A Mac OS X system attached to a network is probably communicating on an Ethernet, which may in turn be linked to other local area networks (LANs) and wide area networks (WANs). Communication between LANs and WANs requires the use of gateways and routers. Gateways translate the local data into a format suitable for the WAN, and routers make decisions about the optimal routing of the data along the way. The most widely used network, by far, is the Internet.
Basic networking tools allow Mac OS X users to log in and run commands on remote systems (ssh, telnet) and copy files quickly from one system to another (scp, ftp/sftp). Many tools that were originally designed to support communication on a single-host computer (for example, finger and talk) have been extended to recognize network addresses, thus allowing users on different systems to interact with one another. Other features, such as the Network Filesystem (NFS), were created to extend the basic UNIX model and to simplify information sharing.
Concern is growing about our ability to protect the security and privacy of machines connected to networks and of data transmitted over networks. Toward this end, many new tools and protocols have been created: ssh, scp, HTTPS, IPv6, firewall hardware and software, VPN, and so on. Many of these tools take advantage of newer, more impenetrable encryption techniques. In addition, some weaker concepts, such as that of trusted hosts, and some tools, such as finger and rwho, are being discarded in the name of security.
Two major advantages of computer networks over other ways of connecting computers are that they enable systems to communicate at high speeds and that they require few physical interconnections (typically one per system, often on a shared cable). The Internet Protocol (IP), the universal language of the Internet, has made it possible for dissimilar computer systems around the world to communicate easily with one another. Technological advances continue to improve the performance of computer systems and the networks that link them.
One way to gather information on the Internet is via Usenet. Many Mac OS X users routinely read Usenet news (netnews) to learn about the latest resources available for their systems. Usenet news is organized into newsgroups that cover a wide range of topics, computer related and otherwise. To read Usenet news, you need to have access to a news server and the appropriate client software. Many modern mailers, such as Mozilla and Netscape, can display netnews.
The rapid increase of network communication speeds in recent years has encouraged the development of many new applications and services. The World Wide Web provides access to vast information stores on the Internet and makes extensive use of hypertext links to promote efficient searching through related documents. It adheres to the client/server model so pervasive in networking. Typically the WWW client is local to a site or is made available through an Internet service provider. WWW servers are responsible for providing the information requested by their many clients.
Safari is a WWW client program that has enormous popular appeal. Safari and other browsers use a GUI to give you access to text, picture, and audio information: Making extensive use of these hypermedia simplifies access to and enhances the presentation of information.