Question 1 (Week 7) (14 marks)
Working for a software company you are attending a meeting to discuss the development of a
new application which will allow massive volumes of data to be transferred over several days.
One of the topics for discussion is whether the TCP or UDP protocol should be used. One of your
colleagues is convinced that TCP must be used as it provides services such as error control and
flow control which are critical for the data delivery task. Another colleague however points out
that the requirement for data transfer to occur over several days mandates the use of UDP, as
even a temporary network outage could cause the TCP connection to be dropped, in turn causing
the transfer to be aborted. In response, you tell them that they’re both wrong, and that either
protocol could be used. For both TCP and UDP:
i. Briefly explain how the protocol could successfully be used for this application;
ii. Briefly explain two advantages and two disadvantages of using the protocol for this
application.
Question 2 (Week 8) (17 marks)
Consider the operation of the SMTP protocol as illustrated in Week 8 Slide 59:
i. Briefly describe what is happening at each step of this exchange
ii. Briefly describe three services of the underlying transport layer and how they are
used/exploited by this application protocol.
iii. Briefly explain why this particular style of message exchanges and the formatting of the
email data section have been chosen for this application protocol.
Question 3 (Week 9) (16 marks)
Consider the Management Information Base proposed/defined for the TCP protocol in RFC4022:
https://tools.ietf.org/html/rfc4022
Briefly discuss what information you could learn about your network from the following objects:
• tcpAttemptFails
• tcpEstabResets
• tcpRetransSegs
• tcpConnectionTable
For each of the objects identified above:
i. Briefly describe what information the object contains (must be in your own words)
ii. Discuss what can be learned about what’s happening in the network on the basis of this
information, e.g., what would a low value versus a high value in object X potentially mean
is happening on the network?
Question 4 (Week 7-9 Prac) (9 + 4 + 6 = 19 marks)
a) Demonstrate the use of sequence numbers and acknowledgement numbers by the TCP
protocol to send a random short phrase which is divided into three segments, two of which
are delivered and acknowledged, before the final segment is delivered and acknowledged.
Note that only segment data content, sequence number, and acknowledgement numbers
are required.
Hint 1: Running a Google search for “short quotes” or similar will result in many short
phrases that could potentially be used (remember Code of Conduct rules apply, nothing
offensive/ abusive can be used).
Hint 2: A figure such as those prepared for Problem Solving Report 2 could help you to
answer this question!
b) In the Week 8 lab task, we examined the behaviour of the DNS protocol. Identify what
layer of the TCP/IP model the DNS protocol runs at and explain why.
c) In the Week 9 practical we examined the SNMP protocol (addressed in Question 3) and the
NetFlow protocols. Briefly describe what kind of information is provided by the NetFlow
protocol and briefly discuss what this information could be used for.
