DataCom exam11 - STUDENT ID NO MULTIMEDIA w UNIVERSITY Em...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Background image of page 7
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: STUDENT ID NO MULTIMEDIA w UNIVERSITY Em MULTIMEDIA UNIVERSITY THIRD TRIMESTER EXAMINATION, SESSION 2007/08 ECP2056 — DATA COMMUNICATIONS AND COMPUTER NETWORKING (EE, TE, CE, ME, MCE, OPE, NANO and BMM) 20 MAY 2008 9.00 AM — 11.00 AM (2 Hours) INSTRUCTION TO STUDENT 1. This Question paper consists of 7 pages including cover page with 6 Questions only. 2. Attempt FOUR out of SIX questions. All questions carry equal marks (25 marks) and the distribution of the marks for each question is given. 3._ Please print all your answers in the answer Booklet provided. ECP2056 DATA COMMUNICATIONS AND COMPUTER NETWORKING MAY 2008 Question 1 (3) Briefly explain three basic key elements of a networking protocol. [6 marks] (b) State two reasons why standards are needed for communications. [2 marks] (c) State the functions of the following protocols: (1') ICMP (ii) SNMP (iii) SMTP [3 marks] (d) The Open Systems Interconnection (081) model consists of several layers. Name all layers and state one function of each layer. [14 marks] Question 2 (a) NRZ-L, R2, and Manchester coding schemes are three examples of polar coding scheme. (i). Given the data to be transmitted as a sequence of 1 0 0 1 1 O 0 1 1 0, draw the digital signals generated by NRZ-L coding, RZ coding, and Manchester coding schemes. [9 marks] (ii). Out of NRZ-L, R2, and Manchester coding schemes, which coding scheme has the highest complexity and why? [3 marks] (b) State the three main processes involved in Pulse Code Modulation (PCM). [3 marks] (6) (i). Define Nyquist theorem with regards to the sampling rate. [3 marks] (ii). Calculate the bit rate required to transmit a signal through a low-pass channel with bandwidth of 360 kHz. The signal is encoded with 8 bits per sample. [2 marks] (d) A telephone line has a useful bandwidth of 4 kHz for data transmission. If the power of the signal is 20 W and the noise power is 500 nW, what is the maximum data rate that can be supported by the telephone line? [5 marks] Continued ...... . . WWW ECP2056 DATA COMMUNICATIONS AND COMPUTER NETWORKING MAY 2008 Question 3 (a). Name the two major categories of transmission media and describe how they differ. [2 marks] (b). What are the three major classes of guided media? [3 marks] (c). What is refraction? What is reflection? [3 marks] (d). A beam of light moves from one medium to another medium with less density. The critical angle is 60°. Do we have refraction or reflection for each of the following incident angles? Show the bending light ray in each case. i) 40° ii) 60° iii) 80° [6 marks] (e) The minimum number of columns in a routing table for datagram network is two, whereas the minimum number of columns in a routing table for virtual circuit network is four. Explain the reason behind this and is this difference related to the type of addreSSes carried in the packets of each network? [5 marks] (i). What are the two approaches to packet switching? [2 marks] (g).Briefly describe the differences between a circuit switched network and a packet switched network. [4 marks] Continued W E P2056 DATA COMMUNICATIONS AND COMPUTER NETWORKING MAY 2008 Question 4 (a) The following table shows the relationship between dataword and codeword. Based on the table, answer these questions: i) What is the minimum Hamming distance of the coding scheme? [4 marks] ii) How many errors can it detect and how many errors can it correct? [2 marks] iii) Does it belong to the class of linear block codes? Why? [4 marks] (b) The following figure shows the structure of an encoder and a decoder. Sender Receiver Datawo rd Datawo rd I Correction - logic --1 Generator ll Unreliable transmission masseuse Codeword Figure 1 Continued m ECP2056 DATA COMMUNICATIQNS AND COMPUTER NETWQRKING MAY 2008 (i)- (ii). The generator functions that create three parity checks (r0, r;, and r2) are: ro= a2+a1+a0 modulo 2 r1= a3+a2+al modulo 2 1'2: al+ao+a3 modqu 2 What would be the codeword, if the following datawords were to be transmitted? o 0101 o 1101 [4 marks] The checker functions that create 3 bit syndromes (so, s1, and 32) are: ' so: b2+b1+b0+qO modulo 2 81: b3+b2+b1+q1 modulo 2 $2: bl+b0+b3+q2 modulo 2 What would be the 3 bit syndromes, if the folIowing codewords are received? 0 010091; 0 0011M [4 marks] (c) If the sequence numbers used are 0, 1, 2, 3, 29, 30, and 3], what are the maximum size of the sender and receiver windows if Stop-and—Wait ARQ, Go-Back— N ARQ and Selective Repeat ARQ are used? AWNIWMD/SJOIGHA/LSL [7 marks] Continued Page 5 of 7 ECP2056 DATA COMMUNICATIONS AND COMPUTER NETWORKING MAY 2008 Question 5 (a) Briefly discuss the three reasons why wireless LANS should not implement CSMA/CD. [6 marks] (b) The original ALOHA called pure ALOHA is a simple but elegant protocol. However, as simple as it can be, the number of collisions rises rapidly with increased load. To improve efficiency, a modification of ALOHA known as slotted ALOHA was developed. (i). With the aid of a diagrams, briefly explain how frame collisions occur in the pure ALOHA, and then discuss how slotted ALOHA can help in improving the efficiency. [8 marks] (ii).0ne hundred stations on a pure ALOHA network share a Z-Mbps channel. If the frames are 2000 bits in length and each station sends 10 frames per second, find the throughput. [2 marks] (iii). Repeat part ii) for slotted ALOHA and compare the answers. [3 marks] c) Figure 2 shows the 10base5 network with a medium propagation delay of 10ns/ m. Station Z starts sending a data frame at t = 0 , then followed by station Y at t = LHS . Find: (i). the time when station Y detects the collision, [3 marks] (ii). the number of bits station Z sent before detecting the collision. [3 marks] x v I Figure 2 Continued ...... .. AWNIWMDISJOJGHAILSL Page 6 of 7 CP2056 DATA COMMUNICATIONS AND MPUTER NETWORKING MAY 2008 Question 6 (a) A 4480-oetet datagram is to be transmitted and fragmentation is required as it will pass through an Ethernet with a Maximum Transfer Unit (MTU) of 1500 octets. What are the corresponding Total Length, More Flag, and Fragment Offset values in each of the resulting fragments? [12 marks] (b) Given a network IPv4 address of 166.48.13.50 and a subnet mask of 255.255.2480, answer the following questions: (i). What is the network class of this address? [2 marks] (ii).How many subnets are created? [3 marks] (iii).How many hosts are there per subnet‘? [3 marks] (0) Explain how error control can be handled by TCP (Transmission Control Protocol). [5 marks] End of Paper W AWNIWMD/SJO/GHAJLSL Page 7 of 7 ...
View Full Document

This note was uploaded on 08/27/2009 for the course FET etm taught by Professor Hi during the Spring '09 term at Multimedia University, Cyberjaya.

Page1 / 7

DataCom exam11 - STUDENT ID NO MULTIMEDIA w UNIVERSITY Em...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online