Final answer:
An intranet is a private network used by an organization like a college, protected from public access, contrary to the public Internet. An extranet extends intranet capabilities to trusted outsiders, and a perimeter network provides extra security between a LAN and the Internet.
Step-by-step explanation:
The network that is used exclusively by certain businesses such as colleges is known as an intranet. An intranet is a private network accessible only to an organization's staff. Often a wide range of information and services from the organization's internal IT systems are available on the intranet. Unlike the Internet, which is a public network, intranets are protected from unauthorized access with security measures such as firewalls.
Whereas an extranet is an extension of an intranet that allows secure communications to users outside of the organization, like suppliers or partners, but not to the general public. Perimeter networks, also known as demilitarized zones (DMZs), are small networks set up separately from a company's private LAN and the internet to provide an additional layer of security.