Computer Networks PDF

COMPUTER NETWORKS 1  Course Objective To provide the basic understanding of the fundamental principles of data communication and networks. How do computer networks and internet operate ? COMPUTER NETWORKS Department of Information Security...

COMPUTER NETWORKS 1  Course Objective To provide the basic understanding of the fundamental principles of data communication and networks. How do computer networks and internet operate ? COMPUTER NETWORKS Department of Information Security 2  Reference Material Data Communication and Networking by Behrouz A. Forouzan, McGraw-Hill Science, 5th edition. Computer Networks and Internets by Douglas E. Comer, 5th edition. Data and Computer Communication by William Stallings, 10th edition. Computer Networks by Andrew S. Tanenbaum, David J. Wetherall, 5th edition. Computer Networking: A Top-Down Approach Featuring the Internet, 6th. edition by James F. Kurose and Keith W. Ross COMPUTER NETWORKS Department of Information Security 3  COMPUTER NETWORKS INTRODUCTION NETWORK: A network is defined as a system for connecting computers using a single transmission technology. The computers can communicate with each other in a network. They can send and receive data from each other when they are in a network. INTERNET: The Internet is defined as the set of networks connected by routers that are configured to pass traffic among any computers attached to any network in the set. By internet many computers which are at longer distances from each other can communicate with each other. COMPUTER NETWORKS Department of Information Security 4 CLASSIFICATION OF NETWORKS Computer networks are classified by four factors which are as follow: 1) BY SIZE: 2) BY CONNECTIVITY: 3) BY MEDIUM: 4) BY MOBILITY: COMPUTER NETWORKS Department of Information Security 5 BY SIZE According to their size there are two classifications of networks. 1. Local Area Network. ( LAN) 2. Wide Area Network (WAN) MAN ? In LAN network occupies the smaller area like a room a floor or a building. In WAN, network occupies larger areas like cities & countries. Internet is a Wide Area Network. LAN & WAN are compared by the speed of transmission, bandwidth and latency, management, security, reliability, billing and their standards. COMPUTER NETWORKS Department of Information Security 6 BY CONNECTIVITY Networks are also classified by connectivity in which two topologies are discussed. a) Point-to-Point b) Broadcast a) POINT-TO-POINT: In Point-to-Point topology there are two topologies. 1) STAR topology: In star topology each computer is connected to a central hub. 2) TREE topology:The communication takes place through the hub. COMPUTER NETWORKS Department of Information Security 7 BY CONNECTIVITY COMPUTER NETWORKS Department of Information Security 8 BY CONNECTIVITY b) BROADCAST: In broadcast topology there are further two categories 1) SATELLITE\RADIO 2) RING TOPOLOGY In a satellite or radio topology all computers are connected to each other via satellite or radio wave. In a ring topology each computer is connected to other thorough a ring, COMPUTER NETWORKS Department of Information Security 9 BY CONNECTIVITY COMPUTER NETWORKS 10 Department of Information Security BY MEDIUM The classification of networks is also based on the Medium of transmission. Following are the mediums of transmission: Copper wire Co-axial cable Optical fiber Radio waves All these mediums differ from each other with respect different parameters. These parameters are speed of transmission, range of the receiver and transmitter computer, sharing of information, topology, installation & maintenance costs and reliability. For example the range of radio waves will be much more than an optical fiber. Similarly other mediums differ from each other and appropriate medium is selected for the sake of transmission. COMPUTER NETWORKS 11 Department of Information Security BY MOBILITY The networks are also classified according to their mobility. In this respect there are two types of networks. Fixed networks Mobile networks Mobile networks have been emerged in 90’s. In this regard there are some issues which are attached with the mobility of networks which are as follows: Location and tracking Semi persistent connections Complex administration and billing as devices and users move around the network. COMPUTER NETWORKS 12 Department of Information Security NETWORKS IN DAILY LIFE The major use of networks is in business side. Networks are used for advertising, production, shipping, planning, billing and accounting purposes. In fact now there is an entire industry that develops networking equipment. In addition to this networks are being used in homes as well for example, to switch and control different devices from one place. Networks are very much useful at government level as federal government, local government and military organization use networks for communication purposes. In education we have online libraries which we can visit at our home PC. This is all just due to the networks. COMPUTER NETWORKS 13 Department of Information Security COMPLEXITY OF NETWORK SYSTEMS: A computer network is a complex subject due to the following reasons: MANY DIFFERENT TECHNOLOGIES EXIST: The first reason for the complexity of networks is that there are many different technologies exist for networking and each technology features is different from the other. This is because many companies have developed networking standards, which are not compatible with each other. In this way multiple technologies exist that are used to connect different networks. NO SINGLE UNDERLYING THEORY OR MODEL: The second reason for the complexity of networks is that there is no single underlying theory or model, which specifies or defines different aspects of networking. Rather, various organizations and research groups have developed conceptual models that can be used to explain differences and similarities between network hardware and software. COMPUTER NETWORKS 14 Department of Information Security COMPLEXITY OF NETWORK SYSTEMS: MODELS ARE EITHER SO SIMPLISTIC OR SO COMPLEX: Another reason for the complexity of networks is that the conceptual models made by organization are either so simplistic that they do not distinguish between details, or they are so complex that they do not simplify the subject. NO SIMPLE OR UNIFORM TERMINOLOGY: One reason for the complexity of networks is that there is no simple or uniform terminology that can be used for the same feature. Different technologies use different terminologies. In this way terms are confused with product names. COMPUTER NETWORKS 15 Department of Information Security