CI7110: Data Communications

The TLS Handshake Protocol establishes an authenticated key exchange between a Web server and client.

a) Give a high-level overview of how the TLS handshake protocol works, including messages sent at the TCP/IP layer. You may use diagrams to further explain the protocol traces.

b) What is the purpose of the Master Secret (MS), in the context of TLS key exchange, and how is it securely communicated?

c) Navigate to Kingston University's public website at www.kingston.ac.uk, using a web browser of your choice. The following questions require

you to inspect the site's certificate:

What type of certificate is it, when was it created, and when will it expire? What is the name of Kingston's Certificate Authority (CA)? In your opinion, why might the university have chosen this particular CA?

2. (a) Describe phase shift keying (PSK) and quadrature amplitude modulation (QAM) and explain the differences between these two modulation methods. Draw graphs to illustrate the two methods.

(b) Explain with the aid of constellation scatterdiagrams the performance of PSK and rectangular QAM with the same signal to noise ratio and alphabet size of M symbols. Your answer should include consideration of at least two symbol sizes (M) and different signal to noise ratios in order to discuss their effects on bit error rate and symbol error rate.

(c) Describe how QAM and PSK are used in digital communications. As part of your answer you should consider the implications of their performance considerations addressed in part b.

If you use MATLAB or Simulink to help answer this question you should explain the MATLAB code and/or Simulink model as well as also uploading the .m, .mlx and/or .slx file(s).

3. (a) Describe and explain with the aid of graphs how a square wave pulse train with frequency f and amplitude A can be generated using Fourier series. As part of your answer you should include consideration of the effect of increasing the number of Fourier series terms used.

(b) Describe and explain Nyquist’s sampling theorem and its relevance in communications systems. Using graphs of sine waves with different frequencies, explain the importance of sampling rate and quantisation.

(c) With the aid of graphs, explain what signal conditioning would be desirable prior to transmission of a rectangular pulse train signal down a communications channel.

(d) Explain the use of channel coding in Digital Communications and explain how the Hamming distance can be determined for Block Codes.

If you use MATLAB or Simulink to help answer this question youshould explain the MATLAB code and/or Simulink model as well as also uploading the .m, .mlx and/or .slx file(s).

4. (a) Assume you open a browser and enter www.google.com in the address bar. What happens up until the webpage is displayed? Provide details about the protocol(s) used and a high level description of the messages exchanged. Your answer will need to show all assumptions and reasoning required.

(b) You are a network programmer and were asked to develop a platform for streaming on-demand and real-time video over IP network. What transport protocols will you use for such application? List three reasons for selecting such transport protocols. In addition, state how will you select the source and destination port numbers. Your answer will need to show all assumptions and reasoning required.

(c) How long does it take a packet of length L to propagate over a link of distance d, propagation speed s, and transmission rate R bps? Does this delay depend on packet length? Does this delay depend on transmission rate? How long does it take a packet of length 1,000 bytes to propagate over a link of distance 2,500 km, propagation speed 2.5 × 108 m/s, and transmission rate 2 Mbps? Explain how this delay contributes to the efficiency of Carrier Sense Multiple Access/ Collision Detection (CSMA/CD).

5. (a) Two small companies have merged resulting in a complete reorganisation of the resultant merged company and require a complete redesign of the IP addresses for its intranet. It has been allocated an internet IP address of 201.1XY.60.0/23*. The requirements for the intranet are as follows: A Headquarters site has 28 hosts. Two remote sites each requiring 7 hosts. Each remote site is to be interconnected to the Headquarters site via a serial link. Design a suitable subnet IP addressing scheme based on the maximum number of hosts required by the largest subnet.

In your design clearly show the subnet mask, the subnets’ addresses, first and last IP host addresses for each subnet together with the subnets broadcast address.

Your answer will need to explain all assumptions and reasoning behind the design.

* ‘XY’ in the network address above should be replaced with the following:

X is the fourth number digit from your K number starting from the left, and

Y is the fifth number digit from your K number starting from the left.

(b) Explain and compare the two main approaches used in networking to control traffic congestion. If you are a network application programmer, which approach do you prefer and why?

(c) Explain the main functionalities of the data plane and control plane of the network layer. Suppose you wanted to implement a new routing protocol in the Software Defined Network (SDN) architecture, explain at which plane and layer you would implement that protocol