DataCom exam6 - STUDENT ID NO mum-mom UNIVEva [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 mum-mom UNIVEva [Em MULTIMEDIA UNIVERSITY THIRD TRIMESTER EXAMINATION, SESSION 2005/06 ECP2056 — DATA COMMUNICATIONS AND COMPUTER NETWORKING (EE, TE, CE, ME, MCE, OPE and BM) 27 MAY 2006 9:00AM— 11:00AM (2 Hours) INSTRUCTION TO STUDENT 1, This Question paper consists of 7 pages including cover page with 2 Sections and 6 Questions only. 2. Attempt TWO out of THREE questions from EACH SECTION. All questions carry equal 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 2006 SECTION A (Attempt any 2 out of 3 questions from this section) Question 1 (a) Briefly explain the importance of protocol in communications. Name six 01' the layers defined in the 081 model. [5 marks] (b) Decode the data stream below if the data stream is encoded using: i. Manchester encoding [1.5 marks] ii. Differential Manchester encoding (assume previous signal is from high to low) [1.5 marks] (c) Given a FCS (remainder) of 1112 (at the sender side), a data unit of 101100112, and a polynomial divisor of x3 + 1, is there an error in the data? Interpret the result, why? [5 marks] (d) Character Stuffing is used in maintaining the data transparency in data communications. Briefly explain what is character stuffing. [3 marks] (e) Briefly explain phase modulation and amplitude modulation. What is the major factor that makes phase modulation superior to amplitude modulation? [6 marks] (1‘) Suppose the bandwidth of a telephone line is Ski-12. If the signal strength is 0.1W and the noise strength is 0.2mW, what is the maximum data rate supported by this telephone line? {3 marks] Continued AKSJGHA/TMi/WMDiMiHI 7 ' i 2 f 7 ECP2056 _ DATA “COMMUNICATIONS AND COMPUTER NETWORKING MAY 2006 Question 2 (a) Five signal sources are multiplexed using TDM. Each source produces 100 8-bit characters per second. Assume that byte interleaving is used and that each frame required 1 bit for synchronization. i. What is the frame rate? [2 marks] ii. What is the size of the frame? [4 marks] iii. What is the bit rate on the link? [3 marks] (b) What does the number on ACK and NAK frame means for Selective Repeat ARQ? [3 marks] (0) A Selective Repeat ARQ is using 7 bits to represent the sequence numbers. What is the size of the window? [3 marks] (d) Consider the use of lOOO—bit frames on a leps satellite channel with a 270ms propagation delay. What is the maximum link utilization for i. Stop-and-wait flow control? [4 marks] ii. Selective Repeat ARQ with a window size of 64? [3 marks] iii. Go-Back~N ARQ with a window size of 127? [3 marks] The utilization is given as: l W 2 2a +1 U _ W W < 2a +1 2a + 1 Where W is the window size, a is the ratio of propagation delay to frame transmission time. Continued AKS/GHAJTWH/WMD/MHH 3 x' 7 ECP2056 DATA COMMUNICATIONS AND COMPUTER NETWORKING MAY 2006 Question 3 (a) Name and sketch four different topologies that are widely used in Local Area Networks (LANS). ' [6 marks] (b) What are the three reasons why Wireless LAN cannot implement CSMA/CD‘? [6 marks] (c) An Ethernet network system with CSMA/CD aCcess scheme is rated at IOMbps. The stations are connected with 5 hubs. These hubs have negligible delay. i. If the longest distance between any two end-stations is 2km, what woald be the minimum frame length so that collision detection would be able to work? [3 marks] ii. Determine the new minimum frame length if we take into consideration the hub’s delay which is 1 usec. [4 marks] iii. If the range of utilization to be reached is 0.5 to 0.8 and the average frame size is lOOObyte, what will be the range of acceptable propagation delay? [6 marks] Assume that the propagation speed 011 the medium is 2><108 m/s and the utilization is given by: U: ] l+5a where a is the ratio of propagation delay to frame transmission time. Continued KKSIGHm-frw-WWMD/MHH 4 / 7 ECP2056 DATA COMMUNICATIONS AND COMPUTER NETWORKING MAY 2006 SECTION B (Attempt any 2 out of 3 questions from this Section) Question 4 (a) (b) (C) AKS/GHAITWH/WMDIMHH In a token ring network with 10 equally spaced stations, the length of the ring is 30km with 100 repeaters. If each repeater introduces a delay of 1 bit time, determine the average frame length if the network efficiency is 60% with a throughput of 600kbps. Assume that the propagation speed on the medium is 2><108 m/s and the token generation time is negligible. [6 marks] The efficiency of the network is given by U = l a(1 + M.) where a is the ratio of propagation delay to frame transmission time, N is the number of stations on the network. Two stations, X and Y, are attached to opposite ends of a 500m cable, and they each have a frame of 1500 bits (including overhead bits) to send to each other. There are four repeaters between X and Y, each introducing a store-and-forward delay of 20 bit times. Assume the transmission rate is lOMbps, and CSMA/CD with backoff intervals of multiples of 512 bit times is used. If collision is detected, each station will issue a 48-bit jam signal. After its backoff time has expired, a station must sense that the channel is idle for 96 bit times before it can transmit its frame. Suppose both stations attempt to transmit at time t E 0. After the first collision, X draws K = 0 and Y draws K = l in the exponential backoff protocol. i. What is the one-way propagation delay (including repeater delays) between X and Y in seconds? Assume that the signal propagation Speed is 2X108ms'] [3 marks] ii. At what time (in seconds) after I = 0 has X’s frame completely arrived at Y? [7 marks] iii. Now suppose that only X has a frame to send and that the repeaters are replaced with switches. If each switch has a processing delay of 20 bit times in addition to the store-and-forward delay, how long (in seconds) does it take for the lirst bit of the frame to arrive at Y. [3 marks] State and briefly elaborate three advantages of Virtual Local Area Network (VLAN). [6 marks] Continued 5/7 ECP2056 DATA COMMUNICATIONS AND COMPUTER NETWORKING MAY 2006 Question 5 (a) State two main differences between a local area network (LAN) and a wide area network (WAN)? [2 marks] (1)) i. Give a brief description of: 0 Circuit switching [2 marks] a Packet switching [2 marks] ii. State an application associated with each of the above switching. [2 marks] iii. State two advantages that packet switching has over circuit switching. [2 marks] (0) The solution to the limitations of the crossbar switch is the multistage switch, which combines crossbar switches in several stages. Referring to Figure Q50: i. Find the number of crosspeints required. [3 marks] ii. How many crosspoints are required if we use only one crossbar switch? [2 marks] iii. How much is the efficiency improved if we use three stages instead of one? [2 marks] ' “I 1 Stage 1 Figure Q56 ((1) Discuss two advantages and two disadvantages of frame relay compared to X25. [4 marks] (e) State and briefly elaborate two differences between Asynchronous Transfer Mode (ATM) and frame relay. [4 marks] Continued . . . AkS/GHA/Twn/WMD/Mfih" V 6 f 7 ECP2056 DATA COMMUNICATIONS AND COMPUTERNETWORKINQWn MAY 2006 Question 6 (a) The TCP/IP protocol suite is made of five layers. i. Which layer contains the TCP (Transmission Control Protocol) and UDP (User Datagram Protocol)? [1 mark] ii. Briefly explain the differences between UDP and T CP. [2 marks] iii. Draw the user datagram (UDP) format. Label the name of each control field in the header together with its length. Explain the function of each control field. [9 marks] (b) You are the new network engineer for a company. The company has a network address of 126.xxx.xxx.xxx. Your employer requested that you design the network so that it has a maximum of 62 usable subnets. i. In which class does the company network address belong to? [1 mark] ii. Draw a diagram showing the IP address formats of your network address class. Specify the name and length of each field in the diagram. [4 marks] iii. Deduce the maximum number of hosts in each subnet. [6 marks] iv. Find out which subnet mask should you assign. Write your answer in binary representation and dotted decimal. [2 marks] End of Paper ItiékéHA/rfiinwpmna 7 f 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 exam6 - STUDENT ID NO mum-mom UNIVEva [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