Dccn Paper

Topics: OSI model, Data Link Layer, OSI protocols Pages: 6 (951 words) Published: March 14, 2013
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Sri Lanka Institute of Information Technology

B. Sc. Special Honours Degree 000823 in CSN ! IT! IS
Final Examination Year 1, Semester 2 (2008)

Data Communications & Computer Networks, I (111)
Duration: 3 Hours Wednesday, 15th October 2008 , (Time: 1.00 p. m. - 4.00 p.m.)

Instruction to Candidates: • This paper has 5 Questions. • Answer All Questions. • Pay attention to marks allocated for each part of the question. • This paper contains 5 pages and cover page.

Final Examination - 2008 Data Communication & Computer Networks I - 2nd Semester


Question 01)

(20 Marks)

1.1 Briefly explain Asynchronous Transmission mode and Synchronous Transmission mode with aid of sketch. (4 Marks) 1.2 What do you understand by 'Clock Pulse' 1.3 Draw Primary Multiplexer with input and output data rates. (2 Marks) (3Marks)

1.4 PDH and SDH are two digital Hierarchies used. Explain the advantage of SDH (2 Marks) over PDH. 1.5 Draw the following bit pattern using RZ (50% duty cycle), AMI and Manchester encoding methods. Bit Pattern: 10110001 (9 Marks)

Question 02)

(20 Marks)

2.1 Physical layer defines the DTE / DCE interface standards. What are the four main characteristics and explain them. (4 Marks)

2.2 Draw the Ethernet frame structure and describe the functions of each field. 2.3 Write two data link layer protocols. (6 Marks) (1 Marks)

2.4 FEC and BEC are error correction methods. Briefly explain them. (3 Marks) 2.5 Draw the timing diagram for the following ARQ methods. (Assume Selective ARQ and Go-Back-N ARQ uses 4 frames buffer size.) a. Send 3 frames using Idle ARQ and frame having errors. frame having errors. (6 Marks)


b. Send 5 frames using Selective ARQ and 3rd frame having errors. c. Send 5 frames using Go-Back-N ARQ and 3rd

Sri Lanka Institute of Information Technology Page 1of5

Final Examination - 2008 Data Communication & Computer Networks I - 2nd Semester

Question 03)

(20 Marks) (3 Marks)

3.1 Explain bus topology and star topology with aid of diagrams.

3.2 Explain CSMA / CD and Control Token methods.

(6 Marks)

3.3 Explain the circuit switching advantages, disadvantages.)

and packet switching.

(You may write the (4 Marks)

3.4 What is the data rate and frequency used in IEEE 802.11g standard? (2 Marks)

3.5 Compare the TCP / IP model with ISO-OSI reference model. You may use Diagrams. (5 Marks)

Question 04) 4.1 Briefly explain the Iterative server and Concurrent server?

(20 Marks) (2 Marks)

4.2 Explain connection oriented method and connection less method used in transport layer including advantages and disadvantages. (4 Marks)

4.3 Briefly explain any four of following protocols. 1. DHCP 11. 111.

(2x4 Marks)




Sri Lanka Institute of Information Technology Page 2 of5

Final Examination - 2008 Data Communication & Computer Networks I - 2nd Semester

4.4 Host A in LAN P needs to access the Web server in LAN Q. Explain the TCP/IP operation in LAN and WAN with aid of diagrams. (6 Marks)



Question 05) 5.1 Briefly explain the followings, a. Dial-up connection b. ISDN c. ADSL d. IP-VPN

(20 Marks) (4 Marks)

5.2 Explain the following devices used in networking. Your answer should include Main task of the device, it operates in which layer of OSI model, Number of collision domains and Number of broadcast domains. (6 Marks)

a. Hub
b. Switch c. Router

Sri Lanka Institute of Information Technology Page 3 of5

Final Examination - 2008 Data Communication & Computer Networks I - 2nd Semester

5.3 Answer the following multiple choice questions. [You may write the question number and the correct answer (a, b, c or d) only.] (10 Marks)


Which of the following is not defined at the physical layer of OSI reference model? a. Hardware Address b. Bit stream transmission c. Voltage level d. Physical interface

II What is the...
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