Summary of basic concepts in networking
IP address
Identifies where the device resides on the network
The port number
identifies a specific application
protocol
protocol in network communicationmost coreThe concept of
the so-called agreement is a communication between the two partiesagreement, to discuss the format in which the data is transmitted
protocol layering
reason
Due to the complex demand scenarios and complex functions of network communication, its learning cost, use cost and maintenance cost will be very high
Actual practice
For complex large agreements,to splitinto several relatively simple small protocols (Each protocol is responsible for a part of the functionality), the functions and effects of some protocols are similar, and for these small protocols, "classify" (layered), just like the code is split into many classes, and some classes have similar functions, so they can be placed in the same package
benefit
1. Reduced learning and maintenance costs (encapsulation)
2. Flexible replacement for a certain layer of protocols here
encapsulation
Meaning : When the application layer data is sent to the network through the protocol stack, each layer protocol must add adata header(Including the length of the header, the length of the payload, what the upper layer protocol is, etc.) (header) is called encapsulation.
In layman's terms, from the application layer to the physical layer,top to bottom，layer upon layerthe process of.
The following isPackage Example Diagram：
share
Meaning : The data is encapsulated into a frame and sent to the transmission medium. After reaching the destination host, each layer protocol strips off the corresponding header, and hands the data to the corresponding upper layer protocol for processing according to the "upper layer protocol field" in the header.
In layman's terms, from the physical layer to the application layer,bottom up，Layer by layer analysisthe process of.
client
get serviceOne of the processes is called the client (a program for users)
Server
In common network data transmission scenarios, theProvide servicesOne of the processes, called the server (a program that provides user services), can provide external services