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Wednesday, 22 June 2016

High Speed Networks and Internets-Model Question Paper



1(a) List the major advantages with layered approach to protocols. (5 Marks)
(b) Describe some circumstances where it might be desirable to use source routing rather than let the routers make the routing decision. (4 marks)
(c) Compare the individual fields of the IPv4 header with the IPv6 header. Account for the functionality provided by each IPv4 field by showing how the same functionality is provided in IPv6. (8 Marks)
(d) There is no error detection mechanism (frame check sequence) in X.25. Isn’t this needed to assure that all of the packets are delivered properly? (3 Marks)
2(a) List all possible values of the GFC and the interpretation of each value. (8 Marks)
(b) Write a note on the emergence of High-Speed LANs. (4 Marks)
(c) Mention five applications of fiber channel. (5 Marks)
(d) Write a short note on service area requirement for a wireless LAN. (3 Marks)
3(a) Show that, all other things being equal, the greater the correlation coefficient of two random variables, the greater the variance of their sum and the less the variance of their difference. (6 Marks)
(b) The owner of a shop observes that on average 18 customers per hour arrive and there are typically 8 customers in the shop. What is the average length of time each customer spends in the shop? (4 Marks)
(c) Consider a single queue with a constant service time of 4 seconds and a poisson input with mean rate of 0.20 items per second. Find the mean and standard deviation of (i) queue size and (ii) residence time. (6 Marks)
(d)Show that the Cantor set consists of all points in the interval [0,1] that have no 1’s in their base-3 expression. (4 Marks)
4(a) Write a note on effects of congestion. (6 Marks)
(b) Explain the terms committed burst size and excess burst size. (6 Marks)
(c) A channel has a data rate of 4 kbps and a propagation delay of 20 ms. For what range of frame sizes does stop and wait give an efficiency of at least 50%? (4 Marks)
(d) A TCP entity opens a connection and uses slow start. Approximately how many round trip timers are required before TCP can send N segments? (4 Marks)
5 (a) Write a note on cell delay variation in ATM network. (4 Marks)
(b) Explain three ATM QoS parameters defined by the ATM forum. (6 Marks)
(c) The graph Kn, called the complete graph of n vertices, has n vertices and every vertex is joined to every other vertex by an edge. Find a formula for the number of edges in Kn. (6 Marks)
(d) Will Dijkstra’s algorithm and the Bellman-Ford algorithm always yield the same solutions? Explain. (4 Marks)
6(a) When multiple equal cost routes to a destination exist, OSPF may distribute traffic equally among the routes. This is called load balancing. What effect does such load balancing have on a transport layer protocol, such as TCP? (4 Marks)
(b) Assume a router has 30 routes to advertise using RIP, requiring one datagram with 25 routes and another with the remaining 5. What happens if once an hour the first datagram with 25 routes is lost? (4 Marks)
(c) IGMP specifies that query messages are sent in IP datagrams that have the Time to Live field set to 1. Why? (4 Marks)
(d) Explain in detail why MOSPF would be inefficient in a sparse multicast environment. (8 Marks)
7(a) What is Bit-Round Fair Queuing (BRFQ)? (4 Marks)
(b) Illustrate how the last two fields in RTCP SR or RR receiver report block can be used to calculate round-trip propagation time. (8 Marks)
(c) In RSVP, because the UDP/TCP port numbers are used for packet classification, each router must be able to examine these fields. This requirement raises problems in the following areas: (i) IPv4 header processing and (ii) IP-level security. Indicate the nature of the problem in each area, and suggest a solution. (8 Marks)
8 (a) Write a note on characteristics of the Huffman code. (6 Marks)
(b) How can the BWT algorithm improve compression performance? (4 Marks)
(c) JPEG has defined four modes of operation. Explain. (4 Marks)
(d) In a straight forward implementation of LZ77 coding, which step would be faster, compression or decompression.? Why? (6 Marks)

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