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

ADCA / MCA (II Yr)
Term-End Examination

June, 1999

CS09 : Data Communications and Networking

Time: 3 hours
Maximum Marks: 75

1 Consider a half-duplex point to point link using a stop and wait scheme.

(i) What is the effect on line utilization of increasing the message size so that fewer messages will be required? Other factors remain constant. [2]

(ii) What is the effect on line utilization of increasing the number of frames for a constant message size? [2]

(iii) What is the effect on line utilization of increasing frame size? [2]

(iv) In the following figure, frames are generated at node A and sent to node C through B. Determine the minimum transmission rate required between B and C so that the buffers of node B are not flooded, base don the following: [10]

· The data rate between A and B is 100 Kbps.
· The propagation delay is 10 m sec/mile for both sides.
· Full duplex lines between nodes.
· All data frames are 1000 bits long; track frames are separate frames of negligible length.
· Between A and B, a sliding-window protocol with a window size of 3 is used.
· Between B and C, stop and wait is used.
· No errors.

(v) Using Dijkstra’s algorithm, generate a least-cost route to all other nodes for nodes A to K. Do the same for Bellman-Ford algorithm.

(vi) Could HDLC be used as a data link control proto col for a LAN? If not, what is missing? [5]

2 Discuss in detail about the physical description, applications and transmission characteristics of the following:
(i) Coaxial Cable [4]
( ii) Microwave [4]
(iii) Satellite [4]
(iv) Broadcast Radio [3]

3 (a) How does digital transmission work? How does DM (deta modulation) improve the performance of PCM (Pulse Code modulation)? [7]

(b) Discuss the characteristics of T1 carrier. [4]

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

4 Discuss the following in context of FDDI MAC protocol:
(a) List two key differences between FDDI and IEEE 802.5 [3]
(b) Illustrate graphically the operation of FDDI token ring. [4]
(c) FDDI frame formats description [6]
(d) Priority scheme [2]

5 Answer the following questions related to IP (Internet Protocol):

· Describe a way to do reassembly of IP fragments at the destination. [6]

· The protocol field used in the IPV4 header is not present in the fixed IPV6 header. Why not? [3]

· Describe IP address formats. [6]

6 Compare the following through examples.
· Transparent bridge and source routing bridge. [6]
· Two-way handshake and three-way handshake. [3]
· Credit allocation flow control and sliding window flow control mechanism. [3]
· Upward multiplexing and downward multiplexing. [3]