studymaterials: computer networks univquestionbank

B.E/B.Tech DEGREE EXAMINATION Apr/May2008
Fifth semester
Computer Science and Engineering
CS1302 -COMPUTER NETWORKS
(Regulation 2004)
Time: 3 hours Maximum marks: 100

Answer ALL questions

PART A (10 x 2 =20 marks)

1. Draw a hybrid topology with a star backbone and four ring networks?

2. What is the significance of twisting in twisted pair cable?

3. What is the main purpose of the second ring in the FDDI protocol?

4. Assume a Go-Back-N protocol is used with a window size of 4 and that the ACK for packet 2 gets lost. Show the events until packet 2 is acknowledged at the sender side.

5. Is 3.54.81.76 a class A, B, C or D IP address? What are the network ID and host ID in decimal notation? Assume that subnets are not used.

6. What are the two main reasons that hierarchical routing is employed in the Internet, rather than using a single link-state or distance vector protocol to route packet globally?

7. Suppose we are downloading a file over 1.5 Mbps link using a TCP connection under slow start with RTT of 100 milliseconds. What will be the window size when the link is fully utilized?

8. What field in the IP datagram header is used to avoid forwarding datagram’s endlessly through routing loops? How is the header used to accomplish that?

9. Distinguish between iterative and recursive DNS queries?

10. Compare the way SMTP and HTTP transmit the images. Which one do you think is more efficient? Why?

PART B (5 x 16 = 80)

11. (a) What is the difference between a protocol and a service interface? Explain your answer in terms of the ISO seven layer models. (16 marks)
(or)
11. (b) Explain how guided media differ from unguided media? Briefly explain any three methods used for data transmission using guided media and two methods used for data transmission using unguided media. (16 marks)

12. (a) Go-back-n and selective-reject are two basic approaches to deal with transmission errors.
(i) Compare the two approaches in terms of storage and bandwidth requirements. (8 marks)

(ii) With the aid of a packet sequence (timing) diagram, show the operation of go-back-n when a data-packet/ACK-packet/NAK-packet is corrupted. (8 marks)
(or)
12. (b) Station A has two frames in a queue ready to send at the same time. On an 802.3 CSMA/CD network, is it guaranteed that Station B’s frame will be transmitted before the second frame of Station A is transmitted? Why? What is the answer for the same scenario on an 802.5 token ring network? Assume all frames have the same priority. (16 marks)

13. (a) 13. (a) Given the network topology below, use a link-state algorithm to compute the shortest path from A to all other nodes. Make sure to show the results of the computation at each step. (16 marks)
(or)
13. (b) (i) How do subnetting and supernetting enhance scalability? What is the purpose of a subnet mask and a supernet (CIDR) mask? Is a subnet mask visible outside an IP network? Is a CIDR mask visible outside an IP network?

13. (b) (ii) What are the network number, subnet number, and host number for address 135.104.192.100, mask 255.255.128.0 ?

13. (b) (iii) How many addresses are spanned by the CIDR address 205.12.192.0/20, and what range do they span?

14. (a) Compare and contrast the two TCP/IP transport protocols: TCP and UDP, in terms of demultiplexing, reliability, and flow control. How does TCP identify a connection? Is the information needed for this identification readily available to the TCP software in the received TCP segment? Explain. With the help of a diagram, explain how a connection is established in TCP. (16 marks)
(or)
14. (b) How many RTTs does it take until the sender’s congestion window reaches 1Mbytes? Recall that the congestion window is initialized to the size of a single segment, and assume that the slow-start threshold is initialized to a value higher than the receiver’s advertised window. If the time to send the file is given by the number of required RTTs times the RTT value, what is the effective throughput for the transfer? What percentage of the link bandwidth is utilized? (16 marks)

15. (a) You are going to use a terminal of the host xyz.cse.edu to write an email from your email account to my email account, with the content “I wanna pass!” Write down in sequence the commands in SMTP, along with any necessary argument, that you need to use to send this email. (16 marks)
(or)
(b) (b) Describe with an example how does a HTTP request retrieves the document usr/users/doc/doc 1. Use atleast two general headers, two request headers and one entity header. Show the response if the document has moved to usr/deads/doc 1 and if there is a syntax error in the request. (16 marks)

B.E/B.Tech DEGREE EXAMINATION Nov/Dec 2006
Fifth semester
Computer Science and Engineering
CS1302 -COMPUTER NETWORKS
(Regulation 2004)
Time: 3 hours Maximum marks: 100

Answer ALL questions

PART A (10 x 2 =20 marks)

1. State the major functions performed by the presentation layer of the ISO OSI model.

2. A sine wave has a frequency of 6Hz. What is its period?

3. Briefly discuss stop-and-wait method of flow control.

4. List the two types of data frames in FDDI.

5. List the two forms in which virtual circuit packet switching is implemented.

6. Which class does the following IP address belong to?

7. What is a datagram socket?

8. “TCP software is implemented as a Finite State Machine”, Discuss.

9. What is a Domain Name Server?

10. State the application layer protocol in the TCP/IP protocol suite that provides access to a networked file server.

PART B (5 x 16 = 80)

11.(a) (i) What is a Protocol? List the three key elements of a protocol.

(a) (ii) With relevant examples differentiate between simplex, half duplex and full duplex communication.

(a) (iii) A Sine wave completes one cycle in 25 μs. What is its frequency? Express the frequency in KHz.

(a) (iv) A digital signal has a bit interval of 40 μs. What is the bit rate? Express the bit rate in Kbps.
(or)
11.(b) (i) An analog signal carries four bits in each signal element. If 1000 signal elements are sent per second, find the baud rate and the bit rate.

11. (b) (ii) Discuss the role played by repeaters in Terrestrial Microwave communication? Is the distance between repeaters fixed? Discuss.

11. (b) (iii) A network has ‘n’ devices. Determine the number of cable links required for a mesh, ring, bus and star topology.

12. (a) (i) A block of 32 bits has to be transmitted. Discuss how the thirty two bit block is transmitted to the receiver using Longitudinal Redundancy Check.

12. (a) (ii) Consider a 32 bit block of data 11100111 11011101 00111001 10101001 that has to be transmitted. If Longitudinal Redundancy Check is used what is the transmitted bit stream?

12. (a) (iii) In the Hamming code, for a data unit of m bits how do you compute the number of redundant bits ‘r’ needed?

12. (a) (iv) What kinds of errors can Vertical Redundancy check determine? What kinds of errors it cannot determine?
(or)
12. (b) (i) List the three main functions performed by the data link layer of the ISO OSI model.

12. (b) (ii) Explain the working of Carrier Sense Multiple Access protocol.

12. (b) (iii) How does a Token Ring LAN operate? Discuss.

12. (b) (iv) List and briefly discuss the two different basic transmission technologies that can be used to set up wireless LAN’s.

13. (a) (i) State which layers of the ISO OSI model does the following interconnecting devices operate.

13. (a) (ii) State the major difference between Distance Vector Routing and Link State Routing. Discuss how these routing techniques work.
(or)
13. (b) (i) What is subnetting? Discuss. Also state which classes of IP address can be subnetted.

13. (b) (ii) What is subnet masking? Discuss.

13. (b) (iii) How can we prove that we have 2, 147, 48, 648 address in class A?

13. (b) (iv) What is the subnetwork address if the destination address is 200.45.34.56 and the subnet mask is 255.255.240.0?

14. (a) (i) List and discuss the various primitives for a simple transport service.

14. (a) (ii) “DNS can use the services of UDP or TCP using port 53”. Discuss when UDP is used and when TCP is used.

14. (a) (iii) Highlight the features of UDP and briefly discuss the same.
(or)
14. (b) (i) Discuss connection establishment and connection release in TCP.

14. (b) (ii) Discuss how TCP provides reliability using error control.

14. (b) (iii) Discuss the strategies TCP uses to avoid congestion.

15. (a) (i) With a relevant example discuss how the domain space is divided.

15. (a) (ii) Distinguish between a fully qualified domain name and a partially qualified domain name. Give relevant example.
(or)
15. (b) (i) Discuss how Simple Mail Transfer Protocol (SMTP) works? Can multimedia messages be transmitted using SMTP? Discuss.

15. (b) (ii) Is Common Gateway Interface a language? Discuss.

B.E/B.Tech DEGREE EXAMINATION May/Jun 2007
Fifth semester
Computer Science and Engineering
CS1302 -COMPUTER NETWORKS
(Regulation 2004)
Time: 3 hours Maximum marks: 100

Answer ALL questions

PART A (10 x 2 =20 marks)

1.State the purpose of layering in networks?

2.At which level of OSI model does repeaters, bridges, routers and gateways operate?

3.State the difference between token ring and FDDI?

4.Give the structure of encoder and decoder in error correction.

5.What is meant by IP spoofing? How can be router be used to prevent IP spoofing?

6.What kind of routing information do routers exchange among themselves while running distance vector algorithm? In particular, briefly describe the format of the routing information that is exchanged.

7.Briefly describe two advantages of using packet switching for data transmission.

8.Explain how TCP flow control works.

9.Why is DNS necessary? State it significance.

10.What is Security Parameter Index?

PART B (5 x 16 = 80)

11 (a) (i). List four properties by which transmission media can differ. (4)

(a) (ii). Three packets – switching networks each contain n nodes. The networks has a star topology has a star topology with a central switch, a ring respectively and a third is fully interconnected with a wire form every node to every other node. What are the best, average and worst case transmission paths in hops? (12)
(or)
11.(b) (i). Describe the key elements of protocols and the standards. (8)

(b) (ii). Explain in detail the data transmission in OSI reference model. (8)

12. (a) (i) How does the 802.11 media access control protocol ensure that the receiver has a greater chance to transmit the acknowledgement frame before any other wireless stations grab the media? Does it always guarantee that the acknowledgement frame sent by the receiver will not collide with another frame transmitted by another wireless station? (8)

(a) (ii) Describe the collision avoidance mechanism used in 802.11 wireless LAN. In particular, how such a mechanism solves the hidden terminal problem. (8)
(or)
12. (b) Describe two approaches by which packet loss is detected in a Go back –N ARQ protocol and Selective Repeat.

13(a) (i). How is the looping problem solved by switches and by routers? How do switches and by routers. How do switches/routers handle link failure? (8)

13. (a) (ii). Explain the IP addressing. (8)
(or)
13. (b) (i). Compare and Contrast Link State and Distance Vector algorithms. (8)

13. (b)(ii). In the virtual circuit network service model, before a virtual circuit is setup, the source router needs to specify a path (e.g., the shortest path) from the source to the destination. What additional information do we need to maintain in the routing table to support this function? Write down the resulting routing table. (8)

14. a) If UDP does not provide any service guarantees or reliable transfer, why can’t application directly access IP and do without it? Explain UDP in details. (16)
(or)
14. (b) What is QoS in internetworking? State the technique to improve QoS. (16).

15. (a) What are the following acronym SMTP, FTP, WWW and HTTP stand for? Explain their uses and state the strengths and weaknesses of each of them.(16)
(or)
15. (b) (i). Explain in role of a DNS on a computer network, including its involvement in the process of a user accessing a web page. (8)

15. (b) (ii) Describe about symmetric – key Cryptography. (8)

B.E/B.Tech DEGREE EXAMINATION Nov\Dec2007
Fifth Semester
Computer Science and Engineering
CS1302 – COMPUTER NETWORKS
(Regulation 2004)
Time: 3 hours Maximum marks: 100

Answer ALL questions

PART A (10 x 2 =20 marks)

1. Define the term Protocol and give its key elements.

2. List the issues associated with RS-232 standard.

3. What is Modulo-2 arithmetic?

4. Define the term SONET?

5. Give an account on Private addresses.

6. What is the meaning of multiple IP address of Router?

7. Give the format for UDP datagram and give the meaning for each field.

8. Define the terms (a) Jitter (b) Socket address.

9. What is MIME?

10. Give an account on Steganography.

PART B (5 x 16 = 80)