Shulou(Shulou.com)06/02 Report--

First, the overview of the transport layer protocols of the TCP/IP protocol family:

1P TCP: transmission control protocol

2dint UDP: user Datagram protocol

Second, the detailed explanation of TCP/UDP protocol:

1,TCP

A.TCP is a connection-oriented, reliable process-to-process communication protocol

TCP provides full-duplex service, that is, data can be transmitted in both directions at the same time.

B.TCP message paragraph:

TCP groups several bytes into a packet. It's called the newspaper paragraph. TCP message segments are encapsulated in IP datagrams.

Detailed explanation of data segment:,

Serial number (32): the sender numbers each byte to facilitate the normal reorganization of the receiver.

Confirmation number (32): used to confirm the information of the sender.

Window size (16): used to indicate the number of locally acceptable data segments, the window size is variable.

SYN: the request token for establishing a connection

FIN: request to disconnect

ACK: a request to confirm the connection

RST: reset (in case of failure)

URG: emergency pointer bit (1: on 0: off) is directly submitted to the other party without caching

PSH: quick reception and delivery to the application layer (1: enable 0: off) need to be cached, and a batch of message segments will be sent directly to the application layer.

c. Common TCP port numbers and their functions

Port protocol description 21F T PFTP server open control port 23TELNET for remote login, can remotely control the 25SMTPSMTP server open port for sending files 8 0HTTP Hypertext transfer Protocol 11 0P0P3 for mail acceptance

Expansion: port 20 is the data connection of FTP, port 21 is the control connection of FTP, port 22 SSH protocol is used for remote ciphertext transmission, 23 is plaintext, port 443HTTPS is secure transmission protocol.

D.TCP connection

The process of establishing a connection in TCP is called a second handshake.

Four waves of disconnected TCP

Semi-closed concept

2,UDP

A.UDP protocol: ① connectionless, unreliable transport protocol, low cost of ②

The header format of the b.UDP message

Source port number (16) destination port number (16) UDP length (16) UDP checksum (16)

UDP length: used to indicate the total length of the UDP and add data to the header

Checksum: used to complete error checking of UDP data. It is the only reliable mechanism provided by UDP protocol.

Common port number of c.UDP and its function

Port protocol description 69TFTP simple file transfer protocol 111RPC remote procedure call 123NTP network time protocol

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