CISSP For Dummies

Data networks are generally classified as local area networks (LANs) and wide area networks (WANs). You should understand the fundamental distinctions between these two types of network classifications.

Local area network (LAN)

A local area network (LAN) is a data network that operates across a relatively small geographic area, such as a single building or floor. A LAN connects workstations, servers, printers, and other devices so that network resources, such as files and e-mail, can be shared. A few variations of basic LANs include

• Campus area network (CAN): A network that connects multiple buildings across a high-performance backbone.

• Metropolitan area network (MAN): A network that extends across a large area, such as a small city.

• Wireless local area network (WLAN): A wireless LAN using 802.11 technology. Also known as WiFi.

 Instant Answer   A local area network (LAN) is a data network that operates across a relatively small geographic area.

See the upcoming section “The OSI Reference Model” for a discussion of the LAN function at the Physical and Data Link layers of the OSI Reference Model.

Wide area network (WAN)

A wide area network (WAN) connects multiple LANs and other WANs by using telecommunications devices and facilities to form an internetwork.

 Instant Answer   A wide area network (WAN) is a data network that operates across a relatively large geographic area.

Examples of WANs include

• Internet: The Mother of all WANs, the Internet is the global network of public networks originally developed by the U.S. Department of Defense (DoD) Advanced Research Projects Agency (ARPA). Users and systems connect to the Internet via Internet Service Providers (ISPs).

• Intranet: An intranet can be thought of as a private Internet. An intranet typically uses Web-based technologies to disseminate company information that’s available only to authorized users on the company network.

• Extranet: An extranet extends the basic concept of an intranet to include partners, vendors, or other related parties. For example, an automobile manufacturer may operate an extranet that connects networks belonging to parts manufacturers, distributors, and dealerships. Extranets are commonly operated across the Internet by using a Virtual Private Network (VPN), which we discuss later in this chapter, in the section “Virtual Private Networks (VPNs),” or other secure connection.

See the next section for a discussion on the WAN function at the Physical, Data Link, and Network layers of the OSI Reference Model.