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6 Further System Fundamentals (HL)

6 Further System Fundamentals (HL). 6.4 Further Network Fundamentals. 6.4.1 Network Characteristics. Server - client. Network server : with a network OS, serves out files (e.g. shared databases), controls security and permissions, and access to (through firewall) the web proxy server.

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6 Further System Fundamentals (HL)

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  1. 6 Further System Fundamentals (HL) • 6.4 Further Network Fundamentals

  2. 6.4.1 Network Characteristics

  3. Server - client • Network server: with a network OS, serves out files (e.g. shared databases), controls security and permissions, and access to (through firewall) the web proxy server. • Client : a normal workstation with application software.

  4. Peer-to-peer • Two or more computers connect without one having more authority. • Such networks can be faster, but are less secure.

  5. Local vs. wide • Local area network (LAN): within one building or site (e.g. a school), connection requires a network interface card (NIC). • Wide area network (WAN): involves many LANs, connection to a WAN requires a modem for digital/analogue conversion of the signal on a telephone line.

  6. ISPs • Internet service providers offer servers for their clients and connection to the internet • Also email, web hosting, etc. services.

  7. Transmission speed • Measured in bits per second (bps). • Typical dial-up bandwidth was 56kbps. • Broadband is achieved using different channels over the same line (allowing up to 10Mbps). • Serial transmission is faster over long distances, parallel over shorter. • Ethernet (a common network protocol) can transmit up to 100Mbps.

  8. Transmission speed • Simplex: data transmission is only possible in one direction e.g. a radio broadcast. • Half-duplex: in both directions, but not at the same time e.g. a walkie-talkie. • Full-duplex: two-way all the time e.g. telephone or IRC.

  9. Transmission media • A telephone wire is a pair of copper wires (slow, poor quality and liable to interference). • Coaxial cable (TV aerial cable) is thicker, some shielding , cheap. • UTP: standard network cable, cheap (also called CAT5 or ethernet cable). • Wi-Fi : convenient for mobile devices, avoids cables.

  10. Transmission media • Optic fibre: fast but expensive, uses light, no metal so no interference. • Microwave: for long distances, expensive and needs line-of-sight connection. • Satellite: very expensive, available anywhere so useful for remote locations.

  11. Network devices • Hub: a simple junction box. • Switch: like a hub, but it filters the data according to what it’s connected to. • Gateway: allows connections between LANs. • Router: actually directs data traffic across a network, therefore allow the internet to function.

  12. ISDN and ASDL • ISDN is still used in business, requires a special modem and line, and can transmit voice, data and video. • ADSL uses a normal telephone line, but splits the voice and data into channels, also with a greater download than upload capacity (asynchronous).

  13. Public vs. private • Most internet connections are over public telephone networks. • Private telephone lines are possible for very secure needs or heavily-used networks.

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