Jan 2001

Question Paper of CS-09 – Data Communication & Network of Jan 2001 from IGNOU

1 (i) Suppose that the Aloha Protocol is used to share a 56 Kbps satellite channel. Suppose that packets are 1000 bits long. Find the maximum throughput of the system in packets/second.

(ii) Does Ethernet provide connection oriented or connectionless service? How is the transfer of frames in Ethernet similar to the transfer of frames in a packet switching network? How is it different?

(iii) What difference does it make to the network layer if the underlying data link layer provides a connection oriented service versus a connectionless service?

(iv) Use IEEE 802.3 and IEEE 802.11 to discuss three differences between wired and wireless LANs.

(v) � Identify the address class of the following IP addresses: 208.58.20.165 and 128.167.23.20.
� Identify the range of IPV4 addresses spanned by class A, Class B and class C.
(vi) List the important QoS ATM parameters.

2 (i) Discuss the important features of the following techniques:
(a) Wavelength Division Multiplexing
(b) PCM
(c) Delta Modulation (DM)
What are the improvements of DM over PCM?

(ii) A signal is transmitted digitally over a 4-KHz noiseless channel with one sample every 125 m sec. How many bits per second are actually sent for the following encoding methods?
� DPCM with a relative signal value
� DM

3 (i) A 10 kHz baseband channel is used by digital transmission system. Ideal pulses are sent at the Nyquist rate, and the pulses can take 8 levels. What is the channel capacity of the system?

(ii) Discuss the following transmission techniques for wireless transmission:
(a) Microwave Transmission
(b) Radio Transmission
(c) Infra-red

4 (i) Discuss the following in the context of token ring:
� How does token ring define the start and end delimiters?
� Main problems of a token ring network and methods used to overcome them.
� Main advantages of MAUs in a token ring network.

(ii) With reference to transport layer, outline the operation of 3-way handshaking. How does the 3-way handshake prevent old duplicate connection initiation from causing confusion?

(iii) Discuss the possible scenario for a transport connection over a connection-oriented network layer. [3]

5 (i) Discuss the important features of the following internet control protocols:.

� The Address Resolution Protocol (ARP)
� Open Shortest Path First (OSPF)

(ii) Explain the data format of ISDN.

6 Discuss the following:
(i) Internet multicasting
(ii) Firewalls
(iii) Multipurpose Internet Mail Extensions

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