A computer network is a communication network that allows different devices or computer systems to share data and/or services among each other. A computer network may contain a minimum of two end-points. The largest computer network in existence is the internet which connects several billion end-points.
With the advent of such large networks, it was needed to split the networks into different segments for better management and ease of operations. To address this issue, network was re-defined into three major segments.
- 1. Local Area Network (LAN)
- 2. Metropolitan Area Network (MAN)
- 3. Wide Area Network (WAN)
The local area networks connect devices present in a limited premises such as a home, school, office, university or a factory. A metropolitan area network covers the devices which are installed in a premise larger than a normal home, office or a university campus. Examples of metropolitan area networks include a huge factory, industrial areas and inter-city networks.
Wide area network (WAN) is a type of computer network that spreads over a large physical area connecting one or more local area networks (LAN) together. The geographical area covered by a wide area network is significantly larger than the areas covered by a typical LAN or MAN. Internet is the largest wide area network. WAN consists of different components that combine together to form a wide area network.
- 1. Routers, Switches and Modems (Edge Device)
- 2. Connecting Media (Fiber, Wireless, Microwave or Satellite)
- 3. Customer Premises Equipment (CPE)
Figure 1 shows the basic layout of a wide area network.
WAN usually connects more than one local area networks together, a router or layer-3 switch or modem is used to connect the local area network to the WAN. The edge device advertises the details of the LAN that is connected to it so that the other edge devices know which network is behind a particular router. Similarly, the edge devices also receive the information from other edge devices regarding the networks connected to them.
The medium used for connecting the LANs to the WAN can be fiber optic cable or other wireless medium such as radio waves, microwaves or satellite connections. UTP cabling cannot be used as the size of WAN is significantly larger than the supported maximum by the UTP cables. WAN links can also use the ordinary copper PSTN networks for connectivity.
A customer premises equipment is installed at the end-customer’s home or office to provide the last-mile interface for WAN connection. For home and small offices, a CPE may be a low cost device which is usually provided by the service provider on easy installments or free of cost. Large enterprises and corporate offices use enterprise-grade routers or layer-3 switches as CPEs. Many large enterprises use their private WAN to connect between their different offices situated in several countries around the world.
A large public WAN may consist of hundreds and thousands of LANs, the data from origin to destination is guided by the help of routers installed on the edge of each LAN. These routers use the routing algorithms to guide the data packet correctly from its origin to its destination. Commonly used routing algorithms are RIP, OSPF and EIGRP etc.
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