Home > IB Computer Science 2014, IB Computer Science 2015 > Lessons from the Networks test

Lessons from the Networks test

January 28, 2014 Leave a comment Go to comments

Work harder. Don’t be complacent. Don’t use lessons as your only resource for learning.

The truth is that there are only about 100 possible questions that you could be asked in Computer Science, and it would not be difficult to learn all the answers. You need to use the Guide to help you decide what to learn, and then you should use me, my blog, your textbook, other IB Comp Sci web pages, and finally Wikipedia, to produce your own set of perfect notes. Then you should learn them. Simple.

Belt and braces approach when questions overlap

Don’t be afraid to put some of the same content in two related questions if you’re not sure where it should go. An example was the LANs question.

(a) Define LAN [1 mark]

    • Local Area Network
    • Restricted to a single location, e.g. a school or office

(b) Outline two features of a LAN [2 marks]

    • Restricted to a single location, e.g. a school or office
    • Uses wires to connect computers, e.g. Ethernet cable
    • Allows users to share resources such as printers and files

Notice that each answer is surely enough to score the full marks, but that since you don’t know whether the definition requires you just to say what LAN stands for, you have put one of the responses in both answers, just to make sure.

Use Plain English. Get the fundamental concepts across. If in doubt, just answer the questions: What, when, why and what happens next

Describe how a check sum could ensure data integrity in the transmission of data. [3 marks]

    • A mathematical calculation is done using the bits of the data to be transmitted.
    • The result is put into the header of the data packet before it is sent.
    • The receiver does the same calculation on the bits and compares with the result in the header.
    • If the two results are different then an error has occurred and the packet is requested to be resent.

Always spell out what acronyms stand for and provide simple definitions of terms, even when not directly asked to.

Use bullets correctly.

Bullets help to structure your answer to some questions. Other, longer questions require you to arrive at some sort of synthesis (bringing together) or conclusion and bullets are to be used sparingly in those questions.

You can use bullets exclusively on this question:

Explain how data is transmitted using packet switching [3 marks]

But you should provide at least one unbulleted paragraph at the end of this question:

Evaluate the effect that increased networking has had on people’s lives [6 marks]

Don’t hint or imply that you know something. State it boldly and clearly.

If you are asked “How can data transmission speeds be increased?” don’t just say “By improving hardware”. Improving hardware how?? State it clearly, preferably with an example: “By using a faster transmission medium, for instance fibre-optic cable instead of copper wire.”

Don’t brain-dump

Students often write everything they know about a topic, instead of answering the specific question. You are better to write one relevant answer than two irrelevant ones.

Give examples, even when not required to

There are often extra marks set aside in mark schemes for examples.

Protocols are agreed sets of rules governing communication between two parties, e.g. Internet Protocol (IP) governs the transmission of data from one host to another on a network.

Use the language to show the structure of your answer

  • If the encrypted message is intercepted on the network, then it won’t be possible to read its contents.
  • Networking has been thought to contribute to obesity because people no longer have to leave the home to work or shop.
  • There is no longer a clear boundary between work life and home life so people often find themselves working longer hours and spending less time with their families.

If the question is worth 1 mark, give 2 points. If it is worth 2 marks, give 3 points.

A good way to show that you understand why something is done is to state the consequences of not doing it.

In networking, protocols are agreed sets of rules governing how data should be interpreted. Without protocols, computers would not be able to understand the data that they receive.

Make sure you refer to the context of the question if you are asked to. A good way to answer context-dependent questions is by outlining the sequence of events.

Outline the way in which encryption should be used when logging into a website [3 marks]

    • When the user types in their username and password, these should be encrypted.
    • Once they are encrypted, they can be sent out across the network. 
    • If they are intercepted on the network, the attacker will not be able to read them.
    • When they reach the destination server, they can be decrypted using a special key.
    • Then the website can authenticate the user.
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