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 》.

Basic knowledge

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

* rate
* bandwidth
* throughput
* 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 :

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