Chapter-1

Ans-1:
I. Delivery: The system must deliver data to the correct destination. Data must be received by the
intended device or user and only by that device or user.

2. Accuracy: The system must deliver the data accurately. Data that have been altered in transmission
and left uncorrected are unusable.

3. Timeliness: The system must deliver data in a timely manner. Data delivered late are useless. In the
case of video and audio, timely delivery means delivering data as they are produced, in the same order
that they are produced, and without significant delay.

4. Jitter: Jitter refers to the variation in the packet arrival time. It is the uneven delay in the delivery
ofaudio or video packets. For example, let us assume that video packets are sent every 3D ms. Ifsome
ofthe packets arrive with 3D-ms delay and others with 4D-ms delay, an uneven quality in the video is the
result.

Ans-2:
I. Message. The message is the information (data) to be communicated. Popular forms ofinformation
include text, numbers, pictures, audio, and video.

2. Sender. The sender is the device that sends the data message. It can be a computer, workstation,
telephone handset, video camera, and so on.

3. Receiver. The receiver is the device that receives the message. It can be a computer, workstation,
telephone handset, television, and so on.

4. Transmission medium. The transmission medium is the physical path by which a message travels
from sender to receiver. Some examples of transmission media include twisted-pair wire, coaxial cable,
fiber-optic cable, and radio waves.

5. Protocol. A protocol is a set of rules that govern data communications. It represents an agreement
between the communicating devices. Without a protocol, two devices may be connected but not
communicating, just as a person speaking French cannot be understood by a person who speaks only
Japanese.

Ans-3:
1. Text:
The American Standard Code for Information Interchange (ASCII), developed some decades ago in the
United States, now constitutes the first 127 characters in Unicode and is also referred to as Basic Latin.
Appendix A includes part ofthe Unicode.

2. Numbers:

Numbers are also represented by bit patterns. However, a code such as ASCII is not used to represent
numbers; the number is directly converted to a binary number to simplify mathematical operations.
Appendix B discusses several different numbering systems

Ans-4:
1. Simplex: In simplex mode, the communication is unidirectional, as on a one-way street. Only
one ofthe two devices on a link can transmit; the other can only receive.
Eample : Mainfram to Monitor.

2. Half-Duplex: In half-duplex mode, each station can both transmit and receive, but not at the
same time. : When one device is sending, the other can only receive, and vice versa
3. Full-Duplex: The full-duplex mode is like a tW<D-way street with traffic flowing in both
directions at the same time

Ans-5:
1. Performance: Performance can be measured in many ways, including transit time and response
time.
2. Reliability: In addition to accuracy ofdelivery, network reliability is measured by the frequency of
failure, the time it takes a link to recover from a failure.
3. Security: Network security issues include protecting data from unauthorized access, protecting
data from damage and development,.

Ans-6:
1. Mesh: Mesh In a mesh topology, every device has a dedicated point-to-point link to
every other device.
 2. Star Topology : In a star topology, each device has a dedicated point-to-point link only to
a central controller, usually called a hub.

3. Bus Topology: Bus Topology The preceding examples all describe point-to-point
connections. A bus topology, on the otherhand, is multipoint

4. Ring Topology: A ring is relatively easy to install and reconfigure. Each device is linked to
only its immediate neighbors (either physically or logically).

Ans-7:
1.Syntax: The term syntax refers to the structure or format ofthe data, meaning the order in which they
are presented.

2. Semantics. The word semantics refers to the meaning of each section of bits

3. Timing. The term timing refers to two characteristics: when data should be sent and how fast they can
be sent.

Chapter-2

Ans-1: Seven layers ofthe OSImodel

71. Application

61. Presentation

51. Session

41. Transport

31. Network

21. Data link

1. Physical
Ans-2:
Phusycal Layer : The physical layer is responsible for movements of individual bits from one hop
(node) to the next.

1. Physical characteristics of interfaces and medium:

Ans-3:
1. Framing:
2. Physical addressing
3. Flow control
4. Error control:
5. Access control:

Ans-4:
Network Layer: The network layer is responsible for the delivery ofindividual packets from the
source host to the destination host.

1. Logical addressing.
2. Routing

Ans-5:
1. Service-point addressing.
2. Segmentation and reassembly.
3. Connection control.
 4. Flow control.
5. Error control.

Ans-6:
1. Dialog control.
2. Synchronization

Ans-7:
1. Translation.
2. Encryption
3. Compression

Ans-8:
1. Network virtual terminal
2. File transfer, access, and management.
3. Mail services.
4. Directory services