The devolved nature of IT provision within Oxford University means that there is no single central directory service for managing desktops. Instead departments and colleges run their own according to their requirements. Departments and Colleges running Active Directory generally install and run their own self-contained, single-domain Active Directory forest.
It is not compulsory to run one Active Directory forest per department, and there are some instances where several departments share a common Active Directory infrastructure. Although less common, this configuration is equally valid.