Dcn Ppt.pptx

Some Useful Services of Internet • FTP-: File transferring can be done using internet between sender and receiver using FTP (File Transfer Protocol) as download & upload of data.

• E-Mail-: Electronics Mail is one of the most popular service of internet by which, messaging along with file attaching can be done. • Video Conferencing-: It is another useful service of internet that facilitates audio/video communication between two person or more person.

• Telnet-: Remote Desktop Login is another service of internet using which one can access someone computer’s desktop. This type service can also be possible through ‘Telnet’ which is a remote login program. ‘Telnet’ stands for ‘Tele Communication Network’. • Online Chatting-: It can be done using internet by using different types of applications like messenger, whatsapp, facebook etc. • Using News group we can post, share news online.

Types of Internet • Internet-: Internet is a globalize network provide services world wide. Ex-: www • Intranet-: Intranet is a private networking system that made between similar branches of private companies which is not allowed to access for public purpose. Thus, intranet is a internetworking system between different sub branches of a single company. • Extranet-: Extranet is also a private networking system but it is made between only the authorized outsiders, which is also not allowed to access for public purpose. Ex- In Banking Sector.

What is Data? • As we know data are raw facts and figures that may be the name or address of a person, location, rollno of a student etc. which is converted into information when it express in meaningful way. • Finally these related information are collected through special file called database that either stored in local server or web server. • Thus acommunicationgetestablishedbetween data.

What is Communication? • Generally Communication means to convey a message, an idea, data by receiving from a sender and providing to a receiver. • Communication may be close by or far away. • Different types of communication can be done depending upon situation, it may be face to face, telephonic, e-mailing, postal, hand to hand etc. • Communication can be done with or without the presence of the person at the current time.

What is Data Communication? • It is the way exchange of information from device to device that may be between computers, mobile phones or other devices. • When data are send as information from a sender to receiver then a communication made between the computer of that sender & receiver that type communication is called data communication. • The data communication requires some tools or items in order to communicate like data, sender, receiver, signal, network, media, protocol etc. for successful communication.

What is Communication Channel? • A communication channel provides the medium to move electromagnetic energy from a source to one or more destination points. • It is a pathway over which data are transferred between remote devices. • When a message is sent from source to destination, first that data convert into electromagnetic energy using some conversion mechanism, then that is passed through a communication channel either wirelessly or wired base. Finally it reached to its destination.

What is Baud Rate & Bit rate? • Baud is the number of signal changes per second. Baud rate is a measurement of the digital signal rate in a communication channel. Baud rate is the rate at which information is transferred in a communication channel. • Bit rate is the no of pulses also called flip flop sent in 1 second. It is a measurement of the digital bit values which the communication channel conveys with each baud. • In digital data transmission, Baud rate & Bit rate are almost equal, but technically baud rate is always smaller than the bit rate.

What is Bandwidth, Broadband & Baseband?

• Bandwidth is the range of frequencies with in a band i.e how much information can be carried in a given time period (usually a second) over a specific wired or wireless communications link. Higher bandwidth communication channels support higher data rates. It is expressed in bps. • Broadband is a wide bandwidth data transmission system in which several analog signals share the same physical network channel. It has the fastest signal carrying capacity. • Baseband is a signal that has a very low frequency range where the entire bandwidth of the cable is utilized for a single channel. Baseband is commonly used for LAN.

What is Computer Network? • A Network is a group of computers connected together along with other computing devices attached with them. • A network may be serve as a server computer into which other computers and computing devices get connected as clients. • The main benefit of a computer network is that it can be share with others for data, printer etc.

What is Networking? • An arrangement of two or more computers interconnected together as a network for sharing information among each other is called as networking. • In networking the connecting media can be a wire, cable, radio wave, fiber optic etc. depending upon the architecture of the network.

Some Useful Services Through a Computer Network

• File sharing can be possible through a network with or without internet. • Device sharing can be possible by setting under a network like a printer.

• Messages can be sent or share. • It can be wired or wireless.

• Internet can be shared. • Other important application, antivirus can also be shared.

Software Tools Needed For Computer Network

• Networking/Non Networking OS

• Networking Application Program • LAN/Ethernet Driver • LAN Configuration • Modem Driver (If Applicable) • WIFI/WLAN Driver(Auto) • Authentication Connectivity using ID & Password.

Hardware Needed For Computer Network/Networking Components • • • • • • • • • • •

LAN Card & LAN cable Modem (If Applicable) Telephone Line Server PC Client PC Router Switch Hub Repeater Bridge Gateway

Networking Components

(Modem)

(LAN Cable) (LAN Card)

Some More Networking Components • • • • • •

Switch Hub Router Repeater Bridge Gateway

Hub • It is a device where data arrives from one or more nodes and forwarded to one or more other nodes • It has 4,12 RJ-45 ports. • It also has light indicators. • It is other wise known as multi port repeater.

Switch • It is a Network device that select a path or circuit for sending a data unit to its next destination. • It required in large internet works. • It consists of various LAN Ports for connecting LAN cables from different client Pcs. • It has light indicators against each LAN port. • It comes as 6,8,12,24,32 based RJ-45 ports.

Difference between a Hub & a Switch • The main difference between a hub & a switch is that in a hub anything that comes in one port is inform & sent out to all other ports in that network. Means if a message comes for computer ‘A’ then that message is also informed & sent to all other ports in that network. When computer ‘A’ responds, its response also goes out to each port on the hub. That means every computer connected to the hub sees everything that every other computer on the hub sees. But in case of a switch it can able to send link simultaneously and need not to do that a hub does.

Router • It is a Device containing software that helps in determining the bestpathoutof theavailablepathsforaparticulartransmission. • It contains both hardware & software. The hardware itself is a device and the software is its operating system to route network traffic and the routing protocol (RIP, Routing Information Protocol) used for it. • A router between two LANs receives messages from both network, checks their destination and transmit the message to the required LAN since messages are stored in the routers before re-transmission, thus routers are said as the storeand-forward technique. • A router operates exactly as a switch, a router used for WAN for greater networking range and switch used for LAN.

Repeater • A repeater is a networking component that extends a network by boosting the signal where it amplify and regenerate signal for long distance cable runs. • Using repeater the signal is received on one side of the repeater, can be duplicated boosted and regenerated to its original strength and then passed to the next section of cable.

Bridge • Bridges are the devices used to transmit data between two separate LANs. • It divides a large network into smaller segments. • It also filter the data and keep the traffic separate for each segments.

Gateway • A gateway is a network point that regard as both software and hardware that acts as an entrance between either two similar network or two dissimilar network so that data can be transferred between a number of computers. • For example, when you send an e-mail or log in to a website, there the gateway allows the connectivity between that two network. • It handle messages, addresses and protocol conversions. • It can receives messages in one format and convert them in another format.

Types of Networking • • • • • • • • • • •

Peer to Peer Client/Server LAN (Local Area Network) WAN (Wide Area Network) MAN (Metropolitan Area Network) PAN (Personal Area Network) VAN (Value Area Network) CAN (Campus Area Network) SAN (Storage Area network) WLAN & WWAN (Wireless LAN & Wireless WAN) VLAN (Virtual LAN)

PEER TO PEER NETWORK • A peer-to-peer (P2P) network is a type of decentralized and distributed network architecture in which individual nodes called peers share resources among each other without the use of centralized administrative system. • This network act as both suppliers and consumers of resources i.e act as both server and client computers.

CLIENT/SERVER NETWORK • In client server network, client nodes request servers to access resources. • Clients and servers exchange messages in a request response messaging pattern. • The client sends a request, and the server returns a response.

LAN NETWORK • LAN stands for Local Area Network. • It is a group of computers that are interconnected with each other in a limited geographical area usually 5-6 kms like in a home, school, computer laboratory, or in an office building etc either wired base or wirelessly . • It has high speed data transfer rate like 100 mbps. • It needs low cost implementation. • It provides full time connectivity to local computers. • LAN allows users to share various things like printers, scanners, storage applications, data etc.

LAN NETWORK ARCHITECTURE

LAN Type-1

LAN Type-2

LAN Type-3

WAN NETWORK • WAN stands for Wide Area Network. • It is a network that covers a broad area that links across metropolitan, regional, or national boundaries. • The Internet can be considered as a WAN that is used for businesses, government works for different purposes like to share data among employees, clients, buyers & suppliers from various geographical locations. • A collection of multiple LANs can also be called as a WAN.

WAN NETWORK ARCHITECTURE

MAN NETWORK • • • •

MAN stands for Metropolitan Area Network. It is used in metropolitan area i.e in metro cities. It covers 5 to 50 kilometers. This network is in between LAN and WAN.

VAN NETWORK • VAN stands for Value Added Network. • This is another communication system that is used by the telephone company to offer customer to communicate with a toll-free number.

PAN NETWORK • A personal area network (PAN) is a computer network used for data transmission amongst devices such as computers, telephones, tablets and personal digital assistants with in the range ofan individual person (10mtr) • Forexample,apersontravellingwithalaptop,apersonaldigital assistant (PDA) or a portable printer could interconnect them withouthavingtopluganythingin,usingsomeformofwireless technology. • This network generally refers to the devices connected with Bluetooth.

SOME OTHER NETWORKS • • • • •

CAN (Campus Area Network) SAN (Storage Area network) WLAN(Wireless LAN) VLAN (Virtual LAN) A VLAN is a group of devices on one or more LANs that are configured to communicate as if they were attached to the same wire, when in fact they are located on a number of different LAN segments. Because VLANs are based on logical instead of physical connections, they are extremely flexible.

Networking/Communication/ Transmission Modes

• Simplex • It is a simple method of data communication in which there is one way communication system. • Television transmission is a very good example of simplex communication. Here the main transmitter sends out a signal but doesn’t except a reply back to this transmitter. • Some other example of it could be a printer or a keyboard. So due to this the simplex communication system never used because a return address is general needed to send acknowledgment orreply. Sender

Receiver

(Simplex Communication)

Half Duplex • In this system both side part should be communicate over the same medium, but only one part can send data at a time, while another part can receive data at a time. • This communication is like two person talking to each other, where one talks, the other listens, but both of them could not talk at the same time. • A VHF (very high frequency) radio device used in police station to send and receive messages can be an example of it. The walkie-talkie device which is a two way portable radio device can also be its example. Sender & Receiver

(Half Duplex Receiver & Sender Communication)

Full Duplex • In full-duplex communication system there perform simultaneous transmission in both directions, so that it is suitable in all the fields of communication. • An example of this type communication system is a telephone or mobile phone. Sender & Receiver

(Full Duplex Receiver & Sender Communication)

SOME IMPORTANT INTERNET PROTOCOLS

• TCP/IP-:TCP/IP dictates how information should be packaged (turned into bundles of information called packets), sent, and received, as well as how to reach to its destination, it tells packets where to go and how to get there. TCP/IP was developed in 1978 and driven by Bob Kahn and Vint Cerf. As the name implies, TCP/IP is a combination of two separate protocols: Transmission Control Protocol (TCP) & Internet Protocol (IP). • FTP, PPP • HTTP(USED TO DELIVER WEB PAGES REQUESTED/FORWADED BY WEB SERVERSTOTHECLIENTVIAWEBBROWSER). • ARP (PC’s Physical i.e System address in a network) • RARP (Internet address of a pc) • SLIP (for internet connection via a dial-up connection, developed in 80s when modem communications typically were limited to 2400 bps. It was designed for simple communication over serial lines.

• TELNET (INTRODUCED IN 1972 COMES FROM THE WORD ‘TELEPHONE NETWORK’ TERMINAL EMULATION PROTOCOL FOLLOWS UNDER TCP/IP SUITABLE FOR CUI ENVIRONMENT.)

• ICMP (Internet control message protocol) inform sender about error during data transmission. • UDP, • SNMP(Simple Network Management Protocol)

DHCP • DHCP stands for Dynamic Host Configuration Protocol. • It is a network protocol that enables a server to automatically assign an IP address to each client computer that connected into that network. • Through it dynamic IP addresses are assigned. • The main work of it to control the host i.e. client computers by assigning IP address as dynamically. • It is suitable for a LAN. • DHCP assigns an IP address when a system is started. The client PC sends a broadcast request (called a DHCPDISCOVER) to the DHCP server in order to connect under it.

SOME IMPORTANT MAILING PROTOCOLS • SMTP (PROTOCOL FOR MESSAGE FORWARD) • POP (PROTOCOL FOR INBOX) • IMAP(INTERACTIVE MAIL ACCESS PROTOCOL) FOR ACCESSING MAIL • MIME (HELPS TO ATTACH MULTIMEDIA DATA)

Transmission Media • The transmission media is the media through which a channel get form between a sender & a receiver. • It is of two types like (a) Guided Media (b) Un-Guided Media.

The Guided Media • The Guided media is the media which have the control over it. • Generally the guided media are the wired base like cables. • Ex. Of Guided Media are Twisted Pair Cable, Coaxial Cable & Fiber Optic Cable.

Twisted Pair & Coaxial Cable)

(STP Twisted Pair Cable)

(Coaxial Cable)

(UTP Twisted Pair Cable)

(Coaxial Cable)

Fiber Optic Cable

Twisted Pair Cable • Twisted pair cable consist of two insulated copper wires about 1mm thickness, which are twisted together for the purposes of twisting the wires as to reduce the electromagnetic interference (EMI) from similar pairs that are close by. • Twisted pair wires are commonly used in local telephone communication and also in LAN cable. • Its data transmission speed is 9600 bits per second. • Again it has two type one is shielded twisted pair (STP) and another is unshielded twisted pair (UTP).

Its Advantages • It is used for both analog and digital data transmission. • By using it in telephone system signals can travel several kms without amplification. • RJ-11 type twisted pair cables are used for telephone system, whereas RJ-45 type twisted pair cables are used for computer LAN for networking, Internet. • If some portion of a twisted pair cable is damaged, then the entire network is not stop working.

Its Disadvantages • Here error rate is high because, it can easily pick noise signal. • Due to thin in its size it is likely to break easily.

Coaxial Cable • The Coaxial cable consist of a hard copper wire as the core surrounded by an insulating material. • Again the insulator is surrounded by a cylindrical conductor as a closed braided mesh (like a rope having hole). • The outer of the conductor is covered in a protective plastic cover. The signal is transmitted by the inner copper wire. The coaxial cable can support up to 10 mbps data rates. • Generally the coaxial cable is used in dish connection, CCTV Camera etc.

Its Advantages • It has better outer cover against EMI than the twisted pair cables. • It is also used for both analog & digital data transmission. • It has higher bandwidth as compared to twisted pair cable. • It has lower error rates than twisted pair cable because the inner conductor is shield.

Its Disadvantages • It requires high installation cost than the twisted pair cable. • It is susceptible that coaxial cable may be damage by lightning strikes. • It requires amplification to strengthen the weak signal in order to retransmit after long distance journey.

Fiber Optic Cable • An optical fiber is a thin, flexible, transparent fiber that acts as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. • It is mostly used in scientific and engineering field as very costly purpose. • Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and higher bandwidths (data rates) than other forms of communication.

Its Advantages • It has much greater bandwidth than metal cables. • It has less susceptible than metal cables to interference. • It is much thinner and lighter than the metal cable.

Its Disadvantages • Fiber Optic cables are expensive to install as these are so costly. • They are more fragile(break) than wire. • These are difficult to splice(joint as a rope).

The Unguided-Media • The Un-guided media is the media which don’t have any control over it, so it is called as un-guided. • Generally the unguided media are the non-wired basis i.e wireless medias like wave, wi-fi, infrared, Bluetooth etc. • Ex. of Un-Guided Media are Radio Wave, Micro Wave & Light Wave.

Radio Wave • It is an example of unguided media whose examples are VHF, UHF, FM etc. • Its wave length is between 10 khz to 1ghz. • All radio wave devices uses signal during transmitting via television & radio devices. • Radio waves can be broadcasted in any place and as one directionally. • Various kinds of antenna can be used to broadcast radio signals. • A trans-receiver is used to receive signals over the medium such as copper wire or fiber optics.

Its Characteristics • • • •

It is easy to generate It can travel long distances. It can penetrate buildings easily. Radio waves are omnidirectional (can travel in all directions) . • It is suck up by rain.

Micro Wave • It can travel in straight line therefore it focuses signal as narrowly thus uses a parabolic antenna. • Before the invention of fiber optic cables micro waves were used for telephony transmission system. • In order to keep away from the problems like weak signals, for power amplification the microwave system uses repeaters at the intervals. • Unlike radio waves at lower frequencies microwaves do not pass through building. • It permits data transmission rate of about 16 gbps. • Terrestrial, VSAT are some examples of it.

Terrestrial Micro Wave Systems • The Terrestrial microwave system uses the directional parabolic antenna to send & receive signals in lower hertz range. • Relay towers & repeaters are used to extend signals. • This system is used when ever cabling is not possible such as in hilly areas or crossing rivers etc, because this system doesn’t use cables. • This terrestrial transmission covers distance by relaying signals from station to station.

Satellite Micro Wave Systems •The satellite microwave system also uses the directional parabolic antenna to send & receive signals in lower hertz range. •The satellite system is placed with one antenna in geosynchronous orbit about 36,000 kms above the equator, thus it can reach most remote places on earth and communicate with mobile devices. •In orbit there the speed of the satellite matches the earth’s rotation speed. •The signal become weak due to travel of long 36,000 km distance. So due to this the satellite also uses transponder to amplifies weak signal & send them back with good signal to the earth which is received by the transmitter at the earth.

On earth, Dish shaped (curve shaped) antennas can be placed up to 30 miles apart (but the path between them must be unobstructed). A satellite orbiting the earth at approximately 22,000 miles acts as a relay station, transmitting the signal it receives from one earth station to another earth station.

VSAT • VSAT stands for Very small Aperture Terminal, that is a tiny terminal of 1 meter wide antenna run with speed of 19.2 kbps uplink & 512 kbps downlink. It uses a hub, an antenna, an amplifier to relay. • It is used in the earth station that can also communicate on data, voice and video signals excluding broadcast television. • A VSAT consist of two parts one is a transreceiver that is placed in outdoor as direct line to satellite and another is a device that is placed in indoor to interface the transreceiver with a computer. The transreceiver receives or send signal from ground station to satellite on sky.

Light Wave • It is another unguided media used with in a LAN via lasers. • Infrared could be an example of it. • In this system the bandwidth is very high at very low cost. • It is easy to install. • It doesn’t require any license.

Infrared • Infrareds are widely used for short range of communication can be used as a LAN. • The remote controllers used on TV, DVD player, AC etc uses the infrared communication system. • They are directional, cheap but do not pass through solid objects. • An infrared system in one room of a building will not interface with a similar system in separate room. • There is no chance of weak signal in this system as compared to other communication systems.

What is a Modem? • Modem stands for modulation and demodulation. • A modem is a device that enable a computer to connect to a networkor web for data communication. • The main work of a modem is to perform modulation & demodulation worksbased on digital and analog signal. • Computer, Mobile Phones are the examples of digital signaling devices, whereas telephone system parabolic antennas are the examples ofanalog signal. • A modem can be installed internally or externally. As internally a computer or mobile devices are their self internal modem, whereas a dongle, bluetooth or data cable based connecting mobile devices arethe examples ofexternal modem.

What is Modulation and Demodulation? • The term ‘Modulation’ means that it is the process of converting digital signal into analog signal. • The term ‘De-Modulation’ means that it is the process of converting analog signal into digital signal. • When a computer wishes to send digital data through web then that data must be first convert from digital to analog by that sender’s modem ,then at the receiver computer, again that analog data converted into digital signal by the receiver’s modem.

Different Types of Modulation AM • AM stands for Amplitude (extended signal strength) Modulation. • This type of modulation or it is a modulation technique that can be used for both analog and digital signaling via radio carrier wave. • Songs transmitted via Akash Vani on wave is an example of it. • It is affected by the electrical noise signal. • Amplifier used with it to avoid the weak signal affect.

PM • PM stands for Phase Modulation. • It uses two analog signal, where the first signal is a carrier, and the other signal modifies the carrier signal to convey information. • In PM system, the phase change takes place whenever the bit level changes from 1 to 0 or 0 to 1. • This system generally used in Telephonic System or Color TV to carry or convey color information as signal at a higher data rates.

FM • FM stands for Frequency Modulation. • It has a constant amplitude and has a much higher frequency than the information signal it has to transport. • The FM wave is least affected by noise. • FM signal has a wide range of frequencies therefore it needs much higher bandwidth than AM.

PCM • PCM stands for Pulse Code Modulation • It is a digitalize process in which an analog signal is represented or converted in digital form.

What is Multiplexing and De-multiplexing?

• Multiplexingalsocalledmuxingisawayofsendingmultiplesignals orstreamsofinformationoveracommunicationslinkatthesame timeintheformofasinglesignal. • Its reverse work called de-multiplexing or de-muxing is a way of retrievingorseparatingthesignalsintheformofmultiplesignals. • Multiplexing allows multiplestreamsofelectronic messagesto be transmittedoverthesameconnection. • DTHservicehavingmorenosofchannelscouldbeitsexample. • It is the method of dividing a physical communication channels intomanylogicalchannels.

What is Multiplexing and De-multiplexing?

Different Types of Multiplexing • There are different types of Multiplexing like (a) FDM (b) TDM (c) CDM (d) WDM

What is FDM? • FDM stands for Frequency Division Multiplexing. • This type Multiplexing used in telephone trunk circuit. • In FDM the available bandwidth of a physical medium is divided into several smaller logical bandwidths, where all that separated bandwidth component used as a separate communication channel. • The best example of it could be various stations in Akash Vani(AIR), where each radio station is assigned with a frequency range with in the total bandwidth. • A radio receiver’s antenna receives signal that transmitted by all the stations. • Error checking is done during data transmission.

What is TDM? • TDM stands for Time Division Multiplexing. • In TDM separate signals combined into a single high speed transmission, in which the transmission time is broken into segments, each ofwhich carriesoneelement ofonesignal. • In another sentence TDM is a method of sharing a communication channel in which the total time available in the channel is divided between several users and each user of the channel isallotted atime during the transmission. • TDM is more efficient that FDM, because it does not requires the guard bands and can operatesdirectly in digital form. • TDM is fast because it does not involve in error checking, because data aretransparent toit due to time limit.

What is CDM and WDM? • CDM stands for Code Division Multiplexing. • In CDM transmissions from different stations are multiplexed bydifferent channel codesand send onacommon channel. • Butthedifferenttransmissionsusethesamefrequency,where eachuser isseparated byacode. • At the receiving end, these data codes are removed from the desired signal. • WDM stands for Wavelength Division Multiplexing. • It is the new technology operates on high data rates over fiber optic cables replaced byTDM.

Asynchronous Data Transmission System • Asynchronous data transfer system refers to non-continuous data transmission, where data is transmitted character by character atirregular intervals. • There used the start and stop bit procedure for each character between two nodes for which two extra bits one for the start bit and another forthe stop bit getused. • Asynchronous data transmission system does not work until the hardwareonthecommunicationlineisreadytotransmit. • The best suitable example of this type of transmission is the communicationbetweenacomputerandakeyboard. • Itdoesnotrequireanylocalstorageforeachcharacter. • Ithaslowerdatatransferrate.

Synchronous Data Transmission System

• Synchronous data transfer system refers to continuous data transmission, where data is transmitted character by character atregular intervals. • LikeAsynchronousdatatransmission,itdoesnotusestart&stop bits between two nodes during data transmission at intervals of charactersandthesenderandreceiverishandleddifferently. • Ithasbettererrordetectionsystem. • The best suitable example of this type of transmission is the communicationbetweenacomputerandaprinter remotely. • It requireanylocalstorageforeachcharacter. • Ithashigherdatatransferrate.

Asynchronous & Synchronous Data Transmission System Images

Its Some More Images

What is Cryptography

• Cryptographymeanssecretcode.Astheinternet&e-communication become more necessary, so e-security also become increasingly important,thusasystemcryptographyusedforthistoprotecte-data. • Encryption and Decryption are the two most important jobs of cryptography. • Cryptography can be used to protect e-mail messages, credit cardinformation, confidential data, data integrity, OTP&others. • One of the most popular cryptography system used on the internet is ‘Pretty GoodPrivacy(PGP)’. • In cryptography there used two key, one is a public key that is known to everyone and another is a private key that only the actual recipient can know.

What is Encryption System? • The word encryption comes from the Greek word ‘kryptos’ which means hidden or secret. Encryption is the most effective way to achieve data security. • To read an encrypted file, you must have access to a secret key or password that enables you to decrypt it. • Unencrypted data is called ‘Plain Text’ and encrypted data is referred to as ‘Cipher Text’. • Encryption is the conversion of electronic data into another form, called cipher text, which can’t be easily understood by anyone except authorized users. • The encryption system is used to protect the confidentiality of digital data stored on computer systems or transmitted via the internet or other computer networks.

Encryption System Continues… • The purpose of encryption is to ensure that only somebody who is authorized to access data will be able read it using the decryption key. • Without the required decrypted key it is impossible to read the encrypted information. • Devices like modems, smart phones, set-top boxes, smart cards, SIM cards, protocols like SSL, TLS (Transport Layer Security),HTTPS,SMIME, SET Digital Certificates, Digital Signature Systems and many more are uses the encryption system to protect/encrypt sensitive data.

What is Decryption System? • Decryption isthe reverseoperation ofEncryption system. • Decryption is the process of taking encoded or encrypted text orother dataandconverting itbackinto itsoriginaltextor data form that youorthe computer canreadand understand. • Thedecryptionworkcanbepossibleonlyifthedataencrypted. • In other sentence decryption is the process of decoding data that has been encrypted into a secret format using a password sothatitcanbeaccessedagainbytheauthorizedusers. • An authorized user can only decrypt data because he/she only knowsthesecretkeyorpasswordofthatencryptdata.

Encryption & Decryption System

What is PGP? • PGP stands for Pretty Good Privacy that is one of the most popular cryptography system used ininternet. • It is a data encryption and decryption computer program that provides cryptographic privacy and authentication for data communication. • It is used to encrypt and decrypt email messages over the internet as well as authenticate messages with digital signatures and encrypted stored files. • PGP uses the public and private key system, where the public key is known to each user whereas the private key is known only to the authorized user. • PGP uses a faster encryption and decryption algorithm to encrypt and decrypt the messages.

What is SSL? • SSL stands forSecureSocketLayer. • It is the standard security technology for establishing an encrypted link between awebserver and abrowser. • This link ensures that all data passed between the web server and browserremain private and integral. • SSL allows sensitive information such as credit card numbers , social security numbers, and secret login id and passwords to betransmitted securely. • Moreover SSL is a security protocol that ensures the secure datatransmissionbetweenawebserver&anuserviabrowser. • SSL secures millions of people’s data on the internet every day, especially during online transactions or when transmitting confidentialinformationthroughinternet.

What is TLS? • TLS stands forTransport Layer Security. • TLS isasuccessor to SSL. • Like SSL, TLS also provides secure communications on the internet for e-mail, e-faxand e-transactions other transfers. • TLS is a protocol that provides privacy and data integrity between twocommunicating applications. • It is the most widely deployed security protocol used today for web browsers and other applications that require data to be securely exchanged over a network, such as file transfers, VPN connections, instant messaging etc. • Majorwebsitesuse TLS to secureallcommunications between theirserversandwebbrowsers.

Circuit Switching • Circuit switching was an oldest methodology for implementing a communication network in which two network nodes establish a dedicated communication channel (circuit) through the networkbeforethe nodes may communicate. • The circuit functions as the nodes were physically connected with an electrical circuit. • An example of a circuit-switched network is the early analog telephone network. • When a call is made from one telephone to another, switches within the telephone exchanges to create a continuous wire circuit between twotelephones, till the callends.

Packet Switching • When data is send from one computer to another at that time it is broken in to pieces called packets by the TCP. Each packet has the address ofthe sender & receiver in IP format. • All the data packets are send from one network to another network till they all reach their destination. At the destination the TCP again reassemble the packets into a complete message. Thistechnologyiscalledpacketswitchingtechnology. • The Advanced Research Projects Agency Network (ARPANET) was one of the world's first operational packet switching technology, which is also the first network to implement TCP/IP and to provide global internet.

Difference between Circuit and Packet switching Technology Circuit Switching

Packet Switching

(1) Circuit-switched networks needs (1) The Packet-switched networks moves data separately with dedicated point-to-point connecsmall blocks of packets based tions during calls. on destination address in each (2) It is used for phone calls. packet. (3) It reserve a dedicated channel for the entire communication to (2) It is used for managing data over internet. send signal via switches. (3) It uses data packets called data (4) It is limited to voice signal only. grams for communication. (4) It can send sound, video, images, text as breaking into data packets.

OSI Model • OSI stands for Open System Interconnection. It was setup by Geneva–based International Organization for Standardization (ISO) in 1977as the aim to standardize the procedures for exchange of information between computers in networking. • For data sending easily the OSI model divides the communication tasks into smaller subtasks which specifies by different layers with particular network function like addressing, flowcontrol,errorcontrol,reliablemessagetransferetc. • The OSI model has seven layers namely Application (7th) Presentation(6th) Session(5th) Transport (4th) Network (3rd) DataLink(2nd) Physical(1st). • When a message is sent from any computer to any other computer over the internet, actually it travels between these seven layers as from lowerlevel to the upper level.

OSI Model Continues… • In total of 7 layers of OSI model, the layers 1st and 2nd are mandatory in order to transmit and receive messages in any communication system. • Layer 3rd, 4th and 5th are provided by the controlling network software. • Finally the 6th and 7th layer finalize the sent work.

Physical Layer (Layer-1) • This layer is the first layer from the bottom of seven layered fashion ofOSI. • This layer is mandatory in order to transmit and receive messages. • This layer defines all the electrical and physical specifications for devices like wiring connectivity, voltage control etc. • It includes the physical parts like cables, hubs, switch, connector, trans-receiver etc.

Data Link Layer (Layer-2) • This is the second layer from the bottom ofOSI model. • The data link layer provides the means to transfer data between network equipments. • It detects and corrects possible errors that may occur in the Physical layer like data flow control, hardware addressing errorchecking. • This layer specify how data bits are grouped into logical chunk (large pieces) of data, known as frames by arranging bits from the physical layer • Again this layer has two sub layer one is LLC (Logical Link Control) & MAC (Media Access Control).

Network Layer (Layer-3) • This is the third layer from the bottom of OSI model. • This layer performs the routing function and forward data packets to upper level. • This layer also breaks the large packets into smaller packets and report delivery errors. • This layer translates the logical network address into physical machine address. • This layer defines IP address, create packet headers for each packet. • This layer is helpful for transport layer and other layers above it to send packets. • Router and Gateway operate in this layer.

Transport Layer (Layer-4) • This is the fourth layer from the bottom ofOSI model. • This layer also breaks large messages into packets to be sent to the destination computer. • The transport layer provides transparent transfer of data between computers. • It typically send an acknowledgment to the originator for receiving the message. • This layer ensures the complete data transfer. UDP is relating to this layer.

Session Layer (Layer-5) • This is the fifth layer from the bottom of OSI model. • This layer defines how connection can be establish, maintain and terminate, where it queues the incoming messages & is also responsible for recovering from abnormally terminated session. • This layer allows application to the destination computer as a connection called session. • The session layer controls the connections (sessions) between computers. • It also provides for data synchronization as a result, if an event ofa networkfailure,then only the data can sent and the failure eventcan be resent.

Presentation Layer (Layer-6) • This is the sixth layerfrom the bottom of OSI model. • This layer translate data in to different formats, which the network required and the computer accept. • This layer performs protocol conversion, data encryption, data translation, data compression etc.

Application Layer (Layer-7) • This layer is the seventh and the final layer of OSI model. • The application layer provides a means for the user to access information on the network through an application like networkdatabase. • This layer is the main interface for users to interact with the application in the network. • The protocols at this level includes FTP, HTTP, SMTP, POP etc.

TCP/IP (DOD) Model • TCP/IP, is a suite of protocols used for communication over the internet, which is named after the two most important protocols one is Transmission Control Protocol (TCP) and another is Internet Protocol (IP). • The TCP/IP model is similar to the OSI model but there the layers are revised as 4 instead of 7 for bringing international standard on internet for people. • The TCP/IP model was developed about 10 years after the develop of OSI model. The TCP/IP is also called as DOD model (Department ofDefense).

OSI Model layer Vs TCP/IP(DOD) Model

Computer Network Topologies • The way in which components of a computer network arephysically organized is known asTopology. • Topology means the structure of cabling system. • There available 5 different types of computer network topologies such as Bus, Ring, Star, Tree, Mesh etc.

BUS TOPOLOGY • In Bus topology all the computers are connected by a single lengthofcablewithaterminatorateachend. • ThistopologyisthesimplestandmostwidelyusedforLAN. • Itisapassivetopologythatmeansonlyonecomputeratatime cansendamessage,asaresultacomputermustwaituntilthe busisfreebeforeitcantransmittowardsnextcomputer.

Advantages & Disadvantages of BUS TOPOLOGY Advantages • It is simple to use and requires few amount of cable to connect the computers together. • It is easy to extend a bus through a connector. • Failure ofone device doesn't effect transmission. Disadvantages • Due to connectivity of heavy network, traffic can slow down a bus. • It is difficult to troubleshoot a bus because a cable may malfunctioning at any where which can causes break in connection.

RING TOPOLOGY • It is another network topology whose work is similar with bus topology except that the nodes are connected between computers using cable as in a circle. • Data travels around the ring in the direction from one computer to another computer by acting as a repeater. • Each node passes information to the next node until it reachesits destination. • There is no chance of signal loss which is shown in bus topology because ofno end ofthe ring. • This type of topology can be found in peer to peer networking. • It uses a token for transferring data among computers.

Diagram of RING TOPOLOGY

Advantages & Disadvantages of RING TOPOLOGY

Advantages • It is implemented with low cost. • Because of every computer is given equal access, so no single computer can try to monopolize in the network. • Due to the equal sharing of the network there perform slower operation but instead of fail. • No limitation on the length of the networks. Disadvantages • Failure of one computer in the network results into failure of entire network. • Transmission is affected by the numbers of nodes connected to the ring.

STAR TOPOLOGY • Instar topologytheremadethe arrangementofcomputerslike astarshape. • Inthistopologyaddinganewmachinetothenetworkissimple. • Failure of one node does not affected the entire network, but if cablebreaksthenentiresystemmayfailtoserve. • Failureofcentralnoderesultsentirefailureofnetwork.

TREE TOPOLOGY • Itsacombinationofbusandstartopologywiththestructurelike abranchesofatree. • Herethecentralhubconnectedasabussystem. • Failure of one node does not affected the entire network, but if cablebreaksthenentiresystemmayfailtoserve.

Mesh Topology • In this topology all computers serves as a client and server due toequalsharingofoneanother. • If one node fails, rests of the nodes continue to work without disruption. • Duetoalotofcable,thistopologyisexpensivetoimplement.

Internet Protocol (IP) • • • •

The IP worksat the networklayer ofOSI & DOD model. It is a connectionless datagram protocol. For addressing, IP uses the logical networkaddress. For switching, IP uses the packet switching methodology.

Functional items of IP • Datagram (1) Packets in the IP arecalled datagram. (2) Adatagram isavariable length packetup to65,536 bytes that consist oftwoparts oneisheaderand another isdata. • Header (1) A header contains essential source & destination information up to 20-60 bytes that needs during routing &delivery. The remaining bytes areused for general data. (2) TCP receives data bytes from the upper layers, then assembles them into packets and at the destination IP again reassemble that data by checking errors on header with ‘checksum’ method.

What is an IP address ? • An IP is an unique identifier managed by Internet Assigned Numbers Authority (IANA) used to identify computers in a networktoconnect.Thatallowstransfersofdata,files&e-mail. • Currently there used the most popular version ipv4 of 32 bits, butalsothereusinganotheripv6of128bits. • IP addresses are binary numbers, but they are usually stored in textfilesanddisplayedinhumanreadablenotations. • IPv4 addresses are represented in dot-decimal notation, which consists of four decimal numbers, each ranging from 1 to 255, separated by dots, e.g., 172.16.254.1. Each part represents a groupof8bits(octet)oftheaddress. • Among four section, the first two section is used for network id andthesecondtwosectionisusedforhostid.

Classes of IP address • Therearetotally 5Classes ofIP address ABCD&E. • Class Aisreserved for governments with asmall network. • Class B is reserved for medium companies like commercial organizations, Universities etc. • Class Cisreserved forsmall companies. • Class D is reserved for multicasting (a group of destination computer.Itisacommunication betweensinglesenderand multiple receiveronnetwork). • Class Eisreserved for future use. • N.B-: Notice that currently both class A and B are full. The address areavailable in class Conly.

Classes of IP address continues…

MAC Address • • • • •

MACstandsforMediaAccessControlthatworksinDLLofOSI. ItisanuniquevalueassociatedwithaNetworkAdaptors. ItisotherwiseKnownashardwareaddressorphysicaladdress. TheyuniquelyidentifyanadapteronaLAN. It’s address are 12-digit hexadecimal numbers (48 bits in length). In its address the first half number refers to the ID number of the adapter manufacturer and the second half number is refers to the serial number assign to the adapter providedbythemanufacturer. • 00:A0:C9:14:C8:29(anaddressindicatedbyIntelCorporation).

MAC vs IP Address

Sub Netting/Subnet Mask • It is a segment of network having 32 bits address like IP address. • It is a technique that allows network administrator to divide one physical network into smaller logical network in order to controltheflowoftrafficforsecurityandefficiencyreason. • Assubnettingthebaseaddresstodefine startingpointofthe networkis‘192.168.1.0’. thatindicatesthatthenetworkbegin with this i.e. 192.168.1.0, so the first possible host IP of addresswouldbe192.168.1.1,then192.168.1.2andsoon.

Network Administration

Network Administration Continues… with Networking Operating Systems

Network Administration • • • • • •

TheNetworkAdministratorshould Installing and configuring the network with using a NetworkOS. Creating usersandgroups. AlloworDenyPermissionstotheusersandgroups. ConfigureLANnetworktoprovideservicetotheusersand groups. Sharingfilesandfolders Sharingprinterandotherimportantnetworkdevices.

What is Network Operating System? • Anetworkoperatingsystemisanewkindofoperatingsystem otherthanthenormaloperatingsystem. • The network operating system is specially designed for networkingwork. • A networking operating system consist of server, client (users &Groups),network,permissionetcasitsmainparts. • Windows NT, Windows Server 2000, 2003, 2008 are some examples of popular Network operating system by Microsoft. Beside this ‘Novel Netware’ is an example of Network Operating system by ‘Novel’ company. ‘Unix’, ‘Linux’ (through telnet,remotelogin)canbeusedasNetworkOS.

What is Windows NT/Characteristic Features of Windows NT?

• Windows NT is a Networking operating system designed by Microsoft,thefirstversionofwhichwasreleasedinJuly1993. • It was a powerful high-level-language-based, multiprocessing, multi-useroperatingsystemwithfeaturescompatibletoUnix. • NT was the first fully 32-bit version of Windows. • It has a built-in networking & communication features. • It provides strict system security. • Its design is based on processor independent so that it can be easily ported to many different machines.

Anatomy/Components of Windows NT • • • • • • •

Server Client (Users) Groups Network Sharing Features Security/Authentication Rights/Permissions

Creating of User And Group • Type of User account • Local • Domain (For access to network resources in the domain).

User Account • User are also created on domain controllers automatically when Active Directory is install • Administrator– Cannot be deleted – Disable

• Guest Account – Disable by default

Right To Group • • • • • •

Account Operation Administrators Back Up Operator Creator Owner Print Replicator

File Sharing • Sharing permission – Full Control – Read – Change

• Hidden Sharing

Printer Sharing • Sharing permission – Full Control – Manage Documents – Print – No Access