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VTU Electronics and Communication Engineering (Semester 7)
Computer Communication Networks
December 2011
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 (a) Explain the differences between OSI reference modeland TCP/IP reference model.
5 M
1 (b) Match the following to one or more layer in OSI model:
(i) Route determination
(ii) Flow control
(iii) Interface to transmission media
(iv) Provides access for the end user
(v) Format and code conversion services.
5 M
1 (c) What is DSL technology? What are the services provided by the telephone companies using DSL? Distinguish between DSL and DSLAM
10 M

2 (a) In stop and ARQ system, the bandwidth of the line is 1Mbps and it takes 20 ms to make round trip. What is the bandwidth delay product? if the system data frames are of 1000 bit length, what is the uitilization percentage of link? What is the channel uitilization percentage of link if the protocol that can send up to 15 k mes before stopping and worrying about the acknowledgement? Write the comment.
5 M
2 (b) Explain briefly the bit and charter stuffing.
5 M
2 (c) With a near diagram, explain the HDCL frame form.
10 M

3 (a) Write a different physical topologies used in the logical ring method and explain briefly
10 M
3 (b) In CSMA/CD, the data rate is 10 Mbps, the distance between the stations 'A' and 'C' is 2000 m and propagation is 2 × 108 mts. Station A starts sending a long frame at time t1=0; station C starts sending a long frame at t2=3 micro sec. The size of the frame is long enough to guarantee the detection of collision by the stations.
Find
(i) The time when station 'C' hears the collision (t3)
(ii) The time when station 'A' hears the collision (t4)
(iii) The number of bits station A has sent before detecting the collision
(iv) The numeber of bits station C has sent before detecting the collision
10 M

4 (a) Mention the four different types of Ethernet format. Explain the same briefly.
10 M
4 (b) List the different goals of giga bit Ethernet and expalin the different implementation of same.
10 M

5 (a) Why spanning tree algorithm is used? Explain the same, with graphical representation.
10 M
5 (b) Mention the different characteristics of VLAN and explain briefly.
10 M

6 (a) Find the range of address in the following blocks
(i) 123.56.77.32/29
(ii) 200.17.21.128/27
(iii) 17.34.16.0/23
(iv) 180.34.64.64/30
10 M
6 (b) Expalin the IPV4 datagram format.
10 M

7 (a) Explain the Dijkstra alogorithm for the example shown in fig. Q7(a)

10 M
7 (b) Explain the different forwarding techniques used to forward the packet from source to destination.
10 M

8 (a) Explain the user daragram format.
5 M
8 (b) Explain the features of TCP.
10 M
8 (c) Suppose a TCP connection is transferring a file of 5000 byes, the 1st byte is numbered 10,001. What are the sequence nos of each segment, if data are sent in 5 segment each carrying 1000 bytes?
5 M

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