22322 Data Communication External Oral / Viva Practice Questions with Answers
1.What is Data Communication?
Data Communication and Computer
Networks in which Data Communication means the exchange of data between two
devices via some form of transmission medium such as a wire cable. For data
communications to occur, the communicating devices must be part of a
communication system made up of a combination of hardware (physical equipment)
and software (programs).
2. What are the Characteristics of
Data Communications?
The effectiveness of a Data
Communication and Computer Networks system depends on four fundamental
characteristics: delivery, accuracy, timeliness, and jitter.
- 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.
- Accuracy: The system must deliver the data accurately.
Data that have been altered in transmission and left uncorrected are
unusable.
- 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. This kind of
delivery is called real-time transmission.
- 4.
Jitter: Jitter
refers to the variation in the packet arrival time. It is the uneven delay
in the delivery of audio or video packets. For example, let us assume that
video packets are sent every 3D ms. If some of the packets arrive with
3D-ms delay and others with 4D-ms delay, an uneven quality in the video is
the result.
.
3. What are the Components of Data
Communication?
The different components of Data
communication are shown in the following figure.
- Message: The message is the information (data) to be
communicated. Popular forms of information include text, numbers,
pictures, audio, and video.
- Sender: The sender is the device that sends the data
message. It can be a computer, workstation, telephone handset, video
camera, and so on.
- Receiver: The receiver is the device that receives
the message. It can be a computer, workstation, telephone handset,
television, and so on.
- 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.
- 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.
4. What are Different Data Flow
Directions?
Communication between any two devices
can be simplex, half-duplex, or full-duplex.
- Simplex: In simplex mode, the communication is
unidirectional, as on a one-way street. Only one of the two devices on a
link can transmit; the other can only receive which can be represented in
the following figure. Keyboards and traditional monitors are examples of
simplex devices. The keyboard can only introduce input; the monitor can
only accept output. The simplex mode can use the entire capacity of the
channel to send data in one direction.
- 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 which will represent in the following figure.
The half-duplex mode is like a
one-lane road with traffic allowed in both directions. When cars are traveling
in one direction, cars going the other way must wait. In a half-duplex
transmission, the entire capacity of a channel is taken over by whichever of
the two devices is transmitting at the time. Walkie-talkies and CB (citizens
band) radios are both half-duplex systems.
The half-duplex mode is used in cases
where there is no need for communication in both directions at the same time;
the entire capacity of the channel can be utilized for each direction.
- Full-Duplex: In full-duplex mode (also called duplex), both stations can transmit and receive simultaneously as shown in the following figure.The full-duplex mode is like a two-way street with traffic flowing in both directions at the same time. In full-duplex mode, signals going in one direction share the capacity of the link: with signals going in the other direction. This sharing can occur in two ways: Either the link must contain two physically separate transmission paths, one for sending and the other for receiving; or the capacity of the channel is divided between the signals traveling in both directions
One common example of full-duplex
communication is the telephone network. When two people are communicating by a
telephone line, both can talk and listen at the same time. The full-duplex mode
is used when communication in both directions is required all the time. The
capacity of the channel, however, must be divided between the two directions.
5. Different Types of Connections
A network is two or more devices
connected through links. A link is a communications pathway that transfers data
from one device to another. For communication to occur, two devices must be
connected in some way to the same link at the same time.
There are two possible types of
connections: point-to-point and multipoint.
- Point-to-Point: A point-to-point connection provides a dedicated link between two devices. The entire capacity of the link is reserved for transmission between those two devices. Most point-to-point connections use an actual length of wire or cable to connect the two ends, but other options, such as microwave or satellite links, are also possible which are shown in the following figure.
- 2.Multipoint: A multipoint (also called multidrop) connection is one in which more than two specific devices share a single link as shown in the following figure.
In a multipoint environment, the capacity of the channel is shared, either spatially or temporally. If several devices can use the link simultaneously, it is a spatially shared connection. If users must take turns, it is a timeshared connection.
6. Explain Types of Networks
Network category is determined by its
size, ownership, the distance it cover and its physical architecture. The types
of networks are local-area networks and wide- area networks. The category into
which a network falls is determined by its size. A LAN normally covers an area
less than 2 miles, a WAN can be worldwide. Networks of a size in between are
normally referred to as metropolitan area networks and span tens of miles.
- Local
Area Network: A
Local Area Network (LAN) is usually privately owned and links the devices
in a single office, building, or campus (see Figure 1.10). Depending on
the needs of an organization and the type of technology used, a LAN can be
as simple as two PCs and a printer in someone's home office; or it can
extend throughout a company and include audio and video peripherals.
Currently, LAN size is limited to a few kilometers.
LANs are designed to allow resources
to be shared between personal computers or workstations. The resources to be
shared can include hardware (e.g., a printer), software (e.g., an application
program), or data.
- Wide
Area Network: A
Wide Area Network (WAN) provides long-distance transmission of data,
image, audio, and video information over large geographic areas that may
comprise a country, a continent, or even the whole world. A WAN can be as
complex as the backbones that connect the Internet or as simple as a
dial-up line that connects a home computer to the Internet.
- Metropolitan Area Network: A Metropolitan Area Network (MAN) is a network with a size between a LAN and a WAN. It normally covers the area inside a town or a city. It is designed for customers who need a high-speed connectivity, normally to the Internet, and have endpoints spread over a city or part of city. A good example of a MAN is the part of the telephone company network that can provide a high-speed DSL line to the customer.