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CN.PROTOCOLS (CN 211) UE 2023-2024 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 2023/2024 Academic Year

Course Name: Computer Networking Protocols
Paper Code Number: CN 211
Date of Examination: 6th March, 2024
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

INSTRUCTIONS TO CANDIDATES

i. This examination paper consists of TWO (2) sections with EIGHT (8) questions in THIRTEEN (13) printed pages.
ii. The total score for this examination is 100 points. Marks are allocated at the end of each question.
iii. Answer all questions in Section A and THREE (3) questions in Section B.
iv. ALL responses should be written in the answer book provided.
v. Insert the examination paper into the answer book after the examination. Students should not take any examination paper(s) out of the examination room.
vi. All regulations guiding the administration of university examinations apply.

SECTION A: (40 MARKS)

Answer ALL questions in this section.

Question One - Multiple Choice

(0.5 Mark Each)

1. What is the correct number of usable subnetworks and hosts for the IP network address 192.168.35.0 submitted with a /28 mask?

  • A. 12 networks /11 hosts
  • B. 12 networks /12 hosts
  • C. 12 networks /14 host
  • D. 14 networks /14 hosts
  • E. 13 networks /13 hosts

2. Which OSI layer header contains the address of a destination host that is on another network?

  • A. Application
  • B. Session
  • C. Transport
  • D. Network
  • E. Data link

3. Refer to the Figure 1. If host A sends an IP packet to host B, what will the destination address be in the frame when it leaves host A?

  • A. DD:DD:DD:DD:DD
  • B. 172.168.10.99
  • C. 172.168.10.65
  • D. AA:AA:AA:AA:AA:AA
  • E. BB:BB:BB:BB:BB

4. A network administrator is adding a new LAN to a branch office. The new LAN must support 25 connected devices. What is the smallest network mask that the network administrator can use for the new network?

  • A. 255.255.255.228
  • B. 255.255.255.192
  • C. 255.255.255.224
  • D. 255.255.255.240
  • E. 255.255.255.128

5. Which frame field is created by a source node and used by a destination node to ensure that a transmitted data signal has not been altered by interference, distortion, or signal loss?

  • A. Frame check sequence field
  • B. Error correction process field
  • C. Flow control field
  • D. Time to Live field
  • E. User Datagram Protocol field

6. An administrator is trying to configure the switch but receives the error message. What is the problem?

Switch1> config t
Invalid input detected at '^' marker.
  • A. The entire command, configure terminal, must be used.
  • B. The administrator must connect via the console port to access global configuration mode.
  • C. The administrator is already in global configuration mode.
  • D. The administrator must first enter privileged EXEC mode before issuing the command.
  • E. Nothing is wrong.

7. What will happen if the default gateway address is incorrectly configured on a host?

  • A. The host cannot communicate with hosts in other networks.
  • B. The host cannot communicate with other hosts in the local network.
  • C. A ping from the host to 127.0.0.1 would not be successful.
  • D. The switch will not forward packets initiated by the host.
  • E. The host can communicate with other hosts

8. Which scenario describes a function provided by the transport layer?

  • A. A student has two web browser windows open in order to access two web sites. The transport layer ensures the correct web page is delivered to the correct browser window.
  • B. A student is using a classroom VoIP phone to call home. The unique identifier burned into the phone is a transport layer address used to contact another network device on the same network.
  • C. A corporate worker is accessing a web server located on a corporate network. The transport layer formats the screen so the web page appears properly no matter what device is being used to view the web site.
  • D. A student is playing a short web-based movie with sound. The movie and sound are encoded within the transport layer header.
  • E. All of the above

9. Which two protocols operate at the top layer of the TCP/IP protocol suite?

  • A. POP and IP
  • B. DNS and DHCP
  • C. POP and DNS
  • D. IP and TCP
  • E. POP, IP and TCP

10. Which layers of the OSI model map to the application layer of the TCP/IP model?

  • A. Transport, Network and Application.
  • B. Application, Session and Data link.
  • C. Application, Session and Presentation.
  • D. Application, Session and Transport.
  • E. Transport, Network and Presentation and Session.

11. Which two statements are correct in a comparison of IPv4 and IPv6 packet headers?

  • A. The Destination Address field is new in IPv6.
  • B. The Time-to-Live field from IPv4 has been replaced by the Hop Limit field in IPv6.
  • C. The Source Address field name from IPv4 is kept in IPv6.
  • D. The Version field from IPv4 is not kept in IPv6.
  • E. All of the above

12. A client packet is received by a server. The packet has a destination port number of 67. What service is the client requesting?

  • A. Telnet
  • B. FTP
  • C. SSH
  • D. DHCP
  • E. FTP and SSH

13. What is an advantage to using a protocol that is defined by an open standard?

  • A. An open standard protocol is not controlled or regulated by standards organizations.
  • B. A company can monopolize the market.
  • C. It encourages competition and promotes choices.
  • D. The protocol can only be run on equipment from a specific vendor
  • E. All of the above

14. Which information does the show startup-config command display?

  • A. The IOS image copied into RAM
  • B. The bootstrap program in the ROM
  • C. The contents of the saved configuration file in the NVRAM
  • D. The contents of the current running configuration file in the RAM
  • E. Just the bootstrap program

15. Which one of the following fields is present in both TCP header and UDP header?

  • A. Acknowledgement number
  • B. Urgent pointer
  • C. Sequence number
  • D. Checksum
  • E. None of these

16. Which of the following is incorrect about User Datagram Protocol?

  • A. UDP is unreliable Transport Protocol
  • B. There is no window mechanism in UDP
  • C. There is a robust error control mechanism in UDP
  • D. The user may overflow with incoming messages
  • E. All of the above

17. Which value that is contained in an IPv4 header field is decremented by each router that receives a packet?

  • A. Differentiated Services
  • B. Time-to-Live
  • C. Fragment Offset
  • D. Header Length
  • E. Checksum

18. What is the purpose of the TCP sliding window?

  • A. To ensure that segments arrive in order at the destination
  • B. To request that a source decrease the rate at which it transmits data
  • C. To inform a source to retransmit data from a specific point forward
  • D. To end communication when data transmission is complete
  • E. None of the above

19. What are the three parts of an IPv6 global unicast address?

  • A. subnet ID, global routing prefix and interface ID
  • B. global routing prefix, interface ID and subnet mask
  • C. interface ID, broadcast address and subnet mask
  • D. subnet ID, interface ID and subnet mask
  • E. subnet mask, interface ID.

20. What is one main characteristic of the data link layer?

  • A. It generates the electrical or optical signals that represent the 1 and 0 on the media.
  • B. It converts a stream of data bits into a predefined code.
  • C. It shields the upper layer protocol from being aware of the physical medium to be used in the communication.
  • D. It accepts Layer 3 packets and decides the path by which to forward the packet to a remote network.
  • E. None of the above.

Question Two - Fill in the Blanks

(1 Mark Each)

i. ______ is a 32-bit number used to divide an IP address into network and host portions and determine the network’s size.

ii. ______ is the 128-bit addressing scheme, developed to handle expansion and scalability of modern networks.

iii. ______ and______ are both network communication protocols.______ ensures reliable, ordered, and error-checked delivery of packets, while______ is faster but does not guarantee delivery or order.

iv. ______ is a decentralized naming system for computers, services, or any resource connected to the Internet or a private network, which translates domain names into IP addresses.

v.______ is the command that is used to test network connectivity between devices, but it can also be used to determine how many routers are in between a source and a destination.

vi. Special condition in a network where more data packets are coming to network devices than they can handle, is called ______.

vii. All computers connected to the internet and wanting to use it for sending/receiving data must follow a common set of rules or guidelines for communication called______.

Question Three - Short Answer

a. Briefly explain the techniques that have been used to deal with the scarcity of IPv4?
(3 Marks)

b. Differentiate between OSI and TCP/IP model.
(4 Marks)

c. Differentiate IPv4, MAC and port addressing.
(3 Marks)

Question Four - IPv6 & Addressing

a. Write the value of the version control field of IPv4 and IPv6 in binary numbers.
(1 Mark)

b. Express the IPv4 address 192.168.10.51 in IPv6 format.
(2 Marks)

c. What are the techniques that help to migrate from IPv4 to IPv6?
(3 Marks)

d. Express the IPv6 address in a compressed format: 2001:0db8:0000:0000:0a50:0000:0000:0001
(1 Mark)

e. Express the following IPv6 address in a standard format: 2002:420:c4:1008:25:190::990
(1 Mark)

f. What IP addresses does this combination isolate?
(1 Mark Each)

i. Base IP Address: 172.16.10.37 and Wildcard Mask: 255.255.255.255

ii. Base IP Address: 10.10.10.1 and Wildcard Mask: 0.0.0.0

SECTION B: (60 MARKS)

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

**Question Five

a. Write at least three primary differences between TCP and UDP protocols.
(3 Marks)

b. TCP protocol maintains two key dynamic values per connection: a sequence number and congestion window size.
(4 Marks)

i. Why these 2 values are important for TCP protocol?

ii. Describe briefly how each value is computed and how is it used by TCP.

c. What is the need for the UDP? Would it not have been enough to just let user’s processes send IP packets without using a transport protocol? Explain in a few sentences.
(6 Marks)

d. Explain what will happen when two applications (one using TCP, the other using UDP) that want to send as much data as possible compete for bandwidth.
(7 Marks)

Question Six

a. You are tasked with assigning IP addresses for your new MAN with 8 buildings; each building will have 255 workstations. Use 172.31.0.0 network. Determine:
(2 Marks Each)

i. Subnet masks
ii. Network addresses
iii. Broadcast address for each subnet
iv. Valid host ranges on each subnet
v. Reserved subnets and addresses

b. Subnet the network topology using 172.30.4.0/22 space. Provide answer in table format.
(10 Marks)

Question Seven

a. Suppose a computer has MAC address “fc:99:47:75:ce:e0”. What will be:
(5 Marks Each)

i. The LLA IPv6 address if configured with SLAAC using EUI-64 process

ii. The GUA IPv6 address if configured with SLAAC using random generated 64-bit number

b. Draw the IPv6 packet header format and provide a brief explanation of each field in the header.
(10 Marks)

Question Eight

a. Suppose Juma, with a Web-based e-mail account, sends a message to Anna, who accesses his mail using POP3.

i. Discuss how the message gets from Juma’s host to Anna’s host.
(2 Marks)

ii. What are the series of application-layer protocols that are used to move the message between the two hosts?
(4 Marks)

b. Consider an HTTP client that wants to retrieve a Web document at a given URL. The IP address of the HTTP server is initially unknown. What transport and application-layer protocols besides HTTP are needed in this scenario?
(4 Marks)

c. Study the captured HTTP response and answer:
(8 Marks Total)

HTTP/1.1 200 OK<cr><lf>Date: Tue, 07 Mar 2008 12:39:45 GMT<cr><lf>
Server: Apache/2.0.52 (Fedora)<cr><lf>Last-Modified: Sat, 10 Dec2005 18:27:46 GMT<cr><lf>
ETag: "52663-122-a88a4e80"<cr><lf>Content-Length: 3874<cr><lf>
Content-Type: text/html; charset=ISO-8859-1<cr><lf><cr><lf>
<ldoctype html public "-//w3c//dd html 4.0 transitional//en"></lf>
<html></lf><head></lf><meta name="GENERATOR" content="Mozilla/4.79 [en] (Windows NT 5.0; U) Netscape]"></lf>

i. What operating system is running on the server?

ii. When the document was last modified?
(1 Mark)

iii. What Webserver software is running on the server?
(2 Marks)

iv. What is the version of the webserver software?
(1 Mark)

v. Was the server able to successfully find the document or not? Justify your answer.
(2 Marks)

vi. How many bytes are there in the document being returned?
(1 Mark)

vii. What time was the document reply provided?
(1 Mark)

END OF EXAMINATION PAPER

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