Computer Networks PDF

3. COMPUTER NETWORKS Introduction A computer network is a group of computer systems and other computing hardware devices that are linked together through communication channels. It facilitates communication and resource- sharing among a wide range of users by a stan...

3. COMPUTER NETWORKS Introduction A computer network is a group of computer systems and other computing hardware devices that are linked together through communication channels. It facilitates communication and resource- sharing among a wide range of users by a standard protocol. It is an interconnected collection of autonomous computers that shares the resources. A network may contain two or more computers and other devices such as printers, scanner etc. Advantages of computer network ▪ It shares resources ▪ High reliability ▪ Exchange of information ▪ Access to files and data of different computers ▪ Reduces the cost ▪ Saves memory Components of network Page 20 of 33 A network consists of various resources like hardware and software. The hardware components may include server, node, NIC, Modem, Switch/Hub etc. Let us discuss these components briefly. Page 21 of 33 Server A server is the main computer in the networking system. It is simply a computer with higher configuration that delivers information and software to other computers that are linked to it by a network either through cables or wirelessly through a router. It holds the control of all the resources and software that are to be shared among all the users of the network. Server Requirements ▪ Multi core processors ▪ Faster RAM memories ▪ Multiple hard disks for storing volume of data with backup ▪ Server based operating systems like windows server 2022 ▪ Switch/hub to connect with multiple computers ▪ Internet connection Servers are classified as dedicated server and non-dedicated server based on the way how it is being used in the network environment. Node or Clients Any system or device connected to a network is called as node or client. For example, if a network connects a file server, five computers, and two printers, there are eight nodes on the network. Each device on the network has a network address which uniquely identifies each device. Page 22 of 33 Network Interface Card (NIC) A network is made up of various components. A Network Interface Card (NIC), is also known as an Ethernet card or Network Adapter. It allows connecting a computer with other devices such as Laptop, Server, Mobile, Desktop etc. via Ethernet cable. It is essential in network setup to allow the resources to communicate and share the information. Connectors A connector is a device that helps to connect various components like hub, switch and server with a computer through guided media (cables). Page 23 of 33 Switch/Hub A switch or hub is used to as a networking device to connect various devices into a network. A hub is a networking device that allows various computers/PCs and other devices to connect to a single network. A hub has many ports, and a computer that wants to connect to the network plugs into one of them. A switch is a networking device that connects multiple devices on a single computer network but it is more intelligent than hub. Cables These are simply called as wire and it is used to connect various devices in a network. These cables are used to transfer data between the devices. Cables are classified into various categories depending upon their physical structure and it uses. Some of the types are coaxial cables, twisted pairs, fiber optical fibers, patch cables, data cables etc. Other Resources A networking system contains various resources like printer, disks, scanner, memory etc for the access by the programs. These devices can Page 24 of 33 be shared for the group of computers connected in the network for effective utilization. Types of network Computer networks are classified into several categories depending upon the communication requirements, geographical area and the hardware used in the network. The major types of network is given below Page 25 of 33 Personal Area Network (PAN) A PAN network interconnects various devices within the short range of around 10 meters for a personal use. It is typically used for home or small office. It can transfer data through wireless or wired medium. Some of the devices that can be used in PAN are laptops, smart phones, tablets, wearables, printers and entertainment devices etc. Page 26 of 33 LAN A LAN is a Local Area Network, interconnecting large number of computers and other resources in a limited geographical area say within 1 km. Normally LANs are implemented in a single building or in a campus of an organization. It is generally used in colleges, Schools, research organizations, offices etc. In LAN system, nodes are connected to server via cables. MAN A MAN is a Metropolitan Area Network that connects different LANs in a particular city or town. It covers about few hundred kilometers which is smaller than WAN. These type of networks are used in telephone companies, cable TV, internet providers or organizations with offices in multiple locations. WAN A WAN is a Wide Area Network meant for digital communication system which interconnects different sites, computer installations and user terminals. It may also enable LANs to communicate with each other. A Page 27 of 33  WAN is also known as Long Area Network. It may cover the whole country or the world. Internet is an example for WAN. Difference between LAN & WAN S.No LAN WAN 1. Interconnection within small Interconnection of LAN & MAN area like building i.e. Country or world. 2. Data transfer rate is high. Data transfer rate is slow 3. Generally co-axial cables or Links are provided using fibre optic are used to telephone lines or microwave connect the LAN. towers or satellites. 4. Minimum errors in data Due to long distance and short transmission circuit errors, noise errors are higher. 5. Star or Ring topology can be Hybrid topology is used provoked. 6. Cost is less. Cost is high. 7. Number of nodes are limited Many nodes can be connected 8. It follows digital network It uses both digital and analog signal Internet Interconnection of networks is called as internet ie., network of networks. The term internet (small ‘i’) refers to large network made up of small network and Internet (capital ‘I’) refers global network. Global Internet comprises of millions of web pages, e-mails, servers etc. Internet was originally developed for U.S military and then later it was extended for educational and research purpose and finally the network was extended for the whole world. Network topology Page 28 of 33 It is an arrangement of computers, server and various components of a network in a particular order; here the arrangement refers to physical and logical arrangement of devices. It is a layout of networks in which the admin can easily locate the nodes and helps for data transmission. Some of the network topologies are given below. BUS Topology It is a simple topology in which all the computers and other devices in the network are connected along a single cable that runs from one end to other. The drawback of this topology is it uses only one cable for data transmission and if the cable breaks, the whole network cannot function. STAR Topology Page 29 of 33 In this layout, all the nodes are connected to a central server in star pattern. Each and every node is directly connected to the switch/hub and then to the server. All cables run to a central connection point. If one cable breaks or fails, only the computer that is connected to that cable is unable to use the network. This is the most widely used topology in LAN type of computer network. Ring Topology A ring topology connects the nodes in a circular path in which each computer will have direct connection with two computers. The data flows in a circular path, if first computer wants to send data to 5th computer in a ring topology, then it has to cross 2 through 4 to reach 5. The major disadvantage of a ring topology is that if any individual connection in the ring is broken, the entire network is affected. Hybrid Topology It is a combination of one or more topologies such as bus, ring, star etc. It is very effective and flexible. Network can be altered by adding or Page 30 of 33 removing the nodes easily. The main drawback of this topology is that it is expensive and the design is difficult. Network operating systems A Network Operating System (NOS) is an operating system meant for the workstations or networks in which multiple nodes, server and other devices are connected through guided or wireless media. It manages data of various computers or servers in a secured manner and shares it with the permitted users. It helps to share various resources and files. Some of the Network Operating Systems are as follows Microsoft Windows Server: It is the most common NOS available in market. It is extremely powerful and takes care of every aspect of network. The latest version is Windows Server 2022. UNIX Operating System: was first developed by AT&T Corporation’s Bell Laboratories in the late 1960s. The UNIX operating system is simple, multi-tasking, multi-user, portable and stable that is used for web servers, laptops, and desktop computers. LINUX Operating System: Linux is one of the most popular and open source operating system that is used in mobile phones, routers, super Page 31 of 33 computers, mainframe computers, and server applications. The Linux Operating System is free and its source code is available to use. Novell NetWare: It was a powerful network operating system that offers essential features like user management, file sharing, and data security. It was discontinued and not available in the market. EXERCISE A. Multiple Choice Questions 1. Which of the following is not a feature of network? a. shares resources b. exchange of information c. requires no operating system d. reduces the cost 2. Full form of NIC in network is a. Network Interface Card b. National Informatics Centre c. Network Initiative Card d. Network Internal Computer 3. Which of the following device is used for connecting computers to a network? a. Printer b. Scanner c. Mobile d. Switch 4. _______type of network is used to cover the entire world. a. PAN b. MAN c. LAN d. WAN 5. Which of the following refers to global network? a. Internet b. externet c. Intranet d. Extranet 6. Which of these is a combination of one or more topologies? a. Star b. Ring c. Hybrid d. Bus B. Give very short answer for the following 1. What do you mean by network? 2. Name any four components required for creating a network? 3. What is a node? 4. What is the purpose of connectors? 5. Which cable is fastest? 6. What do you mean by network topology? 7. Differentiate LAN and WAN. Page 32 of 33 C. Answer the following 1. Explain the types of computer networks. 2. How will you differentiate Intranet and Extranet? 3. What are the various operating systems available for networking? 4. Explain networking with a diagram. 5. Explain different topologies with suitable diagrams. Page 33 of 33