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Due date: 11:45pm AEST, Friday, Week 10 ASSESSMENT Weighting: 25% 2 Objectives This assessment task requires you to demonstrate your knowledge of routing concepts by completing a number of exercise...

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Due date:

11:45pm AEST, Friday, Week 10

ASSESSMENT

Weighting:

25%

2

Objectives

This assessment task requires you to demonstrate your knowledge of routing concepts by completing a number of exercise questions.

The questions are designed to help you to achieve the unit learning outcomes as listed in the unit profile.

Instructions

You must do this assignment on your own – it is not a group assignment.

These questionswill require more time and effort than the first assignment so plan ahead and start as early as possible. Question #3 may require additional research and analysis to complete.

Type all your answers in the ‘Template for Your Answers’ Section of this document and upload only that template. You can do that by copying the Template section into a new Word document for uploading. Answers that are not typed into the “Template for Your Answers” section may not be marked, or may be returned to you for re-typing and re-submission – late penalties will apply.

Where instructed, you must show the steps you took to arrive at your answers. Write your answers in your own words to avoid potential plagiarism and copyright violations.

You must submit the Answer section as a Word file (.doc or .docx). Do not submit PDF’s or any other type of file without express permission from the Unit Coordinator.

Plagiarism Procedures can be found in the CQUniversity Policies section of the Unit Profile.

Assessment Requirements and Marking Criteria

There are 3 main questions each with sub-questions and the requirements are stated for each one. You must answer all questions and their sub-questions. Marks are indicated in the Answer Template.

The questions will be marked on correctness, logic and clarity, and addressing all parts of the question.

The Assignment Questions begin on the next page.

REMEMBER, USE THE ANSWER TEMPLATE FOR ALL YOUR ANSWERS

Question 1 – Routing (10 marks)

Given the following network diagram, assume that all the networks shown are aware of each other and have fully updated routing tables. Answer the questions that follow.

The questions (1 mark each except q.8):

1. From the point of view of router R4, what is the next-hop address for a packet addressed to host XXXXXXXXXX/18?

2. From the point of view of router R1, which of its interfaces would it choose for a packet being sent to network XXXXXXXXXX/18?

3. A host with an IP address of XXXXXXXXXX/24 has just sent a packet to a host with address XXXXXXXXXX/18. How many hops is required between source and destination?

4. A packet originating from network XXXXXXXXXX/24 arrives at router R1, however, R1 determines that the destination network is not in its routing table. What does R1 do with the packet?

5. A packet arrives at router R2 with a destination address of XXXXXXXXXX/22. Which interface port does R2 forward the packet out of?

6. A packet at router R3 has a destination address of XXXXXXXXXX/26. What next-hop address would R3 use for this packet?

7. A packet is waiting at router R4 for forwarding. If the next-hop was a “direct delivery”, which of these three networks is the destination network? XXXXXXXXXX/16, or XXXXXXXXXX/18, or XXXXXXXXXX/24?

8. Complete the information in the routing table for router R2 as shown in the Answer Template for networks XXXXXXXXXX/16, XXXXXXXXXX/18, and the Default network. Show the masks in longest mask order using CIDR format (3 marks).

Question 2 – Fragmentation in IPv4 (5 marks)

An IP datagram 5,400 bytes long with no options arrives at a router, which determines that the next destination has an MTU of 1,500 bytes. Use the Answer Template to complete the following questions, showing your calculations and reasoning.

a) Assuming that the router decides to fragment the packet into 4 fragments, determine a correct size for each fragment, and identify the starting byte and ending byte of each fragment (2.5 marks).

b) Calculate the fragmentation offset for each fragment (1.5 marks).

c) State whether the total number of bytes from all 4 fragments leaving the router will be greater than the initial datagram size that arrived, or less than the initial datagram size, and the reason (1 mark).

Question 3 – Congestion controls in TCP XXXXXXXXXXmarks)

This question affords you the opportunity to extend your thinking about congestion controls in TCP beyond the textbook to observe what a real-world technology company, Google, is doing in this space.

First, read this Network World article that reports on Google’s approach to improving congestion controls in TCP:

https://www.networkworld.com/article/3218084/lan-wan/how-google-is-speeding-up-the-internet.html?idg_eid=f32fc7aec843db7ef67d0a4f08e3322d&email_SHA1_lc=&cid=nww_nlt_networkworld_daily_news_alert_ XXXXXXXXXX&utm_source=Sailthru&utm_medium=email&utm_campaign=NWW%20Daily%20AM%20Alert% XXXXXXXXXX&utm_term=networkworld_daily_news_alert

You should also read the following more technical paper about it: https://tools.ietf.org/id/draft-cardwell-iccrg-bbr-congestion-control-00.html

After reading both articles, answer the following questions:

1. Write a brief summary of the congestion controls currently available in TCP as covered in this Unit (1 mark)

2. Identify and explain two problems with current congestion controls in TCP that are pointed out in the articles (2 marks)

3. Summarize in your own words the difference(s) between the current TCP congestion controls and Google’s new BBR protocol (3 marks)

4. The Network World article points out that it is difficult to get a new protocol accepted as a global standard for TCP/IP. Why do you think this is the case? Give carefully thought out reasons for your answer. (4 marks)

Important: for every direct quotation you use from these two sources or any other source, you must immediately, after the quote, provide your own explanation of the quotation (for example, explain why are you quoting it, how does it help answer the question, how does it support what you are saying?) – marks will be deducted for failure to do so. In addition, correct referencing conventions must be used throughout your work using the Harvard referencing convention. Your answers will be marked on clarity, logic, relevance, use of own words and fully addressing all parts of each question.

Remember that quotations alone will not be accepted as your explanation of the questions. Quotations can support your explanations, but you must still provide the explanations yourself. Best way forward is to keep direct quotations to a minimum, and use your own words.


TEMPLATE FOR YOUR ANSWERS

Type your answers in this section in the spaces provided. Spaces can expand as you type.

First Name:_________________________ Last Name:____________________________

Student ID: __________________________

Question Number

Mark

allocated

Marks earned

Question 1: (10 marks)

1.

2.

3.

4.

5.

6.

7.

8.

q.8 Routing table of router R2:

Prefix

Network address

Next-hop address

Interface

XXXXXXXXXXmark each, q.8 3 marks

Question 2: (5 marks)

a)

2.5

b)

1.5

c)

1

Question 3: (10 marks)

1.

1

2.

2

3.

3

4.

4

Total marks awarded

25 (max)

Less late penalties if applicable

Less plagiarism penalties if applicable

Total marks earned

Markers comments:

Answered Same Day May 14, 2020 COIT20261 Central Queensland University

Solution

Dr answered on May 16 2020
146 Votes
COIT20261 Network Routing and Switching (Term 1, 2018)
Assignment item —Written Assessment-2
First Name:_________________________    Last Name:____________________________
Student ID: __________________________
    Question Numbe
    Mark
allocated
    Marks earned
    Question 1: (10 marks)
    
    
    1.
2.
3.
4.
5.
6.
7.
8.
    Router R1
Interface m2
2 Hops, R4 and R3
Drops the Packet
Interface m0
Next hop address 150.3.0.3/16
150.3.0.0/16
Routing table of router R2:
    Prefix
    Network address
    Next-hop address
    Interface
    1
    150.3.0.0/16
    ---
    m0
    2
    150.32.0.0/18
    150.3.0.1/16
    m0, m0
    3
    Default Network
    ---
    m0
    1-7 1 mark each, q.8 3 marks
    
    Question 2: (5 marks)
    
    
    a)
    The IP datagram of 5400 bytes, there is an IP header of 20 bytes. Therefore, there is 5380 bytes are actual data in IP datagram and 20 bytes of IP header as 5380 + 20 = 5400 bytes. It is given that router has to fragment the IP datagram in 4 fragments. The network MTU size is 1500 bytes, thus the maximum fragmented packet can be 1500 bytes long.
With this scope in each of 1500 bytes of fragmented packet 20 bytes for the IP header. Thus, each packet will contain 1500 – 20 = 1480 bytes of actual data and 20 bytes of IP header. Hence, for each packet the coi
ect size, start byte and end byte are as follows.
    Fragment No.
    Co
ect Size
    Start Byte
    End Byte
    1
    1480 byte data and 20 byte IP heade
    1
    1500
    2
    1480 byte data and 20 byte IP heade
    1501
    3000
    3
    1480 byte data and 20 byte IP heade
    3001
    4500
    4
    940 byte data and 20 byte IP heade
    4501
    5460
    2.5
    
    b)
    The fragment offset is taken by measure of 8 byte block. Thus, the fragment offset of each of the four fragments are as follows.
Having 8 byte block 1480 byte = 185 x 8. Thus, the fragment offset is calculated by 185 blocks of 8 bytes. Now, the first fragment is 0 and next is obtained by adding 185 in just previous fragment. Thus, the fragment offset of each of the fragment is as follows.
1st fragmented packet - fragment offset = 0
2nd fragmented packet – fragment offset = 0 + 185 = 185
3rd fragmented packet – fragment offset = 185 + 185 = 370
4th fragmented packet – fragment offset = 370 + 185 = 555
    1.5
    
    c)
    The datagram that comes on the router was 5400 byte long. Router fragments the IP datagram of 5400 byte in four fragments and total bytes of four fragments are after the fragmentation becomes 5460 byte. The reason behind that there is only one IP header of 20 bye in original datagram of 5400 bye, but after fragmentation, each fragment packet has 20 byte IP header. Thus, 80 byte are IP header and 5400 byte data in four fragments.
Thus, total data in byte which is going out from the router greater than the original datagram which comes on the router. The reason behind this is additional IP header of 80 byte.
    1
    
    Question 3: (10 marks)
    
    
    1.
    The congestion control cu
ently available with TCP with following three phases
1. Slow start phase
2. Congestion avoidance phase
3. Congestion detection phase
(GeeksforGeeks, n.d.) states that the slow start phase is basically starting phase of the TCP communication. After each of RTT the congestion window size of the TCP increases exponentially.
Suppose, that initial congestion window size is 1, then after 1 RTT the congestion window size becomes 21 and after 2nd RTT the congestion window size of TCP will become 22 and...
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