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Ch.4 Information Networks

Ch.4 Information Networks. Networks A set of computers connected together so that they can communicate network cards in each computer cabling to a central device called a hub Operating systems uses (protocols) that enables computers to communicate over a network.

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Ch.4 Information Networks

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  1. Ch.4 Information Networks

  2. Networks A set of computers connected together so that they can communicate network cards in each computer cabling to a central device called a hub Operating systems uses (protocols) that enables computers to communicate over a network. Ex: TCP/IP or Transmission Control Protocol / Internet Protocol.

  3. Know the Definitions of Local Area Networks (LAN) and Wide Area Networks (WAN). • LAN • A LAN (Local Area Network) is a system whereby individual PCs are connected together within a company or organization within the same building, or within a group of buildings that are in close proximity • WAN • A WAN (computers over a wider area (across the same town or acWide Area Network) as the name implies allows you to connect to other across a country or even across the world). • Apart from distance, the other feature that distinguishes as WAN from a LAN is that the WAN would make use of a range of communication technologies such as telephone, microwave and satellite links.

  4. Advantages of Networking • If ten people are working together within an office it makes sense for them all to be connected. • In this way the office can have a single printer and all ten people can print to it. • In a similar way other devices such as modems or scanners can be shared. • Users can access their work from any workstation connected to the network. • The ability to share information and files when connected to a network. • Software only needs to be installed on the applications server instead of each workstation.

  5. Intranet, Extranet, Internet

  6. Internet • The internet is the collection of all computers across the world which can access each other in some way. • Intranet • similar to the Internet in operation. However, it is limited to an organisation. An intranet can be thought of as a private Internet. • Extranet • Is an extension of organization’s intranet to include outside users. The purpose of the extranet is to facilitate business transactions with other organizations.

  7. Uses of the Internet • Integrate the operations of multinational corporations. • Provide access to and share information and databases. • Transfer and share files between computers. • Facilitate business transactions. • Share resources. • Promote scientific co-operation between research institutions. • Provide a communications channel for the military.

  8. The World Wide Web • The Web, is a way of accessing information over the medium of the Internet. • Web is the largest and most popular subnetwork on the Internet based on hypertext transfer protocol, the language which allows you and me to brows any web page using a web browser such as Internet Explorer. • the web site must contain files that have a format HyperText Markup Language or HTML. • The HTML documents are stored as web pages on special servers known as web servers.

  9. The Telephone Network in Computing

  10. PSTN • PSDN or Public Switched Telephone Network is simply the technical name for the telephone system in use today. • To connect a computer to a telephone network, you need a modem (modulator-demodulator). • ISDN • Stands for "Integrated Services Digital Network." , able to make use of PSTN cabling to transmit digital signals. • ISDN allows much faster transfer rates than when using modems. Using ISDN, you can transfer 64K or 128Kb of data per second. • If you wish to connect a computer to an ISDN line you need a special ISDN modem. • ADSL • Asymmetric Digital Subscriber Lines allow the transmission of high speed digital data over ordinary telephone lines using certain modulation technology.

  11. Analogue and Digital signals • Analogue signals are used on the PSTN as well as for normal AM and FM radio transmissions. An analogue signal is one which varies continuously as, for example, in ordinary speech. • Digital signals are used in ISDN and ADSL connections. These are two state signals corresponding to a switch (on or off).

  12. Modem • Short for “MODulate/DEModulate”. The modem sends information from your computer across the telephone system. • The modem at the other end of the phone line, converts the signal back into a format that can be used by the receiving computer. • Note that the modem used to connect to an ISDN line is different to that used to connect to an analogue line

  13. Data transfer rates • The speed of a data transfer is measured by the number of bits that can be transferred each second or bps (bits per second). This is also sometimes called the baud rate or bandwidth. High speed lines have their speed measured in kbps or Mbps.

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