CS339 - COMPUTER NETWORKS

[aruljothi]

CS339 - COMPUTER  NETWORKS

Time:   Three Hours                   Maximum:   100 Marks
Answer All The Questions

PART – A (10 x 2 = 20 Marks)

1.     Why network software is organized as a series of layer?

2.     What are the two kinds of light sources used in fiber cables?

3.     Reliability of CRC is better than that of simple parity and LRC. Justify this statement.

4.    What is meant by bit stuffing?

5.     Write short notes on virtual circuit organization of the subnet.

6.     Differentiate between adaptive  and non-adaptive routing algorithms.

7.     What is meant by upward and downward multiplexing.

8.     Mention some applications where UDP is preferred over TCP?

9.     Mention the layer in which email gateway function. Also mention some of its    applications

10.    Define encryption
      
PART – B (5 x 16 = 80 Marks)

11.i)   Compare OSI and TCP / IP reference models on form of their merits and demerits.                                         (10)

    ii)   Differentiate between broadcast networks and point to point networks.          (6)

12.a)i)   Explain the CSMA/CD protocol with binary exponential back off algorithm used internet.                                (10)

ii)   Assume that a network can cover a distance of 5000 meters and the RTT is 100 μ sec of the network operates at a speed of 20Mbps. What should be the minimum frame size to employ CSMA / CD?                                           (6)

(OR)

12.b)i)   Explain the sliding window protocol and compare its performance against the simple stop and wait protocol.                       (10)

ii)   Given message is M(X) = X5 + X4+ X + 1 and the generator is G(X) = X4+X3+1 Compute CRC.                               (6)

13.a)i)    Explain the distance vector routing algorithm.                   (

ii)   Find the shortest path from node A to node D in the following network using the Bell mark kord routing algorithm.                         (

      

(OR)

13.b)i)   Given three IP addresses are 32.46.7.3, 200.132.110.35 and 140.75.8.92. Find their classes, network addresses, broadcast address and their subnet marks.          (6)

ii)    Explain the token breket algorithm and compare its performance against the leaky bueket algorithm                              (10)

14.a)i)   Explain the Bres-way handshak protocol used to establish the connection in the transport layer. Also explain the protocol used to release the connection.           (

ii)   Explain the transport service access point and the various schemers used by the transport layer to find the TSAP at a server.                      (

(OR)

14.b)i)   Explain the various fields of TCP header.                      (

       ii) Write short notes about the pseudo header included in the TCP checkroom.       (4)

      iii)   Draw the UDP header and explain its fields                       (4)

15.a)   Explain the DNS in terms of name space, resource record and name server.     (16)

(OR)

15.b)   Explain the architecture of WWW as on client / server application           (16)

-----

[sams.raghu]

B.Tech I Semester Supplimentary Examinations, February 2008

2008 Jawaharlal Nehru Technological University

COMPUTER NETWORKS

( Common to Computer Science & Engineering and Information Technology)

Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks

1. (a) How would you utilize an existing telephone network for Computer-to-Computer
data communications?
(b) "Bad Timing" is also a problem for OSI reference model. Discuss. [8+8]
2. (a) Television channels are 6MHz wide. How many bits/sec can be sent if four
level digital signals are used? Assume a noiseless channel
(b) How does a virtual circuit differ from a physical circuit? What advantages
would a virtual circuit provide? [8+8]
3. (a) Explain about the various services that the data link layer offers to the upper
layers?
(b) Compute the fraction of the bandwidth that is wasted on overhead (headers
and retransmissions) for sliding window protocol using selective repeat on a
heavily loaded 50-kbps satellite channel with data frames consisting of 40
headre and 3960 data bits. ACK frames never occur. NAK frames are 40 bits.
The error rate for data frames is 1 percent, and the error rate for NAK frames
is negligible. The sequence numbers are 8 bits. [8+8]
4. (a) What is the prime difference between a token bus and a token ring?
(b) A large population of ALOHA users manages to generate 50 requests/sec,
including both originals and retransmissions. Time is slotted in the units of
40 msec.
i. What is the chance of success on the first attempt?
ii. What is the probability of exactly k collisions and then a success?
iii. What is the expected number of transmission attempts needed? [4+12]
5. (a) Network layer can provide either connection oriented service or connection less
service. Which one you prefer. Justify your answer.
(b) Define Virtual circuit and Datagram. Compare Virtual circuit subnet with
Datagram Subnet.
(c) Is Virtual circuit same as Physical connection. Comment. [5+8+3]
6. Explain routing in mobile hosts. [16]
7. (a) Why Pseudo header is used in computing TCP Checksum?
(b) Explain how TCP controls congestion? [6+10]
1 of 2
Code No: R05310504 Set No. 4
8. (a) What is Domain? Explain the Internet domain space in the context of DNS.
(b) What is resource record? What is its format?
(c) What are the record types of DNS resource record? [6+5+5]