Internet an how it works..

Internet and how it works..

The Internet, sometimes called simply "the Net," is a worldwide system of computer networks - a network of networks in which users at any one computer can, if they have permission, get information from any other computer.

Data packetsare sent between computers using protocolsthat manage how data is sent and received. The internet also uses different models - such as theclient-servermodel and theP2P model - to connect computers in different ways.

Internet share binary information..Every information on the internet is send in the form of bits.

Bits are in the form of 0 or 1. It can also mean ON or OFF, YES or NO.Because the bit has 2 possible states, it is called binary code.

Data can be transferred in different forms like:ElectricityLight Radio waves

Through Electricity

Copper cable uses electrical signals to pass data between networks. There are three types of copper cable:Coaxialdegenerates over long distances.Unshielded twisted pairis made by twisting the copper cables around each other and this reduces degeneration.Shielded twisted pairuses copper shielding around the twisted wires to make them less susceptible to interference.

Advantagesa cabled telephone can be powered directly from the copper cable, so the phone will still work if there is a loss of powercopper can be cheaper to set up than fibre optic cabling.

Disadvantagesdegenerates over long distances

Through light Fibre optic cabling is made from glass that becomes very flexible when it is thin. Light is passed through the cable using atransmitter.Light travels quickly through the light-reflecting internal wall of the cable.

The transmitter in theroutersends light pulses representingbinarycode. When the data is received, it is decoded back to its binary form and the computer displays the message.

Advantagesthe individual cables are thinner, so larger quantities of cable can be joined together compared to copperthere is less interference than copperthere is less chance for degeneration

Disadvantages

the UK telephone network still has areas that use copper cablereplacing copper with fibre optic cabling is expensive

Through radio wave

Information is send in the form of radio signals.Data is converted from binary form into radio waves of different frequencies

The receiving machine convert this signal again into binary form.

How information is transmitted?

To connect a computer or a device to the internet, you need:anISPamodemorrouter(wired or wireless)aweb browserorappa connection to the network (through a copper wire or afibre optic cable)

AnInternet Service Provider(ISP) is a company that provides you with access to the Internet, usually for a fee. The most common ways to connect to anISPare by using a phone line (dial-up) or broadband connection (cable or DSL).

Routers Arouteris a device that forwards data packets alongnetworks. A routeris connected to at least twonetworks, commonly two LANs or WANs or a LAN and its ISP'snetwork.Routersare located at gateways, the places where two or morenetworksconnect.

Broadband connectionsThe internet is transmitted both on physical wires and wireless connections.Broadbandinternet is transmitted onphysical wires that run underground and under the oceans.

Downloadspeeds tend to be faster thanuploadspeeds. More bandwidth is assigned for downloading because there is a higher demand for downloads. Network speeds are measured by how many megabits they can download per second (Mbps).

ADSL(Asymmetric digital subscriber line)

The speed that data can be transferred is dependent on a number of factors:Signal quality can vary between phone lines itaffect data transmissions.The distance between the modem and the telephone exchange has an effect on the speed at which data is transferred. A distance of 4 km is considered the limit for ADSL technology, beyond which it may not work.An ADSL modem orrouteris needed for broadband internet access over ADSL. This is usually provided by theISP.

ProtocolsThe internet is similar to a road network in that it has rules (protocols) that you need to follow and only a certain number of vehicles (data) can get through at a time (bandwidth). If too many vehicles try to go down the same road you get congestion (reduced bandwidth).

When two devices send messages to each other it is calledhandshaking- theclientrequests access, theservergrants it, and theprotocols are agreed. Once the handshaking process is complete, the data transfer can begin.

Protocols establish how two computers send and receive a message. Data packetstravel between source and destination from onerouter to the next. The process of exchanging data packets is known as packet switching

TCP/IP (transmission control protocol/internet protocol)Back in 1970s there was no standard method for networks to communicate.

What is protocol??Protocol is a well known set of rules used to communicate between machines.

TCP/IP (also known as the internet protocol suite) is the set of protocols used over the internet. It organizes how data packets are communicated and makes sure packets have the following information:

source- which computer the message came fromdestination- where the message should go

packet sequence- the order the message data should be re-assembleddata- the data of the messageerror check- the check to see that the message has been sent correctly

IP addressEvery device on the internet has aunique IP address. The IP addressis included in a data packet.An address on the internet is just a number like phone no. or street adddress.

IP addresses are either 32-bitor 128-bit numbers. The address is broken down into four 8-bit numbers (each is called anoctet).

This version of IP addressing is called IPV4.It was designed in 1973 and adopted in 1980s.IPv4 addresses are represented indot-decimal notation , which consists of four decimal numbers, each ranging from 0 to 255, separated by dots, e.g., 172.16.254.1.It provide 2^32 possible unique addresses.

It provides more than 4 billion unique addresses for the devices to be connected to the internet.But the internet is so wide that this 4 billion unique address are not enough.So a more enhance addressing mechanism was introduced

IPV6The address size was increased from 32 to 128bits(16octets) providing up to 2128(approximately3.4031038) addresses.

The large number of IPv6 addresses allows large blocks to be assigned for specific purposes and for efficient routing.It provide 340 undecillion unique addresses and its more than enough.

Encryption and securityAs we know internet is an open system.We exchange a lot of private data like credit card no., bank information, password etc.So there should be a mechanism to keep our data secret.

Data can be kept secret by a process called encryption.

It is the scrambling or changing of the message to hide the original text.The scrambled message is called cipher text.

Decryption is the unscrambling of that message to make it readable.The unscrambled message is called plain text.

Message are encrypted and decrypted with the help of keys.A key is a secret password to unlock a message.A keyspecifies the transformation of plaintext into ciphertext, and vice versa for decryption algorithms.

Public key: it is shared with everybody so that anybody can encrypt the message.Private key: a secret can only be decrypted with anybody with the private key.

Types of encryptionSymmetric key algorithmsuse related or identical encryption keys for both encryption and decryption.

Asymmetric key algorithmsuse different keys for encryption and decryptionthis is usually referred to as Public-key Cryptography.

Symmetric key encryption

Symmetric-key algorithms can be divided into two parts.stream ciphersblock ciphers

In a stream ciphereach plaintext digit is encrypted one at a time with the corresponding digit of the key stream, to give a digit of theciphertext stream.block ciphers take a number of bits, often in blocks of 64 bits at a time, and encrypt them as a single unit.the more popular and well-respected symmetric algorithmsAES(Rijndael),,RC4,TDES, andIDEA.

Asymmetric key encryption

Asymmetric encryption uses different keys for encryption and decryption. The message recipient creates a private key and a public key. The public key is distributed among the message senders and they use the public key to encrypt the message. The recipient uses their private key any encrypted messages that have been encrypted using the recipients public key.

How Encryption Secures Communication on the WebThe SSL (Secure Sockets Layer) protocol has been securing web transactions using encryption between your web browser and a web server, protecting you from anybody that might be snooping on the network in the middle.

SSL itself is conceptually quite simple. It begins when the browser requests a secure page (usually https://)

The web server sends its public key with its certificate.

The browser checks that the certificate was issued by a trusted party (usually a trusted root CA), that the certificate is still valid and that the certificate is related to the site contacted

The browser then uses the public key, to encrypt a random symmetric encryption key and sends it to the server with the encrypted URL required as well as other encrypted http data.

The web server decrypts the symmetric encryption key using its private key and uses the browsers symmetric key to decrypt its URL and http data.

The web server sends back the requested html document and http data encrypted with the browsers symmetric key. The browser decrypts the http data and html document using the symmetric key and displays the information.

Thank you