Final answer:
Application layer protocols in computer networks are categorized as those serving users directly and those providing utility services to the system. Utility services support the network's operations, management, and infrastructure.
Step-by-step explanation:
Application layer protocols are essential in managing the interactions between end-user software and network services. They fall into two categories:
- Protocols that provide services directly to users, such as HTTP for web browsing or SMTP for sending emails.
- Protocols that offer utility services to the system, which support the underlying operations of the networks themselves.
Since the question specifically asks for the part of the computer networking system that application layer utility protocols serve, the answer is system. This includes protocols that help network management, authentication, and directory services, among others. These protocols ensure that network resources are correctly managed and that services operate smoothly across the Internet, which has vastly expanded since its inception by researchers in partnership with the Department of Defense in the 1960s and 1970s.