MCA - 2201
2393-1/02

M.C.A. DEGREE EXAMINATION-2002
Second Year - Second Semester
COMPUTER NETWORKS
(Effective from the admitted Batch of 2000-2001)

Time: Three hours
Maximum: 75 marks

First question is compulsory.
Answer any FOUR from the remaining questions.
All questions carry equal marks.
Write all bits of the first question at one place.

1. (a) What are the advantages of packet switching over circuit switching?

(b) What are the key elements of a protocol?

(c) Define a router.

(d) Write short notes on PDU.

(e) Write short notes on E-mail.

(f) Write short notes on WWW. (6 x 21 = 15)

2. Explain in detail about the OSI reference model. (15)

3. (a) If a Binary signal is sent over a 3-kHz channel whose signal to noise ratio is 20 db. What is the maximum achievable data rate?

(b) A Noiseless 4-kHz channel is sampled every 1 m sec. What is the maximum data rate?

(c) A cable TV has 100 channels all of them altering programs with advertising. Is this more like TDM or like FDM. (5+5+5)

4. (a) If the bit string 0111101111101111110 bit stuffed, what is the output string?

(b) Data link protocols almost always put the CRC in a trailer, rather than a header. Why?

(c) A 100 KM long cable runs at the T1 data rate. The propagation speed in the cable is 2/3 the speed of light. How many bits fit in the cable. (5+5+5)

5. (a) Measurements of a slotted ALOHA channel with an infinite number of users. Show that 10 percent of the slots are idle.

(i) What is the channel load, G?

(ii) What is the throughput?

(iii) Is the channel under loaded or over loaded?

(b) Sketch the differential Manchester encoding for the bit stream : 0001110101. (10+5)

6. (a) Write about Token Ring MAC sub layer protocol.

(b) Compare 802.4 and 802.5. (8+7)

7. (a) Explain about the Token Bucket algorithm.

(b) Compare virtual circuits and datagrams. (8+7)

8. Write short notes on:

(a) Network security

(b) DNS

(c) SNMP. (5+5+5)