I have been busy with the progress of the project before, I finally have time to study the network knowledge system, take notes, in case of emergency, please skip the network god
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The network can be divided into four layers (some say seven layers, please refer to Baidu for specific content, this thing may be used in addition to interviews, and it is not used at all at other times):
They are the application layer, the transport layer, the network layer, and the link layer.
Protocol layering:
1 ) Application layer: Responsible for handling specific application details. For example: Telnet FTP http , etc., and 99% of the protocols of the application layer are encapsulated by the upper layer of TCP/UDP .
2 ) Transport layer: Provides end-to-end communication for applications on two hosts, that is, the next layer protocol serving the application layer. The famous TCP UDP is located in this layer.
A) TCP: Transmission Control Protocol (Transmission Control Protocol), TCP provides reliable data communication for two hosts.
B) UDP: User Datagram Protocol (User Datagram Protocol), which provides a fast communication method for two hosts, and cannot guarantee the reliability of data.
3) Network layer: The next layer of the transport layer, which is used to handle the activity of packets in the network. This layer includes: IP protocol, ICMP protocol, IGMP protocol.
A) IP : Internet Protocol (Internet Protocol). It is the next layer protocol of TCP/UDP and is mainly responsible for adding TCP/UDP data to the IP address of the target address. Of course, the IP protocol can also be directly invoked by the application layer.
B) ICMP: (Internet Control Message Protocol) Internet Control Message Protocol . It is a sub-protocol of the TCP/IP protocol suite and is used to transmit control messages between IP hosts and routers. Of course, ICMP can also be called directly by the application. The commonly used Ping command is the ICMP protocol.
C) IGMP: (Internet Group Management Protocol) Internet Group Management Protocol. It is used to multicast a UDP packet to multiple hosts.
4) Link layer: It is often referred to as the Ethernet layer or the MAC layer. It usually includes device drivers in the operating system and corresponding network interfaces in the computer. Apart from that, it also contains ARP and RARP protocols.
A) ARP: (Address Resolution Protocol) Address Resolution Protocol is a protocol for obtaining physical addresses based on IP addresses .
B) RARP protocol (Reverse Address Resolution Protocol), reverse address translation protocol , which is the reverse protocol of ARP.