If you are looking for centralized authentication then Michael's recommendation is one of the better options. However, if you are looking for authorization controls then you will probably need to consider a provisioning tool. One that I looked at a while ago is developed and maintained by Unimax (http://www.unimax.com/). When I looked at it the CUCM hook-in was relatively new and immature, but that was well over 3 years ago. The other Unimax hooks have been pretty solid and I suspect that the CUCM integration has matured considerably.
Around the same time I was looking at a product from Digital Fairway which was very solid. We were going to buy it and deploy it for a 6 cluster/13,000 node system but were blocked due to an acquisition. It just so happens the company making the acquisition was Cisco Systems and I believe the technology acquired was incorporated into Cisco's Provisioning Manager (http://www.cisco.com/en/US/products/ps7125/tsd_products_support_series_home.html). Now, I haven't looked at Provisioning Manager for production deployment and can't attest on the multi-cluster support or the enforcement of authorization/accounting rules, but the Digital Fairway product/technology was really solid.
So, bottom line for authorization (and decent centralized accounting) would be a 3rd party application. I'd recommend doing a read through for Cisco's solution as well as the Unimax solution. Others in this forum may have more options for you.
HTH.
Regards,
Bill
