fill up a 100mb pipe from the AP to switch. Turns out their solution didn't solve any problems we were having. It's extremely likely most people don't really need gig ports for their 11n 5ghz APs since they won't use over 100mb of RF traffic anyway.

Just some food for thought.