WIDE AREA NETWORK AND INTERNET CONCEPTS

WIDE AREA NETWORK AND INTERNET CONCEPTS

Wide Area Network Concepts

A wide area network (WAN) is very similar in concept to a widely distributed client/server LAN. In a wide area network, some distances typically separate computers. A typical WAN is a local city- or countywide network, like the one in the following figure. This network links network members together through a Bulletin
Board Service (BBS). Users can access the bulletin board’s server with a simple telephone call.

A Country-Wide Network

Several types of communication systems connect WANs together. These communication paths are referred to as links. In some areas, high-speed intermediate-sized networks, referred to as Metropolitan Area Networks (MANs), are coming up. These networks typically cover areas up to 30 miles or 50 kilometers in diameter and are operated to provide access to regional resources. They are like LANs in speed and operation, but use special high-speed connections and protocols to increase the geographic span of the network, like a WAN.

Internet Concepts

The most famous WAN is the Internet. The Internet is actually a network of networks, working together. The main communication path for the Internet is a series of networks, established by the U.S. government, to link supercomputers together at key research sites. This pathway is referred to as the backbone and is affiliated with the National Science Foundation (NSF). Since the original backbone was established, the Internet has expanded around the world. It offers access to computer users in every part of the globe.

The TCP/IP protocol divides the transmission into packets of information, suitable for retransmission across the Internet. Along the way, the information passes through different networks that are organized at different levels. Depending on the routing scheme, the packets may move through the Internet using different routes to reach the intended address. At the destination, the packets are reassembled into the original transmission.
The packets movement around the Internet is shown in the following figure.

Data Packet Moving Through Internet

As a message moves from the originating address to its destination, it may pass through LANs, mid-level networks, routers, repeaters, hubs, bridges, and gateways.
A mid-level network is simply another network that does not require an Internet connection to carry out communications.
A router receives messages, amplifies them, and retransmits them to prevent the messages from deteriorating as they travel.
Hubs are used to link networks together, so that nodes within them can communicate with each other.
Bridges connect networks together, so that data can pass through them as it moves from one network to the next. A special type of bridge, called a gateway translates messages as they pass through, so that they can be used on different types of networks, such as Apple
networks and PC networks.