I am having a discussion with a workmate regarding when and how many Wireless LAN controllers are needed when deploying an Enterprise WLAN. Is there a document or link that shows the best practices on when to deploy and how many Wireless LAN Controllers should be deployed based on the amount of APs, sites, branches etc.
I'm designing a WLAN for an organization that will have a central office and six remote sites within the WAN (bonded T1 connectivity). We will start out with 25 APs at each site. A Wireless Guest network will be configured so non-employees have the option to authenticate to the WLAN at each site. I have planned for a Wireless LAN Controller at each site to streamline the deployment of AP's now and in the future. My workmate is arguing that I should just use two Wireless LAN Controllers and position these at the central office and all AP's will be centrally managed by these two controllers. My thought on this is that if all my sites have their own networks/VLANs. Also, with the need for Guest access at each site, I would want a Wireless LAN Controller to facilitate this mobility option within each site's LAN.
Is there any documentation that I can consult for best practices on the deployement of Wireless LAN Controllers?