A/AS Level Computer Science for WJEC
Activity 10.2 This task requires you to use Linux. This can be done by installing a Linux distribution of your choice, using a Raspberry Pi or using a virtual machine. The commands listed below will not work on a Windows PC. Run the command ifconfig and write down the MAC address and the IP address of your current computer.
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Run the command dig www.pwnict.co.uk +short. What does this command do?
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Install traceroute (sudo apt-get install traceroute).
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Run the command traceroute www.pwnict.co.uk. Explain the output of this command.
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Run the command netstat -tp. Explain the result of this output.
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Read over the tutorial for programming sockets in Python. A socket is a programming term for making and using a network connection.
Handshaking
Tip
In order to set up a communication link, both devices need to agree on a set of protocols to use. This must occur before a single byte of data is sent and is known as handshaking. The handshaking signal is sent from one device to the other and is acknowledged by the second device. It is entirely possible that the second device disagrees with the choice of protocols, so either another set must be chosen or communication will fail.
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A lot of the theory of handshaking is covered in this chapter. Make sure, where relevant, to make use it in your answers. The exam will normally focus on handshaking for communication over a cable rather than a network.
Networking hardware In order to connect computers together into a network, certain hardware is required. There is a massive range of hardware solutions for networking and the ones described in this chapter are the main ones.
Network interface card
In order for a PC to connect to a computer network, it needs a special piece of hardware called a network interface card or NIC. This hardware is responsible for placing packets onto network cables in the form of electronic signals, or bursts of light if the cable is optical. NICs produce electric signals based on the physical protocol being used on the network, one of the most common data transmission systems being Ethernet. NICs tend to be built into most modern motherboards, so extra hardware is not needed. Home networks make use of Ethernet and twisted pair cables, also known as CAT5. Wireless interface cards, or WICs, are needed if the connection to the network is wireless. Most devices have WICs built onto their motherboards, with the exception of desktop PCs. Wireless networks make use of the 802.11.x protocol rather than Ethernet. Again, this is a physical protocol and uses electromagnetic waves to transmit data.
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