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SIXTH SEMESTER B.Tech.(C0)

MID SEMESTER EXAMINATION MARCH-2020

CO-306 COMPUTER NETWORKSS

Max. Marks: 30
Time: 1:30 Hours
Note: Answer ALL FIVE questions. All questrions carry equal marks,
Assume suitable missing data, if any.
1[a] Explain the five components of a data communication system. of OSI
and Session layer
b] What are the responsibilities of Presentation layer
model?
1001110101 is transmitted the standard CRC
using
2[a] Define CRC. A bit stream

method described in the text. The generator polynomial is x+x+1. Show the
actual bit string transmitted. Suppose the fourth bit from the left is inverted
is detected at the receiver's end.
during transmission. Show that this error

what should be the minimum Hamming

b] lfwe want to detect two-bit errors, then
distance?
send consisting of 9 packets to Station B using a
3 [a] Station A needs to a message
size 3) and control strategy. All
go-back-n error
sliding window (window
available for transmission. If every 5th
packets are ready and immediately
no acks from B ever get lost), then what
packet that A transmits gets lost (but
is the number of packets that A will transmit for sending the message to B?

[b] Why is acknowledgement numbered in Stop-And-Wait protocol? Discuss the

situation when unnumbered acknowledgements can create confusion in the
sender and receiver end.

stream: 0001110101
4[a] Draw the following encoding scheme for the bit
I. NRZ II. Manchester coding
in CSMA/CD LAN, the maximum end to end propagation delay is
(b] Suppose a

25.6 usec. If the line is operating in 100MBPS then what will be the
minimum frame length (in bytes) of the LAN?
5 Write short notes:
[a]Virtual circuit switching
b] Network Routing
[c) IEEE 802.3
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Total No. of Pages:1 -|19 B. Tech.(CO)
SLXTH SEMESTER

MID SEMESTER EXAMINATION MAR-2019

co-306 COMPUTER NETWORKS

Time: 1:30 Hours Max. Marks: 30

Note: Ail questions are coimpulsory. Assume suitable missing data, if any.
All questions carry equal marks.
Q.1 (a) Write the diference between bit stuffing and character stuffing.

)Sketch the waveform for the bit steam 10110010 in differential

Manchester encoding scheme.

Q.2(a) Explain the IP hcader format of IPv4 in detail.

bHow is CSMA a clear improvement over ALOHA? How is it further

improved by implementing CSMA/CD?

03 ()A channel has a bit rate of 4kbps and propagation delay of 20ms.What is
the minimum size of frame does stop and wait give efficiency of atleast 50%?

b) Categorize thre basic topologies and give an advantage and disadvantage of

each type.

Q4(a)A bit stream 10011101 is transmitted using the standard CRC method. The
generator polynomial is x' +1.Show the actual bit string transmitted. Suppose the
third bit from the left is inverted during transmission.

(bExplain the distance vector routing algorithm and give the limitations of this
algorithm.

Q5Write short notes on any two of the following:

(a)IPv6
(b)HDLC
(c) PCM
(d) IEEE 802.5
Total No. of Pages: 2 Roll No.
SIXTH SEMESTER B.TECH TCOEI
MID SEMESTER EXAMINATION(MARCH 2018)
Co-306 COMPUTER NETWORKS

Time:1.5 hours Max. Marks: 30

Note:Attempt all questions.
Assume suitable missing data, if any.

1. Explain OSI layers and with the help of diagram show the interaction
among different layers of OSI.
Assume that source S and destination D are connected through two
intermediate routers labeled R. Detemine how many times each packet
has to visit the network layer and the data link layer duringg a transmisS1on
trom S to D. 7 marks

The address of a class B host is to be split into subnets with a 6-bit subnet
2
number. What is the maximum number of subnets and the maximum

number of hosts in each subnet? Consider

the following routing table at

an IP router

Network No. Nel Mask Next Hop

128.96.170.0 255.255.254.0 Interface 0
128 96.168.0 255.255.254.0 Inlerface 1
128 96.166.0 255.255.254.0 R2
128.96.164 0 255.255 254.0| R3
O000 Defaul R4
address in Column 1, match the correct entries to Next Hop in
For each IP
5 marks
Column I.

the the final distance vectors at different nodes for the

3. What will be
following given network where NI,N2,N3,N4,NS represents Nodes of the
network? 4 marks
 2
N4 N3
4. Explain Go back N protocolL In Stop and wait protocol, derive the
relation between the length of the packet (L), bandwidth of the Channel
(B) and time of propagation (Tp) to achieve 50% efficiency. 7 marks

5. Write Short notes on any two: 3.5x 2 7 marks

a. Flow diagram of Pure Aloha
b. Virtual Circuit Switching vs Circuit Switching
C. Flow diagram of CSMA/CD
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SIXTH SEMESTER
END TERM EXAMINATION
(IMay 2018)
c o 3 0 6 COMPUTER NETWORKS

Max. Marks: 40
Time:3 hours Each question is of 10 marks.
Note: Attempt any four questions.
Assume suitable missing data, if any.

Consider a
example.
1. a.Explain Selective Repeat Protocol with
located 8000 km apart. The
network connecting two systems
second. The
bandwidth of the network is 500x 10° bits per
4 x 10° meters per second. It is
propagation speed of the media is
Go-Back-N sliding window protocol for this
needed to design a
The network is to be
network. The average packet size is 10' bits.
Assume that processing delays at nodes
used to its full capacity.
are negligible. What is the minimum size in bits of the sequence

number field?

back N
b. Let the system wants to send 10 packets using Go
protocol with sliding window size (N) as 3. What are the total no
of transmissions if every 5th packet is lost. (10 marks)

2. a. A user downloads the file of 4.5 MB from the website. The files
routes through two routers RI with maximum transmission unit
(MTU) as 2.5 MB and router R2 with MTU as 1500 KB before
finally reaching to the cient. Show the fragmentation at each
router and calculate the speed at which the file is downloaded by
the client. Consider an instance of TCP°s Additive Increase
Multiplicative Decrease (AIMD) algorithm where the window
size at the start of the slow start phase is 2 MSS and the threshold
at the start of the first transmission is 8 MSS. Assume that a
timeout occurs during the fifh transmission. Find the congestion
window size at the end of the tenth transmission. (Assume 1 MB
=
1000KB and IPv4 Header Length= 20KB ).
P.T.O.
 Ior
algorithm
b. For a host machine that uses
the token bucket
of1 megabyte
control, the token bucket has a capacity
congestion second. Tokens
rate is 20 megabytes per
and the maximum output
10 megabytes per
arrive at a sustain output at a rate of
rate to needs
token bucket is currently full and the machine
second. The
minimum time required
to send 12 megabytes of data. What is the
(10 marks)
to transmit the data.

ofa class B
address
3. a. Explain IPv4 Classful IP addressing? The
host is to be split into subnets with a 6 bit
-
subnet number. What
maximum number of
is the maximum number of subnets and
hosts in each subnet?
b. What is count to infinity problem in DVR. Explain
Link state
router?
algorithm with example. How is switch different from
(10 marks)

4. a. Explain DHCP protocol? What is the difference between

multicast and broadcast? Suppose there aren stations in a slotted
LAN. Each station attempts to transmit with a probability 'p' in
each time slot. What is the probability that only one station
transmits in a given slot.

b. The bank uses RSA algorithm at the presentation layer to

encrypt the message M= 88 with its public key, e = 7. If the two
prime no. used for encryption are p=l7 and q=11, show the
encrypted cipher and decrypted message at the receiver end. What
is the remainder when 3232
is divided by 9? 10 marks)
5. Write short note on (any two) (5x2-10 marks)
a. Channel Access Methods
b. Mail Transfer Agent, SMTP, POP,IMAP
c. Virtual Circuit Network
d. ICMP

END