What is the purpose of making the domain controller a global catalog server?

The purpose of making a domain controller a global catalog server is primarily to improve authentication speed. A global catalog server stores a partial replica of every object in the directory for all domains within the forest, along with the full attributes of those objects. When a user in one domain tries to authenticate against a domain controller in another domain, the global catalog can provide the necessary information to expedite the authentication process without needing to query each domain controller individually.

This efficiency not only reduces the time it takes to authenticate users but also streamlines the resolution of security identifiers (SIDs) and group memberships, which are critical for determining access rights within the network. The presence of a global catalog allows applications and services that rely on Active Directory to perform searches more quickly since they can access necessary data from a centralized point.

In contrast, the other options do not accurately reflect the primary function of a global catalog server; while they touch on significant aspects of network operations, they do not specifically address the core advantage of enhanced authentication speed that a global catalog server provides.