NATIONAL OPEN UNIVERSITY OF NIGERIA

UNIVERSITY VILLAGE, PLOT 91, CASDASTRAL ZONE, NNAMDI AZIKIWE EXPRESS WAY, JABI, ABUJA.
FACULTY OF SCIENCES
SEPTEMBER 2020 EXAMINATION

COURSE CODE: CIT 311

COURSE TITLE: COMPUTER NETWORKS

CREDIT: 3 UNITS

TIME ALLOWED: 2½ HOURS

INSTRUCTIONS: ANSWER QUESTION ONE (1) AND ANY FOUR (4) OTHERS

1(a) What is computer network? (2 marks)

1(b) Why is computer network necessary in Communication? (4 marks)

1(c) Differentiate between OSI Reference Model & TCP Reference Model. (4 marks)

1(d) With example each, classified transmission media. (3 marks)

1(e).What is Multiplexing? (2 marks)

1(f).Outline three services provided by the Logical Link Layer. (3 marks)

1(g) Explain integrated services in ISDN. (4 marks)

2(a) As a computer network engineer, a company whose head and sub offices spread within a geographical area of 50km. Which of the network topology will be more appropriate to recommend to the company and why? (3 marks)

2(b) Outline the seven layers of the OSI model reference (3 marks).

2(c) i. When does congestion occur in the network? (2 marks)

ii. Explain ISDN (3 marks)

2(d) Why was Spanning tree protocol developed (1 mark)

3(a) i. Outline the generic application of computer network (3 marks)

ii. State the main Objectives of OSI Reference Model? (4marks)

3(b) i. When is transmission said to be simplex, half duplex, and Full duplex (3 marks)

ii. Data Link Layer is divided into two sub layers, explain. (2 marks)

4(a) i. In Static Algorithm, explain flooding? (2 marks)

ii. Express 4 typical routing protocols and their associated network operating systems? (4 marks)

4(b) i. What is Congestion? (2 marks)

ii. Inside the subnet, several trade–offs exist between virtual circuits and datagrams, discuss two of them? (4 marks)

5(a) i. Report four functions of repeaters? (4 marks)

ii. Briefly explain upward and downward multiplexing (4 marks)

5(b) i. Briefly examine the need for multiplexing. (2 marks)

ii. Differentiate between a router and a bridge (4 marks)

6(a) i. Discuss in details the Domain Name System (DNS). (4 marks)

ii. Explain the term: Transmission Control Protocol (TCP) (2 marks)

6(b) i. Write short notes on the following Repeaters Switches Bridges and Hubs (4 marks)

ii. Explain the Importance of bridges and routers in a network? (2 marks)