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  • 1. Data Communications and Internet Technology
  • 2. Fundamental Networking Concepts
    • A computer network is a collection of computers that communicate with one another over transmission lines.
    • Three basic types of networks are:
      • Local area networks (LANs)–connects computers that reside in a single geographic location on the premises of the company that operates the LAN.
      • Wide area networks (WANs)–connects computers at different geographic sites.
      • Internets–a network of networks
  • 3. Fundamental Networking Concepts (Continued)
    • The networks that comprise an Internet use a large variety of communication methods and conventions, and data must flow seamlessly across them.
    • To provide seamless flow, an elaborate scheme called a layered protocol is used.
  • 4. Figure 5-1 Major Network Types
  • 5. Figure 5-2 Example Networks
  • 6. Communications Protocols
    • A protocol is a standard means for coordinating an activity between two or more entities.
    • A communications protocol is a means for coordinating activity between two or more communicating computers.
    • Two machines must agree on the protocol to use, and they must follow that protocol as they send messages back and forth.
    • Communications protocols are broken into levels of layers.
  • 7. Figure 5-5 TCP/IP-OSI on Your Computer
  • 8. Layer 4
    • An email program (which uses SMTP) interacts with another protocol called TCP , or Transmission Control Program (TCP).
  • 9. Local Area Networks
    • A local area network (LAN) is a group of computers connected together on a single company site.
    • Usually the computers are located within a half mile or so of each other, although longer distances are possible.
      • The key distinction, however, is that all of the computers are located on property controlled by the company that operates the LAN.
    • Computers and printers are connected via a switch , which is a special-purpose computer that receives and transmits messages on the LAN.
  • 10. Local Area Networks (Continued)
    • Each device on a LAN (computer, printer, etc.) has a hardware component called a network interface card (NIC) that connects the device’s circuitry to the cable.
      • The NIC works with programs in each device to implement Layer 1 and Layer 2 protocols.
      • Each NIC has a unique identifier, which is called the (MAC) media access control address.
    • The computers, printers, switches , and other devices on a LAN are connected using one of two media.
      • Most connections are made using unshielded, twisted pair (UTP) cable.
      • A device called an RJ-45 connector is used to connect the UTP cable into NIC devices on the LAN.
  • 11. Figure 5-6 Local Area Network
  • 12. LANs with Wireless Connections
    • Wireless connections have become popular with LANs.
    • The NIC for wireless devices have been replaced by wireless NIC (WNIC).
      • For laptop computers, such devices can be cards that slide into the PCMA slot or they can be built-in, onboard devices.
    • Several different wireless standard exist
      • As of 2005, the most popular is IEEE 802.11g
      • The current standard, 802.11g allows speeds of up to 54 Mbps.
      • The WNICs operate according to the 802.11 protocol and connect to an access point (AP).
  • 13. Figure 5-10
  • 14. Wide Area Networks
    • A wide area network (WAN) connects computers located at physically separated sites.
      • A company with offices in Detroit and Atlanta must use a WAN to connect the computers together.
      • Because the sites are physically separated, the company cannot string wire from one site to another.
    • An Internet service provider (ISP) has three important functions:
      • It provides you with a legitimate Internet address.
      • It serves as your gateway to the Internet.
      • It receives the communication from your computer and passes them on to the Internet, and it receives communication from the Internet and passes them on to you.
  • 15. DSL Modems
    • A DSL modem is takes the place of a cable connection.
    • DSL stands for digital subscriber line.
    • DSL modems operate on the same lines as voice telephones and dial-up modems.
      • They operate so that their signals do not interfere with voice telephone service.
      • They provide much faster data transmission speeds than dial up modems.
      • They always maintain a connection.
  • 16. Virtual Private Network
    • Virtual private network (VPN) is the fourth WAN alternative.
    • A VPN uses the Internet or a private internet to create the appearance of private point-to-point connections.
    • A VPN uses the public Internet to create the appearance of a private connection.
    • A connection called a tunnel , is a virtual pathway over a public or shared network from the VPN client to the VPN server.
  • 17. Virtual Private Network (Continued)
    • VPN communications are secure.
      • The VPN client software encrypts , or codes, the original messages so that its contents are hidden.
    • Virtual private networks offer the benefit of point-to-point leased lines, and they enable remote access, both by employees and by any others who have been registered with the VPN server.
  • 18. Figure 5-18 Remote Access Using VPN: Actual Connections
  • 19. Domain Name System
    • IP addresses are useful for computer-to-computer communication, but they are not well suited for human use.
    • The purpose of the domain name system (DNS) is to convert user-friendly names into their IP addresses.
    • Any registered, valid name is called a domain name.
    • The process of changing a name into its IP address is called resolving the domain name.