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	TYPES OF NETWORKS MAINFRAME Mainframe computers are typically large, metal boxed computers with large processing abilities. The terminals are called "dumb terminals" because they only send and receive data, leaving the processing to the mainframe. CLIENTS The client/server refers to the way two computer programs interact with each other. The client makes a request from the server, who then fulfills the request. Although this idea can be used on one computer it is an efficient way for a network of computers in different locations to interconnect. Local Area Network (LAN) The first LANs were created in the late 1970s. LANs are small networks constricted to a small area, like a city. LANs are used to share resources like storage, internet, et cetera. A 'node' on a LAN is a connected computer or device like a printer. Wide Area Network (WAN) WANs are very large networks that interconnect smaller LAN networks, for a large geographic area like a country (i. e., any network whose communications link crossmetropolitan, regional, or national boundaries.) WANs are usually for private companies, however, some built by internet service providers connect LANs to the internet. WAN can use a combination of satellites and microwaves, and can link a variety of computers from mainframes to terminals. A 'node' on a WAN is a LAN. Metro Area Network (MAN) Metropolitan area networks, or MANs, are large computer networks usually spanning a city. They typically use wireless infrastructure or Optical fiber connections to link their sites. When the LANs that you want to connect are not far apart, just blocks away, then you can make a MAN. The main difference between a WAN and a MAN network is the speed of the connection. Because the LANs are so close in a MAN, high speed fiberoptic cables are affordable. Campus area network (CAN) A Campus Area Network is a computer network made up of an interconnection of local area networks (LANs) within a limited geographical area. It can be considered one form of a metropolitan area network, specific to an academic setting. In the case of a university campus-based campus area network, the network is likely to link a variety of campus buildings including; academic departments, the university library and student residence halls. A campus area network is larger than a local area network but smaller than a wide area network (WAN). The main aim of a campus area network is to facilitate students accessing internet and university resources. Personal Area Network (PAN) A personal area network is a computer network used for communication among computer devices (including telephones and personal digital assistants) close to one person. The devices may or may not belong to the person in question. The reach of a PAN is typically a few meters. PANs can be used for communication among the personal devices themselves (intrapersonal communication), or for connecting to a higher level network and the Internet (an uplink). Home Area Network (HAN) The Home Area Network uses cable, wired, or wireless connections to connect a homes' digital devices. For example, fax machines, computers, DVD's etc. Garden Area Network (GAN) A Garden Area Network is a similar system and allows for one system to control such devices like garden lights, sprinkler systems and alarm systems. HARDWARE: Topologies bus All nodes are connected to a single wire or cable (the bus) which has two endpoints. Each communications device on the network transmits electronic messages to other devices. If some of those messages collide, the sending device will wait and then try to transmit again. The advantage of bus network is that it is can be organized as a peer-to-peer network or client/server network. It is also relatively inexpensive to install. The disadvantage is that if the bus network fails, the whole system network fails. The wider the bus the better! ring The ring network is a network in which all communications devices and microprocessors are connected in a continuous loop. Electronic messages pass around the ring until they reach the correct destination; there is no central server. The advantage of a ring network is that messages only flow in one direction. The disadvantage is that if a single connection is broken, the whole network stops working. The distributed star or tree topology can provide many of the advantages of the bus and the star topologies. It connects workstations to a central point, called a hub. This hub can support several workstations or hubs which, in turn, can support other workstations. Distributed star topologies can be easily adapted to the physical arrangement of the facility site. (Integrated Publishing) star A network that links all microcomputer and other communication devices through a central server. The advantages of this hub is that it prevents impact between messages. The network forms a star shape having the central server in the middle with a single branch outward, the branch will not branch to another device. Other Advantages Include: * Good performance. * Scalable, Easy to set up and to expand. * Any non-centralised failure will have very little effect on the network, whereas on a ring network it would all fail with one fault. * Easy to detect faults * Data Packets are sent quickly as they do not have to travel through any unnecessary nodes. * It is used for centralised control.