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Unit1: Introduction to Networks
1.1 Learning Objectives: After successful completion of this unit, you will be able to: Individually understand basics of computer network technology. Understand the need for computer networks Understand various applications of computer network Understand the use of different components of computer network Understand different network benefits Understand different classifications of computer network Classify the network by its components and roles
1.2 Introduction to Computer Networks: The combining of computers and communications has a great impact on the way computer systems are organized. The old model of standalone computers working for the whole organizations need has been replaced by one in which the large no of separate but interconnected computers does the job. These interconnected systems are called as a computer network. Nowadays the Computer Networks have changed the way of business and the other daily business works. Today most of the Governmental Organizations, Business Enterprises, Educational Institutions and individuals rely on computer networks and internetwork.
1.2.1 Fundamentals of Computer Network (Definition): Communication is the process in which two or more computers or other devices transfer’s data and instructions, share information and resources. A group of two of more computers that shares services and interacting in some manner is known as Computer Network. This interaction is, accomplished through a shared communication link, with the shared components being data. A network is a collection of machines those are linked both physically and through software components to facilitate communication and the sharing of information. A network is a set of devices often mentioned as nodes connected by media link. A node can be a device which is able to send or receive data generated by other nodes on the network, for e.g. a computer, printer etc. These links connecting the devices are called Communication channels. A computer network is a communication channel used to share data or information. It is also called data network. The best example of the computer network is Internet. A computer network can be two or more inter-connected computers. Figure 1. shows an example of a computer network comprising a local area network or LAN connecting computers and various devices with each other. A physical pathway is known as the transmission medium, that connects the systems and a set of rules determines how they communicate. These rules are known as protocols. A network protocol is a software installed on a machine that determines the agreed upon set of rules for two or more machine to communicate with each other.
Networks are widely used by companies or on a personal level also. Network for companies should provide high reliability, cost efficient, and resource sharing. A network must be able to meet certain criteria, these are mentioned below: Performance Reliability Scalability
Figure 1.1 Computer Network
1.2.2 Need of Computer Network: Today no one can imagine the world without emails, online newspapers, blogs, chat and the other services those are offered by the internet. Computer networks support users on the network to share the information, services, and information.
Computer Network benefits in: Cost reduction by sharing hard- and software resources High reliability by having multiple sources of supply Cost reduction by downsizing to microcomputer-based networks instead of using mainframes Greater flexibility because of possibility to connect devices from various vendors
Networking increases efficiency and reduces costs. These goals can be achieved in three primary ways: Sharing information (or data) Sharing hardware and software Centralizing administration and support.
File transfer protocol (FTP): An application that facilitates the transfer of files from one computer to another e.g. from a client to a server. There are two common processes involved in FTP o Downloading : It is the process of getting files from a server to a local computer or a client (for example when you download programs and music from a server). o Uploading : It is the process of getting of files transferred from a local computer or a client to a server (for example attaching and uploading of documents to a server). TELNET: An application that allows a local computer or a client to access the server for an application program. TELNET enables to control the server and communicate with other servers on the network. Groupware: Applications those are used for atomization of the administrative functions of a modern office for example video conferencing and chatting. They facilitate the work of groups and improve their productivity.
b. Stand Alone Applications : These are the applications those run on standalone computers. To enhance their activity, these programs are rebuilding to run on network environments. For e.g. word processors, database management systems, spreadsheets, graphics presentations, project management etc. They function even when the computer is offline. Besides these applications are also categorized on the basis of their place of usage like: Business: Banking: Insurance: Education: Marketing: Health Care: Engineering Design: Military: Communication: Government:
1.2.4 Components of Computer Network: Computer networks share common devices, functions, and features including servers, clients, transmission media, shared data, shared printers and other hardware and software resources, network interface card(NIC), a local operating system(LOS), and the network operating system (NOS). Computer network components consists of the main parts those are required to install a network mutually at the office and home level. Computer network components include cable, Hub, Switch, NIC (network interface card), modem and router. Depending on the type of network some of the components can be eliminated. For example, wireless network cables and hubs are not needed.
Essential Components for Computer Networks are: Network Interface Card (NIC) Hub Switches Cables and connectors Crimping Tool LAN tester Router Modem Bridge
Network Interface Card (NIC): It is a hardware component that connects a computer to a computer network. It is also known as network interface controller, network adapter, LAN adapter. Now a day’s almost all computers have built-in NIC, i.e. functionality of NIC is available on the motherboard directly.
HUB: Hub is a device used to divide a network connection into several computers. It is a distribution center. Hubs are generally used to connect segments of a LAN. A hub contains multiple ports. When a packet reaches at the port, it is transmitted to the other ports hence all segments in the LAN can see all packets.
Figure 1.2: Network Interface Card (NIC)
Figure 1.3: HUB
LAN Tester: T esters assist in the installation and control of networks. LAN testers are able to determine IP addresses, connected port, identify polarity, and link connectivity. Even they can test fiber optic cables. They also show cable break points, incorrect connections in fiber optic lines.
Router: Router is a networking device that forwards data from one network to another. It forwards data packets between computer networks, creating an overlay internetwork. A router is used to connect two or more connections from different networks. When a data packet arrives in one of the lines, the router examines the address info in the packet to determine its ultimate destination.
Modem: It is a device that enables computers to transfer data from one location to another location via the telephone line. It mod ulates the (converts) digital signal to analog at the transmission end and dem odulates (converts/ reverts) analog signal to digital signal.
Figure 1.7: LAN Tester
Figure 1.8: Router
Figure 1.9: Modem
Bridge: It is a device that connects two parts of a network together at the data link layer (layer 2 of the OSI model). Bridges work like the network switches, but the traffic is controlled otherwise. A bridge only transmits traffic from one side to the other side if it is going to a destination. This is unlike to a layer 1 switch that transmits all traffic from either side. Sometimes network bridges are called layer 2 switches.
Self-Test (Multiple Choice Questions):
- A network consists of what minimum number of entities sharing resources and information? a. One b. Two c. Three d. Ten
- Which of the following is required before a computer network is present? a. Two or more computing devices b. Connections between devices c. Electronic resources and information to share d. All of the above
- A network must be able to meet which of the following certain criteria? a. Performance b. Reliability c. Scalability d. all of above Self-test question:
- Fill in the blanks. a. A Network is a group of two or more computer system sharing ……….
- Define Computer Network. Describe fundamentals of a computer network in brief.
- Describe the needs of Computer Networks in brief?
- What are the applications of Computer Network?
- Enlist different network component. Explain any four components.
1.3 Network Benefits: 1.3.1 Sharing Information (File Sharing, E-mail): Networks allow users to share information in various ways. The most conventional way of sharing information is to share specific files. For example, many people can work together on a single document like spreadsheet file or word-processing. In most of the networks, a large hard disk is set up on a central server computer as a shared storage area where users can store files to be shared.
Figure 1.10: Bridge
the installations are stored on servers and are made accessible in the network. The maintenance personnel simply logs on from a client computer and install the needed applications using the installation software stored on the server. In the past few years, more savings have been accomplished by having the centralized server initiate the software installations or updates on the client computers without the need for maintenance personnel to actually visit any of the clients.
1.3.5 Maintaining the Network: Purchasing similar equipment for use on the network means that network maintenance costs are reduced because there are fewer dissimilar components. Maintenance workers no longer have to attend numerous training sessions on many different components, which meant they could spend more time maintaining the actual components.
1.3.6 Backing up data: Along those same lines, a network minimizes the time spent backing up (saving extra copies, called backups) of necessary files. If a hardware or software failure causes information or applications lost, vital information and necessary applications can be restored with the help of existing backup. The backup process is normally a regular activity in a company, and all transactions between scheduled backups are recorded so that the files can be restored as completely as possible. Technicians can access the backup files and recorded transactions from a central location without having to physically visit the source computers.
Self-test question:
- What are the benefits of Computer Network? Explain any two.
1.4 Computer Network Classifications: Networks are classified by using one or more technical or functional properties like the type of technology used or number of users and devices it connects. One basic property used to classify networks is its geographic area, where a network is categorized on the basis of the physical area covered by it. The five basic types of networks in terms of geographical area from the smallest to the largest are: Personal Area Networks (PAN) Local Area Networks (LAN) Campus Area Networks (CAN) Metropolitan Area Networks (MAN) Wide Area Networks (WAN)
1.4.1 Personal Area Networks (PAN): PAN cover the areas related with specific workspaces like a home office or an office workspace. Within PAN, an individual network connecting two or more devices may be facilitated using wireless technologies, as shown in Figure 1.11. PAN is a personal network equipped within a limited area. PAN consists of mobile devices like cell phone, tablet, and laptop. Such network can also be wirelessly connected to the Internet. PAN handles the
interconnection of networking devices nearby of a single user. Usually, PAN contains appliances like wireless mouse and keyboards, wireless phone, Bluetooth.
Figure 1.11: Personal Area Networks (PAN)
Advantages: Portable: Since it is a portable type of network, if a person is traveling he can carry his portable devices such as laptops, mobile phones, personal digital assistant and etc. So it is possible for him to establish his network wherever he wishes without using any wire, only by using wireless technology. Security: Since the information stored in the devices is shared with only authorized peoples within the network. Hence it is secure to transfer information between devices. PAN is expedient, lucrative and handy.
Disadvantages: Health Issue: Since most devices used for communication are wireless, use microwave signals as a medium for communication. Working for a long time within this signals radius may lead to some brain and heart-related problems. Expensive: Since expensive devices like smartphones, laptops, Digi camera, PDA and etc. are used. Sometimes has a bad connection to other networks at the same radio bands. Bluetooth networks have slow data transfer speed, but comparatively safe. Bluetooth has distance limits.
1.4.2 Local Area Networks (LAN): LAN cover the limited geographical area like some or complete space within a building and usually owned and maintained by a single organization. LAN is mostly used to connect PC’s and workstations at home, in company offices and factories, to share resources and information. They are classified as other types of the network by their size, transmission technology, and topology. Since are relatively small in size, network management is relatively easy,
Disadvantages: High Setup Cost: Initial setup cost of installing Local Area Networks is very high. Privacy Violations: Since LAN administrator has rights to check personal data, he can check the personal use history of the LAN users. Data Security Threat: If the centralized database is not secured properly by the LAN administrator any unauthorized user can access the important data of an organization. Slow Internet Speed: Since single internet connection is shared and if all computers will run at once, lead to slow internet speed for each LAN Maintenance Job: Since Local Area Network requires a LAN Administrator. Full-time LAN Administrator is needed. Covers Limited Area: Local Area Network covers very small area like one office or one building.
1.4.3 Campus Area Networks (CAN): Campus Area Network is an interconnection of local area networks within a limited geographical space, like a school campus or a military base. CANs are formed by connecting the LANs situated in two or more buildings those are mostly close to each other, as shown in Figure 1.13. Connections between the buildings can be done using cables or wireless devices. Term campus LAN is used to describe CAN. CAN is one of the types of MAN but the area is smaller than MAN. Generally the CAN uses various LAN technologies like Ethernet, Token Ring, Fiber Distributed Data Interface (FDDI), Fast Ethernet, Gigabit Ethernet, and Asynchronous Transfer Mode (ATM).
Figure 1.13: Campus Area Networks (CAN)
1.4.4 Metropolitan Area Networks (MAN): It is a network that is used to connect computers in a larger geographic area than that is covered by a CAN but smaller than the area that is covered by a WAN. MANs are formed by connecting the networks located at two or more sites within the same city. Connections are done by using cables or wireless technologies, often optical fiber cabling is used to connect networks to the facility provided by a telecomm service provider, as shown in Figure 1.14. MANs are generally described by very high-speed connections using fiber optical cable or other digital media.
Figure 1.14: Metropolitan Area Networks (MAN)
1.4.5 Wide Area Networks (WAN): A computer network that covers a relatively large geographical area. WAN connects various small networks that includes local area networks (LANs) and metro area networks (MANs). Computers are connected through public networks to a WAN, for example public telephone system. WAN can also be connected via leased lines or satellites. An example of largest WAN is the Internet. WANs are created by linking the networks located at two or more sites over geographic distances that extend beyond the span of a single metropolitan area. These include links between cities, countries, and in the case of global WANs, continents. Telecommunications circuits link each building to facilities operated by a telecommunications provider (same as MANs), as shown in Figure 1.15. WAN works similarly like a LAN, on a greater scale. TCP/IP is the protocol used for a WAN in combination with devices such as routers, switches, firewalls, and modems.
specifically on which computer controls that operation. Networks can be classified on the basis of role in two basic types: Peer-to-Peer Networks Server-Based Networks The basis of difference between these two is that, which computer is Incharge of the network. A third classification, client-based networks, has come into existence because of the increased capabilities of the typical client computer
1.5.1 Peer-to-Peer Network: Peer-to-peer networks have no centralized control. A peer is considered an equal. All computers on a peer-to-peer network can be considered equals, as shown in Figure 1.16. That is to say, no one computer is in charge of the network’s operation. Each computer controls its own information and is capable of functioning as either a client or a server depending on which is needed at the time. Peer-to-peer networks are very popular since they are inexpensive and easy to install are used in home networks and in small companies. Many operating systems comes with built in peer-to-peer networking capability. The only other cost involved with setting up a peer-to-peer network comes into play if a computer does not have a network interface card, or NIC (the device that physically connects your computer to your network’s cabling), already installed. Typical initial peer-to-peer networking involves no security measures. Rather, each peer simply shares its resources and allows others open access to them. Actually, a peer-to-peer network is difficult to manage if more and more security is given to the resources. This is because users control their own security by adding password protection to each share they create. Shares are any resources users control on their computers, such as document folders, printers, and other peripherals. Each shared resource can actually have its own password. Someone wanting access to numerous shared resources has to remember many passwords. Security on a peer-to-peer network can quickly become complex and confusing.
Figure 1.16: A peer-to-peer network. While peer-to-peer networks are inexpensive to set up, they are extremely limited in scope. The maximum number of peers that can be accepted to operate on a peer-
to-peer network is ten. They are, therefore, not appropriate for larger, more secure networks.
1.5.2 Server-Based Network: Server-based networks involve centralized control. A server-based network provides centralized control and is created for secure operations, as shown in Figure 1.17. Although there are both clients and servers on a server-based network, network is controlled by a dedicated server. A dedicated server is one that, operates solely as a server for all practical purposes. In a server-based network, a dedicated server serves its network clients by storing data, applications, and other resources, and then provides access to those resources when called for by a client. When a client requests for a resource such as a document, the server transmits the document over the network to the client. When it is processed it is returned to the server for continued storage. Dedicated servers can also control the entire network’s security from one central location or share that control with other specially configured servers. This central network control gives contribution to the financial system of scale briefed in the “Facilitating Centralized Management” section earlier in this chapter and makes the server-based network the leading networking model that is used in networks today.
Figure 3.17: A server-based network
1.5.3 Types of server: Client-based networks are a further refinement of the concept of a server based network that relieves the heavy burden on the network’s capacity resulting from frequent server-performed transactions. A client-based network takes better advantage of the server’s powerful processors and of the increasingly powerful computers used in typical workstations. Client-based networks, therefore, take advantage of the powerful processing capabilities of both the client and the server, as shown in Figure 1.18.
network. Also, a program or mechanism that enables the required processes for file sharing can be called a file server. File servers are generally originated in organization settings, such as company networks, today they are also used in schools, small organizations, and even at home networks.
Print Server: A software application, network device or dedicated computer that manages one or more printers within a network. The print server manages print requests and provides printer queue status information to end users and network administrators. Print servers are useful since they allow users to print a job avoiding to move files from computer to computer before printing. Print servers usually supports one or more TCP/IP printing protocols. Common print protocols include: LPR/LPD (Line Printer Protocol) TELNET or stream IPP (Internet Print Protocol) Microsoft print protocol Self-Test (Multiple Choice Questions) Self-test
- Fill in the blanks. a. In client server model users are called as ……………….. b. The collaborative computing is also known as ………………..computing. c. In centralized computing network is done at ………………….
- Match the following a. Network a. Response b. Client b. Group of computers c. Server c. Request
- Fill in the definitions for the following Functional relationships terms, Client Server Peer-to-Peer (P2p) Client-Server Network
1.6 Summary: In this chapter, it is explained that the old model of an individual computer serving all of the organization's computational need has been replaced by one in which the large no of separate but interconnected computers does the job. These systems are called as a computer network. A computer network is a collection of more than one computer systems used for sharing services and interacting in some manner. At the end, it is shown that Computer networks are mainly divided into Local Area Network, Metropolitan area network, wide area network, wireless networks, Internetworks. 1.7 Exercise (short answer questions)
- Writes Notes on (Draw diagrams when necessary) a. Types of networks b. Client Server Model c. Internetworks
- Explain the centralize computing?
- Explain in brief. a. Domain b. Workgroup
1.8 References 1.8.1 Books Computer Networks: Andrew S. Tanenbaum Networking Essentials: Emmett Dulaney 1.8.2 Wikipedia http://en.wikipedia.org/wiki/Computer_networking
1.8.3 MOOCs 1.8.4 YouTube Videos https://www.youtube.com/watch?v=mxK4cH6DJwo&list=PLftmDuo1- PWKJIApmovOsChz7a-bPKAZC https://www.youtube.com/watch?v=R2mEK- LnaVk&list=PLoCUlAGhY8dL_glrT5IEORrcEIkuXk3vL
1.8.5 OER
