Data Communication: Networks, Topologies, and Transmission Media, Lecture notes of Computer Science

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Chapter 4

4. Data Communication & Computer Networking

 Outline :

 (^) Data communication  (^) Computer networks  (^) Types of networks  (^) Network topologies  (^) Network devices and transmission media

1. Data Communication

 (^) Exchange of data b\n devices via wired or wireless transmission medium.  (^) Data Communication Components :

1. Message : is an information that is to be communicated 2. Sender : is the device that sends the message 3. Receiver : is the device that receives the message. 4. Medium : The transmission medium is the physical path that communicates the message from sender to receiver. 5. Protocols : set of rules that coordinates the exchange of information.

Transmission Medium

 (^) Physical media which is communication signals/data are transmitted.

1. Guided Media: use cable that guide/bound data signals along a specific path. i. Coaxial: ii. Fiber optics: **iii. Twisted Pair:

1. Unguided/ Media/Wireless** : data signals that flow through air waves, radio I. Infra-red: point-to-point signaling method over medium distances. II. Radio Frequency : Signals vary in strength (Amplitude) & tone (Frequency) in order to offer a broad range of services, from short-range to extremely long-range. III. Microwave : used in satellite communications.  (^) They are meant for extremely long-range communications,

2. Computer Network

 (^) Computer network is a collection computers connected together by telephone lines, coaxial cables, satellite links to share information. Classification of Network

A. Classification Based on “Coverage Area”

 (^) Personal Area Network (PAN)  (^) Local Area Network (LAN)  (^) Metropolitan Area Network (MAN)  (^) Wide Area Network (WAN)

3. Metropolitan Area Network (MAN)  (^) MANs are large computer networks usually cover a campus or a city.  (^) Can cover a group of nearby corporate offices & be private or public.  (^) It can support both data & voice. 4. Wide Area Network (WAN): Spans a relatively large geographical area.  (^) Often connected through public networks, such as the telephone system.  (^) They can also be connected through leased lines or satellites.  (^) The largest WAN in existence is the internet.

(^) WANS differ from LANS in the following ways:

 (^) cover greater distance, speeds are slower  (^) WANs can use either full- or half-duplex communications

3. Network Architecture

 (^) It is logical and structural layout of network, consisting of transmission equipment, software, communication protocols & infrastructure (i.e. wired or wireless) transmission of data and connectivity between components.  (^) Based on “Security & Access ” network architectures are: 1) Peer-to-peer networks: Each computer can be a client that requests resources and a server that provides resources upon request.  (^) They s are characterized by the following:  (^) Security is not centralized; Network is not scalable;  (^) Each computer is responsible to check access rights for its resources.  (^) It is good for 10 computers. Each user is responsible for local backup.  (^) No specialized operating system is required;

4. Network Topology

 (^) Physical configuration of a network that determines how the network's computers are connected. Common configurations include bus, star and ring topologies.

1. Bus Topology: All computers are connected to a single cable.  (^) The cable is terminated at its ends to avoid signal bouncing.  (^) When a computer wants to send data to another computer.

Advantages: Easy to connect a computer or peripheral to a linear bus.  (^) Requires less cable length than a star topology. Disadvantages: Entire network shutdown if there is a break in main cable.  (^) Terminators are required at both ends of the backbone cable.  (^) Difficult to identify the problem if the entire network shuts down.  (^) Network can slow down in heavy traffic.

2. Star Topology: each computer in a star topology is connected to a central device (hub)

by a separate cable.  (^) When a computer wants to send data to another computer, it sends the data and address of the recipient computer to the hub, which in turn, sends it to every computer connected to it.  (^) Only computer whose address is included with data accepts the data.

3. Ring Topology: Each computer is connected to two computers in network.  (^) Data moves down a one-way path from one computer and if the next computer is the recipient it accepts the data; otherwise it amplifies it and sends it to the next computer down in the path.  (^) Any break disrupts the entire network and hence the physical ring topology is seldom used. Advantages: System provides equal access for all computers.  (^) Performance is even despite many users. Disadvantages: Failure of one computer can impact the rest of the network.  (^) Problems are hard to isolate.  (^) Network reconfiguration disrupts operation

4. Mesh Topology: Each computer is directly connected to every computer.  (^) become quite complex as wiring and connections increase rapidly with the increase of computers to connect.  (^) For n computers, n(n-1)/2 cables are required. Disadvantages: System is expensive to install b/ce it uses a lot of cabling. Advantages: System provides increased redundancy & reliability as well as ease of troubleshooting.

Chapter – 6: Internet

 (^) Internet is the network that is available to users across the globe.  (^) It is called “ the mother of all networks ”.  (^) Extranet is the lowest level of internetworking.  (^) It is restricted to only those users who have login credentials.  (^) Intranet is network that works like internet but only available within a particular organization not public.  (^) Criterial needed to connect the Internet  (^) Web Browser  (^) Modem  (^) Telephone cable  (^) Device(pc…)  (^) ISP

Uses of the internet

 (^) It used to communicate across large or small distances, share information from any place in the world & access information or answers to almost any question in moments.  (^) The Main Uses of Internet are:-  (^) Social media and content sharing;  (^) searching for jobs  (^) Distance learning  (^) Download files  (^) E-mail and discussion groups

 Entertainment

 (^) E-business  (^) Telephony and conferencing

 (^) website is composed of a web page or collection of related web pages.  (^) It has a unique address.  (^) A computer with a domain name is called a website ( site ).  (^) The top-level domains are .com, .edu, .org, and .net.  (^) Web page is a document on the World Wide Web that can include text, pictures, sound and video.  (^) Home page first page you see on a website is like title page of a book

Browser/Web Browser  (^) Is software for connecting with websites, what you use to get around web.  (^) is software that enables users to locate & view web pages & to jump from one page to another.  (^) For example, Internet Explorer, Mozilla Firefox, Google Chrome, etc. What Is A Search Engine?  (^) Search Engines are helps for web Guides  (^) Examples Google, Yahoo, Web Crawler, Net Search, Lycos, AltaVista, Staring Point