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Review + Topology

NETWORKS. Review + Topology. Review. A computer network is a number of computers linked together to allow them to share resources. Networked computers can share hardware , software , and data .

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Review + Topology

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  1. NETWORKS Review + Topology

  2. Review • A computer network is a number of computers linked together to allow them to share resources. Networked computers can share hardware, software, and data. • Most computer networks have at least one server. A server is a powerful computer that provides one or more services to a network at its users. For example, file storage and email.

  3. LANs & WANs • There are two main types of Network: • Local Area Network (LAN) • Wide Area Network (WAN)

  4. LAN • A LAN covers a small area such as one site or building, e.g. a school or college.

  5. WAN • A WAN covers a large geographical area. • Most WANs are made from several LANs connected together.

  6. WAN • The Internet is a WAN. • A network of ATM (bancomat) dispensers is a WAN. • A school network is usually a LAN. • LANs are often connected to WANs, for example a school network could be connected to the Internet. • WANs can be connected together using the Internet, leased lines or satellite links.

  7. DNS • Domain Name Server??? • An Internet service that translates domain names into IP addresses. • Domain names are alphabetic, they're easier to remember. • The Internet however, is really based on IP addresses. • Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address. • For example, the domain name www.example.com might translate to 198.105.232.4.

  8. Advantages & Disadvantages of Networks Advantages • Sharing devices such as printers saves money. • Site (Software) licenses are likely to be cheaper than buying several standalone licenses. • Files can easily be shared between users. • Network users can communicate by email and instant messenger. • Security is good – users cannot see other users’ files unlike on stand-alone machines. • Data is easy to backup as all the data is stored on the file server.

  9. Disadvantages • Purchasing the network cabling and file servers can be expensive. • Managing a large network is complicated, requires training and a network manager usually needs to be employed. • If the file server breaks down, the files on the server become inaccessible. Email might still work if it is on a separate server. The computers can still be used but would be isolated. • Viruses can spread to other computers throughout a computer network. • There is a danger of hacking, particularly with wide area networks. Security procedures are needed to prevent such abuse, e.g. a firewall.

  10. Sample Question on Networks • A school with 20 stand-alone PC’s is considering networking them together and adding a file server. • Consider FOUR possible benefits of doing this.

  11. The Bus Network • In a bus network all the workstations, servers and printers are joined to one cable (the bus). At each end of the cable a terminator is fitted to stop signals reflecting back down the bus.

  12. Bus Network

  13. Bus network animation • http://www.teach-ict.com/gcse_new/networks/topologies/djp/mov_busnetwork.swf

  14. The Ring Network • In a ring network each device (workstation, server, printer) is connected to two other devices, this forms a ring for the signals to travel around. Each packet of data on the network travels in one direction and each device receives each packet in turn until the destination device receives it.

  15. Advantages & Disadvantages

  16. Ring Network animation • http://www.teach-ict.com/gcse_new/networks/topologies/djp/mov_ringnetwork.swf

  17. The Star Network • In a star network each device on the network has its own cable that connects to a switch or hub. A hub sends every packet of data to every device, whereas a switch only sends a packet of data to the destination device.

  18. Advantages & Disadvantages

  19. Star network animation • http://www.teach-ict.com/gcse_new/networks/topologies/djp/mov_starnetwork.swf

  20. More Advanced Networks Tree or star bus Mesh

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