Computer Communication Networks - Dec 2013

Electronics Engineering (Semester 7)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.

Answer Briefly (any four)

1 (a) What is meant by data transparency? How is it implemented in HDLC protocol?(5 marks) 1 (b) What is the difference between congestion control and flow control?(5 marks) 1 (c) Explain various network topologies(5 marks) 1 (d) Compare OSI model with TCP/IP model.(5 marks) 1 (e) List and explain the functions of data link layer.(5 marks) 2 (a) Explain OSI reference model architecture for a network with two intermediate nodes and a neat diagram. Also explain the functions of each layer. Name the layer responsible for
i. End to end reliability
ii. Link to link reliability
(8 marks) 2 (b) What is meant by flow control? Discuss the different flow control methods with neat diagram.(8 marks) 2 (c) Explain different ARQ techniques.(4 marks) 3 (a) Explain ADSL with respect to channel configuration and modulation technique.(8 marks) 3 (b) What are transmission impairments? Explain.Compare co-axial cable, optical fiber cable with respect to transmission characteristics, data rate, applications and bandwidth.(8 marks) 3 (c) List the categories of UTP cables. How is noise ? interference minimized in twisted pair cables.(4 marks) 4 (a) With respect to HDLC protocol, explain the following:-
i. HDLC frame format.
ii. Different HDLC frames.
iii. Data transfer modes.
iv. Balanced and unbalanced configurations.
v. Importance of P/F bit.
vi. "Polling" Technique and ?Select? routine.
vii. Flow control and error control commands.
(10 marks) 4 (b) Sketch the appropriate HDLC frames for the following cenario involving primary station 'A' and two Secondary station B and C.
(i) Primary station 'A' wishes to establish a Normal Respose mode-link with secondary station B and C.
(ii) Both the station B and C, send psitive acknowledgements to A.
(iii) Station 'A' sends a polling command to 'B' and 'B' sends 3 data frames. A sends a positive-Ack to indicates the receipt of error-free data frames.
(iv) Station 'A' sends a 'Select' command to 'C'. When 'C' responds with 'ready' response , 'A' sends 3 data frames to C and C sends positive Ack to indicate the receipt of error-free data frames.
(v) What is the Piggybacking ? Give an example of piggybacked frame.(10 marks) 5 (a) What is meant by 'blocking' in space-div -switching ?
(i) Derive the condition required to make 3-stage space-div-switch to be a non-blocking switch. (4m)
(ii) Sketch a 3 stage space-div-switch and TST switch with N=16, n=4 and K=3. (6m)
(iii) Show how blocking occurs in the above 3 stage space-div-switch diagram. (2m)(12 marks) 5 (b) Draw a diagram of packet-switched network and explain how virtual -circuit packet switching works. And compare circuit-switching, datagram switching and virtual circuit packet switching.(8 marks) 6 (a) Apply Dijkstra's and Bellman ford Routing algorithms to the given network and find the least cost path from source node-1 to all the nodes.(12 marks) 6 (b) Explain LAN protocol architecture with IEEE 802 reference. Sketch the general MAC frame format and LLC PDU structure. Explain the functions of different fields.(8 marks) 7 (a) Explain the functions of different connecting devices Routers, bridges, Repeaters and Switches.(8 marks) 7 (b) Write short notes:
i. ISDN
ii. Congestion control Techniques.
iii. Spanning tree algorithm
iv. Token re-insertion strategies.
v. Routing strategies for Packet switching.(12 marks)