Transmission control protocol TCP

Transmission Control Protocol (TCP) support network in the transport layer. Transmission Control Protocol (TCP) provides a secure connection-oriented services. Connection-oriented, as a client and the server must open a connection before data is transmitted. TCP is determined by RFC 793, and TCP 1122 is as follows:

* Through reliability.
* Data from the new flow of packages.
* Flow Control.

TCP is based on service in the IP network layer to get data from the host. Given the fact that intellectual property is not reliable when it comes to the quality or delivery of communications, TCP should take precautions to ensure that messages are promptly and correctly ("Federal Express"?).
TCP message format

The format of TCP header is as follows:

• Source port number (16 bit)
• Destination port number (16 bit)
• Number (32 bit) - The byte of data that the first byte of this package represents.
• Confirmation number (32 bits) - contains the following sequence number that the sender expects to receive confirmation of the sequence number plus 1 (plus the number of bytes received in the last report?). This number is used only when the flag ACK.
• Length header (4 bits) - length header from 32-bit words, are needed in the field of options for a variable length.
• Reserved (6 bits)
• URG (1 bit) - The urgent pointer valid.
• ACK (1 bit) - If the number of valid acceptance.
• PSH (1 bit) - these high priority to its implementation.
• RST (1 bit) - to restore the connection.
• SYN (1 bit) - occurs when the connection will be established and the number will be the first serial number issued by the host in this regard.
• END (1 bit) - The transmitter sends data.
• The size of the window (16 bits) - the maximum number of bytes that the recipient agree.
• TCP control (16 bit) - calculated on the TCP-header, and TCP pseudo-header.
• Time Index (16 bit) - it is only valid if the URG bit. Urgent a way to transfer information in case of emergencies on the other side of communication. It should be added to the sequence of numbers at the bottom of the segment to generate a number of the last byte of urgent data.
• Options (variable length)

Header, followed by the data. TCP data is full duplex.