TCP and UDP basic principles

　　The main task of the transport layer connection is established between the application end, and provides a reliable or unreliable communication services for data transfer, TCP / IP protocol suite including the TCP transport layer protocol and UDP, TCP is a connection-oriented reliable transport layer protocol that supports reliable connection-oriented data transmission over unreliable networks, UDP is a connectionless transport protocol is mainly used for data transmission on a network of relatively reliable, sensitive to, or to delay applications.

1. The role of the transport layer

　　a>. providing connection-oriented or connectionless service

　　b>. maintains a connection state

　　c>. application layer data segment and package

　　d>. be multiplexed

　　e>. reliable data transmission

　　f>. perform flow control

2.TCP features

3.TCP / UDP port number

Establish a connection 4.TCP

Disconnecting 5.TCP

6. transmission confirmation

7. retransmission timeout

8. sliding window

to sum up:

　　a> .TCP and UDP port numbers identify the upper layer through applications and services

　　b> .TCP through the three-way handshake to establish a reliable connection

　　c> .TCP by checksum error checking by sequence numbers, acknowledgments and timeouts to achieve reliable transmission of retransmission, achieved by a sliding window flow control

　　d> .UDP simple, occupy less resources, practical for high reliability and delay sensitive network by using