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Networks

Networks. A network is two or more computers & devices that are connected via communication devices and transmission media allowing computers to share resources Standalone device, computer not connected. Networks. Networks. For successful communications you need:

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Networks

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  1. Networks • A network is two or more computers & devices that are connected via communication devices and transmission media allowing computers to share resources • Standalone device, computer not connected.

  2. Networks

  3. Networks • For successful communications you need: • Sending device, eg. computer, mobile phone, GPS receivers • Communications device, eg. broadband router, dial up modem • Communication channel or transmission media, eg. phone line, optic fibre, ADSL2 • Communications device to receive, eg. computer, etc.

  4. Networks: Advantages • Facilitating communications • Enabling easy communicating, email, facebook, instant messaging, chat rooms, video conferencing, etc. • Sharing hardware • Networked computers can access peripheral devices, eg. printers, photocopiers, etc. leading to lower costs than each device requiring a printer • Sharing data and information • Any authorised computer can access and store data & information stored on other computers, servers, etc. • Sharing software • Users access networked software based on a site licence; this costs less than buying individual copies of s/ware. • Transferring funds • Networks enable EFT; transfer money, deposit salaries, pay bills online.

  5. Networks: Disdvantages • User dependence • When network is down users are not able to access devices, share data, share software or undertake transfers, etc. • Management of the network • Networks require work to set up and maintain • Require skilled network staff, manager and support personnel

  6. LANs – local Area Network

  7. LANs – local Area Network • Group of computers connected by a neighbouring geographic area • Each computer or device on network is a node • Geographically limited, usually to one site, 5 kms • Usually cabled with CAT 5, (UTP), or wireless lan, WLAN. • Network operating system, (NOS) is system software that organises, controls & coordinates activities on LAN.

  8. LANs – local Area Network • NOS controls attached computer systems & peripheral devices • NOS performs these tasks • Administration, eg. adding, deleting users, backup • File management, locating & transferring files • Printer management • Security, restricting access to network resources • 3 providers of NOS, Microsoft, Novell and Apple

  9. Peer-to-Peer (P2P) networks

  10. Peer-to-Peer (P2P) networks • Simple inexpensive network where each node shares hardware & data with all other computers on network • No server, so costs are low and installation is simple • All computers and users have equal authority and rights • Little protection of one workstation against another • -Used at home or in small organisations with trusted users • -Allows sharing of files, internet connection, printer • -

  11. Client-Server networks

  12. Client-Server networks • One computer program (the ‘client’) asks another computer program (the ‘server’ or host computer) to provide a service, such as looking up and providing data, delivering email, sending web pages, bank balances etc.; eg. server at school • Server computer has more storage capacity and power than clients • Some different types of servers: • file servers, store files for use on client computers • application servers, store applications to enable clients access

  13. Client-Server networks • print servers, accepts print jobs over the network faster than a printer; workstation gets on with other tasks whilst printing is done • Database server; hold d/bases and allows them to be used by many users • web servers, connected to internet and serve webpages to viewers • Advantages/disadvantages: • Costs significantly higher than peer-to-peer & ongoing technical support • Advantages are economies of scale of sharing resources, backup and security against viruses, etc.

  14. Wide area networks, the internet • Wide Area Network (WAN) – broad geographic coverage (e.g. state-wide, country-wide, international) • Communications carried by a medium owned by someone who is not part of the organisation whose data is being transmitted • Transmission media include microwave, fibre-optic, telephone lines & satellite. • WANs include: • Statewide network • National area network • World wide network, eg. internet

  15. Internet-Peer to Peer (P2P) networks • Users must enable their computer to be accessed by others over the internet. This allows copying of files from one hard drive to another via the internet. • P2P, enabling users with same networking software to connect to each other’s hard disks and exchange files directly • Internet music sharing networks such as BitTorrent, Limewire & Kazza are software applications that support peer-to-peer • This style of network can expose your computer to possible security violations.

  16. Internet-Peer to Peer (P2P) networks • Once connected you have access to their hard disks • Examples, Kazaa and Limewire • Exposure to possible security violations, eg. viruses and trojans

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