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Data Communications and Internet Technology. 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:

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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


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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.




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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.



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Layer 4

  • An email program (which uses SMTP) interacts with another protocol called TCP, or Transmission Control Program (TCP).


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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.


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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.



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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).



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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.


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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.


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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.


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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.



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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.


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