Communication and Network
COMMUNICATION AND NETWORK
Modes of transmission:
Transmission: The movement of data from one location to another.
Types of Transmissions:
a) Duplex b) Simplex c) Half / Semi- duplex transmission.
a) Duplex transmission: A data transmission system which allows data to be transmitted in both directions simultaneously.
e.g. Telephone, internet, video conferencing etc.
b) Simplex transmission: the data transmission system where transmission is possible in only one direction. e.g. sending letter by mail, fax, email, radio etc.
c) Half / Semi-duplex transmission: Transmission is possible in both directions but not simultaneously. e.g. walkie talkie.
COMPUTER NETWORK:
In computer science techniques physical connections and computer programs used to link two or more computers is called a computer network.
Or in other words a network is a group of computers hooked together usually by cables or telephone wires for the purpose of sharing information and resources.
Types of Computer Network:
Networks vary widely in their size, complexity and geographical spread. One way of classifying network is based on their geographical spread. On this basis networks can be classified into:
a) Local Area Network (LAN)
b) Metropolitian Area Network (MAN)
c) Wide Area Netwotrk (WAN)
Local Area Network (LAN):
LAN’s are computer networks confined to a localized area, such as an office, an office complex or a factory. The term localized area could mean a small room or factory spanning several acres . So a LAN is a computer network that is confined to a building or a cluster of buildings. They connect computers and allow exchange of data among them.
Elements of LAN ( hardware requirements )
a. The Workstation
b. The Server
c. Network Interface Card / Unit /Ethernet (NIC / NIU)
d. Communication Channels
e. Network Software.
Workstation:
The term workstation refers to the computers that are attached to the LAN and are seeking to share the resources of LAN. (workstation can also be called as NODE or TERMNAL)
The Server:
The Server is a computer that provides the data, software and hardware resources like printers that are shared on LAN.
Types of server:
i) Dedicated server
ii) Non-dedicated server
Dedicated server – In most of the bigger LAN installations the servers only job is to help the workstation access data, software and hardware resources. The server does not double-up as a workstation, such a server is called a dedicated server.
(dedicated server needs to be powerful computers capable of handling huge workloads demanded of them)
Non dedicated server – In many LAN installations the server is just another workstation, thus there is a user working on computer using it as a workstation, but part of the computer also doubles up as a server, such a server is called non dedicated server.
(since it is not completely dedicated to serving such a server is typically used by small LAN installations which have few workstations)
Points to remember – In large LAN installations which have hundreds of workstations sharing resources a single computer is not sufficient to perform the duties of a server. Consequently, the network or LAN may have several servers that allow workstations to share specific resources.
File server – A file server stores files (data, information and programs) that LAN workstations can access. It also allows LAN users to share files on its own hard disk. The file server regulates the amount of space allowed for each user or terminal.
Printer server – A printer server takes care of the printing requirements of a number of workstations. The printer server typically stores the files to be printed on its disks and then executes the request (print the files) on the First –In-First-Out (FIFO) basis.
Modem Server – A modem server helps the users to use a modem to transmit long distance messages. A single modem is used by a number of workstations.
NIC / NIU / ETHERNET : NIC is a device that is attached to each of the workstation and the server. It helps the workstation to establish the all important connection with the network.
( Each NIC that is attached to a workstation has a unique number identifying the node, this number is called Node address. Thus the node address of a workstation means the address of the NIC that is attached to the workstation. )
Communication Channel:
In LAN the word communication channel means connecting cables. The connecting cables are the lifeline of a LAN. The cables that are used in LAN are:
a) Twisted pair cable
b) Coaxial cable
c) Optical cable
Twisted Pair Cable:
The oldest and the least expensive type of cables used for LAN’s are twisted pair.
These cables consist of two insulated copper wires twisted around each other. These cables are also used for short and medium range telephone communication.
Coaxial Cable:
A coaxial cable consist of one or more small cable in a protective covering. Thses are more expensive than twisted pair and perform better.
Optical Cable:
Fiber optic Cables are the latest entrants to LAN cable technology. Thses cables are made up of plastic or glass and are about as thin as a human hair. These cables are highly durable and offer excellent performance. Their speed of transmission is very high however they are expensive, and are still not widely used in LAN installations.
Network Software:
Networking Software controls and manages the network and creates link between the workstations and facilitates the sharing of resources.
Examples of networking software: Novell Netware, Windows NT etc.
Advantages of Network (LAN)
1. File (data and information) and program sharing.
2. Sharing of expensive hardware such as printer, hard-disk etc.
3. Communication and security.
Disadvantage of Network:
1. Sharing of resources may result in access of information by unauthorized personnel.
2. Security problem may arise due to hacking and spreading of unwanted programs
Types Of LAN’s:
Generally LAN’s are categorized into two types:
i) Client Server
ii) Peer to Peer
Client Server:
In Client Server LAN, the relationship between the workstations is that of master and slave. The master is a dedicated server and slaves are the workstations. Workstations can access data and software from the server and only the server, no workstation can directly access data from another workstation.
Peer to Peer:
In peer to peer LAN, no single computer is designated as the server . All the workstations are called peers. Data and software sharing is possible between all the peers (nodes). If one peer have a printer another would be able to use it.
Limitation of Peer to Peer LAN:
Peer to peer LAN have their own limitations. They are ideal in situations where only a few workstations needs to be networked. As the number of workstation goes up the efficiency of LAN goes down.
Comparision between Client Server and Peer to Peer LAN:
Client serve LAN’s are much more efficient than the peer to peer LAN. On account of the fact, that in client server LAN, there is a powerful dedicated server that provides the resources, they can therefore support large number of workstation which a peer to peer LAN cannot.
Network Topology:
The physical arrangement of the cables, computers and other peripheral devices to form a network is known as a topology .
Types of Network Topology:
There are four main types of Network Topology:
a) Bus Topology
b) Ring Topology
c) Star Topology
d) Mesh Topology
Bus Topology:
The bus topology involves one line of communication and is arranged in a line with all the nodes connected with a single cable.
The network would have a two distinct ends. All nodes have the same access to the network. If one node wants to communicate with the server a broadcast is sent out through the bus in both directions.
All the nodes read the broadcast to determine whether the information is meant for them when the message reaches the correct node, the computer accepts the message and processes it, while the other nodes ignores the message.
Advantage of bus topology:
In a bus network configuration, each node is
c connected to one main communications line.
With this arrangement, even if one of the
Nodes goes down, the rest of the network
can continue to function normally.
· In a small network bus topology works well
Disadvantage of Bus Topology:
If one part of the cable is interrupted the entire network can go down. It is very difficult to track and find faults on this topology.
Cannot support large number of workstations.
Ring Topology:
Ring topology takes the shape of a circle each node is connected with small pieces of cable making each node dependent upon the next. Messages sent from one node to another move around the ring until they reach the right node moving in one direction only. Peer to Peer network works well on this topology.
Advantage of ring topology:
Not much cable is required so its relatively less expensive.
Easier to detect faults.
Disadvantage of ring topology:
In a ring topology each node is connected to the ones beside them if one computer goes down the network goes down as well.
The number of PC’s included in the loop is sometimes finite because once a ring network is set up it is not easy to expand. Also if there is a need to add additional PC’s the entire network must be taken down.
Star Topology:
The star topology has a distinct switching device called a hub. From hub each node is connected with a cable so that the formation resembles the spokes of a bicycle wheel. In star topology every node has its own connection to a central hub. When one node sends a message to another node the message first goes to the hub where it is processed then it is forwarded to the correct node. Client server network are often set up on star topology.
Advantage of star topology:
Star topology is fairly stable, if a node goes down the
whole network will not be affected.
Changes and additions are easier to make and trouble
shooting is centralized.
Disadvantage of star topology:
More network cabling is required and if the hub goes down the entire network will crash as well.Mesh topology
A mesh topology is a mixed type of topology.
If the LAN system is very big it could be a
mixed topology of any two or all the three topologies.
Metropolitan Area Network (MAN) – MAN’s are network that links computer and facilities within a metropolitan area.
Wide Area Network (WAN) – WAN’s are network spread across countries as well as continents. In the broadest sense a WAN is a group of computers that are separated by large distances and are linked together.
The vast majority of WAN’s use satellites as the primary transmission media.
Internet – There are local, national and international networks in current use and most major networks are inter-connected. There is one global network called the Internet which is in effect an international network of inter-connected computer networks.
Evolution of Internet – In 1969 U.S. defense department connected four computers and called the network ‘DARPNET’. In 1972, 32 computers were connected and it was called ‘ARPANET’. In 1984 NFSNET was established and Internet came into being by 1990.
Requirements for getting connected to Internet:
a) A computer system
d) Communication software (web browser e.g. microsoft edge, Mozilla firefox etc.)
e) An account with an ISP
Uses of Internet:
a) Information browsing (www)
b) Electronic mail (email)
c) Chat
d) E-fax
e) E-commerce
f) Video conferencing
g) Newsgroups
h) Access and use of other computers by TELNET etc,
i) File transfer
a) World Wide Web (www) – Web is one of the services provided by Internet. The www service can be accessed by using a protocol called http (hyper text transfer protocol). The www provides information on various topics through different web sites. Searching and finding information has become convenient and easier through the www.
b) Electronic mail (email) – email is the most used feature on the net. All service provider give you an email account as soon as you sign in.
Advantages of email:
i) Fast economic and instant communication media.
ii) Any form of data like text, pictures, audio and video can be sent through e-mail.
iii) A single mail can be sent to many persons at a time.
c) Chat – The Internet relay chat (IRC) or chat is widely used service of Internet, which enables us to send and receive instant messages. To run IRC or chat programs application like yahoo or MSN messengers are needed.
d) E-fax – Electronic fax (e-fax) allows to send and receive faxes directly on computers. Using e-fax one can send document and photos to the other person on the Internet. E-fax messages are directly printed through the printer of the recipient computer and the messages are not stored on the hard disk.
e) E-commerce – Buying and selling of goods and services through Internet is called e-commerce. E-commerce has made business convenient throughout the world.
f) Video conference - Video conference is one of the most advanced services of Internet. Video conferencing enables virtual face to face communication among people from different location and allows exchanges of views and options. Now-a-days video conferencing is mostly use in TV shows.
g) News groups – Newsgroups is a topic forum where people can post questions news and comments, read and respond to such postings. Most publicly available newsgroups are USENET newsgroups.
h) Telnet – Telnet (networking over the telephone) is an Internet exploration tool which allows a person to connect to a remote computer so that the person can use computer from other location. Telnet is frequently used by libraries.
Protocol – A convention used to control the transmission of data in a network is called a protocol.
The common protocols used on the networks are:
a) FTP (File Transfer Protocol)
b) TCP/IP (Transmission Control Protocol/Internet Protocol)
c) SMTP (Simple Mail Transfer protocol)
d) HTTP( Hyper Text Transfer Protocol)
e) POP (Post Office Protocol)
f) IPX/SPX (Internet packet Exchange/Sequential Packet Exchange)
g) NetBEUI (NetBIOS Extended User Interface)
File Transfer Protocol (FTP) – The Internet user can download files from the FTP (file transfer protocol) sites. The FTP application is used to transfer files between hosts. FTP downloads files to your server from remote server that is connected to the Internet.
*** NOTE ***
Internet is a packet switching network. The data to be transmitted is converted into small packets. The software that is responsible for making the Internet function efficiently is TCP/IP. TCP/IP is made up of two components. TCP stands for Transmission Control Protocol and IP for Internet Protocol.
TCP (Transmission Control Protocol ) – TCP breaks up data to be send into little packets. It gurantees that any data sent to the destination computer reaches it intact. It makes the process appear as if one is directly connected to the other.
IP (Internet Protocol) – IP is a set of conventions used to pass packets from one host to another. It is responsible for routing the packets to a desired destination IP address.
SMTP (Simple Mail Transfer Protocol) – SMTP transfers electronic mails and attachment files from one server to another. The end user must use POP to transfer the messages to their machine.
POP (Post Office Protocol) – POP is used for receiving e-mail messages from a email server to a client computer.
HTTP (Hyper Text Transfer Protocol) – HTTP is used to communicate between web clients and web servers. The HTTP moves request made by a user through the web browser to the web server and responses the request.
Commonly Use Network ( connecting ) Devices
1. Bridge : Networks interconnecting one to another across a cabled link is known as a bridge. Bridges are used to connect one or more networks using same or similar communication protocol so they appear as a single large network.
2. Gateway : Computers at separate locations each have their own connection to their network. The point of connection is often called the gateway. Hence a gateway is a connection between similar or dissimilar computer networks.
3. Router : Router links multiple networks using dissimilar communication protocols. Routers are widely used for connecting two or more IP networks. For example Ethernet and token ring can be linked using router.
4. Connector : A connector is a device that is used to join cables or a cable to a device. Bridges, gateways, BNC (Bayonet Naur Connector ) T connector, RJ-45 connector are commonly used as connectors in networks.
5. Repeater : When there are more numbers of nodes on the network, the signals becomes weak due to lengthy connecting wires. A repeater is used on the network to regenerate or amplify the signals. Using a repeater two network segments which use same protocols can be joined.
6. Hub : A hub is a computer networking device that joins multiple computers or other network devices. Hubs can be of two types the active and the passive hub. An active hub can regenerate or amplify electric signals, a passive hub acts as a connecting point and does not amplify or regenerates a signal. A hub is suitable for small network.
7. Switch : A switch is a computer networking device that connects computers, other network devices of LAN segments. A switch is capable of inspecting data packets as they receive and can determine source and destination device of the packet, it reduces the amount of unnecessary network traffic and offers better performance than a hub.
8. Modem : A modem is a device which translates data from digital to analong signals and vice versa that can be transmitted over a telephone network. So a set of modulator and de-modulator is called a MODEM.
Modulation : The process of converting digital signals to an analog one is called modulation.
De-modulation : The process of receiving analog signals and converting it back to digital signal is called de-modulation.
***NOTE***
Types of MODEM –
i) Internal
ii) External
Bandwidth : The data handling capacity of a communication system is called bandwidth or the amount of data transmitted per second is known as bandwidth. Higher bandwidth transmit more information in short time. The bandwidth of digital device is measured in bits per second (bps).
Broad Band Channels : Broad band channels have the ability to carry more data, they are also called wide band channels.
Intranet : An Intranet is a private computer network owned by a company or organization and is accessible only to its members.
Network Services : Network services are the things that a network can do. These are the services provided by the computer. The major services that a network can provide are :
a) File Services – It include file transfer, storage, data migration, file update synchronization and archiving. These features are the most popular reasons for networking.
b) Print Services – Print services produce access to valuable printing devices. A printer that is used as sharing in the network acts as a print server.
c) Message Services – Network facilitates e-mail, messages, manage integrated email and voicemail, co-ordinate object oriented applications. Messaging is an exciting new player at the network party.
d) Application Services – It allows to centralize high profile applications. The server holds the applications and they are accessed by the users in the network.
e) Database Services – It involves the coordination of distributed data and replication. The main server holds the data and determine the number of users that can access the database and modify the data. It also provides the print facility of data in the network. Database services are the new features of recent network versions.
Telecommunication- The transmission of words ,text , sound, images or data in the form of electronic or electromagnetic signals is referred as telecommunication.
Transmission Media- Transmission media for telecommunication includes the telephone (using wire ) or an optical cable, radio, television, microwave and satellite.
Components of data communication system- The basic components of a data communication system used to transmit the messages are:
· A sending device
· A communication link
· A receiving device
Types of signals- The data signals can be divided into two forms-
a) Analog Signal
b) Digital Signal
Analog Signal- An analog signal is a continuous waveform that changes smoothly overtime. The analog signals represent the continuous variation in the data.
Digital Signal- Digital signals which are used by the computers are made up of separate unit usually represented by a series of ones (1’s) and zeros (0’s), which represent discrete values.
Unbound Transmission Media or Wireless Communication- Unbound transmission media extend beyond the limiting confines of cabling. Unbound media typically operate at a very high frequencies. The three types of unbound media are:
a) Radio wave
b) Microwave
c) Infrared
d) Satellite communication.
Radio wave- Radio waves can operate on single or multiple frequency bands. During the time of radio wave propagation , it should be modulated. The following are the different types of modulation:
i) Amplitude Modulation (AM)
ii) Frequency Modulation (FM)
iii) Phase Modulation (PM)
Microwave Communication- Microwave Communication uses a high frequency electromagnetic wave to transmit information. It involves receiving and resending microwave signals between relay stations.
Relay stations often use antennas in high places such as the top of the hills and high buildings. Microwave transmission offers speed , cost effectiveness .
Satellite Transmission- Communication satellites are any orbiting space craft that provides communication over long distances by reflecting or relaying radio frequency signals. In satellite transmission, a satellite acts as a relay station and can transmit data signals from one earth station to another.
Bluetooth - A wireless communication medium operating over short distances. It has a normal range of 3 to 300 feet depending on the devices connecting, the devices can be mobile phonesm laptops digital camera etc.
Infrared- Infrared offers a great unbound photonic solution. Like the fiber optic cabling infrared communication use light, so they are not bound by the limitations of electricity.
Wi Fi – Wireless fidelity is a wireless LAN technology that allows Wi-Fi enabled devices such as smart-phones, laptops and other devices to connect easily to Internet.
Communication
and network questions:
1. Define
transmission-5
2. What
are the types or modes of transmission-6
3. Define
duplex transmission-7
4. What
is simplex transmission-7
5. Define
a half or semi duplex transmission-7
6. Differentiate
between simplex and duplex transmissions-12
7. Define
data-7
8. What
is processing-6
9. What
is information-5
10. Define
a computer network-8
11. What
are the basis for the classification of networks-7
12. Mention
the types of network-7
13. What
is LAN-7
14. List
the elements of LAN-8
15. What
is a workstation-7
16. Define
a server and mention its types-13
17. What
is a dedicated server-10
18. Define
a non dedicated server-10
19. Differentiate
between dedicated and a non dedicated server-10
20. What
is a file server-10
21. What
is a printer server-8
22. What
is a modem server-7
23. Explain
the importance of NIC in a computer network-7
24. What
is a node address-9
25. What
are transmission media or communication channels-9
26. What
are the types of transmission media-5
27. Define
with example bounded/wired or guided media-12
28. Write
a note on twisted pair cable-7.
29. Write
a note on coaxial cable-10
30. Write
a note on optical cable-13
31. Define
with example unbounded/wireless or unguided media-15
32. Write
a note on microwave communication-12
33. Write
a note on satellite transmission- 12
34. Write
a note on radio wave transmission-12
35. Define
infrared and Bluetooth.
36. What
is Wi-Fi?
37. Explain
the importance of a network software-9
38. “computer
network reduces the cost of operation “-explain-12
39. Write
four advantages of a network-8
40. Mention
two disadvantages of a network-10
41. What
is a network architecture-7
42. Mention
the types of LAN architecture-5
43. Define
a client server network-12
44. Mention
two advantages of a client server network-7
45. Mention
two disadvantages of a client server network-7
46. Define
a peer to peer LAN-10
47. Mention
the advantages of a peer to peer LAN-9
48. Mention
the disadvantages of peer to peer LAN-7
49. Differentiate
between client server and a peer to peer LAN-15
50. What
is a network topology-6
51. Mention
the types of network topology-7
52. Expalin
with figure a BUS topology-12
53. Mention
the advantages and Disadvantages of a bus topology-15
54. Define
with figure a ring topology-18
55. Mention
the advantages and disadvantages of ring topology-15
56. Define
with figure a star topology-15
57. Mention
the advantages and disadvantages of star topology-15
58. What
is MAN-7
59. What
is WAN-10
60. Define
Internet-5
61. List
the uses or services of Internet-15
62. What
are the requirements for getting connected to internet-10
63. What
is e-mail-6
64. Mention
the advantages of e-mail-8
65. Differentiate
between email and e-fax-12
66. Why
are chat services used?-7
67. What
is e-commerce?-7
68. Define
video conference-12
69. What
are newsgroups?-7
70. Why
is telnet used-7
71. Define
with example a protocol-6
72. Write
notes on TCP/IP, FTP, SMTP, POP, HTTP
73. What
is www-12
74. Define
with example a web browser-10
75. Define
router-10
76. What
is a bridge- 10
77. Define
a gateway-10
78. What
are connectors-10
79. What
is a repeater-10
80. Define
a hub-12
81. What
is a switch-10
82. What
is modem-6
83. What
are the types of modulation-6
84. Define
modulation-6
85. What
is de-modualtion-6
86. Mention
the types of modem-6
87. Define
bandwidth-12
88. What
is Intranet-6
89. Differentiate
between Internet and Intranet- 8
90. Define
telecommunication-12
91. Write
a note on analog signal-10
92. Write
a note on digital signal-10.
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