Transport layer protocol details (Key 4, white network necessary knowledge)

A First, let's look at transport layer inside the two protocols

TCP protocol features: security, inefficient. UDP protocol features: high efficiency, unsafe

details two .TCP segment of

the TCP protocol is the end and the connecting end, application to application communication
source port number: your own service or application port number of the
destination port number: Corresponding others service or application port number
we look at known port numbers

numbers: the sender for each byte number for the convenience of the correct recombinant
confirmation number: to confirm the sender of the message
header length: the length of the TCP header
flags : URG: urgent pointer bit is 1 is opened, is 0 is closed, without caching directly to the application layer of the other host of
PSH: rapid acceptance passed to the application layer, need to go through the cache, after a segment until complete without queuing directly to the application layer.
ACK: acknowledgment connecting
the PST: reconnecting, reset
the SYN: a request for connection
the FIN: Disconnect
window size: for explaining the number of local data segments may be received. Window size is variable.
Three .TCP three-way handshake, four waved

us to understand, first of PC1 sends a request message SYN connection, Seq is represented by a serial number, to PC2.
PC2 sends an acknowledgment message ACK, to respond by SYN.
PC1 has confirmed that it will respond to this ACK.
Four-way handshake:
We take a look, first of all messages sent PC1 and disconnect confirmation message FIN and ACK
PC2 will receive a confirmation message
PC2 again responded, this disconnect confirmation message
PC1 receive a confirmation message ACK that

there is a TCP half-closed state, in which case the data can be sent to PC1 PC2, PC1 but can not send data to the PC2.