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Networking Concepts Introductory Lecture By Mushhad Gilani
Books & study Material Text Book:- Data Communication and Networking, 4/e. Author: Behrouz A. Forouzan Reference Books/Material Larry L. Peterson and Bruce S. Davies , Computer Networks A Systems Approach, Second Edition
Introduction Meaning: Networking consists of two or more than two computers connected to each other by a medium (cable) so that they can share a data. Definition: A group of computers and other devices connected together is called a network and the concept of connected computers sharing resources is called as “Network”.
Uses of Computer Networks Network for Companies Network for People. Social Issues
Network for Companies. Many Organizations have a substantial number of computers in operation, often located far apart The goal are Resources Sharing High reliability Saving money Scalability
Network for People. Starting in 1990s, computer networks began to start delivering services to private individuals at home. Below we describe some services. Access to remote information. Person to person communication
Social Issues On the other hand The widespread introduction of Networking will introduce new social, ethical, political problems.
1-1 DATA COMMUNICATIONS The term telecommunication means communication at a distance. The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. Components Data Representation Data Flow Topics discussed in this section:
Figure 1.1 Five components of data communication Message Sender Receiver Medium Protocol
Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)
Figure 1.3 Types of connections: point-to-point and multipoint
Explanation: Networking arose from the need to share data in timely fashion. Computers in a network can share: a) Data (b) Messages (c) Graphics (d) Printers (e) Modems.
How Data Communication took Place
Types of Networks There are three different ways in which we classify the networks 1) Organizational Point of View 2) Geographical Point of View 3) Computing Point of View
Organizational Point of View From organizational point of view, networks are divided into two types Peer-to-Peer Server based
Peer-to-Peer These are also called Workgroups. A peer-to-peer network comprises of 10 or less users and is suitable for small-sized business organizations. In this model of networking the resources are randomly scattered on the network with every machine acting as a server as well as client
Server Based networks They are sometimes referred to as Domains. This is a centralized model of networking with resources placed on a dedicated machine called Server. There is no user limit as such, as it depends directly on your hardware resources and capacity to support users.
Geographical Point of View From geographical point of view, there are three types of networks. LAN WAN MAN/CAN
Classification of Geographical Networks by Scale
LAN or Local Area Network A LAN encompasses a small area such as a floor or a building with all the machines connected directly via the same medium generally.
Examples: LAN Two networks: (a) Bus (b) Ring
Local Area Network
WAN or Wide Area Network A WAN comprises of a very large physical area that covers countries and continents. Internet is one good example of a WAN. The machines in a WAN are connected through different mediums and protocols. Generally, the Dial-up- Networks are used for this purpose.
Wide Area Network
Internet MAP This map of the Internet appeared in the December 1998 Wired.
MAN (Metropolitan Area Network) or CAN (Campus Area Network) A MAN is almost similar to a WAN that a MAN only encompasses an area that is within a city. CAN is a campus area Network which is used with in a campus for the sharing of resources.
Example: MAN A metropolitan area network based on cable TV
Metropolitan Area Network
Computing Point of View Networks are divided into two types from the point of view of computing. 1.Centralized Networks 2.Client-Server Networks
Centralized Networks The centralized networks rely totally on one dedicated machine called server for all the processing and computing and the clients or the terminals act as dumb entities. If the client requires a certain set of data, whole of the data set is transferred at the client end, which also is wastage of the network bandwidth.
Client-Server Networks In this model of networking, only the required set of data is returned to the client while both the server and the client take part in the processing or computing of the queries. This is a more efficient way of processing and is hence applied generally more than the centralized method, nowadays..
Topology A topology is the physical layout or design of the networks that specifies the cabling method as well as the arrangement of the computers. It also explains the access method used by the computers that represent that topology. It also explains the access method used by the computers that represent that topology.
Types of Topology There are following types of topologies, generally: Bus Topology Star Topology Ring Topology Mash Topology
Bus Topology The bus topology consists of a long linear cable also called trunk or linear trunk or backbone. In this type of topology, all the computers are connected to this main cable. Bus is a passive topology. The main features of the bus topology are discussed as under: Signal Bouncing This is a phenomena observed in this type of topology. In signal bouncing, the data signal travels across the cable medium from one end to another and if not absorbed at the other end, it will keep on bouncing back and forth across the medium and therefore will stop any further communication on the network. This is called signal bouncing.
Terminator: In order to avoid signal bouncing, a device called terminator is used at one end of the medium that absorbs the signal and hence restricts it from affecting the overall network communication. It could be a grounding method as well with one end grounded into a wall socket. Signal Attenuation: After the data travels a long distance on the cable, it starts becoming weaker and weaker until it reaches a point where it cannot be received in the correct form. This process is called Signal Attenuation. Repeater: The solution to Signal Attenuation is a device called repeater that regenerates or amplifies the signal to make it strong enough to be received correctly at the destination end
Star Topology In star topology there is a central network traffic management device called hub/Switch. All the nodes (computers) are connected directly to the hub and are thereby interconnected with each other. Star topology does not allow direct traffic.
ADVANTAGES Easily Expanded Easier to Troubleshoot Easier to Troubleshoot Multiple cable types Supported by hubs Multiple cable types Supported by hubs
DISADVANTAGES Hub failure Requires more Cable May require a device to re broad cast signals across the network
Ring Topology In ring topology the computers connected with each other via a single cable run constitute a logical ring. Ring is an active topology and also that every computer on the ring acts as a repeater i.e., it regenerates the signal and transmits it onto the cable. Token Passing A frame or sequence of data called token passes from one computer to another on the ring and makes the network communication possible in a way that only the computer with token has the opportunity to transmit data on the ring. Here is how the process works: (Token Travling on the ring.swf) Token Travling on the ring.swfToken Travling on the ring.swf
ADVANTAGES It provides an orderly network in which every device has access to the taken and can transmit It performs well under a heaven load. It performs well under a heaven load.
DISADVANTAGES Malfunctioning workstation and cables create problems for the entire network Changes made when adding or removing a device affect the entire network. Changes made when adding or removing a device affect the entire network.
MESH The mesh topology provides the highest level of fault tolerance. It uses separate cables to connect each device to every other device on the network, providing a Straight Communication path. Dedicated point to point link.
A hybrid topology: a star backbone with three bus networks
Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet
Figure 1.11 WANs: a switched WAN and a point-to-point WAN
Figure 1.12 A heterogeneous network made of four WANs and two LANs
Active Topology Vs Passive Topology The difference between active topology and the passive topology is that in an active topology the computers are themselves responsible for the successful transference of data while in a passive topology this is not the case. Example: In star or the bus topology, if a computer fails, this does not affect the whole network and the communications on the network still go on. While in case of a ring topology, if even a single computer goes down, the whole network comes to a state of being down as the token gets stuck into that computer and thereby stopping all the network communication