Interaction between computers on the Internetis carried out by means of network protocols, which are an agreed set of certain rules, according to which different data transmission devices exchange information. There are protocols for data formats, transmission rates, error control and other types of protocols. In the global interworking, the most commonly used protocol is TCP-IP.
What is this technology?The name of the Internet Protocol TCP-IP came from two network protocols: TCP and IP. Of course, these two protocols do not limit the construction of networks, but they are basic in terms of the organization of data transmission. In fact, TCP-IP is a set of protocols that allow individual networks to unite to form a global network.
TCP-IP protocol, the description of which is impossibledesignate only the definitions of IP and TCP, includes also 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 that is part of the general concept of TCP-IP.
• Internet Protocol (IP) is responsible for direct transmissioninformation on the network. Information is divided into parts (in other words, packets) and transferred to the recipient from the sender. For exact addressing, you need to specify the exact address or coordinates of the recipient. Such addresses consist of four bytes, which are separated from each other by dots. The address of each computer is unique.
However, using only an IP protocolmay not be enough for the correct data transfer, since the volume of most of the transmitted information is more than 1500 characters, which does not fit into one package, and some packets may be lost during transmission or sent in the wrong order.
• Transmission Control Protocol (TCP) is used at a higher level thanprevious. 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 also responds to the separation of transmitted information into separate parts - packets - and the correct recovery of data from packets received after transmission. In this case, this protocol automatically repeats the transmission of packets that contain errors.
Managing the organization of data transmission in largevolumes can be carried out by means of a number of protocols having a special functional purpose. In particular, there are the following types of TCP-protocols.
1. FTP (File Transfer Protocol) organizes the transferfiles and is used to transfer information between two Internet nodes using TCP connections in the form of a binary or plain text file, as a named area in the computer's memory. It does not matter where these nodes are located and how they connect with each other.
2. User Datagram Protocol, or the User Datagram Protocol, is independent ofconnections, it transmits data in packets called UDP datagrams. However, this protocol is not as reliable as TCP, because the poisoner does not receive data about whether the packet was actually received.
3. ICMP (Internet Control Message Protocol) existsto transmit error messages that occur during the exchange of data on the Internet. However, the ICMP protocol just reports errors, but does not eliminate the reasons that led to these errors.
4. Telnet - A network protocol that is used to implement a text interface on the network using TCP transport.
5. SMTP (Simple Mail Transfer Protocol) is a specialan e-mail messaging protocol that defines the format of messages that are sent from one computer called the SMTP client to another computer running the SMTP server. In this case, this transfer can be postponed for a while until the work of both the client and the server is activated.
TCP-IP data transfer scheme
1.The TCP protocol splits the entire amount of data into packets and numbers them by packing them in TCP envelopes, which allows you to restore the order of retrieving parts of the information. When data is placed in such an envelope, the checksum is calculated, which is then written to the TCP header.
2. Then, by means of the IP protocol, all packets are transmitted directly to the recipient.
3.Then, using the TCP protocol, it checks whether all the packets are received. If, at the time of reception, the newly calculated checksum does not match the one indicated on the envelope, this indicates that some of the information was lost or corrupted during transmission, TCP-IP retransmits the packet again. You also need to confirm the arrival of data from the recipient.
4. After acknowledging receipt of all packets, the TCP protocol arranges them accordingly and reassembles them into a single whole.
The TCP protocol uses data retransmissions, wait periods (or timeouts), which ensures the reliability of information delivery. Packages can be transmitted in two directions simultaneously.
Thus, the TCP-IP protocol eliminates the need to use retransmissions and expectations for application processes (such as Telnet and FTP).
