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Department of Computing ITEC647 Data Communications Assignment 1, 2018 Semester 2
Due: Thursday 25th October, 2018, 6 pm Marks: 60 Value: 15%
Topics
• Security
• TCP
Submission
Submit on line via Turnitin link on ITEC647 iLearn page.
Please do not double space lines.
Assignments will be marked and returned online. There are no hardcopy submissions for written assignments.
1. TCP (20 marks)
Host A and B are communicating over a TCP connection, and Host B has already received from A all bytes up to byte 126. Suppose Host A then sends two segments to Host B back-to-back. The first and second segments contain 80 and 40 bytes of data, respectively. In the first segment, the sequence number is 127, the source port number is 3024, and the destination port number is 80. Host B sends an acknowledgement whenever it receives a segment from Host A.
b. (4 marks) In the second segment sent from Host A to B, what are the sequence number, source port number, and destination port number?
c. (4 marks) If the first segment arrives before the second segment, in the acknowledgement of the first arriving segment, what is the acknowledgement number, the source port number, and the destination port number?
d. (4 marks) If the second segment arrives before the first segment, in the acknowledgement of the first arriving segment, what is the acknowledgement number?
e. (8 marks) Suppose the two segments sent by A arrive in order at B. B sends acknowledgements for both segments, but the first acknowledgement is lost and the second acknowledgement arrives after the first timeout interval. Draw a timing diagram showing these segments and all other segments and acknowledgements sent (you can assume no other segment loss). For each segment in your diagram, provide the sequence number and the number of bytes of data; for each acknowledgement that you add, show the acknowledgement number.
2.Security (15 marks)
Review Kerckhoff’s six principles of design for security. Explain these in the context of modern electronic communications. How are they still relevant and applied today.
3.Security (10 marks)
What are steganography and cryptography in information security? How are these different? Can they be used together and if so how?
4.Backbone Networks (15 marks)
You have been hired as a network consultant by an large company called Soylent Foods. Your job is to recommend an elegant solution to support their needs and to address their current problems. The IT manager of Soylent Foods wants you to be aware of the following facts:
• The organization has 3 departments. All addressing is done using IP.
• Key servers are currently randomly placed in different departments. So a user in one department X reads and writes to file servers in another department Y. Similarly, users in departments X and Y would read mails from a server in department Z.
• The traffic and broadcast storms originating in one department is causing bandwidth saturation in other departments.
• The core of the network is slow and is unable to meet the response time requirements of various critical business applications.
Propose remedial solutions with adequate justification. In particular, in your recommendation you need to suggest the following:
a) Core technology design.
b) Specific LAN technologies to be used in each department.
c) Specific design solutions to address inter-departmental traffic issues. ((600 words)
Assessment
For all questions in this assignment not only content but also presentation will affect your mark. You will lose marks (and not necessarily only a small portion) if there are problems with the presentation, particularly with clarity. This means that your answers to each question should be a coherent statement and that the spelling and grammar of your submission will be taken into account in assessing its presentation.
For full marks, your answers should all be clear, coherent and correct.
The standards of marking described in the unit outline L.O. 1-4 will be applied to this assignment as relevant to the assignment topics.
In addition, the following particular standards will be applied in marking this assignment:
Correctness of approach
Incorrect answers with the correct logic or approach will receive no more than a pass for the individual question.
Correct answers within correct logic or approach will receive no more than pass for the individual question.
Incorrect answers with no explanation of the approach taken or with the incorrect approach will receive a fail grade for the individual question.
The questions will be marked individually, the marks totalled, and a final grade assigned that is no more than indicated by the total marks, and no more than allowed by the standards specified above and in the unit outline. Clarity
Multi-paragraph answers should be structured into sections and subsections with appropriate headings and subheadings.
Ambiguous or poorly worded answers will receive a grade no more than a pass for the individual question.
Minor issues of clarity will receive a grade no more than credit for the individual question.
Spelling and grammar
Assignment submissions with more than 4 spelling or grammatical errors will not achieve a grade higher than distinction; submissions with more than 8 such errors will not achieve a grade higher than credit.
Bibliography Guidelines
Choose a bibliography style and use it consistently.
Originality
All material must be in your own work and expressed in your own words.
Plagiarism
You should be well aware by now of the University's plagiarism policy. In this assignment, you must be particularly careful to avoid plagiarising your articles or any other sources of information. If you wish to directly quote any portion of another document, you must enclose your quotation in quotation marks and immediately following the quotation you must identify your source. It is important that you do not attempt to write your essay by pasting together pieces of text that you find on the Internet. You need to write your own words and phrases that express your own ideas. You must also list all sources used in your answer/essay in a bibliography at the end of the answer/essay.

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