Reaching Beyond the Local-Area Network--the Wide-Area Network

As your network continues to function successfully, users may need to access information available from other companies, institutes of higher learning, and other organizations not on your LAN. To obtain this information, they may need to communicate over a wide-area network (WAN), a network that covers a potentially vast geographic area and uses network media such as leased data or telephone lines, X.25, and ISDN services.

A prime example of a WAN is the Internet, the global public network that is the successor to the WANs for which TCP/IP was originally developed. Other examples of WANs are enterprise networks, linking the separate offices of a single corporation into one network spanning an entire country, or perhaps an entire continent. It is entirely possible for your organization to construct its own WAN.

As network administrator, you may have to provide access to WANs to the users on your local net. Within the TCP/IP and UNIX community, the most commonly used public network has been the Internet. Information about directly connecting to the Internet is outside the scope of this book. You can find many helpful books on this subject in a computer bookstore.

Security

Connecting a LAN to a WAN poses some security risks. You must make sure your network is protected from unauthorized use, and control access to data and resources. An overview of security issues is provided in the System Administration Guide. Further help can be found in Firewalls and Internet Security by William R. Cheswick and Steven M Bellovin (Addison Wesley, 1994).

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