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Eti 2206: Computer Networks Question Paper

Eti 2206: Computer Networks

Course:Bachelor Of Science In Telecommunication And Information Engineering

Institution: Multimedia University Of Kenya question papers

Exam Year:2012

QUESTION ONE - 30 MARKS (COMPULSORY)

a. A mesh network topology has 5 nodes. Determine the:

i. Total number of cable links required;
ii.Number of ports for each node. (4 marks)

b. Describe the Carrier Sense Multiple Access with Collission Detection (CSMA/CD) medium access protocol. (4 marks)

c. A given host IP address is 17.110.25.6 and subnet mask is 255.224.0.0. Determine the:
i. Last host IP address of the major network;
ii. Subnet address for the given host IP address;
iii. Range of host addresses for this subnet;
iv. Broadcast address for this subnet; (6 marks)

d. A series of information frames with a mean length of 100 bits is to be transmitted across a data link 4000 km long at data rate of 2 Mbps. If the link has a velocity of propagation of 2 * 10^8 m/s and a bit error rate (BER) of 10^-4. Determine the link utilization efficiency assuming that only one frame is transmitted and acknowledgement received before another is sent. (5 marks)

e. With the aid of a block diagram describe how the transfer of data from application layer X to application layer Y is achieved in network with respect to OSI model. (11 marks)

QUESTION TWO - 20 MARKS

a. Describe Token Ring LAN medium access protocol. (10 marks)

b. A connection-oriented network has the following characteristics:
Length between any pair of stations = 500 Km.
Number of nodes across the network = 50
Data rate = 10^4 bps
Propagation velocity = 2 * 10^8 m/s
Set up time required by each node = 20 ms
i. Compare the total times required to transmit messages of lengths 10^6 and 10^3.
ii. Compare the efficiencies of transmitting the two messages.
(10 marks)
QUESTION THREE - 20 MARKS

a. Describe the Carrier Sense Multiple Access with Collission Avoidance (CSMA/CA) medium access protocol. (8 marks)

b. Consider a TCP connection using the slow-start congestion control scheme with an initial THRESHOLD value of 64 KB and a Maximum Segment Size (MSS) of 4KB. The receiver''s advertising window is initially 24 KB. The first transmission attempt is numbered 0, and all transmission attempts are successful except for Timeouts on attempt number 4. In the ACKs for transmission attempt number 9 and subsequently, the receiver''s advertised window is reset to 20 KB. Find the size in KB of the sender''s congestion window for its first 12 transmission attempts i.e., transmission numbers 0 - 11.
(12 marks)
QUESTION FOUR - 20 MARKS

a. Draw the TCP segment format and briefly describe the function of each field.
(13 marks)
b. Consider a 200-meter 4Mbps token ring containing 20 stations, each transmitting with equal priority. Suppose no station is allowed to transmit more than 5000 data octets before giving up the token. Once a station gives up a token how long wikll it take (in the worst case) for that station to get the token again? (7 marks)

Eti 2206: Computer Networks Question Paper

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