I have an heterogeneous system in my office with different OS and they change rapidly. I was looking for a solution to get authentication in a distributed way like OpenID so I can login machine_A using user@machine_B, is not important to get authorization and accounting globally distributed only authorization matters, and LDAP is too big for my needs. cheers
I have a few customers who have Small Business Server with just 2 people, so you are not too small for LDAP.
Windows SBS (or Foundation server once it arrives in the next few months) would be fine otherwise any Linux or Mac server will provide Kerberos & LDAP for what you need.
Check out OS X Server's Open Directory. it'll authenticate Macs, Linux and Windows (via a NT4 style domain, but it works). More importantly, it's just a bunch of easy clicky buttons to set everything up; very little in the way of difficult configuration is necessary to get it going. It does tend to be a bit of a black box when anything goes wrong, but is rather stable and so that doesn't happen terribly often. The only thing is it doesn't scale all that well over remote links; so if you have WAN connections in the middle of some of your users you probably want to look elsewhere.