More concretely, it would involve (on the "master" side) :
- Setting up an LDAP directory, mostly for user authentication and NSS
- Setting up a DNS zone for the domain
- Generate a root CA, and a certificate for the master
- Generate a ssh authentication key pair
- Setting up a monitoring system
... etc
When a "client" is added to the "domain", it would involve :
- Adding the client in the domain's DNS zone
- Generate a certificate for this client, and send it to the client
- Make PAM and NSS on the client use the LDAP directory
- Install root's ssh public key in the client's authorized_keys file
- Install on the client any agent required by the monitoring service
... and so on