A perimeter network, also called a DMZ, is the area that is between the Internet and an intranet that hosts the Internet which is accessible from servers. Perimeter networks provide protection for the Internet-facing servers and separate the servers from the internal network. In perimeter networks, servers are available from everyone on the Internet, although this network provides protection. Due to this protection, perimeter networks are indeed safer than the basic Internet, however not as secure and Intranets. One advantage of a perimeter network is the ability to use 2 separate vendors, such as different firewalls; having 2 firewalls from different manufactures further prevents the likelihood of security risks.
Intranets, also called LANs, are private networks that use TCP/IP protocols to distribute and share resources within the network. The intranet is the most secure network security zone for clients on the internal network. Administrators can also control these computers connected on the Intranet and add additional layers of security. Intranets use private IP addresses, whereas public IP addresses are used on the regular Internet. To help communication between these 2, NAT (Network Address Translation) is used. Intranet applications generally involve any software that is used on the Intranet, such as Internet browsers and instant messengers.
Perimeter networks are not under the user’s control, therefore do not offer as strong of security as in Intranets. Generally, perimeter networks are created to place firewalls between them and the outside world and also to separate one type of network traffic from another. While this is useful, Intranets provide the best security due to only allowing certain users to connect to it. Intranets can also be less expensive to create and manage than private networks. Using a combination of Perimeter and Intranet networks is ideal for forming multiple layers of security in a network as well as extending its functionality.
Gibson, Darril. (2011). Microsoft Windows Networking Essentials (Exam 98-366). Sybex.