computer networking

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Computer Network Slides Prepared by sir Khuram Rizvi....


  • 1. Computer Network Section - IV Stage II -ICMAP

2. Outline

  • Fundamentals
  • Types of Network
    • (LAN, WAN,MAN,VAN,VPN,Intranet,Extranet)
  • Protocols
  • Network Topologies
    • (Star, Bus, Ring, Mesh, Hybrid)
  • Network Devices
  • Network Media/Cables
  • Internet Security Risk
  • Security Measures

Stage II -ICMAP 3. Computer Network

  • The connection or two or more computer systems using a communication channel is called computer network.
  • Group of connected computer connected through a hub/switch/modem to share information through communication medium is called network.

Stage II -ICMAP 4. Centralized Data Processing

  • Places all hardware, software, and processing in one location
  • Very inconvenient and inefficient
    • Input data had to be physically transported to computer
    • Processed material had to be delivered to users

Return Stage II -ICMAP 5. Distributed Data Processing

  • Uses computers that are at a distance from central computer
  • Local computers had access to central computers
    • Some processing done on local computers, some on central computers

Return Stage II -ICMAP 6. Digital and Analog Transmission

  • Digital transmission
        • Sends data as distinct pulses, either on or off
        • Similar to how data travels through computer
  • Analog transmission
      • Continuous electrical signal in the form of a wave
        • Called carrier wave
      • Many communications media already in place for analog (voice) transmission
        • Phone lines are most common

Stage II -ICMAP 7. Components of Communication System

  • 1. Transmitter
  • 2. Medium
  • 3. Receiver

Stage II -ICMAP 8. Asynchronous Transmission

  • Also called start/stop transmission
    • Start bit transmitted at the beginning of each group of bits
    • Stop bit sent at end of each group
    • Each group typically consists of one character
  • Receiving device gets start signal and sets up mechanism to accept the group
  • Used for low-speed communications

Return Stage II -ICMAP 9. Synchronous Transmission

  • Large block of characters transmitted
  • Internal clocks of devices synchronized
  • Error-check bits make sure all characters received
  • Much faster, but equipment is more expensive

Return Stage II -ICMAP 10. Transmission Mode

  • 1. Simplex
  • 2. Half-Duplex
  • 3. Full-Duplex

Stage II -ICMAP 11. Simplex, Half-Duplex, and Full-Duplex Transmission

  • Simplex transmission sends data in one direction only
    • Example: television broadcasting
  • Half-duplex transmission sends data in both directions, but only one way at a time
    • Example: bank teller sends data about a deposit; after data received, a confirmation returns
  • Full-duplex transmission allows transmission in both directions at same time
    • Example: a conversation
    • Typically used for high-speed data communication

Stage II -ICMAP 12. Simplex Communication

  • Simplex communication is a mode in which data only flows in one direction.Because most modern communications require a two-way interchange of data and information, this mode of transmission is not as popular as it once was.
  • However, one current usage of simplex communications in business involves certain point-of-sale terminals in which sales data is entered without a corresponding reply.

Stage II -ICMAP 13. Half-Duplex Communication

  • Half-duplex communication adds an ability for a two-way flow of data between computer terminals. In this directional mode, data travels in two directions, but not simultaneously.
  • Data can only move in one direction when data is not being received from the other direction. This mode is commonly used for linking computers together over telephone lines.

Stage II -ICMAP 14. Full-Duplex Communication

  • The fastest directional mode of communication is full-duplex communication. Here, data is transmitted in both directions simultaneously on the same channel. Thus, this type of communication can be thought of as similar to automobile traffic on a two-lane road.
  • Full-duplex communication is made possible by devices called multiplexers. Full-duplex communication is primarily limited to mainframe computers because of the expensive hardware required to support this directional mode.

Stage II -ICMAP 15. Network Uses

  • Electronic mail (e-mail)
  • Facsimile (fax) technology
  • Groupware
  • Teleconferencing
  • Electronic data interchange
  • Electronic fund transfers
  • Computer commuting
  • The Internet

Stage II -ICMAP 16. The Internet

  • A global network of hundreds of thousands of Computers
  • Widely considered to be the defining technology of the beginning of this century

Return Stage II -ICMAP 17. The Internet Service Provider and the Browser

  • An Internet service provider (ISP) provides the server computer and software to connect to the Internet
    • Online service, such as America Online, includes Internet access, Internet service, and a browser
  • When you connect to the Internet, the browser displays a home page

Return Stage II -ICMAP 18. Uniform Resource Locator (URL)

  • The complete, unique address of a Web page
    • Web page URL begins with http
      • HyperText Transfer Protocol allows communication by using links to transfer data between sites
    • Domain name address of sites host computer
      • Last part of domain name is called a top-level domain
      • Identifies country or purpose of organization

Return Stage II -ICMAP 19. Local Area Network (LAN)

    • Contains printers, servers and computers
    • Systems are close to each other
    • Contained in one office or building
    • Organizations often have several LANS
    • LAN is a number of computers connected to each other by cable in a single location, usually a single floor of building or all the computers in a small company

Stage II -ICMAP 20. Wide Area Network (WAN)

  • Set of connecting links between LAN. These links are made over telephone lines leased from various telephone companies
  • Wide Area Networks (WAN)
    • Two or more LANs connected
    • Over a large geographic area
    • Typically use public or leased lines
      • Phone lines
      • Satellite
    • The Internet is a WAN

Stage II -ICMAP 21. Difference between LAN & WAN Stage II -ICMAP LAN WAN

  • Covers small geographical area
  • Computers are directly connected through physical cable for data transmission
  • LAN card is used for data transmission
  • Data transmission speed is very high
  • Installation and configuration cost is less than WAN

Covers large or wide geographical area No physical cable or wire is used and data is sent and received through microwave system or satellite. Modem is used for data transmission slow Higher than LAN 22. Metropolitan Area Network (MAN)

  • Metropolitan Area Network (MAN)
    • Large network that connects different organizations
    • Shares regional resources
    • An example of a regional resource is a supercomputer. For example, Pittsburgh has the Pittsburgh Super Computing center ( The various colleges in Pittsburgh connect to the center through a MAN in Pittsburgh.

Stage II -ICMAP 23. Client/Server Network

    • Nodes and servers share data roles
    • Nodes are called clients
    • Servers are used to control access