[offtopic] Architecture Question

[Laurent Michenaud]

Hi,
 
We have two tomcat servers.
One is located at our enterprise.
The other is located at our hosting provider.
They can see each other by Internet.
 
We would like to set up an unique authentification system for both
server.
The authentification system will be on the server at our entreprise.
The web applications on both servers will query the authentification
system.
 
What's the best/clean/nice way to do this ?
JAAS ? Web services ? SSL keys ?
 
 
Thanks