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Topics Lesson 7 Basic Telecommunication Concepts Telecommunication Models Networking Client/server Computing Telecommunication Standards Wireless Communications Internet Modems Baud - transfer rate (bits per second) Analog signals: continuous Digital signals: discrete

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Topics Lesson 7

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Topics Lesson 7

  • Basic Telecommunication Concepts

  • Telecommunication Models

  • Networking

  • Client/server Computing

  • Telecommunication Standards

  • Wireless Communications

  • Internet


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Modems

  • Baud - transfer rate (bits per second)

  • Analog signals: continuous

  • Digital signals: discrete

  • Modulation: translating digital data to analog

  • Demodulation: translating analog data to digital

  • Modems modulate & demodulate data

  • Fax/Modem

    • telephone as well as facsimile


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Modems

  • A typical telephone line can only accommodate an analog signal (a continuous, curving signal)

  • A computer generates a digital signal representing bits

  • Modem: a device that translates data from digital to analog and analog to digital


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Figure 6.8: How a Modem Works


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Figure 6.3: Elements of a Telecommunications System


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Electronic Communication Terminology

  • Simplex

    • one way (i.e. transmit, or receive)

  • Half Duplex

    • both directions (one-at-a-time)

  • Full Duplex

    • both directions at the same time

  • Baud vs. bit/s (bps)


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Electronic Communication Modes

  • Communications Protocols

  • Handshaking

  • Redundancy

    • CRC – Cyclic Redundancy Checking


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Multiplexers

  • Multiplexers (a.k.a. “mux”): device that allows several telecommunications signals to be transmitted over a single communications medium at the same time

  • Demultiplexer (“demux”)

  • http://en.wikipedia.org/wiki/Multiplexer


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Front-End Processors

  • Front-end processors: special-purpose computers that manage communications to and from a computer system (to networks, peripheral devices)

  • Connect a midrange or mainframe computer to hundreds or thousands of communications lines


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Figure 6.9: Use of a Multiplexer to Consolidate Data Communications onto a Single Communications Link


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Figure 6.10: Front-End Processor


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Telecommunications Media


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Connections

  • Micro to micro (modem)

  • (Dumb) Terminal to host (mainframe/minicomputer) (direct wiring)

  • Micro to micro (direct)

  • LAN, WAN, PAN – Computer Networks

  • Uploading vs. downloading


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Fig 6.19


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Types of Media

  • Twisted Pair

  • Coaxial Cable

  • Fiber-Optic Cable

  • Wireless

    • Microwave Transmission, RF (WiFi, Bluetooth, cellular), Inferred


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Twisted Pair

  • Fig 6.4


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Coaxial Cable

  • Fig 6.5


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Fiber Optic Cable

  • Fig 6.6


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Microwave Transmission

  • Fig 6.7


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Satellite

  • Fig 6.8


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Cellular

  • Fig 6.9


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Infrared Transmission

  • Line of sight

  • Short distances


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Local Area Networks

  • Server Based (Novell/Microsoft Active Directory)

  • Peer-to-Peer (LANtastic, Windows)

  • Physically most common: Ethernet over unshielded twisted pair.


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Figure 6.15: The Basic Network Topologies


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Other

  • Gateway – for attaching different networks – converts one protocol to another.

  • WAN

  • Wireless (Wi-Fi (802.11), Bluetooth)

    • PAN


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What Is Client/Server?

  • Client/serveris a term used to describe a computing model for the development of computerized systems. This model is based on the distribution of functions between two types of independent and autonomous processes; servers and clients.

  • A client is any process that requests specific services from server processes.

  • A server is a process that provides requested services for clients.

  • The key to client/server power is where the requested processing takes place.


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What Is Client/Server?

Basic Client/Server Computing


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Client/Server Systems Benefits

  • Client/Server Benefits

    • Platform-independent system development

    • Optimized distribution of processing activities among different platforms

    • Use of user friendly, cost effective, and compatible techniques, methodologies, and specialized tools


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Managerial Expectations ofClient/Server Systems Benefits

  • Organizational Expectations of Client/Server Benefits

    • Flexibility and adaptability

    • Improved employee productivity

    • Improved company work flow and a way to re-engineer business operations

    • New opportunities to provide competitive advantages

    • Increased customer service satisfaction


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Client/Server Architecture

  • Components of Client/Server Architecture

    • Client.The client is any computer process that requests services from the server. It is also known as the front-end application.

    • Server.The server is any computer process providing services to the clients. The server is also known as the back-end application.


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Client/Server Architecture

  • Client Components

    • Powerful hardware

    • An operating system capable of multitasking

    • A graphical user interface (GUI)

    • Communications capability


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Client/Server Architecture

  • Types of Services

    • File services

    • Print services

    • Fax services

    • Communications services

    • Database services

    • Transaction services

    • Application services

    • Web Services


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The Internet, Intranets, and Extranets


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Types of Internet Connections

  • Dialup (Modem)

  • ISDN (It Still Does Nothing, Innovations Subscribers Don't Need)

  • Broadband (“high speed”)

    • DSL (ADSL) – (Asynchronous Digital Subscriber Line)

    • Cable

  • T1, T2, T3, T4


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Use and Functioning of the Internet


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The Internet

  • See Introduction to the Internet and the WWW


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What is the Internet

  • a global set of interconnected data networks running the TCP/IP protocols

  • Traditional services include email, file transfer (FTP); current focus is on the World Wide Web

  • Largely self-financing; no single point of control or administration (ANARCHY)


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How the Internet Works

  • Hosts

  • Routers forward packets to other networks

  • Internet Protocol Stack (TCP/IP)

    • Internet Protocol (IP)

    • Transport Control Protocol (TCP)

  • Backbones


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How the Internet Works

  • Uniform Resource Locator(URL)

  • http://www.whitehouse.gov

World Wide Web

Domain category

Hypertext transfer protocol

Host Network Name


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Table 7.1


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Figure 7.3: Several Ways to Access the Internet


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Structure of the Internet

  • National/global backbone networks

    • Network Access Points (NAPS) connecting the major commercial backbones

  • Internet Service Providers (ISPS)

    • “wholesale”:selling access to Users and other ISPS

    • “retail”:resell access to someone else's backbone


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The World Wide Web


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The World Wide Web

  • World Wide Web: AKA the Web, WWW, or W3

  • A menu-based system that uses the client/server model

  • Organizes Internet resources throughout the world into a series of menu pages, or screens, that appear on your computer

  • Hypermedia: tools that connect the data on Web pages, allowing users to access topics in whatever order they wish


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The World Wide Web (continued)

  • Hypertext Markup Language (HTML): the standard page description language for Web pages

  • HTML tags: inform browsers how to format text on a Web page, and whether images, sound, and other elements should be inserted

  • Extensible Markup Language (XML): markup language for Web documents containing structured information, including words, pictures, and other elements


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  • Html and XML Demo


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Figure 7.4: Sample Hypertext Markup Language


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Web Software

  • Web browsers

  • Search engines

    • Keyword indexes: fast & broad

    • Subject indexes: focused searches


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Table 7.7


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Webcasting

  • aka Push Technology

  • Consolidates information according to a user’s profile & displays in the browser


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Internet Services


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Web Services

  • Web services: standards and tools that streamline and simplify communication among Web sites for business and personal purposes

  • XML is used within a Web page to describe and transfer data between Web service applications


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Web Services (continued)

  • Besides XML, other components are used in Web service applications:

    • SOAP (Simple Object Access Protocol)

    • WSDL (Web Services Description Language)

    • UDDI (Universal Discovery Description and Integration)


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Internet and Web Applications

  • E-mail and instant messaging

  • Instant messaging: a method that allows two or more individuals to communicate online using the Internet

  • Internet cell phones and handheld computers

  • Career information and job searching


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Internet and Web Applications (continued)

  • Telnet and FTP

    • Telnet: a terminal emulation protocol that enables users to log on to other computers on the Internet to gain access to public files

    • File Transfer Protocol (FTP): a protocol that describes a file transfer process between a host and a remote computer and allows users to copy files from one computer to another


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Internet and Web Applications (continued)

  • Web log (blog): a Web site that people can create and use to write about their observations, experiences, and feelings on a wide range of topics

  • Usenet and newsgroups

    • Usenet: a system closely allied with the Internet that uses e-mail to provide a centralized news service; a protocol that describes how groups of messages can be stored on and sent between computers

    • Newsgroups: online discussion groups that focus on specific topics


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Internet and Web Applications (continued)

  • Chat room: a facility that enables two or more people to engage in interactive “conversations” over the Internet

  • Internet phone and videoconferencing services

  • Content streaming: a method for transferring multimedia files over the Internet so that the data stream of voice and pictures plays more or less continuously without a break, or very few of them; enables users to browse large files in real time

  • Shopping on the Web


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Fig 6.24


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Figure 7.7: How Voice Over IP Works


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Internet and Web Applications (continued)

  • Web auctions

  • Music, radio, and video on the Internet

  • Office on the Web

  • Internet sites in three dimensions

  • Free software and services


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Table 7.6: Summary of Internet and Web Applications


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Table 7.6: Summary of Internet and Web Applications (continued)


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Intranets and Extranets


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Intranets and Extranets

  • Intranet

    • Internal corporate network built using Internet and World Wide Web standards and products

    • Slashes the need for paper

    • Provides employees with an easy and intuitive approach to access information that was previously difficult to obtain


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Intranets and Extranets (continued)

  • Extranet: a network based on Web technologies that links selected resources of a company’s intranet with its customers, suppliers, or other business partners

  • Virtual private network (VPN): a secure connection between two points across the Internet

  • Tunneling: the process by which VPNs transfer information by encapsulating traffic in IP packets over the Internet


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Table 7.11: Summary of Internet, Intranet, and Extranet Users


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Figure 7.8: Virtual Private Network


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Net Issues


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Net Issues

  • Management issues: preventing attacks

  • Service and speed issues

    • Web server computers can be overwhelmed by the amount of “hits” (requests for pages)

    • Routers can become bottlenecks


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Figure 7.9: Typical Sources of Internet Attacks


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Net Issues (continued)

  • Privacy

    • Spyware: hidden files and information trackers that install themselves secretly when you visit some Internet sites

    • Cookie: a text file that an Internet company can place on the hard disk of a computer system

  • Fraud

    • Phishing


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Net Issues (continued)

  • Security with encryption and firewalls

    • Cryptography: converting a message into a secret code and changing the encoded message back to regular text

    • Digital signature: encryption technique used to verify the identity of a message sender for processing online financial transactions

    • Firewall: a device that sits between an internal network and the Internet, limiting access into and out of a network based on access policies

  • Unauthorized sites


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Figure 7.10: Cryptography process


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New Organizations are Emerging

  • “Virtual Corporations”

  • Increasing usage of consultants; temporary employees

  • Telecommuting


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Questions (?)


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