Q4)What is
Modem?Discuss The Characteristics Of Modems?(VIMP)
Ans: Modem is short
for MOdulator/ DEModulator
· Special
device used for conversion of digital data to analog form (modulation) and
vice-versa (demodulation)
· Essential
piece of hardware where two digital devices (say two computers) want to
communicate over an analog transmission channel (say a telephone line)
Factors for
selecting the MODEM:
• Transmission
speed
• Internal
versus external
• Facsimile facility
Modulation Techniques
• Amplitude
Modulation (AM): Two binary values (0 and 1) of digital data are
represented by two different amplitudes of the carrier signal, keeping
frequency and phase constant
• Frequency
Modulation (FM): Two binary values of digital data are represented by two
different frequencies, while amplitude and phase are kept constant
• Phase Modulation (PM): Two binary values of digital data are represented by shift in phase of carrier signal
Characteristics
Of Modems
1. Speed: It specifies the
rate of data transmission. If the rate of data transmission is high, then the
speed of modem can be measured in terms of BPS(Bits per second). Otherwise it
is measured in terms of Baud rates. Now a days, most of the networks uses only
high speed modems.
2. Flash Memory:
The
memory which is used by modems is called as Flash RAM. Flash RAM supports new
protocols whenever they added or updated.
3. Data
Compression: Modems
perform the data compression for transfer the data at high speed. Some of the
modems uses data compression techniques to compress the data and de-compress
the data.
4. Voice/ Data: Many of the
modems are provided with a switch known as voice/ data switch, which is used to
change the mode of the modem either in voice mode or in data mode. If a modem
is switched to a data modem, then it is behaves like regular modem. If a modem
is switched to a voice modem, then it is behaves like regular telephone. A
modem in voice mode contains built-in loud speaker and microphone to support
the voice communication.
5. Auto-Answer: Modem processes
auto-answer characteristics. This characteristic will enable the system to
receive calls without any external interference in the absence of a user.
6. Fax
Capability: Most
of the modems are having the ability of transmitting and receiving the
electronic documents as faxes. A fax modem is similar to that of a regular
modem along with the capability of sending documents to a fax machine or to
some other fax modem. These types of modems performs double duty.
Q5)Explain types
of networks available? (Classification Of Networks)(VVVIMP)
Ans: A
computer network is a group of computers linked to each other that enables the
computer to communicate with another
computer and share their resources, data, and applications. A computer network
can be categorized by their size. A computer network is mainly of four
types:
1. LAN (Local Area
Network)
2. PAN (Personal Area
Network)
3. MAN (Metropolitan
Area Network)
4. WAN (Wide Area Network)
LAN(Local Area
Network)
· Local Area
Network is a group of computers connected to each other in a small area such as
building, office. LAN is used for connecting two or more personal computers
through a communication medium such as twisted pair, coaxial cable, etc.
· It
is less costly as it is built with inexpensive hardware such as hubs, network
adapters, and ethernet cables.
· The
data is transferred at an extremely faster rate in Local Area Network.
· Local Area Network provides higher security.
PAN(Personal
Area Network)
· Personal
Area Network is a network arranged within an individual person, typically
within a range of 10 meters. Personal Area Network is used for connecting the
computer devices of personal use is known as Personal Area Network.
· Thomas Zimmerman was the first research scientist
to bring the idea of the Personal Area Network. Personal Area Network covers an
area of 30 feet.
· Personal
computer devices that are used to develop the personal area network are the
laptop, mobile phones, media player and play stations.
· There
are two types of Personal Area Network.
-Wired Personal
Area Network
-Wireless
Personal Area Network
· Wireless Personal Area Network: Wireless
Personal Area Network is developed by simply using wireless technologies such
as WiFi, Bluetooth. It is a low range network.
· Wired Personal Area Network: Wired Personal Area Network is created by using the USB.
MAN(Metropolitan
Area Network)
A metropolitan area network is a network that covers a larger geographic area by interconnecting a different LAN to form a larger network. Government agencies use MAN to connect to the citizens and private industries.
In MAN, various LANs are connected to each other through a telephone exchange line. The most widely used protocols in MAN are RS-232, Frame Relay, ATM, ISDN, OC-3, ADSL, etc. It has a higher range than Local Area Network(LAN).
Uses Of
Metropolitan Area Network:
· MAN
is used in communication between the banks in a city.
· It
can be used in an Airline Reservation.
· It
can be used in a college within a city.
· It can also be used for communication in the military.
WAN (Wide Area
Network)
A Wide Area
Network is a network that extends over a large geographical area such as states
or countries. A Wide Area Network is quite bigger network than the LAN.
A Wide Area Network is not limited to a single location, but it spans over a large geographical area through a telephone line, fiber optic cable or satellite links. The internet is one of the biggest WAN in the world. A Wide Area Network is widely used in the field of Business, government, and education.
Examples of Wide
Area Network:
-Mobile
Broadband: A 4G network is widely used across a region or country.
-Last mile: A
telecom company is used to provide the internet services to the customers in
hundreds of cities by connecting their home with fiber.
-Private
network: A bank provides a private network that connects the 44 offices.
This network is made by using the telephone leased line provided by the telecom
company.
6Q) Explain
About Different Types Of Topologies (LAN Topologies)?(VVIMP)
Ans:
Topology defines
the structure of the network of how all the components are interconnected to
each other. A topology, which is a pattern of interconnections among nodes,
influences a network's cost and performance.
There are 6
topologies in network.
1. Bus Topology
2. Ring Topology
3. Star Topology
4. Tree Topology
5. Mesh Topology
6. Hybrid
Topology
1. Bus Topology
The bus topology is designed in such a way that all the stations are connected through a single cable known as a backbone cable. Each node is either connected to the backbone cable by drop cable or directly connected to the backbone cable. When a node wants to send a message over the network, it puts a message over the network. All the stations available in the network will receive the message whether it has been addressed or not.
The
configuration of a bus topology is quite simpler as compared to other
topologies. The backbone cable is considered as a "single lane" through
which the message is broadcast to all the stations. The most common access
method of the bus topologies is CSMA (Carrier Sense Multiple Access).
Advantages of
Bus topology:
· Low-cost cable: In bus topology, nodes are
directly connected to the cable without passing through a hub. Therefore, the
initial cost of installation is low.
· Familiar technology: Bus topology is
a familiar technology as the installation and troubleshooting techniques are
well known, and hardware components are easily available.
· Limited failure: A failure in one node will not
have any effect on other nodes.
Disadvantages of
Bus topology:
·Extensive cabling: A bus topology is quite simpler,
but still it requires a lot of cabling.
·Difficult troubleshooting: It requires
specialized test equipment to determine the cable faults. If any fault occurs
in the cable, then it would disrupt the communication for all the nodes.
· Signal interference: If two nodes
send the messages simultaneously, then the signals of both the nodes collide
with each other.
· Reconfiguration difficult: Adding new devices to the network would slow down the network.
2. Ring Topology
All the nodes in
a Ring Network are connected in a closed circle of cable. Messages that are
transmitted travel around the ring until they reach the computer that they are
addressed to, the signal being refreshed by each node. In a ring topology, the
network signal is passed through each network card of each device and passed on
to the next device. Each device processes and retransmits the signal, so it is
capable of supporting many devices in a somewhat slow but very orderly fashion.
There is a very
nice feature that everybody gets a chance to send a packet and it is guaranteed
that every node gets to send a packet in a finite amount of time.
Advantages
· Broadcasting
and multicasting is simple since you just need to send out one message
·Less
expensive since less cable footage is required
· It
is guaranteed that each host will be able to transmit within a finite time
interval
· Very
orderly network where every device has access to the token and the opportunity
to transmit
· Performs
better than a star network under heavy network load
Disadvantages
· Failure
of one node brings the whole network down
· Error
detection and network administration becomes difficult.
· Moves,
adds and changes of devices can effect the network
· It is slower than star topology under normal load
3. Star
Topology:
Star topology is
an arrangement of the network in which every node is connected to the central
hub, switch or a central computer. Signals are transmitted and received through
the Hub. The central computer is known as a server, and the peripheral
devices attached to the server are known as clients. It is the simplest
and the oldest and all the telephone switches are based on this. In a star
topology, each network device has a home run of cabling back to a network hub,
giving each device a separate connection to the network. So, there can be
multiple connections in parallel.
Advantages
· Network
administration and error detection is easier because problem is isolated to
central node
· Networks
runs even if one host fails
· Expansion
becomes easier and scalability of the network increases
· More
suited for larger networks
Disadvantages
· Broadcasting
and multicasting is not easy because some extra functionality needs to be
provided to the central hub
· If
the central node fails, the whole network goes down; thus making the switch
some kind of a Bottleneck
· Installation costs are high because each node needs to be connected to the central switch
4. Tree topology
Tree topology
combines the characteristics of bus topology and star topology. A tree topology
is a type of structure in which all the computers are connected with each other
in hierarchical fashion. The top-most node in tree topology is known as a root
node, and all other nodes are the descendants of the root node. There is only
one path exists between two nodes for the data transmission. Thus, it forms a
parent-child hierarchy.
Advantages of
Tree topology
· Tree
topology is mainly used to provide broadband transmission, i.e., signals are
sent over long distances without being attenuated.
· We
can add the new device to the existing network. Therefore, we can say that tree
topology is easily expandable.
· Easily manageable: The whole network is divided
into segments known as star networks which can be easily managed and
maintained.
· Error
detection and error correction are very easy in a tree topology.
· The
breakdown in one station does not affect the entire network.
·Point-to-point wiring: It has
point-to-point wiring for individual segments.
Disadvantages of
Tree topology
· Difficult troubleshooting: If any fault
occurs in the node, then it becomes difficult to troubleshoot the problem.
· High cost: Devices required for broadband
transmission are very costly.
· Failure: A tree topology mainly relies on main
bus cable and failure in main bus cable will damage the overall network
· Reconfiguration difficult: If new devices
are added, then it becomes difficult to reconfigure.
5. Mesh Topology
Mesh technology is an arrangement of the network in which computers are interconnected with each other through various redundant connections. There are multiple paths from one computer to another computer. It does not contain the switch, hub or any central computer which acts as a central point of communication. The Internet is an example of the mesh topology.
Mesh topology is
mainly used for WAN implementations where communication failures are a critical
concern. Mesh topology is mainly used for wireless networks.
Advantages of
Mesh topology:
Reliable: The mesh
topology networks are very reliable as if any link breakdown will not affect
the communication between connected computers.
Fast
Communication:
Communication is very fast between the nodes.
Easier
Reconfiguration:
Adding new devices would not disrupt the communication between other devices.
Disadvantages of
Mesh topology
Cost: A mesh topology
contains a large number of connected devices such as a router and more
transmission media than other topologies.
Management: Mesh topology
networks are very large and very difficult to maintain and manage. If the network
is not monitored carefully, then the communication link failure goes
undetected.
Efficiency: In this topology, redundant connections are high that reduces the efficiency of the network.
6. Hybrid
Topology
The combination of various different topologies is known as Hybrid topology. Hybrid topology is a connection between different links and nodes to transfer the data. When two or more different topologies are combined together is termed as Hybrid topology and if similar topologies are connected with each other will not result in Hybrid topology.
For example, if
there exist a ring topology in one branch of ICICI bank and bus topology in
another branch of ICICI bank, connecting these two topologies will result in
Hybrid topology.
Advantages of
Hybrid Topology
Reliable: If a fault
occurs in any part of the network will not affect the functioning of the rest
of the network.
Scalable: Size of the
network can be easily expanded by adding new devices without affecting the
functionality of the existing network.
Flexible: This topology
is very flexible as it can be designed according to the requirements of the
organization.
Effective: Hybrid topology is very effective as it can be designed in such a way that the strength of the network is maximized and weakness of the network is minimized.
Disadvantages of
Hybrid topology
Complex design: The major
drawback of the Hybrid topology is the design of the Hybrid network. It is very
difficult to design the architecture of the Hybrid network.
Costly Hub: The Hubs used
in the Hybrid topology are very expensive as these hubs are different from usual
Hubs used in other topologies.
Costly
infrastructure:
The infrastructure cost is very high as a hybrid network requires a lot of
cabling, network devices, etc
Computer
Protocols
7Q)What is a
communication protocol? Explain about protocol layers structure?
Ans:
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.
OSI Model: OSI stands for
Open System Interconnection is a reference model that describes how information
from a software application in one computer moves through a physical medium to
the software application in another computer. OSI model was developed by the
International Standards Organization (ISO) in 1984, and it is now considered as
an architectural model for the inter-computer communications. OSI model divides
the whole task into seven smaller and manageable tasks.
Each layer is
assigned a particular task.
· Physical Layer—This
layer specifies the basic network hardware. Some of the characteristics defined
in the specification are—interface between transmission media and device,
encoding of bits, bit rate, error detection parameters, network topology, and
the mode of transmission (duplex, half-duplex or simplex).
· Data Link Layer—This
layer specifies the functions required for node-to-node transmission without
errors. It specifies the organization of data into frames, error detection in
frames during transmission, and how to transmit frames over a network.
· Network Layer—The
network layer specifies the assignment of addresses (address structure, length
of address etc.) to the packets and forwarding of packets to the destination
i.e. routing.
· Transport Layer—It
specifies the details to handle reliable transfer of data. It handles end-to end
error control and flow control, breaking up data into frames and reassembling
the frames.
· Session Layer—The
session layer maintains a session between the communicating devices. It includes
specifications for password and authentication, and maintaining synchronization
between the sender and the receiver.
· Presentation Layer—This
layer specifies the presentation and representation of data. Its functions
include translation of the representation of the data into an identifiable
format at the receiver end, encryption, and decryption of data etc.
· Application Layer—This layer specifies how an application uses a network. It deals with the services attached to the data. It contains the protocols used by users like HTTP, protocol for file transfer and electronic mail.
Concepts
relating to networking.
Internet:
The Internet is a network of computers
that links many different types of computers all over the world
· Network
of networks sharing a common mechanism for addressing (identifying) computers,
and a common set of communication protocols
· Evolved
from the basic ideas of ARPANET (the first WAN that had only four sites in
1969) for interconnecting computers
· Initially
used only by research organizations and universities to share and exchange
information
· In
1989, the US Government lifted restrictions on the use of the Internet and
allowed it to be used for commercial purposes as well Internet has rapidly grown and continues to
grow at a rapid pace
· Interconnects
more than 30,000 networks, allowing more than 10 million computers and more
than 50 million computer users in more than 150 countries to communicate with
each other
Basic Services
Of The Internet:
· Electronic Mail (e-mail): Allows user to send a
mail (message) to another Internet user in any part of the world in a
near-real-time manner
· File Transfer Protocol (FTP): Allows user to
move a file from one computer to another on the Internet
· Telnet: Allows user to log in to another
computer somewhere on the Internet
· Usenet News: Allows group of users to exchange their
views/ideas/information
E-MAILE-mail is a rapid and productive
communication tool because:
· Faster
than paper mail
·Unlike
telephone, the persons communicating with each other need not be available at
the same time
· Unlike fax documents, e-mail documents can be stored in a computer and be easily edited using editing programs
File transfer
protocol
Moving a file
from a remote computer to ones own computer is known as downloading
· Moving
a file from ones own computer to a remote computer is known as uploading
· Anonymous
ftp site is a computer allowing a user to log in with a username of anonymous
and password that is user’s e-mail address.
· Anonymous ftp sites are called publicly accessible sites because they can be accessed by any user on the Internet
World Wide Web
Hypertext
documents on the Internet are known as web pages
· Web
pages are created by using a special language called HyperText Markup Language
(HTML)
·WWW
uses the client-server model and an Internet Protocol called HyperText
Transport Protocol (HTTP) for interaction among the computers on the Internet
· Any
computer on the Internet that uses the HTTP protocol is called a web server and
any computer that can access that server is called a web client
· It
uses the concept of hypertext for information storage and retrieval on the
Internet
· Hypertext
documents enable this by using a series of links
· Link is a special type of item in a hypertext document that connects the document to another document providing more information about the linked item
Browser
· Allows
user to create and maintain a personal hotlist of favorite URL addresses of
server computers that user is likely to frequently visit in future
· Allows user to download information in various formats from server computers to user’s own computer
Uses Of Internet
· On-line
communication
· Software
sharing
· Exchange
of views on topics of common interest
· Posting
of information of general interest
· Product
promotion
·
Feedback
about products
·
Customer
support service
·
On-line
journals and magazines
·
On-line
shopping
·
World-wide
video conferencing
No comments:
Post a Comment