Test Papers / Previous Question Papers of IGNOU CS09 Data Communications and Networking December 1999

ADCA / MCA (II Yr)
Term-End Examination

December, 1999

CS09 : Data Communications and Networking

Time: 3 hours
Maximum Marks: 75

1 (a) For the bit stream 100010100 sketch the waveform for Manchester and Differential Manchester Coding and also discuss the advantages of the coding schemes. [5]

(b) The waveform of the following figure belongs to a Manchester coded binary data stream. Determine the beginning and end of bit periods (i.e. extract clock information) and give the data sequence. [6]

(c) Why should PCM be preferable to DM for encoding analog signals that represent digital data? [4]

(d) Exactly how many classes A, B, C network can exist in IP address? Exactly how many hosts can a network in each class have? [5]

(e) In a network that has a maximum TPDU (Transport protocol data unit) size of 128 bytes, a maximum TPDU lifetime of 30 sec and an 8 bit sequence number, what is the maximum data rate per connection? [10]

2 (i) Explain through diagrams the functioning of HDLC protocol for the following:
· Link setup and disconnect
· Two way data exchange
· Busy condition
· Error recovery using REJ command [10]

(ii) What are two types of non-data cells in ATM? How are they distinguished from data cells by the receiver? [5]

3 (i) Compare the priority schemes for IEEE 802.5 token ring and FDDI. What are the relative pros and cons? [9]

(ii) What happens in a token bus if a station accepts the token and then crashes immediately? How does the protocol handle this situation? [6]

4 (i) Compare the individual fields of the IPv4 header with IPv6 header. Account for the functionality provided by each IPv4 field by showing how the same functionality is provided in IPv6. [10]

(ii) How does a gateway do with the “time to live” value in an IP header? [5]

5 (i) Sketch TCP finite state machine and explain its operation in brief. [9]

(ii) Lost TCP acknowledgements do not necessarily force retransmission. Explain why? [6]

6 Discuss in detail the following in the context of the high speed modems:
(i) Quadratum Amplitude Modulation [4]
(ii) Trellis coding [4]
(iii) V.32 and V.34 bits [4]
(iv) MNP5 [3]