Interaction between computers on the Internet is carried out through network protocols, which are an agreed set of specific rules, according to which different data transfer devices exchange information. There are protocols for data formats , bit rates, error control and other types of protocols. Global interworking most commonly uses the TCP-IP protocol.
What kind of technology is this? The name of the Internet Protocol TCP-IP comes from two network protocols: TCP and IP. Of course, the construction of networks is not limited to these two protocols, but they are basic in terms of the organization of data transfer. In fact, TCP-IP is a set of protocols that allow individual networks to come together to form a global network.
The TCP-IP protocol, the description of which cannot be defined only by the definitions of IP and TCP, also includes the protocols UDP, SMTP, ICMP, FTP, telnet, and not only. These and other TCP-IP protocols provide the most complete operation of the Internet.
Below is a detailed description of each protocol included in the general concept of TCP-IP.
• Internet Protocol (IP) is responsible for the direct transmission of information on the network. Information is divided into parts (in other words, packets) and transmitted to the recipient from the sender. For accurate addressing, you need to specify the exact address or coordinates of the recipient. Such addresses consist of four bytes, which are separated by dots. Each computer address is unique.
However, the use of the IP protocol alone may not be sufficient for the correct transmission of data, since the bulk of the transmitted information is more than 1500 characters, which does not fit into one packet, and some packets may be lost during transmission or sent in the wrong order. what is needed.
• Transmission Control Protocol (TCP) is used at a higher level than the previous one. Based on the ability of the IP protocol to transfer information from one node to another, the TCP protocol allows you to send large amounts of information. TCP is also responsible for dividing the transmitted information into separate parts - packets - and the correct recovery of data from packets received after transmission. At the same time, this protocol automatically repeats the transmission of packets that contain errors.
Management of the organization of data transmission in large volumes can be carried out using a number of protocols having a special functional purpose. In particular, the following types of TCP protocols exist.
1. FTP (File Transfer Protocol) organizes file transfer and is used to transfer information between two Internet nodes using TCP connections in the form of a binary or simple text file, as a named area in the computer's memory. In this case, it does not matter where these nodes are located and how they are interconnected.
2. The User Datagram Protocol, or User Datagram Protocol, is independent of connections; it transfers data in packets called UDP datagrams. However, this protocol is not as reliable as TCP, because the poisoner does not receive data on whether the packet was actually received.
3. ICMP (Internet Control Message Protocol) exists in order to transmit error messages that occur during the exchange of data on the Internet. However, the ICMP protocol only reports errors, but does not eliminate the causes that led to these errors.
4. Telnet - a network protocol that is used to implement a text interface on a network using TCP transport.
5. SMTP (Simple Mail Transfer Protocol) is a special protocol for exchanging electronic messages that defines the format of messages that are sent from one computer, called the SMTP client, to another computer on which the SMTP server is running. At the same time, this transfer can be delayed for some time until both the client and server are activated.
TCP-IP protocol data transfer scheme
1. The TCP protocol splits the entire amount of data into packets and numbers them, packing them into TCP envelopes, which allows you to restore the order in which parts of the information are received. When data is placed in such an envelope, the checksum is calculated, which is then written to the TCP header.
2. Further, through the IP protocol, all packets are transmitted directly to the recipient.
3. Then, using the TCP protocol, a check is made to see if all packets are received. If during reception the recalculated checksum does not match the one indicated on the envelope, this indicates that some of the information was lost or distorted during transmission, TCP-IP again requests forwarding of this packet. Confirmation of receipt of data from the recipient is also required.
4. After confirming receipt of all packets, the TCP protocol organizes them accordingly and reassembles them into a single unit.
TCP uses retransmission of data, waiting periods (or timeouts), which ensures reliable information delivery. Packets can be transmitted in two directions at the same time.
Thus, TCP-IP eliminates the need for retransmissions and expectations for application processes (such as Telnet and FTP).