The TCP protocol, unlike the UDP protocol, is connection oriented. When machine A sends data to machine B, machine B is informed of the arrival of this data and confirms its good reception.

Here, the CRC control of data intervenes, which is based on a mathematical equation that allows you to verify the integrity of the transmitted data. In this way, if the received data is corrupted, the TCP protocol allows the recipients to request the sender to send them again.

This protocol is one of the main protocols of the transport layer of the TCP/IP model, since, at the application level, it makes it possible to manage data coming from the lowest level of the model.

So, when data is provided to the IP protocol, it binds it in IP datagrams, fixing the field protocol with 6, so that you know in advance that the protocol is TCP. This protocol is connection oriented, so it allows two machines that are communicated to control the status of the transmission.

Several programs within a data network that are composed of computers can use TCP to create connections between them, by means of which they can send a data flow. Thus, the protocol guarantees that the data will be delivered to its destination. The most important thing to take into account is that it has no errors and maintains the order in which they are transmitted.

On the basis of the preceding example, we can devise the properties of TCP:

• Reliable: The TCP protocol has the ability to manage the attempts that can be made to send a message if a packet is lost, and can resend those fragments that were not sent on the first attempt.
• Ordered: The messages are delivered in a particular order.
• Heavyweight: TCP has the ability to verify that the connection can be established through a socket before any packet can be sent, for which it uses three sending confirmation packets, called SYN, SYN-ACK, and ACK.