June 2001

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

Time: 2 hours
Max. Marks: 75

Note: Question No 1 is compulsory. Attempt three more questions from questions numbered as 2 to 6.

i. Suppose transmission channels become virtually error free. Is the data link layer still necessary? 3 marks
ii. Explain how the notion of multiplexing can be applied at the data link layer, network layer and transport layer 3 marks
iii. Give two features that the data link layer and transport layer have in common. Give two features in which they differ. 4 marks
iv. Explain the following Sliding Window Protocol GO BACK n with example 5 marks
v. Consider a half duplex point to point link using a stop and wait scheme. 5 marks
# What is the effect on line utilization of increasing the message size so that fewer messages will be required? Other factors remain constant.
# What is the effect on line utilization of increasing the number of frames for a constant message size?
vi. Explain the typical characteristics of a LAN in terms of addressing mechanisms, topology, MAC Protocol, channel capacity, cost and application. 10 marks

2. Discuss the following in the context of IEEE 802.3 Standard Backoff Algorithm
i. The Binary Exponential Backoff Algorithm 3 marks
ii. 802.3 Cabling 6 marks
iii. Encoding Techniques 3 marks
iv. 802.3 Performance 3 marks

i. What are the general principles of congestion control? List the policies of different layers affecting congestion. 5 marks
ii. Describe and compare the following two approaches to congestion handling: – 10 marks
# The Token Bucket Algorithm
# Hop-by-Hop Choke Packets

i. What is the basic difference between LAM and WAN in terms of design layout? 5 marks
ii. Identify the address class of the following IP address:,
iii. Describe the following routing algorithms: – 7 marks
# Flow-Based Routing
# Routing for mobile hosts

i. Describe the features of the following devices: – 5 marks
(1) Hub
(2) Switch
(3) Gateway
(4) Repeater

ii. What are the issues to be examined in building a bridge between various 802 LANs? Also outline the functioning of a transparent and source routing bridge.

6. Discuss the following features in the context of the transport layer
(i) Crash Recovery 6 marks
(ii) Flow Control and Buffering 6 marks
(iii) The Socket Primitives 3 marks

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