PLUS ONE
COMPUTER APPLICATION / COMPUTER SCIENCE
Chapter 8 (11 for CS) Computer Networks
(+1. Computer Application Questions and answers from text book)
COMPUTER APPLICATION / COMPUTER SCIENCE
Chapter 8 (11 for CS) Computer Networks
(+1. Computer Application Questions and answers from text book)
1. Name the basic elements needed for a data communication system.
Ans. Message,Sender,Receiver,Medium and Protocol
2. Define resource sharing.
The sharing of available hardware and software resources in a
computer network is called resource sharing. For example, the contents of a DVD
placed in a DVD drive of one computer can be read in another computer. Similarly,
other hardware resources like hard disk, printer, scanner, etc. and software resources
like application software, anti-virus tools, etc. can also be shared through computer
networks.
3. Name two classifications of communication channels between
computers in a network.
Guided and unguided. In
guided or wired medium, physical wires or cables are used and in unguided or wireless
medium radio waves, microwaves or infrared signals are used for data transmission.
4. Name the connecter used to connect UTP/STP cable to a computer.
Ans. RJ -45
5. The cable media that use light to transmit data signals to very long
distances is _________.
Ans. Optical Fibre cable
6. AM and FM radio broadcast and mobile phones make use of
_________ medium for transmission.
Ans. Unguided medium
7. A short range communication technology that does not require line of
sight between communicating devices is _________.
Ans. Infrared waves
8. A communication system that is very expensive, but has a large
coverage area when compared to other wireless communication
systems is _________.
Ans. satellite
9. Compare hub and switch.
A hub is a device used in a wired network to connect computers/devices of the same
network. It is a small, simple, passive and inexpensive device.Computers/devices are connected to ports of the hub using Ethernet cable. When NIC
of one computer sends data packets to hub, the hub transmits the packets to all other
computers connected to it. Each computer is responsible for determining its data packets.
A switch is an intelligent device that connects several computers to form a network. It
is a higher performance alternative to a hub. It looks exactly like a hub. Switches are
capable of determining the destination and redirect the data only to the intended node.
Switch performs this by storing the addresses of all the devices connected to it in a
table. When a data packet is send by one device, the switch reads the destination
address on the packet and transmits the packet to the destination device with the help
of the table
10. What is the use of a repeater?
A repeater is a device that regenerates incoming electrical, wireless
or optical signals through a communication medium .
Data transmissions through wired or wireless medium can
travel only a limited distance as the quality of the signal degrades
due to noise. Repeater receives incoming data signals, amplifies
the signals to their original strength and retransmits them to the
destination.
11. The devices used to interconnect two networks of same type is ______.
Ans. Router
12. Differentiate between router and bridge.
A router is a device that can interconnect two networks of the same type using the same
protocol. It can find the optimal path for data packets to travel and reduce the amount
of traffic on a network. Even though its operations are similar to a bridge, it is more
intelligent. The router can check the device address and the network address and can use algorithms to find the best path for packets to reach the destination.
A bridge is a device used to segmentise a network. An existing network can be split into
different segments and can be interconnected using a bridge. This reduces the amount
of traffic on a network. When a data packet reaches the bridge, it inspects the incoming
packet’s address and finds out to which side of the bridge it is addressed (to nodes on
the same side or the other side). Only those packets addressed to the nodes on the
other side, will be allowed to pass the bridge. Others will be discarded. The packet that
passes the bridge will be broadcast to all nodes on the other side and is only accepted
by the intended destination node.
13. A device that can interconnect two different networks having different
protocols is ______.
Ans. Gateway
14. An electronic device used for communication between computers through
telephone lines is ______.
Ans. Modem
15. In bus topology, when the signal reaches the end of the bus, ______absorbs
the signal and removes it from the bus.
Ans. Terminator
16. In which topology is every node connected to other nodes?
Ans. Mesh
17. Categorise and classify the different types of networks given below.
ATM network, Cable television network, Network within the school,
Network at home using bluetooth,Telephone network, Railway network.
18. What is PAN?
Personal Area Network (PAN) is a network of communicating devices
(computer, mobile, tablet, printer, etc.) in the
proximity of an individual. It can cover an area
of a radius with few meters
19. The transmission media which carry information in the form of light signals is called
__________.
a. Coaxial
b. Twisted
c. WiFi
d. Optical Fiber
Ans. d
20. Different networks with different protocols are connected by a device called _____.
a. Router
b. Bridge
c. Switch
d. Gateway
Ans. d
21. In which topology, the failure of any one computer will affect the network operation?
Ans. Ring
22. To transmit signals from multiple devices through a single communication channel
simultaneously, we use _____ device.
a. Modem
b. Switch
c. Router
d. Multiplexer
Ans. d
23. Satellite links are generally used for
a. PANs
b. LANs
c. MANs
d. All of the above
Ans.
24. Define bandwidth.
A range of frequencies within a given band, in particular that used for transmitting a signal.
25. Switch and Hub are two devices associated with networking. Differentiate them.
Refer Qs 9
26. What is an IP address? Give an example of IP address.
It is a unique 4 part numeric address assigned to each node on a network for unique identification of them. . It is normally expressed in “dotted decimal Number” Eg. 192.165.1.1
There are two types of IP addresses IPV4: A 32 bit address which can identify only 4 billion devices in the net. IPV6: A 128 bit address which can identify 4x4x4 billion devices in the net.
27. What is TCP/IP? What is its importance?
Transfer Control Protocol/Internet Protocol used to interconnect network devices on local network and internet. When data is send from one device to another, the data is broken in to small packets by TCP and send through transmission medium. Delivery of each of these packets to the right destination is done by IP. When the packets are received by the receiving computer, TCP checks packets for error and assemble in to original message.
28. What is Bluetooth?
Its frequency range from 2.402 GHz to 2.480 GHz. It is a short distance communication ( approx 10m). It is uses in cell phones, wireless keyboard etc..
29. Explain the need for establishing computer networks.
30. What are the uses of computer networks?
By networking individual computers,
1. Data communication is possible . Computer network helps user to communicate with any other user of the network through its services like e-mail chatting etc..
2. Resource Sharing: The sharing of available hardware and software resources ( like programs, printers , hard disk etc..)in a computer network is called resource sharing.
3. Reliability: A file can have copies in different computers . So breaking down of one system does not cause data loss.
4. Scalability: Computing and storage capacity can be increased or decreased easily by adding/removing computer or storage devises to the network..
5. Price –Performance ratio: Sharing of hardware and software instead of purchasing saves a lot of money.
31. What is the limitation of microwave transmission? How is it eliminated?
Micro waves have a frequency range of 300 MHz (0.3 GHz) to 300 GHz. Microwaves
travel in straight lines and cannot penetrate any solid object. Therefore, high towers are
built and microwave antennas are fixed on their top for long distance microwave
communication. As these waves travel in straight lines the antennas used for transmitting
and receiving messages have to be aligned with each other. The distance between two
microwave towers depends on many factors including frequency of the waves being
used and heights of the towers.
32. Briefly describe the characteristics of Wi-Fi.
Line of sight between communicating devices is not required
• Data transmission speed is up to 54 Mbps
• Wi-Fi can connect more number of devices simultaneously
• Used for communication upto 375 ft (114 m)
33. An International School is planning to connect all computers, spread over distance
of 45 meters. Suggest an economical cable type having high-speed data transfer,
which can be used to connect these computers.
LAN.
33. Suppose that you are the administrator of network lab in one Institution. Your
manager directed you to replace 10 Mbps switch by 10 Mbps Ethernet hub for
better service. Will you agree with this decision? Justify your answer.
34. You need to transfer a biodata file stored in your computer to your friend’s computer
that is 10 kms away using telephone network
a. Name the device used for this at both ends.
Ans Modem
b. Explain how the file is send and received inside the device, once a connection
between two computers is established.
35. When is a repeater used in a computer network?
A network device used to regenerate or replicate a signal. Repeaters are used in transmission systems to regenerate analog or digital signals distorted by transmission loss. Analog repeaters frequently can only amplify the signal while digital repeaters can reconstruct a signal to near its original quality.
36. Compare infrared and Bluetooth transmission.
Infrared waves have a frequency range of 300
GHz to 400 THz. These waves are used for
short range communication (approx. 5 m) in
a variety of wireless communications,
monitoring and control applications.
Home entertainment remote control devices,
cordless mouse and intrusion detectors are
some of the devices that utilise infrared
communication.
Bluetooth technology uses radio waves in the
frequency range of 2.402 GHz to 2.480 GHz.
This technology is used for short range
communication (approx. 10 m) in a variety of
devices for wireless communication. Cell
phones, laptops, mouse, keyboard, tablets, head
sets, cameras etc. are some of the devices that
utilise bluetooth communication.
37. Identify and explain the device used for connecting a computer to a telephone
network.
38. Briefly explain LAN topologies.
LAN is a network of computing and communicating devices in a room, building, or
campus. It can cover an area of radius with a few meters to a few Kilometers. A
networked office building, school or home usually contains a single LAN, though
sometimes one building can contain a few small LANs (Like some schools have
independent LANs in each computer lab) .Occasionally a
LAN can span a group of nearby buildings. In addition to operating in a limited space,
a LAN is owned, controlled and managed
by a single person or an organisation.
LAN can be set up using wired media
(UTP cables, coaxial cables, etc.) or
wireless media (infrared, radio waves,
etc.). If a LAN is setup using unguided
media, it is known as WLAN (Wireless
LAN).
39. Briefly describe TCP/IP protocol.
Refer Qs 27
40. What is a MAC address? What is the difference between a MAC address and an
IP address?
Media access control Address is universal, unique and permanent address ( 12 digit hexadecimal number) assigned to each NIC by its manufacturer. Its first half contains the ID of the manufacturer and second half is the serial number of the particular adapter. MM:MM:MM:SS:SS:SS
IP address is a unique 4 part numeric address assigned to each node on a network for unique identification of them. . It is normally expressed in “dotted decimal Number” Eg. 192.165.1.1
41. How are computer networks classified, based on size?
Computer networks are typically classified by scale, ranging from small, personal networks to global wide-area networks and the Internet itself.
42. Compare different LAN topologies.
Topology is the way in which computers are physically interconnected to form a network. Common types of topologies are,
a). Bus Topology: There is a main cable called bus from the server to which every node computers are connected by short drop cables. A small device called terminator is attached at the end of the bus. When a data signal reaches the terminator at the end, it is absorbed and the bus is free to carry new signal.
Advantages:
i). Easy to install
ii). Less cable is needed. So less expensive
iii). Failure of node does not affect the network.
Disadvantages:
i). Fault detection is difficult.
ii). Failure of cable, server or terminator will affect entire network.
b). Ring Topology: All node computers are connected to a circular cable. All data is passing through this cable.
Advantages:
i). No signal amplification required because each node do this.
ii). Requires less cable, so cost effective
Disadvantages:
i). If a node fails, entire network will fail.
ii). Addition of nodes is difficult.
c). Star Topology: In star topology there is server at its centre and all other work stations are connected to it through separate connections. All messages are passed through the server. When a message goes from one computer to another , it is first send to the server , which then retransmit the message to the destination computer.
Advantages:
i). If one workstation fails, it does not affect the whole network.
ii). Easy to install
iii). It easy to expand
iv).Easy to find faults and remove workstations.
Disadvantages:
i). Requires more cables than Bus topology
ii). If the central device fails it affect entire net work
d).Mesh Topology: In this Topology each node is connected to other nodes. So there is more than one path between two nodes. So failure of one node may not affect the data communication.
Advantages:
i). If one workstation or a path fails, it does not affect the whole network.
Disadvantages:
i). Requires more cables so very expensive.
ii). Very complex and difficult to manage.
43. Explain various types of guided communication channels.
Guided Media: Here data is transmitted through some physical media such as metal wire or optical cable. 1. Twisted Pair cables: There are two types of twisted pair cables
a). Unshielded twisted pair(UTP): It is commonly used It is cheap and flexible. It consists of two insulated conductors twisted together to avoid noise. Characteristics: Low cost, thin and flexible, ease of installation and carries data up to a length of 100m.
b). Shielded Twisted pair(STP): Here the twisted pair itself is shielded again. Characteristics: protection from electromagnetic noise, difficult to install and expensive.
2. Coaxial cables: It has an inner central metallic core surrounded by an insulating sheath. It is then surrounded with a conducting outer cover and is again covered with a protecting insulation . Characteristics: Expensive high band width, less flexible, difficult to install and carries data up to a length of 500m.
3. Optical Fiber : Optical fiber use light instead of electrical signals. They are made of glass fibers covered by a cladding both are in perfect thickness and in different refractive indices. Then it is covered by a plastic jacket. LED or Laser Diode is used to convert electrical signal in to light signal(modulation). Laser is expensive but can used for long distance transmission. Characteristics: High bandwidth, carries data over a long distance, expensive but effective and difficult to install.
44. Compare different unguided media.
Unguided media: Here data transmission takes place through space or air. Electromagnetic waves are used for it.
1. Radio Waves: Its frequency range from 3 KHz to 3 GHz. It can used for short distance and long distance communication. These waves can easy to generate and can penetrate through most of the objects. So it can be used in indoors and outdoors.
Characteristics of Radio Waves transmission
a). Not a line of sight transmission
b). Inexpensive than wired media
c). Can penetrate through most objects
d). It can affected by electrical equipments like motor
Different types of radio transmissions are,
I). Bluetooth: Its frequency range from 2.402 GHz to 2.480 GHz. It is a short distance communication ( approx 10m). It is uses in cell phones, wireless keyboard etc..
Characteristics:
i). Not a line of sight communication
ii). Can connect up to 8 devices
iii). Slow transfer rate(up to 1Mbps)
II). Wi-Fi: Its frequency range from 2.4 GHz to 5 GHz.
Characteristics:
i) . Not a line of sight communication.
ii). Data transfer speed is up to 54Mbps
iii). Can connect more devices at a time.
Iv). Range up to 114m
III). Wi-Max: Worldwide interoperability for Microwave Access .It combines the benefits of wireless and broadband. Its frequency range from 2 GHz to 11 GHz.
Characteristics:
i). Hundreds of users can connect at a time
ii). Range up to 45 Km
iii). Transmission speed up to 70Mbps
iv). High cost of installation and power consumption.
IV). Satellite Link: These are like repeaters but can cover a large foot area due to its position 36000KM above earth. Geostationary satellites are used for this. Its transponders receive the sending signal from earth(uplink) (frequency 1.6 GHz-30GHz), strengthen them and slightly change its frequency to avoid mixing with the up linking signal and retransmit it to earth(downlink) (frequency 1.5 GHz-20GHz),. The ground station can receive or even the end user can receive it.
Characteristics of satellite transmission
i). satellite cover a large are of the earth.
ii). Requires permission and license
iii). Expensive
2. Microwaves: It use in line of sight method of propagation. These waves can’t travel along the surface of earth. So taller antennas and transceivers uses to receive the wave and strengthen and retransmit.. Eg. Mobile communication.
Characteristics:
1. Inexpensive than wired media
2. Transmission is in straight line
3. Easy communication over difficult areas
3. Infrared Waves: Its frequency range from 300 GHz to 400 THz. It is a short distance communication ( approx 5m) Eg. remote control device
Characteristics:
1. A line of sight transmission.
2. Only two device can communicate
3. Short distance communication
45. Define the term protocol. Briefly describe any two communication protocols.
It is the special set of rules to be followed in a network when devices in the network communicates. Each protocol specifies rules for formatting data, compressing data, error checking making connections and making sure that the data packets reach its destination.
a). TCP/IP: Transfer Control Protocol/Internet Protocol used to interconnect network devices on local network and internet. When data is send from one device to another, the data is broken in to small packets by TCP and send through transmission medium. Delivery of each of these packets to the right destination is done by IP. When the packets are received by the receiving computer, TCP checks packets for error and assemble in to original message.
b) HTTP: Hyper Text Transfer Protocol is a standard protocol for transferring request from client side to receive response from the server side. The HTTP client (Browser) sends a request to the HTTP server (Web server) and server responds with HTTP responds. HTTP is medium independent and stateless( Server and client are aware each other only during a request or response).
46. Briefly describe the various communication devices used in computer networks.
Data communication devices act as interface between computer and the communication channel. They are used to transmit, receive , amplify and route the signals across the communication media.
a). Network Interface Card(NIC): It enables a computer to connect a network and communicate. It can breaks up data into small units, translate the protocols , send and receive data. It may be wired(Ethernet) or wireless(Wi-Fi).
b). Hub: Hub is used in wired network to connect devices of the same network. It transmit data to all the devises connected to it. Only the device to which data is assigned is responds to it. Large network traffic due to this reduces its bandwidth.
c). Switch: Switch can be considered as an intelligent hub. It store addresses of all the device connected to it. Switch read the destination address of the data from the packet and send data to the particular destination device only. So network traffic can be reduced.
d). Repeater: They are used to receive the incoming signal , amplify it to their original strength and retransmit it.
e). Bridge: It is used to interconnect different segments of an existing network. Only those packet addressed to a node on a particular segment allowed to pass the bridge and transmitted to all the nodes in the segment.
f). Router: It can interconnect two networks of the same type using the same protocol. It can find the best path for data packets to travel and can reduce the amount of traffic in the network.
g). Gateway: It can interconnect two different networks using the different protocols. It can translate one protocols to other and can understand the address structure used in different networks.
47. Which is/are communication channel(s) suitable in each of the following situations?
a. Setting up a LAN.
b. Transfer of data from a laptop to a mobile phone.
c. Transfer of data from one mobile phone to another.
d. Creating a remote control that can control multiple devices in a home.
e. Very fast communication between two offices in two different countries.
f. Communication in a hilly area.
g. Communication within a city and its vicinity where cost of cabling is too high
48. Distinguish between router and gateway.
A router is a device that can interconnect two networks of the same type using the same protocol. It can find the optimal path for data packets to travel and reduce the amount of traffic on a network. Even though its operations are similar to a bridge, it is more intelligent. The router can check the device address and the network address and can use algorithms to find the best path for packets to reach the destination.
A gateway is a device that can interconnect two different networks having different protocols . It can translate one protocol to another protocol. It is a network point that acts as an entrance to another network. Its operations are similar to that of a router. It can check the device address and the network address and can use algorithms to find the best path for packets to reach the destination. Further, while interconnecting two networks with different protocols, there must be some mutual understanding between the networks. A gateway is capable of understanding the address structure used in different networks and seamlessly translate the data packet between these networks.
Ans. Message,Sender,Receiver,Medium and Protocol
The sharing of available hardware and software resources in a computer network is called resource sharing. For example, the contents of a DVD placed in a DVD drive of one computer can be read in another computer. Similarly, other hardware resources like hard disk, printer, scanner, etc. and software resources like application software, anti-virus tools, etc. can also be shared through computer networks.
Guided and unguided. In guided or wired medium, physical wires or cables are used and in unguided or wireless medium radio waves, microwaves or infrared signals are used for data transmission.
Ans. RJ -45
Ans. Optical Fibre cable
Ans. Unguided medium
Ans. Infrared waves
Ans. satellite
A hub is a device used in a wired network to connect computers/devices of the same network. It is a small, simple, passive and inexpensive device.Computers/devices are connected to ports of the hub using Ethernet cable. When NIC of one computer sends data packets to hub, the hub transmits the packets to all other computers connected to it. Each computer is responsible for determining its data packets.
A switch is an intelligent device that connects several computers to form a network. It is a higher performance alternative to a hub. It looks exactly like a hub. Switches are capable of determining the destination and redirect the data only to the intended node. Switch performs this by storing the addresses of all the devices connected to it in a table. When a data packet is send by one device, the switch reads the destination address on the packet and transmits the packet to the destination device with the help of the table
A repeater is a device that regenerates incoming electrical, wireless or optical signals through a communication medium .
Data transmissions through wired or wireless medium can travel only a limited distance as the quality of the signal degrades due to noise. Repeater receives incoming data signals, amplifies the signals to their original strength and retransmits them to the destination.
Ans. Router
A router is a device that can interconnect two networks of the same type using the same protocol. It can find the optimal path for data packets to travel and reduce the amount of traffic on a network. Even though its operations are similar to a bridge, it is more intelligent. The router can check the device address and the network address and can use algorithms to find the best path for packets to reach the destination.
A bridge is a device used to segmentise a network. An existing network can be split into different segments and can be interconnected using a bridge. This reduces the amount of traffic on a network. When a data packet reaches the bridge, it inspects the incoming packet’s address and finds out to which side of the bridge it is addressed (to nodes on the same side or the other side). Only those packets addressed to the nodes on the other side, will be allowed to pass the bridge. Others will be discarded. The packet that passes the bridge will be broadcast to all nodes on the other side and is only accepted by the intended destination node.
Ans. Gateway
Ans. Modem
Ans. Terminator
Ans. Mesh
ATM network, Cable television network, Network within the school, Network at home using bluetooth,Telephone network, Railway network.
Personal Area Network (PAN) is a network of communicating devices (computer, mobile, tablet, printer, etc.) in the proximity of an individual. It can cover an area of a radius with few meters
Ans. d
Ans. d
Ans. Ring
Ans. d
Ans.
A range of frequencies within a given band, in particular that used for transmitting a signal.
Refer Qs 9
It is a unique 4 part numeric address assigned to each node on a network for unique identification of them. . It is normally expressed in “dotted decimal Number” Eg. 192.165.1.1
There are two types of IP addresses IPV4: A 32 bit address which can identify only 4 billion devices in the net. IPV6: A 128 bit address which can identify 4x4x4 billion devices in the net.
Transfer Control Protocol/Internet Protocol used to interconnect network devices on local network and internet. When data is send from one device to another, the data is broken in to small packets by TCP and send through transmission medium. Delivery of each of these packets to the right destination is done by IP. When the packets are received by the receiving computer, TCP checks packets for error and assemble in to original message.
Its frequency range from 2.402 GHz to 2.480 GHz. It is a short distance communication ( approx 10m). It is uses in cell phones, wireless keyboard etc..
By networking individual computers,
1. Data communication is possible . Computer network helps user to communicate with any other user of the network through its services like e-mail chatting etc..
2. Resource Sharing: The sharing of available hardware and software resources ( like programs, printers , hard disk etc..)in a computer network is called resource sharing.
3. Reliability: A file can have copies in different computers . So breaking down of one system does not cause data loss.
4. Scalability: Computing and storage capacity can be increased or decreased easily by adding/removing computer or storage devises to the network..
5. Price –Performance ratio: Sharing of hardware and software instead of purchasing saves a lot of money.
Micro waves have a frequency range of 300 MHz (0.3 GHz) to 300 GHz. Microwaves travel in straight lines and cannot penetrate any solid object. Therefore, high towers are built and microwave antennas are fixed on their top for long distance microwave communication. As these waves travel in straight lines the antennas used for transmitting and receiving messages have to be aligned with each other. The distance between two microwave towers depends on many factors including frequency of the waves being used and heights of the towers.
Line of sight between communicating devices is not required
• Data transmission speed is up to 54 Mbps
• Wi-Fi can connect more number of devices simultaneously
• Used for communication upto 375 ft (114 m)
LAN.
Ans Modem
A network device used to regenerate or replicate a signal. Repeaters are used in transmission systems to regenerate analog or digital signals distorted by transmission loss. Analog repeaters frequently can only amplify the signal while digital repeaters can reconstruct a signal to near its original quality.
Infrared waves have a frequency range of 300 GHz to 400 THz. These waves are used for short range communication (approx. 5 m) in a variety of wireless communications, monitoring and control applications. Home entertainment remote control devices, cordless mouse and intrusion detectors are some of the devices that utilise infrared communication.
Bluetooth technology uses radio waves in the frequency range of 2.402 GHz to 2.480 GHz. This technology is used for short range communication (approx. 10 m) in a variety of devices for wireless communication. Cell phones, laptops, mouse, keyboard, tablets, head sets, cameras etc. are some of the devices that utilise bluetooth communication.
LAN is a network of computing and communicating devices in a room, building, or campus. It can cover an area of radius with a few meters to a few Kilometers. A networked office building, school or home usually contains a single LAN, though sometimes one building can contain a few small LANs (Like some schools have independent LANs in each computer lab) .Occasionally a LAN can span a group of nearby buildings. In addition to operating in a limited space, a LAN is owned, controlled and managed by a single person or an organisation. LAN can be set up using wired media (UTP cables, coaxial cables, etc.) or wireless media (infrared, radio waves, etc.). If a LAN is setup using unguided media, it is known as WLAN (Wireless LAN).
Refer Qs 27
Media access control Address is universal, unique and permanent address ( 12 digit hexadecimal number) assigned to each NIC by its manufacturer. Its first half contains the ID of the manufacturer and second half is the serial number of the particular adapter. MM:MM:MM:SS:SS:SS
IP address is a unique 4 part numeric address assigned to each node on a network for unique identification of them. . It is normally expressed in “dotted decimal Number” Eg. 192.165.1.1
Computer networks are typically classified by scale, ranging from small, personal networks to global wide-area networks and the Internet itself.
Topology is the way in which computers are physically interconnected to form a network. Common types of topologies are,
a). Bus Topology: There is a main cable called bus from the server to which every node computers are connected by short drop cables. A small device called terminator is attached at the end of the bus. When a data signal reaches the terminator at the end, it is absorbed and the bus is free to carry new signal.
Advantages:
i). Easy to install
ii). Less cable is needed. So less expensive
iii). Failure of node does not affect the network.
Disadvantages:
i). Fault detection is difficult.
ii). Failure of cable, server or terminator will affect entire network.
b). Ring Topology: All node computers are connected to a circular cable. All data is passing through this cable.
Advantages:
i). No signal amplification required because each node do this.
ii). Requires less cable, so cost effective
Disadvantages:
i). If a node fails, entire network will fail.
ii). Addition of nodes is difficult.
c). Star Topology: In star topology there is server at its centre and all other work stations are connected to it through separate connections. All messages are passed through the server. When a message goes from one computer to another , it is first send to the server , which then retransmit the message to the destination computer.
Advantages:
i). If one workstation fails, it does not affect the whole network.
ii). Easy to install
iii). It easy to expand
iv).Easy to find faults and remove workstations.
Disadvantages:
i). Requires more cables than Bus topology
ii). If the central device fails it affect entire net work
d).Mesh Topology: In this Topology each node is connected to other nodes. So there is more than one path between two nodes. So failure of one node may not affect the data communication.
Advantages:
i). If one workstation or a path fails, it does not affect the whole network.
Disadvantages:
i). Requires more cables so very expensive.
ii). Very complex and difficult to manage.
Guided Media: Here data is transmitted through some physical media such as metal wire or optical cable. 1. Twisted Pair cables: There are two types of twisted pair cables
a). Unshielded twisted pair(UTP): It is commonly used It is cheap and flexible. It consists of two insulated conductors twisted together to avoid noise. Characteristics: Low cost, thin and flexible, ease of installation and carries data up to a length of 100m.
b). Shielded Twisted pair(STP): Here the twisted pair itself is shielded again. Characteristics: protection from electromagnetic noise, difficult to install and expensive.
2. Coaxial cables: It has an inner central metallic core surrounded by an insulating sheath. It is then surrounded with a conducting outer cover and is again covered with a protecting insulation . Characteristics: Expensive high band width, less flexible, difficult to install and carries data up to a length of 500m.
3. Optical Fiber : Optical fiber use light instead of electrical signals. They are made of glass fibers covered by a cladding both are in perfect thickness and in different refractive indices. Then it is covered by a plastic jacket. LED or Laser Diode is used to convert electrical signal in to light signal(modulation). Laser is expensive but can used for long distance transmission. Characteristics: High bandwidth, carries data over a long distance, expensive but effective and difficult to install.
Unguided media: Here data transmission takes place through space or air. Electromagnetic waves are used for it.
1. Radio Waves: Its frequency range from 3 KHz to 3 GHz. It can used for short distance and long distance communication. These waves can easy to generate and can penetrate through most of the objects. So it can be used in indoors and outdoors.
Characteristics of Radio Waves transmission
a). Not a line of sight transmission
b). Inexpensive than wired media
c). Can penetrate through most objects
d). It can affected by electrical equipments like motor
Different types of radio transmissions are,
I). Bluetooth: Its frequency range from 2.402 GHz to 2.480 GHz. It is a short distance communication ( approx 10m). It is uses in cell phones, wireless keyboard etc..
Characteristics:
i). Not a line of sight communication
ii). Can connect up to 8 devices
iii). Slow transfer rate(up to 1Mbps)
II). Wi-Fi: Its frequency range from 2.4 GHz to 5 GHz.
Characteristics:
i) . Not a line of sight communication.
ii). Data transfer speed is up to 54Mbps
iii). Can connect more devices at a time.
Iv). Range up to 114m
III). Wi-Max: Worldwide interoperability for Microwave Access .It combines the benefits of wireless and broadband. Its frequency range from 2 GHz to 11 GHz.
Characteristics:
i). Hundreds of users can connect at a time
ii). Range up to 45 Km
iii). Transmission speed up to 70Mbps
iv). High cost of installation and power consumption.
IV). Satellite Link: These are like repeaters but can cover a large foot area due to its position 36000KM above earth. Geostationary satellites are used for this. Its transponders receive the sending signal from earth(uplink) (frequency 1.6 GHz-30GHz), strengthen them and slightly change its frequency to avoid mixing with the up linking signal and retransmit it to earth(downlink) (frequency 1.5 GHz-20GHz),. The ground station can receive or even the end user can receive it.
Characteristics of satellite transmission
i). satellite cover a large are of the earth.
ii). Requires permission and license
iii). Expensive
2. Microwaves: It use in line of sight method of propagation. These waves can’t travel along the surface of earth. So taller antennas and transceivers uses to receive the wave and strengthen and retransmit.. Eg. Mobile communication.
Characteristics:
1. Inexpensive than wired media
2. Transmission is in straight line
3. Easy communication over difficult areas
3. Infrared Waves: Its frequency range from 300 GHz to 400 THz. It is a short distance communication ( approx 5m) Eg. remote control device
Characteristics:
1. A line of sight transmission.
2. Only two device can communicate
3. Short distance communication
It is the special set of rules to be followed in a network when devices in the network communicates. Each protocol specifies rules for formatting data, compressing data, error checking making connections and making sure that the data packets reach its destination.
a). TCP/IP: Transfer Control Protocol/Internet Protocol used to interconnect network devices on local network and internet. When data is send from one device to another, the data is broken in to small packets by TCP and send through transmission medium. Delivery of each of these packets to the right destination is done by IP. When the packets are received by the receiving computer, TCP checks packets for error and assemble in to original message.
b) HTTP: Hyper Text Transfer Protocol is a standard protocol for transferring request from client side to receive response from the server side. The HTTP client (Browser) sends a request to the HTTP server (Web server) and server responds with HTTP responds. HTTP is medium independent and stateless( Server and client are aware each other only during a request or response).
Data communication devices act as interface between computer and the communication channel. They are used to transmit, receive , amplify and route the signals across the communication media.
a). Network Interface Card(NIC): It enables a computer to connect a network and communicate. It can breaks up data into small units, translate the protocols , send and receive data. It may be wired(Ethernet) or wireless(Wi-Fi).
b). Hub: Hub is used in wired network to connect devices of the same network. It transmit data to all the devises connected to it. Only the device to which data is assigned is responds to it. Large network traffic due to this reduces its bandwidth.
c). Switch: Switch can be considered as an intelligent hub. It store addresses of all the device connected to it. Switch read the destination address of the data from the packet and send data to the particular destination device only. So network traffic can be reduced.
d). Repeater: They are used to receive the incoming signal , amplify it to their original strength and retransmit it.
e). Bridge: It is used to interconnect different segments of an existing network. Only those packet addressed to a node on a particular segment allowed to pass the bridge and transmitted to all the nodes in the segment.
f). Router: It can interconnect two networks of the same type using the same protocol. It can find the best path for data packets to travel and can reduce the amount of traffic in the network.
g). Gateway: It can interconnect two different networks using the different protocols. It can translate one protocols to other and can understand the address structure used in different networks.
48. Distinguish between router and gateway.
A router is a device that can interconnect two networks of the same type using the same protocol. It can find the optimal path for data packets to travel and reduce the amount of traffic on a network. Even though its operations are similar to a bridge, it is more intelligent. The router can check the device address and the network address and can use algorithms to find the best path for packets to reach the destination.
A gateway is a device that can interconnect two different networks having different protocols . It can translate one protocol to another protocol. It is a network point that acts as an entrance to another network. Its operations are similar to that of a router. It can check the device address and the network address and can use algorithms to find the best path for packets to reach the destination. Further, while interconnecting two networks with different protocols, there must be some mutual understanding between the networks. A gateway is capable of understanding the address structure used in different networks and seamlessly translate the data packet between these networks.
