June 2000

Question Paper of CS-09 – Data Communication & Network of June 2000 from IGNOU

1 (a) Using the Nyquist theorem, calculate the sampling rate for the following analog signals:

� An analog signal with bandwidth 2000 Hz
� An analog signal with frequencies from 2000 to 6000 Hz

(b) What is the minimum number of samples for PCM encoding if the frequency ranges from 1000 to4000Hz?

(c) What is the difference between bit rate and baud rate? Give an example where both are the same. Give an example where they are different.

(d) Show by calculation how many hosts per network each IP address class (A,B and C only) can have?

(e) In two byte address fields what is the maximum number of permanent virtual circuits possible? What about a 3 byte address?

2 Answer the following questions:

(a) Contrast the IEEE 802.3 frame with HDLC I-frame.
(b) Contrast the IEEE 802.5 frame with HDLC I-frame.
(c) Why is there no AC field in 802.3 frame?
(d) What are the advantages of FDDI over a token ring?

3 Compare and comment on the following :
(a) Ethernet, token ring and FDDI in terms of access method, address length, signaling, data rate and error control.
(b) Transport and source routing bridge in terms of orientation, transparency, configuration, routing, locating, failures and complexity.
(c) Datagram subnet and virtual circuit subnet in terms of effects of router failure and congestion control.

4 (a) Describe the working principle, advantage and disadvantage of the following routing algorithms:
� Reverse path forwarding
� Multicast routing
Also describe various ways of pruning the spanning tree.

(b) Comment on five important quality of service parameters defined by the ATM standard.

5 Answer the following questions associated with congestion algorithms:

(a) Difference between token bucket and leaky bucket algorithms.

(b) Describe all the parameters used in flow specification technique.

(c) Rate based congestion algorithm in ATM.

6 Discuss the following question related to the transport layer:

(a) Many features of the transport layer (e.g., flow control and reliable delivery) are also handled by the data link layer. Is this duplication of effort ? why or why not?

(b) What are the problems with 2-way handshake in connect establishment and connection termination? How does 3-way handshake resolve it? Explain through diagrams.

(c) Upward multiplexing and downward multiplexing.

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