Download CUSTOMER_CODE SMUDE DIVISION_CODE SMUDE

CUSTOMER_CODE
SMUDE
DIVISION_CODE
SMUDE
EVENT_CODE
APR2016
ASSESSMENT_CODE BCA4010_APR2016
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
4096
QUESTION_TEXT
Explain the Data Link Layer functions and service primitives used.
SCHEME OF
EVALUATION
The services of the data link layer are:
● Unacknowledged Connectionless Service - Brief Explanation (2
Marks)
● Acknowledged Connectionless Service – Brief explanation (2
Marks)
● Connection – oriented Service – Brief explanation (2 Marks)
The service primitives used by the data link layer are:
● Request – used by the network layer to ask the data link layer to do
something
● Indication – usedto indicate to the network layer that an event has
happened
● Response – used on the receiving side by the network layer to reply
to a previous indication.
● Confirm – provide a way for data link layer on the requesting side to
learn whether the request was successfully carried out and if not, why.
(1 x 4 = 4 Marks)
QUESTION_T
DESCRIPTIVE_QUESTION
YPE
QUESTION_ID 72443
QUESTION_T Explain the HDLC (High Level Data Link Control Protocol) along with frame
EXT
formats.
SCHEME OF
EVALUATION
a. HDLC Frame Format.
Bits:1 3 1
3
b.
An Information Frame
c.
A supervisory Frame
d. An Unnumbered Frame
(4 Marks)
HDLC frames can be transmitted over synchronous or asynchronous links.
Beginning and ending of each frame is identified using a frame delimiter
01111110. It consists of 3 different frames:
1. I frames: This frame has the control field as shown in fig (b) and are
used to transport user data from the network layer. Seq define the sequence
number; P/F defines Poll/Final field. It is called Poll when used by the
primary station to obtain a response from a secondary station, and Final
when used by the secondary station to indicate a response or the end of
transmission. Next field gives a number that the source machine is expecting
from the destination machine in a two way communication system. (2
Marks)
2. Supervisory Frames: This frame has the control field as shown in fig (c).
These frames are used for flow and error control whenever piggybacking is
impossible or inappropriate. The various Types defined in the frame are:
a. Receive ready
b. Reject
c. Receiver not ready
d. Selective reject (2 Marks)
3. U Frames: This frame has the control field as shown in fig (d). Are used
for link management. They are used to exchange session management and
control information between connected devices. (2 Marks)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
72446
QUESTION_TEXT
Explain two operational modes of IPSec in detail.
SCHEME OF
EVALUATION
Lpsec Operates In One Of The Following Two Modes:
Transport Mode:
In This Mode, Ipsec Protects What Is Delivered From The Transport
Layer To The Network Layer. I.E. The Transport Mode Protects The
Network Layer Payload, The Payload To Be Encapsulated In The
Network Layer. This Mode Does Not Protect The IP Header, I.E. It
Protects Only The Packet From The Transport Layer
(The Lp Layer Payload). In This Mode, The Ipsec Header And Trailer Are
Added To The Information Coming From The Transport Layer. The IP
Header Is Added Later. (3marks)
This Mode Is Normally Used When We Need Host-To-Host Protection Of
Data. The Sending Host Uses Ipsec To Authenticate And/Or Encrypt The
Payload Delivered From The Transport Layer. The Receiving Host Uses
Ipsec To Check The Authentication And/Or Decrypt The IP Packet And
Deliver It To The Transport Layer. (2mark)
Tunnel Mode:
Tunneling Or Encapsulation Is A Common Technique In Packet-Switched
Networks. It Consists Of Wrapping A Packet In A New One. That Is, A
New Header Is Attached To The Original Packet. The Entire Original
Packet Becomes The Payload Of The New One. In This Mode, Ipsec
Protects The Entire IP Packet. It Takes An IP Packet Including The
Header, Applies Ipsec Security Methods To The Entire Packet, And Then
Adds A New IP Header. (3marks)
Tunneling Requires Intermediate Processing Of The Original Packet
While Enroute. The Destination Specified In The Outer Header, Usually
An Ipsec Firewall Or Router, Receives The Tunneled Packet, Extracts The
Original Packet, And Sends It To The Ultimate Destination. (2 marks)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
72447
QUESTION_TEXT
Explain the four layers of TCP/IP protocol
2.5 each
1. Application layer
SCHEME OF EVALUATION 2. Transport layer
3. Internet work layer
4. Network interface layer
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
116175
QUESTION_TEXT
Explain the layers of OSI model in brief.
The OSI Model is composed of seven ordered layers:
•
Layer 1 – The Physical Layer
•
Layer 2 – The Data Link Layer
•
Layer 3 – The Network Layer
•
Layer 4 – The Transport Layer
•
Layer 5 – The Session Layer
•
Layer 6 – The Presentation Layer
•
Layer 7 – The Application Layer
SCHEME OF EVALUATION
(6 marks)
(2 marks)
(2 marks)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
116176
QUESTION_TEXT
Explain with the waveforms the three major problems from which a
transmission line suffers.
Transmission lines suffer from three major problems:
1.
Attenuation distortion
2.
Delay distortion
3.
●
SCHEME OF
EVALUATION
●
●
Noise
Attenuation distortion: It is the loss of energy as the signal
propagates outward. The amount of energy depends on the
frequency. The signal attenuates as it propagates. If the attenuation
is too much, the receiver may not be able to detect the signal at all,
or the signal may fall below the noise level. (1 marks)
For reliable communication, the attenuation and delay over the
range of frequencies of transmission should be constant. Fig: Signals
loose power at it travels time (2marks)
Delay distortion: The second transmission impairment is delay
distortion. Communication lines have distributed inductance and
capacitance, which distort the amplitude of signals and also delay
the signals at different frequencies by different amounts. It is caused
by the fact that different Fourier components travel at different
speed. Fig; Delay distortion (2marks)
●
●
It is due to velocity of propagation the frequency varies. Thus,
various frequency components of a signal arrive at the receiver at
different times. (1mark)
Dispersion: Signals tend to spread as they travel, with the amount
of spreading dependent on the frequency. (1mark) Noise: Noise is a
third impairment. It can be define as unwanted energy from sources
other than the transmitter. Thermal noise is caused by the random
motion of the electrons in a wire and is unavoidable. Fig: Signal
(2marks) Fig: Noise (1mark)