Hello fellow CSDN users, Xiaoyalan’s computer network column has not been updated for a long time, and the final exam also requires a computer network test, so Xiaoyalan is here to write about computer network content! ! ! Now, let’s enter the world of computer network overview! ! !
The development of computer networks
Computer network categories and switching methods
computer network protocol
The development of computer networks
Computer Communications and Networks
- Some important features of the 21st century are digitization, networking and informatization . The network has now become the lifeblood of the information society and an important foundation for the development of the knowledge economy.
- The computer network represented by the Internet has developed rapidly and has gradually developed from an initial educational and scientific research network into a commercial network.
- The Internet is the biggest change in communication since the invention of printing, and has developed into a global information service infrastructure.
In our lives, there are three major communication networks! ! !
- Telecommunications network: Provides users with telephone, telegraph and fax services. Of course, we no longer use the telegraph service now. As for the fax business, except for individual companies and enterprises, we actually use it very little.
- Cable TV network: It generally sends various TV programs to users in one direction.
- Computer Network: Enables users to transfer data files between computers.
Why can computer networks develop so fast? What is the difference between it and other networks?
- The biggest difference between the computer network and the traditional telephone network and cable TV network is that the terminal equipment of the computer network is a powerful and intelligent computer.
- Using computer networks, various applications running on computers, including email, World Wide Web surfing, information search, instant messaging, Internet telephony, Internet TV, online games, file sharing, etc., provide users with services through communication with each other. More colorful services and applications.
- When we discuss computer networks, we not only include the data communication services provided by computer networks, but also include these colorful network applications.
So what applications and services does the computer network provide us?
Provides us with a platform to browse information and publish information. In the past, we usually obtained news and information through newspapers, radio and television. Now, we have a faster way. Through computer networks, we can obtain information faster and more timely, and in addition to seeing text and pictures, we can , you can also see dynamic videos, and the information obtained is more complete and comprehensive. In addition, in addition to passively receiving information, we can also send information out at any time. In other words, every ordinary person can now become a publisher of information.
It has become a platform for our communication and exchange. In the past, we had to communicate with each other through letters or phone calls, but today, I believe that everyone is more accustomed to using instant messaging software such as QQ or WeChat when communicating, because their communication prices are cheaper. Communication is more convenient.
It is also a platform for leisure and entertainment. We can listen to songs, watch movies, play games, and watch live broadcasts on it. Regardless of men, women, old or young, we can find the fun we want.
It is also a platform for resource sharing. Hardware resources can be shared. For example, a company can share printers, so that it can improve equipment utilization and avoid repeated investment in equipment. Software resource sharing and data resource sharing can also be realized to make full use of existing information resources to reduce labor in the software development process and avoid repeated construction of large databases.
It also provides us with a very good business platform. It provides us with a world-class super store where we can buy a variety of products without leaving home.
It can also be a platform for remote collaboration and online office.
Computer networks have changed our lives, our work, and every aspect of us, leaving us with no way to leave it.
Internet overview
A computer network is composed of several nodes and links connecting these nodes.
Computer network categories and switching methods
Computer network definition and classification
The precise definition of a computer network is not agreed upon!
- Computer networks are mainly interconnected by some general-purpose, programmable hardware that is not designed to achieve a specific purpose (for example, transmitting data or video signals). These programmable hardware can be used to transfer many different types of data and support a wide and growing number of applications.
- To put it more simply, a computer network is a collection of computer systems that use communication lines and communication equipment to connect multiple computers with the basic purpose of transmitting information.
- The simplest computer network has only two computers and a link connecting them, that is, two nodes and a link.
This definition of computer network sounds relatively abstract, so how should we understand its definition?
How do we understand the term "programmable hardware"?
That word means that this hardware must include a central processing unit (CPU).
So, we know the definition of computer network. There are many types of computer networks. We can divide them into different categories in different ways. There are two most common ways of dividing:
It is precisely because of the different coverage of these networks that the problems they face and the technologies they implement are very different. Take, for example, a wide area network. What is the most typical example of this network? It’s the Internet as we all know it! So in the Internet, it is a global communication network with a very wide scope. What is the biggest problem it faces in this network? Let's think about it. Suppose a computer in Beijing wants to communicate with a computer in Changsha. The biggest problem faced by the two computers during the communication process is how to find the communication line between the two computers. There are many communication lines and paths between computers, so we need to find which path between these two computers is the optimal and fastest. This is the biggest problem for the Internet.
Let's take a look at the LAN. The problems it faces in the LAN are very different from those in the WAN. Taking Ethernet, the most typical example of the LAN, as an example, let's take a look at the Ethernet. It is a shared network. In a network, all users are connected to a bus. For these users, the problem they face when communicating is not the problem of finding a path. Why? Because they only have one path to choose when sending, and there is no need to choose. Road, then, what is the problem it faces? When these users send messages, they should try their best to avoid sending messages at the same time as other users. If they send messages at the same time, it will cause conflicts in the messages and the sending will fail. Therefore, among LANs, the problem they face is how to share the transmission medium.
From these two examples, we can see that the different scopes of the network will lead to very different problems they face, so the technologies they implement are very different.
circuit switching
Routers are the key to packet switching! ! !
There is a word here - "exchange"
What is exchange? Why should switching technology be added to the communication network?
It is obvious that we will definitely not be satisfied with the point-to-point communication method in our daily life.
Obviously, the biggest problem with this connection method is that too many lines are used and the cost is too high. So I believe that most operators will not use this method to provide communication services to users.
Although the cost of this fully interconnected method is relatively high, it also has its own advantages. For example, in this connection method, there will be no busy line problem at all. Of course, when the number of telephones is very large and the users are very far apart, , our suppliers will definitely not use this method to provide communication services to users
So since the cost of this method is too high, how can we reduce the cost while providing connected services to users?
In this case, we have to use a switch to connect the telephones
Our next question is: How does the switch implement switching when it is working?
connection-oriented communication
packet switching
computer network protocol
If two computers want to communicate, can they communicate by just connecting a communication medium between the two computers? Obviously this is not possible. To achieve communication between the two parties, both parties must reach many agreements.
Okay, that’s it for today’s overview of Xiaoyalan’s computer network. Keep up the good work! ! ! Must pass the end of term! ! !
