Tcp/ip protocol (UDP)

TCP/IP agreement ： It's a protocol cluster , Contains many protocols ,UDP Also included . The general name is TCP/IP, Because it is the two most important agreements in the agreement

TCP/IP The protocol set includes ： application layer 、 Transport layer 、 The network layer 、 Network link layer

The application layer includes ：
1. Hypertext transfer protocol （HTTP）
2. File transfer protocol （TFTP）
3. Remote login （Telnet）
4. Network management （SNMP Simple network management protocol ）
5. The domain name system （DNS）

The network layer includes ：
1.IP（Internet agreement ）
2.ICMP（Internet Control information protocol ）
3.ARP（ Address resolution protocol ）
4.RARP（ Reverse Address Resolution Protocol ）

TCP and UDP The difference between TCP： Transmission control protocol , It's a connection oriented protocol .（ Before sending data , You must establish contact with the other party first ） UDP： User datagram protocol , It's a connectionless protocol

1.TCP Yes, you need to connect ,UDP There is no need to connect
2.TCP There are many requirements for system resources ,UDP Less
3.UDP The program structure is simple
4.TCP Make sure the data is correct ,UDP You may lose your bag
5.TCP Ensure the order of data ,UDP No guarantee

TCP： Three handshakes , Four waves
Conversation process ：
1. host A Host computer B Send connection request packet ; First conversation ：“ I want to send you data , Is that OK ？”
2. host B Host computer B Send packets that agree to connect and require synchronization （ Two hosts , One is sending , One is receiving ）; Second session ：“ Sure , When do you send ？”
3. host A Send a packet again , Confirm host B Required synchronization ; The third session ：“ I'll send... Now , You go on ”

The purpose of the three dialogues is to make the sending and receiving of data packets proceed synchronously , After three conversations , host A To the host B Send data officially