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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
Topics Lesson 7
  • Basic Telecommunication Concepts
  • Telecommunication Models
  • Networking
  • Client/server Computing
  • Telecommunication Standards
  • Wireless Communications
  • Internet
modems
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
modems3
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
electronic communication terminology
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)
electronic communication modes
Electronic Communication Modes
  • Communications Protocols
  • Handshaking
  • Redundancy
    • CRC – Cyclic Redundancy Checking
multiplexers
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
front end processors
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
slide10
Figure 6.9: Use of a Multiplexer to Consolidate Data Communications onto a Single Communications Link
connections
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
types of media
Types of Media
  • Twisted Pair
  • Coaxial Cable
  • Fiber-Optic Cable
  • Wireless
    • Microwave Transmission, RF (WiFi, Bluetooth, cellular), Inferred
satellite
Satellite
  • Fig 6.8
cellular
Cellular
  • Fig 6.9
infrared transmission
Infrared Transmission
  • Line of sight
  • Short distances
local area networks
Local Area Networks
  • Server Based (Novell/Microsoft Active Directory)
  • Peer-to-Peer (LANtastic, Windows)
  • Physically most common: Ethernet over unshielded twisted pair.
other
Other
  • Gateway – for attaching different networks – converts one protocol to another.
  • WAN
  • Wireless (Wi-Fi (802.11), Bluetooth)
    • PAN
what is client server
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.
what is client server27
What Is Client/Server?

Basic Client/Server Computing

client server systems benefits
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
managerial expectations of client server systems benefits
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
client server architecture
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.
client server architecture31
Client/Server Architecture
  • Client Components
    • Powerful hardware
    • An operating system capable of multitasking
    • A graphical user interface (GUI)
    • Communications capability
client server architecture32
Client/Server Architecture
  • Types of Services
    • File services
    • Print services
    • Fax services
    • Communications services
    • Database services
    • Transaction services
    • Application services
    • Web Services
types of internet connections
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
the internet
The Internet
  • See Introduction to the Internet and the WWW
what is the internet
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)
how the internet works
How the Internet Works
  • Hosts
  • Routers forward packets to other networks
  • Internet Protocol Stack (TCP/IP)
    • Internet Protocol (IP)
    • Transport Control Protocol (TCP)
  • Backbones
how the internet works39
How the Internet Works
  • Uniform Resource Locator(URL)
  • http://www.whitehouse.gov

World Wide Web

Domain category

Hypertext transfer protocol

Host Network Name

structure of the internet
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
the world wide web44
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
the world wide web continued
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
web software
Web Software
  • Web browsers
  • Search engines
    • Keyword indexes: fast & broad
    • Subject indexes: focused searches
webcasting
Webcasting
  • aka Push Technology
  • Consolidates information according to a user’s profile & displays in the browser
web services
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
web services continued
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)
internet and web applications
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
internet and web applications continued
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
internet and web applications continued57
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
internet and web applications continued58
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
internet and web applications continued61
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
intranets and extranets65
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
intranets and extranets continued
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
net issues70
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
net issues continued
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
net issues continued73
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
new organizations are emerging
New Organizations are Emerging
  • “Virtual Corporations”
  • Increasing usage of consultants; temporary employees
  • Telecommuting
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