Internet protocols

Internet protocols are of two types: basic and applied. Basic protocols are responsible for the physical transfer of messages between computers on the Internet. These are the IP and TCP protocols. Applied protocols of the Internet of a higher level, they are responsible for the functioning of specialized services. For example, the HTTP protocol serves for the transfer of hypertext messages, the FTP protocol for file transfer, the SMTP for sending e-mail.

Internet protocols are of two types: basic and applied

A set of Internet protocols of different levels working simultaneously is called a protocol stack. Each underlying layer of the protocol stack has its own rules system and provides a service to overlying protocols. Similarly, each protocol in the protocol stack performs its function without worrying about the functions of the protocol of the other level.

At the lower level, two main protocols are used: IP (Internet Protocol) and TCP (Transmission Control Protocol). The architecture of the TCP/IP protocols is designed to integrate networks. In their quality, different local networks can act, which work in accordance with their principles and type of communication. In this case, each network can receive a packet of information and deliver it to the specified address. Thus, it is required that each network has some kind of end-to-end Internet protocol for the transmission of messages between two external networks.

Suppose there is a message sent by e-mail. The transmission of mail is performed using the SMTP application protocol, which relies on TCP/IP Internet protocols. According to the TCP protocol, the data sent is broken up into small packets of fixed structure and length, labeled so that when data is received, the data could be collected in the correct sequence.

For each TCP packet received, the IP protocol adds information on which it is possible to determine the addresses of the sender and the recipient. This is similar to placing an address on an envelope. For each incoming packet, the router through which the packet passes, according to the IP address, to which of the nearest neighbors it is necessary to forward this packet, so that it is faster to the recipient, i. E. decides on the best way to follow the next package. Geographically, the shortest path is not always optimal (a fast channel to another continent may be better than a slow one to a neighboring city). Obviously, the speed and paths of different packets can be different. Interconnected data packets can be transmitted in various ways. Regardless of the path length as a result of the finite number of transfers, TCP packets reach the destination.

Finally, the TCP receiver module collects and unpacks IP envelopes, then unpacks the TCP envelopes and places the data in the correct sequence. If something does not reach you, it needs to forward this packet again.

It is necessary to emphasize the main difference in the transmission of information over the telephone network and over the Internet. The telephone system when you call by phone in another region or even on another continent establishes a channel between your phone and the one to which you are calling. The channel can consist of dozens of areas of different physical nature - copper wires, fiber optic lines, wireless sites, satellite communications, etc. These sites are unchanged throughout the entire communication session. This means that the line between you and the person you call is constant throughout the conversation, so damage on any part of the line can interrupt your conversation. At the same time, the part of the network you have chosen for others is no longer available. This is a circuit-switched network. The Internet is a packet-switched network.

So, the Internet data in any form - an email, a web page or a downloadable file - is traveled as a group of packages. Each packet is sent to the destination along the optimal path available. Therefore, even if some Internet site is violated, it will not affect the delivery of the package, which will be sent along an alternative path. Thus, during the delivery of data, there is no need for a fixed link between the two users. The principle of packet switching provides the main advantage of Internet - reliability. The network can distribute the load at different sites per thousandths of a second. If a piece of network equipment is damaged, the package can bypass this place and go the other way, ensuring the delivery of the entire message.