我的TCP/IP知识(ENG)

    TCP/IP is the protocol set in our world’s communication network. TCP (Transmission Control Protocol) and IP(Internet Protocol) forms the Internet Protocol Suite. They are used in data transmission via Internet or other networks.
The TCP provides reliability by:
       - TCP will consider the best size to chunk, what is different for the the UDP which will use packets. The unit of information passed by TCP to IP is called Segment
       - Before sending data, TCP will establish a connection first
       - TCP IP will have a signal back to confirm if the message have been sent well or if a problem occurred while the sending operation
       - The probability of loosing data are lower than UDP
       - TCP will keep its checksum on its header so that the recipient will be acknowledge about the quantity of data it is going to receive, if it receive more or less it will send an acknowledgment saying that the data didn’t arrive.
       - TCP will discard duplicated data,
       - The TCP data’s are sent as IP Datagram
       - Multiplexing

Connection Establishment and Termination

The connection establishment and termination happens with two important protocols:
       - Connection Establishment Protocol(three way hand-shake; or 三次握手)
This protocol is characterized by 3 steps, the first one is the client which will send the SYN segment to the server to inform which port of the server it is going to be connected to, the server will immediately send an ACK segment to acknowledge the client, but also sends an SYN segment to inform the client the Initial Sequence Number. At that time the client will immediately acknowledge the server by sending a ACK segment.

       - Connection Termination Protocol(四次断开): When it is about the termination the client will send a FIN segment to inform the server that there will be no more information ( The TCP is a half-closed protocol, the Server will be closed actively), the server will send one segment which will be the SYN to close actively the client but an ACK to acknowledge the client. The last step will that the client, after receiving the SYN segment will send also an ACK segment to the server to terminate the connection.