TCP, or Transmission Control Protocol, is a reliable transport protocol used to transmit data over networks. It provides reliable, ordered, and error-checked delivery of data packets between applications running on different hosts.
Here is a brief overview of how TCP works:
- Establishing a Connection: Before transmitting data, a TCP connection must be established between the sending and receiving hosts. This is done through a three-way handshake process, where the sending host sends an SYN packet to the receiving host, which responds with an SYN-ACK packet, and the sending host then responds with an ACK packet.
- Breaking Data into Segments: TCP breaks the data into small segments that can be transmitted over the network. Each segment contains a sequence number, which identifies the position of the data in the stream, and an acknowledgment number, which indicates the next sequence number the receiving host expects to receive.
- Sending Segments: The sending host sends the segments to the receiving host, which acknowledges receipt of each segment by sending back an acknowledgment packet. If the sending host does not receive an acknowledgment within a certain time, it retransmits the segment.
- Flow Control: TCP uses flow control to ensure that the receiving host can handle the data being sent. It does this by controlling the rate at which data is sent based on the available buffer space on the receiving host.
- Error Checking: TCP includes error checking to ensure that data is transmitted accurately. It does this by using checksums to verify that the data received by the receiving host is the same as the data sent by the sending host.
- Closing the Connection: Once all data has been transmitted, the TCP connection is closed. This is done through a four-way handshake process, where the sending host sends a FIN packet to the receiving host, which response with an ACK packet, and then sends its own FIN packet, to which the sending host responds with an ACK packet.
Overall, TCP is a connection-oriented protocol and it provides reliable, ordered, and error-checked transmission of data over networks, making it a fundamental protocol for internet communication.