Beginner SCIM questions

[sun...@hotmail.se]

Hi

I am reading up on SCIM and I have a few questions:

1. Is the SCIM server a replacement for Active Directory (or similar directories?) or is SCIM best positioned as a mirror of the main directory? or is the SCIM server just a wrapper/abstraction/REST-API for an underlying directory service like Active Directory?

2. Many talks about using SCIM to transfer/exchange identities between system, how is that "exchange" between system done? Does system A talk directly to the SCIM server at System B? or are there some intermediary client that extracts the data from System A and inserts it into SystemB? 

Are there any built in hooks or API-endpoints for allowing SCIM servers to talk directly to other SCIM services? or are there always a client in between orchestrating the exchange?

3. Are there any public test SCIM servers that I can use to explore SCIM further? or what is the easiest way to test an existing SCIM system? Like a Google or Salesforce API?  can anyone point me to what's the best way to start 

without having to install my own system?

Andy