Dec 1999

Question Paper of CS-09 – Data Communication & Network of Dec 1999 from IGNOU

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.

(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.

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

(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?

(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?

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

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

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

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

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.

(ii) How does a gateway do with the �time to live� value in an IP header?

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

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

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

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