Computer Networks 1 - Jun 2012

Computer Science Engg. (Semester 5)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) What is data communication? What are the four important fundamental characteristics?(6 marks) 1 (b) What is protocol? Briefly explain its key elements.(5 marks) 1 (c) Explain the responsibilities of transport layer in OSI reference model.(9 marks) 2 (a) Define bandwidth. A periodic signal has bandwidth of 20Hz. The highest frequency is 60Hz. What is the lowest frequency? Draw the spectrum if the signal contains all frequencies of the same amplitude.(4 marks) 2 (b) Calculate the Shanon channel capacity in the following cases:
(i) Bandwidth=20 kHz SNR_dB=40;
(ii) Bandwidth = 200 kHz SNR_dB=6(6 marks) 2 (c) Define line coding. Describe unipolar NR2, polar NR2-L, bipolar AMI and Manchester encoding by applying on the information sequence 101011100.(10 marks) 3 (a) An analog signal has a bit rate of 8000 bps and a band rate of 1000 band. How many data elements are carried by each signal elements? How many signal elements do we need?(5 marks) 3 (b) Explain the phase modulation with a neat diagram.(5 marks) 3 (c) What is time division multiplexing? Explain how statical TDM overcomes the disadvantages of synchronous TDM.(10 marks) 4 (a) Briefly explain the coaxial cable and optical fiber with their applications.(8 marks) 4 (b) Find the codeword, using CRC given data word "1001" and generator "1011".(8 marks) 4 (c) What is internet checksum? With an example list the steps undertaken by the sender and receiver for error detection.(6 marks) 5 (a) Explain selection repeat ARQ with neat diagrams.(8 marks) 5 (b) What is piggybacking? List its usefulness.(4 marks) 5 (c) Explain the frame format and transitional phases of point-to-point protocol.(8 marks) 6 (a) A pure ALOHA network transmits 200-bit frames on a shared channel of 200 kbps. What is the troughout if the system products 100 frames per second.(6 marks) 6 (b) With a neat diagram explain CSMA/CD protocol.(8 marks) 6 (c) Explain the MAC sublayer of gigabit Ethernet(6 marks) 7 (a) Explain the architecture of IEEE 802.11.(8 marks) 7 (b) Differentiate between repeater and amplifire.(2 marks) 7 (c) How does a VLAN reducer network traffic?(4 marks) 7 (d) Differentiate between bus backbone and star backbone.(6 marks) 8 (a) Explain in detail, the architecture of SONET system.(10 marks) 8 (b) Give the architecture of ATM. Show how VPs and VCs are established.(6 marks) 8 (c) Write a short note on AMPS.(4 marks)