History of Internet
The Internet was the result of some visionary thinking by people in the early 1960s, which saw great potential value in allowing computers to share information on research and development in scientific and military fields. J.C.R. Licklider of MIT, first proposed a global network of computers in 1962, and moved over to the Defence Advanced Research Projects Agency (DARPA) in late 1962 to head the work to develop it. Roberts moved over to DARPA in 1966 and developed his plan for ARPANET. The first networking protocol used on the ARPANET was the Network Control Program. In 1983, it was replaced with the TCP/IP protocol invented by Robert Kahn, Vinton Cerf, and others, which quickly became the most widely used network protocol in the world.
In 1990, the ARPANET was retired and transferred to the NSFNET. The NSFNET was soon connected to the CSNET, which linked Universities around North America, and then to the EUnet, which connected research facilities in Europe. Thanks in part to the NSF's enlightened management, and fuelled by the popularity of the web, the use of the Internet exploded after 1990, causing the US Government to transfer management to independent organizations starting in 1995.
Protocols of Internet
The internet is based on a large number of protocols and conventions. Internet protocols are popular open-system protocol suites. They are used to communicate across interconnected networks. Each such protocol is explained in the technical publication called a request for comment (RFC). An RFC is usually a detailed technical explanation of how something is supposed to work, not an invitation for people to send in comments. Each RFC is given a number and is made available to anyone who wants to read it. TCP (Transmission Control Protocol) and IP (Internet Protocol) are well known communication protocols. The Internet protocols not only houses TCP and IP, but also applications like Email, Telnet, and file transfer.
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| Internet Protocols |
Above diagram shows the set of protocols of TCP/IP along with the corresponding OSI model. it shows all 7 layers of the networking and related protocols for the same. According to this diagram TCP and UDP protocols belongs to the transportation protocol. IP and ICMP are related to the network layer. Let’s discuss some well-known protocol like TCP, UDP and IP in detail.
TCP (Transmission Control Protocol)
The TCP corresponds to the transport layer of OSI reference model, The TCP is known as a connection-oriented protocol, which means that a connection is established and maintained until such time as the message or messages to be exchanged by the application programs at each end have been exchanged. TCP makes sure data gets to the destination without errors. It is also responsible for disassembling and assembling the data. it divides large messages into smaller packets of at the most 15KB size. Each of this packet is called a segment. TCP numbers these segments and hand it over to IP layer.
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| TCP Protocols |
TCP is used along with the Internet Protocol (IP) to send data in the form of message units between computers over the Internet. While IP takes care of handling the actual delivery of the data, TCP takes care of keeping track of the individual units of data (called packets) that a message is divided into for efficient routing through the Internet.
IP (Internet Protocol)
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| IP Address |
IP is the protocol that controls how data moves around on the network. After TCP divides the message into segment, IP labels them with source and destination. These packets are now called IP datagrams. IP is the primary protocol in the Internet Layer of the Internet protocol suite and has the task of delivering datagrams from the source host to the destination host solely based on their addresses. IP also takes care of sending the datagrams by determining the route. These datagrams may hop several networks before reaching the destination. Below diagram 1.3 shows TCP/IP Communications.
In the above diagram 1.3, at the destination the IP verifies the labels and passes them to the TCP. The TCP checks if all the segments have been received. If any of the segments are missing it informs this to the source TCP and requests the segment to be sent again. It is called retry. After verification, the TCP assembles the message from these data segments and supplies to the destination program.
UDP (User Datagram Protocol)
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| User Datagram Protocol |
UDP is connection-less transport layer protocol. The UDP port identifies various applications running on a device. UDP adds no reliability, flow control or error recovery. Each datagram is independent of others, and they may be lost by the networks or arrive out of order. A receiving system remains unaware of the sending of a datagram unless it arrives. UDP is used in situations where reliability is not required and it is helpful in multimedia and multicasting applications.
HTTP
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| HTTP |
The Hypertext Transfer Protocol (HTTP) is a networking protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web.
FTP (File Transfer Protocol)
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| File Transfer Protocol |
FTP is probably the most used resource on the Internet. It is a protocol which allows users on computer to transfer files to another computer or we can say to exchange files over the Internet. FTP works in the same way as HTTP (Hypertext Transfer Protocol) for transferring Web pages from a server to a user's browser and SMTP for transferring electronic mail across the Internet in that, like these technologies, FTP uses the Internet's TCP/IP protocols to enable data transfer.
When you take a file from a remote machine down to your own machine, it is called a download. When the opposite happens and you place a file on a remote machine, it is called an upload. FTP is most commonly used to download a file from a server using the Internet or to upload a file to a server.
SMTP (Simple Mail Transfer Protocol)
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| Simple Mail Transfer Protocol |
SMTP is used for sending E-mail messages between servers. Most e-mail systems that send mail over the internet use SMTP to send messages from one server to another, the messages can then be retrieved with an e-mail client. In addition, SMTP is generally used to send messages from a mail client to mail server.
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