TCP Protocols

Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It provides reliable, ordered, and error-checked delivery of a stream of bytes between applications running on hosts communicating over an IP network.

TCP Flags

TCP flags are control bits in the TCP header that specify the purpose and content of each TCP segment. Here are the main TCP flags and their functions:

SYN (Synchronize)

Initiates a connection between two hosts

Example: Used in the first step of the TCP three-way handshake

ACK (Acknowledgment)

Acknowledges the receipt of a packet

Example: Sent to confirm that data was received successfully

FIN (Finish)

Requests the termination of a connection

Example: Used to initiate the graceful teardown of a TCP connection

RST (Reset)

Abruptly terminates a connection

Example: Sent when a host receives a packet for a connection that doesn't exist

PSH (Push)

Pushes buffered data to the receiving application

Example: Used in interactive applications to ensure data is processed immediately

URG (Urgent)

Indicates that the packet contains urgent data

Example: Used to prioritize certain data, such as interrupt or abort signals

TCP Three-Way Handshake

The TCP three-way handshake is used to establish a connection between a client and a server. Here's an example of how it works:

Client sends a SYN packet to the server
Server responds with a SYN-ACK packet
Client sends an ACK packet to the server

After these three steps, the connection is established and data can be transmitted.

Related RFCs

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