modern society , The network has been connected with water , Electricity has become an indispensable part of our daily needs , It can be said that the Internet is everywhere . As a user , Just learn how to use the Internet , As a computer major , It is necessary for a programmer to have a deep understanding of the principles .
therefore , This chapter mainly introduces some basic definitions of computer network , Network architecture, etc , To learn the basic concepts of computer network , Lay a good foundation for the next network programming .
I studied computer network in my sophomore year , But it's been a long time, a lot of it has been forgotten , So this blog is also a sort of my own knowledge , The main reference book is Xie Xiren's 《 computer network 》.
The most important functions provided by computer network to users are two ：
* Connectivity ： Connectivity means that the network enables users to exchange information , It's like user computers are connected to each other
* Sharing ： Resources can be shared , User friendly
The network can be regarded as a combination of several nodes and links connecting these nodes , Where the node can be a computer , Hub , Router , Switch, etc .
The Internet connects many computers , And the Internet connects a lot of networks . The Internet itself is complex , But it can be divided into the following two parts ：
1. About the edge part ：
The edge part utilizes the services provided by the core part , Make many hosts （ End system ） Ability to communicate , Exchange or share information . Deeper understanding ,
host A And host B signal communication , It's actually a host A A process and host for B One process communication for .
Communication between end systems can be generally divided into two categories , customer - The server （CS Model ）, reciprocity （P2P）.
2. About the core ：
The core part is very complex , Because it serves a large number of hosts on the edge , Enable any host to communicate with other hosts .
among , The router is the key , It is also a special computer , Mainly to realize packet switching , That is, forwarding received packets .
Advantages and disadvantages of grouping ：
Performance index of computer network
* time delay
* round trip time
See Xie Xiren's 《 computer network 》 Sixth Edition p19
Computer network architecture
There are two main models , One is OSI Seven layer model , One TCP/IP Four layer model .
This is in 《 computer network 》 A passage and picture in the book , Used to illustrate network architecture , actually , Our general focus is still on TCP/IP On the four layer agreement .
About why to tier ? The book also shows the benefits of layering ：