Summary
Now that you have completed this chapter, you should have a firm understanding of the following:

Networks are groups of interconnected computers. Local Area Networks (LANs) and Wide Area Networks (WANs) are two basic categories of networks. If computers are relatively close together and the networking equipment and cabling are owned by the organization, this is a LAN. WANs are created by interconnecting two or more geographically separate LANs. The links interconnecting the LANs are not typically owned by the organization. Routers are generally used to connect LANs to WANs.

The computers and networking equipment on both LANs and WANs are connected using various types of media including copper, fiber optic, and various forms of wireless communications.

Ethernet is the most common LAN architecture or technology. Other LAN technologies include Token Ring and FDDI. Switched Ethernet using an extended star topology is the dominant LAN technology being deployed today. Examples of WAN technologies include T1, Frame Relay, ISDN, and ATM.

The most popular data communications protocol is TCP/IP, which is actually a suite of protocols. The Internet and many LANs and WANs use the TCP/IP protocol. Several utilities are part of the TCP/IP protocol suite including: ping, telnet, rlogin and ftp.

The ping command is a low-level troubleshooting tool. Telnet can be used to take over the console of a remote host. Rlogin is used to login and run programs on another computer. FTP or File transfer Protocol is a very useful utility that can be used to transfer file between computers with dissimilar operating systems.

Client server architecture is a popular computing model used with the Internet. It is used to distribute or share processing loads when performing tasks. The server or backend runs software such as a daemon to provide services for client requests.

Sun developed NIS+ and NFS. NIS+ simplifies network administration by providing a centralized database for user account authorization. NFS provides for distributed processing by allowing a file system on a remote computer to appear as part of the local hosts file system.