ch4 ict

• A network is two or more computers that are linked together so that they are able to share resources. (eg. Printer, scanner, data, software and internet connection)
• Network Devices


  • Modems
  • Hubs
  • Switches
  • Bridge
  • Router
  • Network interface card (NIC)
  • Network cables (copper or fibre optics)
• Modem


  Converts a computer's digital signal (i.e. modulates it) into an analogue signal for transmission over an existing telephone line. Converts analogue signals from a telephone line into digital signals (demodulates) to enable the computer to process the data.
• Hubs


  Hardware devices that can have a number of devices/computers connected to them. Used to connect together a number of devices to form a LAN. Does not manage any of the data traffic through it. Take any data packet (this is a group of data being transmitted) received at one of its ports and broadcast it to every computer in the network.
• Switches


  Hardware devices that can have a number of devices (computers) connected to them. Used to connect together a number of devices to form a LAN. Work in a more efficient way compared to hubs. Can direct data to specific computers or devices. Each device or computer on a network has a media access control (MAC) address.
• Bridges


  Connect one LAN to another LAN that uses the same protocol (communication rules). Directs data packets to specific networks. Usually has only two ports.
• Routers


  Connect the LAN to the internet (WAN). Inspect the data packets sent to it from any computer on any of the networks connected to it. Allow private networks to be connected together. Every computer on the same network has the same part of an internet protocol (IP) address. Uses the MAC address to send to correct computer/device. Uses the IP address to work out the best/quickest route.
• Data Packets


  Packets of data usually contain the following information: The sender's IP address, The receiver's IP address, How many data packets make up the whole 'message', The identity number of each packet.
• How data is sent from a networked computer to a computer on a different network using a router

  The network software in the original computer determines that the destination computer is on a different network using IP addresses. Data is sent to the switch and then passed to router. The router then passes it to the router of the other network. That router passes it to the switch to the destination computer.
• How data is sent from a networked computer to a computer on a different network using a bridge


  The computer sends the data to the bridge via the switch using MAC addresses. If the protocol is same, bridge passes data to the other network. Bridge passes it to the switch to destination computer with correct MAC address.
• How a router routes data packets


  Inspects the data packets received. Checks the destination IP address using the stored routing table. It uses a routing table which lists all the different routes to other networks. Uses the IP address to work out the best route sends the data packet to the next router.
• Network Interface Card (NIC)


  A printed circuit board that is installed in a computer so that the computer can be connected to a network (e.g, the internet). Contains the MAC address generated at the manufacturing stage. Some computers, such as laptops, have two NICs: one for wired connections, and one for wireless connections (which uses radio signals instead of wires).
• Copper Cables


  Many computer systems use Wi-Fi, network cables are still used because: Faster data transfer rates than wireless, Can be more secure than wireless networks.
• Fibre Optics Cables


  Advantages of fibre optics compared to copper cables: Offers higher data transfer rates, Better security.
• Internet Protocol (IP) Address


  Unique numerical ID for each device on the Internet. 32-bit/ 4bytes. Written in the form:109.108.158.1. Range from 0.0.0.0 to 255.255.255.255. IP addresses may be static or dynamic. Dynamic IP addresses are assigned when connecting to a network. Static IP address is a fixed address (e.g IP for Web servers). An IP address can be used instead of typing in the full URL. Gives the location of a device on the internet.
• Media Access Control (MAC)

  Hardware Address. Physical Address. Unique address. Identifies each device on the network. Associated with Network card. 48 or 64 bits (12 or 16 hex digits). First 6 or 8 digits = manufacturer ID. Last 6 or 8 digits = serial number of device (NIC).
• IP and MAC Address


  Computer addresses that are stored by the router. MAC address is usually hard coded by manufacturer, never changes. Stores IP addresses. IP address is a unique identifier set up by network manager/ISP. Can change but should match the network it's on. IP address consists of 4 numbers separated by full stops. Stores MAC addresses. 6 pairs of hexadecimal digits.
• How computers use Wi-Fi to connect to networks


  A wireless transmitter (WAP) receives information from a network (e.g broadband connection). Transmitter converts the received information into radio waves. A device (e.g. a computer) receives the radio waves via an installed wireless adaptor which allows it to download the information from the data source.
• Wi-Fi


  Used to provide internet access in homes and public places. Provided you are in range of the wireless router you can access the internet. There are no trailing wires or network wires to install. The range of a WiFi signal depends on the strength of the router and also if there are any obstacles in the way of the signal. Enables local area network and Internet connections. Using WiFi, a laptop or desktop computer can connect to a network's wireless router. WiFi covers a larger distance than Bluetooth. WiFi requires more than ten times more bandwidth than Bluetooth.
• Bluetooth


  Bluetooth sends and receives radio waves. Devices using Bluetooth automatically detect and connect to each other. Devices don't interfere with other devices since each communicating pair uses a different channel. Bluetooth is useful: When transferring data between two or more devices that are very close, When the speed of data transmission is not critical, For low-bandwidth applications. May use of 4 digit code for access.
• Internet


  Worldwide collection of networks. Allows users to: Send and receive emails, Chat online, Transfer files from computer to computer using FTP (File Transfer Protocols), Browse the world wide web. Internet stands for Interconnected Networks. Public network (not policed). WAN (wide area network). Public information system. Web, email, social networking, video conferencing is part of the internet.
• Advantages of policing the internet


  • Helps to prevent illegal materials from being shown
  • Helps to prevent discussion groups that incite hatred, racism
  • Ensure copyright laws are enforced
  • Remove the Dark Net
  • Safeguards the vulnerable
• Disadvantages of policing the internet

  • Unsuitable material is easily available in other ways
  • The rise of mobile communications lessens the impact of the internet
  • Freedom of speech is restricted
  • Very difficult to enforce as the internet spans continents
• Intranet


  Internal restricted access network (secure network). Uses same protocols as the internet. Private network. Used within an organisation eg school. Limited resources.
• Why some companies have intranets

  It is possible to prevent employees accessing undesirable websites. They can ensure that available information is specific to their needs. It is easier to make sure confidential messages stay within the company. There is less chance of company computers being hacked. The amount of information is limited so it is easier to search. Intranets offer better bandwidth than the internet (number of bits per second that can be transmitted are usually higher within an intranet).
• Extranet


  An extranet is part of a company's intranet. The company gives permission for customers and suppliers to access it. Enables businesses to exchange information over the internet in a secure way. Requires username and password to access it.
• Local Area Network (LAN)

  Covers a small area/one building. A school network is a LAN. Consist of a number of computers and devices (for example, printers) That are connected to hubs or switches. One of the hubs or switches will usually be connected to a router and a modem To allow the LAN to connect to the internet. Then becomes part of a WAN.
• Advantages of LAN


  • Data can be shared between computers
  • Software can be shared/updated more easily
  • All computers can access the internet through one connection
  • Can share hardware (eg. Printers, and Scanners)
• Disadvantages of LAN


  • Easier spread of viruses throughout the whole network
  • Printer queues developing, which can be frustrating
  • Slower access to external networks, such as the internet
  • If the main server breaks down, in most cases the network will no longer function
  • Increased security risk when compared to stand-alone computers
• How to set up and configuring a small network


  1. Setting up an IP account if internet access is required

  2. Setting up the system (or buying appropriate hardware correctly configured) to allow for wireless connectivity

  3. Configuring all the hardware and software so that they work correctly together

  4. If internet is required, ensuring that a high-speed broadband connection exists

  5. Putting all the common software onto a server and also making sure that a network licence

  6. Setting up privileges so that each user can only access their own area or common shared area.

  7. Setting up a network-manager-level of privilege do that they can monitor network usage, change passwords
• Wide Area Network (WAN)


  Covers a large geographical area. The Internet. Consists of connected LANs. The network of ATMs (automated teller machines) used by banks.
• Wireless Local Area Network (WLAN)


  Uses radio signals instead of cables to transmit data. Uses Wireless Access Points (WAPs) connected to a wired network. AP receives and transmits data between the WLAN and the wired network structure. End-users access the WLAN through wireless LAN adapters.
• The process of using WiFi to connect to a WLAN


  The computer or device sends data to its wireless adapter. The data is converted into radio waves. The radio waves are transmitted. A wireless adapter receives the radio waves. Radio waves are converted into data. The computer initiates a handshake with the wireless router. The wireless router responds. Establishes a session. Wireless router checks the password is correct. Data is transmitted. User has to enter a password or automatic entry of key for known connections.
• Advantages of WLAN


  • There are no network wires so costs are reduced
  • Safer – no wires to trip over
  • Makes the network more flexible
• Disadvantages of WLAN


  • Slower data transfer rates than wired networks
  • Wireless networks are less secure than wired networks
  • Wireless networks can suffer from interference from other wireless devices
  • Wireless networks have a limited range
• WANs


  Wide Area Networks
• Types of networks


  • LANs
  • WANs
  • WLANs
• Wireless local area network (WLAN)


  • Uses radio signals instead of cables to transmit data
  • Uses Wireless Access Points (WAPs) connected to a wired network
  • AP receives and transmits data between the WLAN and the wired network structure
  • End-users access the WLAN through wireless LAN adapters
• Process of using WiFi to connect to a WLAN

  1. Computer/device sends data to wireless adapter

  2. Data is converted into radio waves

  3. Radio waves are transmitted

  4. Wireless adapter receives the radio waves

  5. Radio waves are converted into data

  6. Computer initiates handshake with wireless router

  7. Wireless router responds

  8. Establishes a session

  9. Wireless router checks password is correct

  10. Data is transmitted
• User access to WLAN


  • Enter password
  • Automatic entry of key for known connections