Page 1 : autonomous computing deer, COMPUTER SCIENCE WITH PYTHON, so as to exchange Informai, 370, 11.2, COMPUTER NETWORKS - AN INTRODUCTION, Two or more autonomous' computing devices connected to, one another in order to exchange information or share, resources, form a computer network. For example, if in your, home, you can connect your smartphone, your laptop with your, smart TV, gaming console and a printer simultaneously either, using cables or through WiFi, it will be termed as a Computer, Network., 1, COMPUTER NETWO, computer, collection, network, of interconne, share resources,, Figure 11.1 shows a sample computer network., Broadband, modem, (to internet, connection), Computer 1, Ethernet or, USB cable, Ethernet, Wi-Fi, cable, WIFI, router, Computer 2, Printers, Ethernet, cable, Entertainment, consoles, Computer 3, Disadvantages of Networks, Advantages of Networks, * If software and files are, held centrally, it mày be, to run. This can add to costs impossible to carry out, any work if the central, server fails. People become, reliant on the communications,, if these fall, it can cause havoc, * The systems are more, sophisticated and complex, * Share resources : such, as printers and scanners., This is cheaper than, buying equipment for, each computer., * Can share software :, Software can be installed, centrally rather than on, each machine. Metering, software can then be used, to limit the number of copies, being run at any one time., This is much cheaper than, buying licenses for every, machine., and you may need specialist, staff to run the network., * If networks are badly, managed, services can, become unusable and, productivity falls., * File security is more, important especialy if, connected to WANS eg., protection from viruses., * Improve communications, Messages can be sent -, * Share storage being, able to access files from, any machines on the network e.g., internal email ., can share data., Figure 11.1 (a) A sample computer network. (b) Advantages and disadvantages of computer netwDR, Computer networks are very useful in many ways. They, facilitate resource, sharing (resources such as storage,, NOTE, software etc. on the network can be shared), enhanced, communication (communicating with devices on a, network is easier), cost reduction (resource sharing cuts, on costs) and so forth. Figure 11.1(b) shows some, advantages and disadvantages of computer networks., Please note thar now omrer,, Fuserthe terms computeb.net, network interchange by, 1. It means that no computing device on a network can start, stop.or ctroLother device()., Scanned mth Camscanner

Page 2 : components that together make a network. We are briefly discussing below, the major, 371, Merely by joining two computers with a cable won't form a network. In fact, there are many, components of a computer network., Major components of a Computer Networks are :, ie) Hosts/Nodes (such as PC, laptops, smartphones etc.), (b) Servers, (c) Client, ) Network hardware (such as NIC, router, switch, hub etc.), ) Communication channel (such as cables, radio-links etc.), () Software (such as protocols, network operating system etc.), 1e) Network services (such as BNS, File-sharing etc.)., Let us talk about these, briefly., aii, (a) Host or Nodes. The term host or node refers to the, computers that are attached to a network and are seeking to, share the resources of the network. Of course, if there were, NOTE, A computer becomes a workstation, of a network as soon as it is, no nodes (also called workstations), there would be no, attached to a network., network at all., So your PCs, laptops, smartphones etc. when connect to a, network become hosts., SERVER, (b) Server. A Server is a very important computer in a, network. A server is responsible for making the networking, tasks happen. In other words, a server facilitates networking, tasks like sharing of data, resource-sharing, communication, Server A computer that facilitates, the sharing of data, software, and, hardware resources (e.g., printers,, modems etc.) on the network, is, termed as a Server., emong hosts etc., On small networks, sometimes, all the shareable stuff (like files, data, software etc.) is stored on, the server. A network can have more than one server also. Each server has a unique name on the, network and all users of network identify the server by its unique name., On big networks, there can be servers dedicated to specialized tasks e.g., a file server only, handles files' related requests ; a printer server only handles printing requests and so on., (c) Clients. Client is a related term. A client computer is a host computer that requests for, Some services from a server, In other words, a server computer serves the requests of client, computers., (d) Network Hardware. Other than hosts and wiring, a network requires specialized, hardware to carry out various roles, such as establishing corrections, controlling network traffic, etc There are many different types of hardware that are required in a network. Some examples, of network hardware are :, > NIC (Network Interface Unit). It is a network.card attached to a host so as to establish, network connections., Hub, switch, router. These are connectivity devices., many others., Sorned mth Camscanner

Page 3 : () Software. The software layers of a network make networking possible. These compris, (8) Network Services. These refer to the applications that provide different functionalitis, A network operating system is a specialized operating system that can handle networking tasks, A protocol refers to a pre-decided set of rules using which all parties of a network connect an:, another through unguided media like radio waves, satellite etc., it is called a wirele, another through guided media like network cables, it is called a wired communitali, in resource sharing. The hardware as weil'as software resources are shared hroush LANS, instance, LAN users can share data, information program5 printers hard disks hodens, factory) are known as Local Area Netoorks (LANSE The key pirpose of a LAN is fo serveint, COMPUTER SCIENCE WITH Prlit, 372, can either be wired or wireless:, with, channel/medium. Examples of wired communication media are., coaxial cables, firbre-optic cables., twisted-pair, cable, with, are, Microwaves, radio waves, satellites, infrared waves, laser etc., of network protocols, network operating system etc., interact with one another., IP) and, over a network, such as DNS (Domain Name System), File sharing, VolIP (Voice over, many more., Armed with this basic knowledge of computer networks, let us further our discussion, talking about types of networks., 11.3 TYPES OF NETWORKS, A computer network means a group of 'networked' computers i.e., computers that are linke, by means of a communication system. A network can mean a small group of linked, computers to a chain of a few hundred computers of different types (e.g., PCs, mimi, mainframes etc.) spread around the world. Thus, networks vary in size, complexity, geographical spread., haat, Let us discuss types of networks based on these parameters., 11.3.1 Types of Networks based on Geographical Spread, Based on network span or geographical spread, networks can be divided into, types :, (i) LAN (Local Area Network), (ii) WAN (Wide Area Network)., 11.3.1A Local Area Network (LAN, Small computer networks that are confined to a ocalised area (ea0 oh, are, Fig. 11.1(a) shows a Local Area Network, Scarned mith CamScanner

Page 4 : server are called workstations. On most LANS, cables are, attached to the network. Computers connected to the, used to connect the network interface cards3 in each, 3. The network interface card (NIC) provides the physical connection between the hetwork and the computer vozkstation., provides telecommunications services to the ndole., 373, NOTE, Traditionally, LANS are said to have, geographical spread of upto 1 km., computer., Figure 11.1(a) that, you, have, seen earlier shows a LAN., The networks spread across countries or on a very big geographical area are known as WANS., A Wide Area Network (WAN) is a group of computers that are separated by large distances and, tied together. It can even be a group of LANS that are spread across several locations and, connected together to look like one big LAN. The WANS link computers to facilitate fast and, efficient exchange of information at lesser costs and higher speeds., Computers connected to a wide-area network are often connected through public networks,, such as the telephone system. Sometimes they can be connected through leased lines or, satellites. The largest WAN in existence is the Internet., Figure 11.2 shows, you a LAN and a WAN., LAN, Site office, LAN, LAN, WAN, LAN, Reglonal, office, Eastern, states office, Head office, Head office, Figure 11.2 LAN vs. WAN., NOTE, There has been traditionally another type of networks -, MAN (Metropolitan Area Network), which refers to a, network that is spread over an area as big as a city. But, these days, this term has become redundant., The Internet is a giant WAN, The weais, also a WAN, Please note thất Web,, World Wide Webl is a part of the, Internet, not the complete lntermet., ver iş a computer that just serves the requests of doing some tasks, made by other commuters in its network.A file server, es the requests related to file sharing, storing etc A print server serves the orinter related requests, and so on, une is a permanent telephone conection between two ponssern by a goverament reglared organizanian that, Sonned mth Camanner, padhaay

Page 5 : by clearly designating servers and chents Snch networks aare called client-server nefmad., Unlike peer-to-peer networks, bigger networks prefer to have dentralized control Ihere, Another parameter based on which you can classify networks is the role played by netwG, computers in the network operation. On the basis of this, there can be two types of compue, COMPUTER SCIENCE WITH F(TH, 374, | able 11.1 LAN vs. WAN, WAN, LAN, S.No., It is spread over a very large, area., 1., It is spread over a small area., It costs higher to set it up., 2., It usually costs less to set it up., It is usually a network of, many networks., 3., It is usually a single network., 11.3.2 Types of Networks by Component Roles, networks :, (i) Peer to Peer networks, (ii) Client/Server Networks., Let us talk about these network types one by one., 11.3.2A Peer-to-Peer (P2P) Networks, Peer refers to someone with equal standing, e.g., look at these example sentences:, The staff is trained by peers., Peer group of children is really important., The peer-to-peer network literally implements the meaning of the word 'peer, ie, a, computer on a peer-to-peer network is equal. That is, each computer can play the role of adie, or a server. In other words, there is no computer designated as in charge of network operaie, Each computer controls its own information and plays role of either a client or a ser, depending upon what is needed at that point of time., adhaai, The computers that serve on a peer-to-peer computer are often termed as non-dedicated series, On small networks, a workstation that can double up as a, server, is known as non-dedicated server since it is not, completely dedicated to the cause of serving. Such servers, can facilitate the resource-sharing among work-stations on a, proportionately smaller scale. Since one computer works as, a workstation as well as a server, it is slower and requires, more memory. Recall that the (small) networks using such, a server are known as PEER TO-PEER networks., NOTE, Peer-to-peet networks are pop, home networks and for use i, 100mpanies as they are neder, easy to install but they ae, SCope and are dificult to sa, Typically a peer-to-peer network has upto ten computers (an accepted m, 11.3.2B The Client-Server Networks, even master-slave networks, Sorned mth Camscanner