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CN.PROTOCOLS (CN 211) UE 2019-2020 SOLVED INTERACTIVE

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Computer Networking Protocols - Exam

THE UNIVERSITY OF DODOMA

OFFICE OF THE DEPUTY VICE CHANCELLOR ACADEMIC, RESEARCH AND CONSULTANCY

COLLEGE OF INFORMATICS AND VIRTUAL EDUCATION
Department of Computer Science and Engineering
End of Semester One University Examination for the 2019/2020 Academic Year

Course Name: Computer Networking Protocols
Paper Code Number: CN 211
Date of Examination: 
Time: 11:45-14:45
Duration: 3 Hours
Venue(s): FL2, LRB 105, 106, 004C, 004D, 101&102
Sitting Programme(s): BSc. CSDFE2, HIS2, CNISE2, DCBE2, TE2, CE2, SE2, BIS2, SE3, CS2, CS3, CNISE3, TE3&CE3

SECTION A: (40 MARKS)

Question One

a. How is Internet Protocol (IP) similar and dissimilar to User Datagram Protocol (UDP)?
(4 Marks)

b. Write similarities and dissimilarities between BOOTP Protocol and Dynamic Host Configuration Protocol (DHCP).
(6 Marks)

c. With at least five reasons, state how TCP is different from UDP.
(5 Marks)

đź’ˇ Question Two

Write short notes on the following:
(1 Mark Each)

a. Best-effort protocol

b. Stateless protocol

c. TCP Sequence numbers

d. Three-way handshake

e. Windowing

Question Three

Short answer questions:
(1 Mark Each)

a. ______ is a protocol behind commands used to establish connectivity problems and paths to remote hosts.

b. ______ field in the IP Packet prevents the packet from looping forever in the Internet.

c. ICMP’s ______ messages were meant to relieve congestions in the network by asking senders to reduce the rate at which they are sending data. This idea is counter-productive because the messages also contribute to congestion and there is no way of informing sending devices that the congestion has been relieved.

d. ______ is a protocol used to address challenges associated with fragmentation by establishing the minimum Maximum Transfer Units (MTUs) of various links between source and destination before attempting to send data.

e. IPv6 addresses have ______ octets.

Question Four

Map each component/issue to the most appropriate layer of the OSI model:

Question Five - Multiple Choice

(0.5 Mark Each)

a. Which one of the following is not an address reserved for private networking according to RFC 1918?

  • A) 10.10.255.255
  • B) 172.16.100.0
  • C) 192.168.16.100
  • D) 196.128.10.254
  • E) 192.168.16.200

b. Which one of the following subnet mask is most often implemented on WAN point-to-point serial links with VLSM?

  • A) 255.255.255.252
  • B) 255.255.255.254
  • C) 255.255.255.248
  • D) 255.255.255.240
  • E) 255.255.255.0

c. You are using a subnet mask submitting scheme that contains 27 bits. How many host bits are there for host addressing?

  • A) 1
  • B) 2
  • C) 4
  • D) 5
  • E) 3

d. You have been asked to come up with a subnet mask that will allow all three web servers to be on the same network while providing the maximum number of subnets. Which network address and subnet mask meet this requirement?

  • A) 192.168.252.0 255.255.255.252
  • B) 192.168.252.8 255.255.255.248
  • C) 192.168.252.8 255.255.255.252
  • D) 192.168.252.16 255.255.255.240
  • E) 192.168.252.16 255.255.255.252

e. Which of the following is the corresponding port number for HTTPS?

  • A) 80
  • B) 8080
  • C) 441
  • D) 443
  • E) 21

f. Domain Name Service is associated with which of the following well-known port numbers?

  • A) 20 and 21
  • B) 23
  • C) 25
  • D) 53
  • E) 80

g. Dynamic Host Configuration Protocol (DHCP) Server listens on port:

  • A) 53
  • B) 80
  • C) 67
  • D) 68
  • E) 23

h. What port number is used when downloading an email from the Mail server to your client computer?

  • A) 25
  • B) 110
  • C) 23
  • D) 21
  • E) 80

i. When a user is opening a website such as www.udom.ac.tr from his/her computer, the source port number is automatically assigned by the computer’s Operating System from the following range:

  • A) 0-1023
  • B) 1024-49151
  • C) 49152-65,535
  • D) 0-49151
  • E) 0-65,535

j. Which of the following is a unicast MAC Address?

  • A) FF-FF-FF-FF-FF-FF
  • B) 65-5A-04-0C-4E-82
  • C) 27-AA-04-0C-4E-85
  • D) 59-33-22-0C-4E-86
  • E) 64-5A-04-0B-4D-8A

đź“š SECTION B: (60 MARKS)

Attempt THREE (3) out of FOUR (4) questions.

** Question Six**

a. What do you understand by UDP?
(2 Marks)

b. Briefly explain when it is appropriate for application designers/developers to use UDP instead of TCP.
(4 Marks)

c. Suppose you are given the following dump of a TCP header in Hexadecimal format as D31C 0050 0001 0001 0002 0000 5002 07FE 0000 0000; analyze the following details:

i. What is the destination port number?
(1 Mark)

ii. What is the source port number?
(1 Mark)

iii. What is the acknowledgement number?
(2 Marks)

iv. What is the sequence number?
(2 Marks)

v. What is the window size?
(2 Marks)

vi. Based on part i. and ii., is the segment from client to server or vice versa?
(2 Marks)

vii. Based on part i., name the intended application layer service as well as its associated protocol.
(4 Marks)

Question Seven

a. Consider a situation where Host W sends two TCP segments back to back to Host Z. The first segment has sequence number 4125; the second has sequence number 4165:

i. What is the window size?
(3 Marks)

ii. Suppose the first segment is lost but the second segment arrives at Z. In the acknowledgement that host Z sends to Host W, what will be the acknowledgement number?
(4 Marks)

iii. Assuming the first segment is retransmitted and the second segment is eventually acknowledged, what will be the sequence number of the third segment?
(4 Marks)

b. Explain three ways through which TCP attains reliable delivery of data.
(9 Marks)

Question Eight

a. State at least two reasons as to why you would use a Web Proxy Server in your organization.
(4 Marks)

b. Study Figure 1 closely and explain why computer A cannot communicate with computer B.
(6 Marks)

c. What are four basic configurations that a DHCP server deploys to the client machine?
(4 Marks)

d. Results of ipconfig command on a Windows machine indicated IP configuration shown in Figure 2, explain this configuration in relation to the DHCP server.
(6 Marks)

Question Nine

a. Discuss the impact of Classless Inter-Domain Routing with respect to:

i. Size of routing tables
(3 Marks)

ii. Routing efficiency
(3 Marks)

iii. Memory requirements of core routers
(3 Marks)

iv. CPU cycles of core routers
(3 Marks)

v. Price of core routers
(3 Marks)

b. Given networks and their corresponding subnet masks as follows:

  • 172.1.4.0/25
  • 172.1.4.128/25
  • 172.1.5.0/24
  • 172.1.6.0/24
  • 172.1.7.0/24

What is the: i. Aggregate route
(3 Marks)

ii. Subnet Mask of the aggregate route
(2 Marks)

c. Suppose router W has built up the routing table shown in Table 1. The router can deliver packets directly over interfaces 0 and 1, or it can forward packets to routers R2, or R3. Describe what the router does with a packet addressed to each of the following destinations:

i. 192.4.153.90
(1 Mark)

ii. 28.96.39.14
(1 Mark)

iii. 128.96.50.12
(1 Mark)

iv. 128.96.50.151
(1 Mark)

v. 192.4.53.17
(1 Mark)

END OF EXAMINATION PAPER

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