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chapter 3. Networks and Computer types
- 1. 1 BULE HORA UNIVERSITY Collageof Business and Economics Department of Business Administration and Information Systems Data Communication and Computer Networks
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- 3. 3 Computer Networks Anetwork is a set of devices (often referred to as nodes) connected by communication links to communicate data. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network.
- 4. 4 Types of Computernetworks Computer networks are classified based on various factors. They include: Geographical span -LAN, MAN and WAN Administration -Private network & public network Architecture-Client/Server & peer-to-peer A private network is used inside an organization.
- 5. 5 Types of Network-Geographical Span LAN A local area network (LAN) is usually privately owned and links the devices in a single office, building, or campus. LAN size is limited to a few kilometres. In the early 1980s, LANs might have consisted of a handful of computers connected in a peer-to-peer fashion. Today’s LANs are typically much larger and more complex client/server networks.
- 6. 6 MAN A metropolitanarea network (MAN) is a network with a size between a LAN and aWAN. It normally covers the area inside a town or a city. MAN-is A network that is larger than a LAN and connects clients and servers from multiple buildings. Because of the distance it covers, a MAN may use different transmission technology and media than a LAN.
- 7. 7 WAN A widearea network (WAN) provides long-distance transmission of data, image, audio, and video information over large geographic areas that may comprise a country, a continent, or even the whole world. The largest and most varied WAN in the world is the Internet.
- 8. 8 Types of Network-Architecture Computers can be positioned on a network in different ways relative to each other. They can have different levels of control over shared resources. They can also be made to communicate and share resources according to different schemes. The following sections describe two fundamental network models: peer-to-peer and client/server.
- 9. 9 Peer-to-Peer In apeer-to-peer network:- There are no dedicated servers. There is no hierarchy among the computers. All the computers are equal and therefore are known as peers. Each computer functions as both a client and a server. There is no administrator responsible for the entire network. The user at each computer determines what data on that computer is shared on the network.
- 10. 10 Peer-to-Peer Networks Thesimplest form of a network is a peer-to-peer network. In a peer-to-peer network, every computer can communicate directly with every other computer. By default, no computer on a peer-to-peer network has more authority than another. However, each computer can be configured to share only some of its resources and prevent access to other resources. Every computer is capable of sending and receiving information to and from every other computer.
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- 12. 12 Client/Server Networks Anetwork that uses a server to enable clients to share data, data storage space, and devices is known as a client/server network. Client—A computer on the network that requests resources or services from another computer on a network. Clients usually take the form of personal computers, also known as workstations. Every computer on a client/server network acts as a client or a server. Clients on a client/server network do not share their resources directly with each other, but rather use the server as an intermediary.
- 13. 13 Client/Server Networks Clientsand servers communicate through connectivity devices such as switches or routers. Server—A computer on the network that manages shared resources; servers usually have more processing power, memory, and hard disk space than clients. To function as a server, a computer must be running an NOS (network operating system). An NOS is a special type of software designed to do the following: Manage data and other resources for a number of clients. Ensure that only authorized users access the network.
- 14. 14 Client/Server Networks Restrictwhen and from where users can access the network. Dictate which rules computers will use to communicate. Supply applications to clients. Examples of NOS: UNIX and Linux, Microsoft Windows Server 2003 or Server 2008, and Mac OS X Server. (But, stand-alone computer, or a client computer, uses an operating system, such as Windows XP/7 or WindowsVista, which has more limited resource management capabilities.)
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- 16. 16 Client/Server In anenvironment with more than 10 users, a peer-to- peer will probably not be adequate. Therefore, most networks have/required dedicated servers. A dedicated server is one that functions only as a server and is not used as a client or workstation. Client requests the server to serve the requests. Specialized Servers Some of the examples of different types of servers included on many large networks.
- 17. 17 Specialized Servers 1-FileServers File servers offer services that allow network users to share files. 2- Print Servers Allow users to share printers Allow multiple and simultaneous access to printing facilities. 3- Database Servers Database server can provide a network with powerful database services. 4 -Application Servers Servers store vast amounts of data that is organized to make it easy to retrieve. An application server differs from a file server in that with file server the data or file is downloaded to the computer which making the request. With an application server, the database /file stays on the server and only the results of a request are downloaded to the computer which making the request.
- 18. 18 Specialized Servers 5-MailServers Mail servers - separate server and client applications. Data selectively downloaded from the server to the client. 6-Web Servers Stores different web pages. 7- Proxy Server A Proxy Server implements Internet connectivity and network security for an entire organization.
- 19. 19 Network Topologies Typesof Connection There are two possible types of connections: point-to-point and multipoint. Point-to-Point A point-to-point connection provides a dedicated link between two devices. The entire capacity of the link is reserved for transmission between those two devices. e.g connection b/n television and its remote control Multipoint A multipoint connection is one in which more than two specific devices share a single link.
- 20. 20 Physical Topology Thetopology of a network is the geometric representation of the relationship of all the links and linking devices (usually called nodes) to one another. The topology- is physical layout of a computer network. Topologies vary according to the needs of the organization, available hardware and expertise. There are five basic topologies possible: Bus Ring Star Mesh Hybrid
- 21. 21 Bus A bustopology is multipoint connection. One long cable acts as a backbone to link all the devices in a network.
- 22. 22 Bus Advantages Connecting acomputer or peripheral to a linear bus is easy. This topology requires least amount of cabling to connect the computers and therefore, less expensive. It is easy to extend a bus since two cables can be joined into longer cable with a connector. Disadvantages Entire network shuts down if there is a failure on the backbone. Heavy traffic can slow down a bus because computers on such networks do not coordinate.
- 23. 23 Ring In aring topology, each device has a dedicated point-to- point connection with only the two devices on either side of it.
- 24. 24 Ring Advantage Ring topologyis easy to install and reconfigure. Every computer is given equal access to the ring. Hence, no single computer can monopolize the network. Disadvantages Failure in any cable or node breaks the loop and can take down the entire network. Maximum ring length and number of nodes are limited.
- 25. 25 Star In astar topology, each device has a dedicated point- to-point link only to a central controller, usually called a hub. The devices are not directly linked to one another.
- 26. 26 Star Advantages ofStar Star topology is easy to install and wire. The network is not disrupted even if a node fails or is removed from the network. Fault detection and removal of faulty parts is easier in star topology. Disadvantages of Star It requires a longer length of cable. If the hub fails, nodes attached to it are disabled. The cost of the hub makes the network expensive as compared to bus and ring topology.
- 27. 27 Mesh In amesh topology, every device has a dedicated point-to-point link to every other device.
- 28. 28 Mesh Advantages ofMeshTopology The use of large number of links eliminates network congestion. If one link becomes unusable, it does not disable the entire system. Disadvantages of MeshTopology The amount of required cabling is very large. As every node is connected to the other, installation and reconfiguration is very difficult. The amount of hardware required in this type of topology can make it expensive to implement.
- 29. 29 Hybrid A networkstructure whose design contains more than one topology is said to be hybrid topology. Hybrid topology inherits merits and demerits of all the incorporating topologies.
- 30. 30 Types of Network,based on Ownership Private Network A private network is a network in which various restrictions are imposed to secure the network, to restrict unauthorized access. This type of network is privately owned by a single or group of people for their personal use. Local Area Network(LAN) can be used as a private network.
- 31. 31 Public Network Apublic network is a network that has the least or no restrictions on it. It can be freely accessed by anyone, without any restrictions. This type of network is publicly owned by the government or NGOs. Metropolitan Area Network(MAN) and Wide Area Network(WAN) can be used as a public network.
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