Shulou(Shulou.com)06/01 Report--

TCP provides reliability in the following ways:

The ◆ application is divided into blocks of data that TCP deems most appropriate to send. The unit of information passed from TCP to IP is called a message segment.

◆ when TCP sends out a message segment, it starts a timer and waits for the destination to acknowledge receipt of the message segment. If it cannot time to receive a confirmation, it will resend the message paragraph.

◆ when TCP receives data from the other end of the TCP connection, it sends an acknowledgement. This confirmation is not sent immediately and is usually delayed by a fraction of a second.

◆ TCP will maintain its header and data verification and. This is an end-to-end checksum designed to detect any changes in data during transmission. If there is an error in the receipt of the message segment, TCP will discard the message segment and do not acknowledge receipt of the message segment.

◆ since TCP message segments are transmitted as IP datagrams, and the arrival of IP datagrams may be out of order, so the arrival of TCP message segments may also be out of order. If necessary, TCP will sort the received data and send the received data to the application layer in the correct order.

◆ since the IP Datagram will be duplicated, the TCP connection must discard the duplicate data.

◆ TCP also provides flow control, and each side of the TCP connection has a fixed size of buffer space. The receiver of TCP only allows the other end to send data that can be accepted by the receiver buffer. This will prevent faster hosts from causing buffer overflows on slower hosts.

In addition, TCP does not explain the content of the byte stream.

TCP provides a solution for one end to tell the other end that some "emergency data" has been placed in an ordinary data stream, allowing the receiver to do special processing of the emergency data. At this point, the URG bit is set to 1, and the 16-bit emergency data is set to a positive offset. By adding this offset to the sequence number field in the header of TCP, the sequence number of the last byte of the emergency data can be obtained. Common applications are transmission interruption keys (during connection through telnet).

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