I can find figures on the max number of AP's per HREAP group depending on controller model and WAN speed link. What about connected clients per HREAP group? When should a branch controller be used over a central controller using HREAP groups (based number of connected clients)? We are planning to use local authentication (branch RADIUS). Im guessing roaming will also influence this decision (CCKM OKC). This section in the "Flex 7500 Wireless Branch Controller Deployment Guide" mentions a scenario with client numbers that is not practical, what is the limit deemed practical (in terms of client numbers)?
CCKM/OKC Fast Roaming
H-REAP Groups are required for CCKM/OKC fast roaming to work with FlexConnect access points. Fast roaming is achieved by caching a derivative of the master key from a full EAP authentication so that a simple and secure key exchange can occur when a wireless client roams to a different access point. This feature prevents the need to perform a full RADIUS EAP authentication as the client roams from one access point to another. The FlexConnect access points need to obtain the CCKM/OKC cache information for all the clients that might associate so they can process it quickly instead of sending it back to the controller. If, for example, you have a controller with 300 access points and 100 clients that might associate, sending the CCKM/OKC cache for all 100 clients is not practical. If you create a H-REAP Group comprising a limited number of access points (for example, you create a group for four access points in a remote office), the clients roam only among those four access points, and the CCKM/OKC cache is distributed among those four access points only when the clients associate to one of them.