Networking Technology and Applications Knowledge Points Summary Book

Network Technology Applications Review Points

The three elements of a network protocol are syntax, semantics, and rules (timing)

Network protocols (Protocols) are a special kind of software that is the most basic mechanism by which a computer network achieves its functions. The essence of network protocols is rules, i.e., common codes that various hardware and software must follow. Network protocols are not a separate set of software, it is integrated in all other software systems, so it can be said that the protocol in the network ubiquitous. Network protocols throughout the various levels of the OSI communication model, from the very familiar TCP / IP, HTTP, FTP protocols, to OSPF, IGP and other protocols, there are thousands of them. For ordinary users, they do not need to care too much about the underlying communication protocols, but only need to understand their communication principles. In actual management, the underlying communication protocols generally work automatically without human intervention. But for protocols above the third layer, manual intervention is often required, such as the TCP/IP protocol requires manual configuration for it to work properly.

The three protocols commonly used in LANs are TCP/IP, NetBEUI, and IPX/SPX. TCP/IP is undoubtedly the most important of these three protocols, and as the foundation of the Internet, it is impossible to connect to the Internet without it, and any operation related to the Internet is inseparable from TCP/IP. However, TCP/IP is also one of the most troublesome of the three protocols to configure, as it is fine for stand-alone Internet access, but when accessing the Internet through a LAN, you need to set up IP addresses, gateways, subnet masks, DNS servers, and other parameters in detail.

TCP/IP protocol family includes hundreds of interrelated protocols, different functions of the protocol is distributed in different protocol layers, a few commonly used protocols are as follows:

1, Telnet (RemoteLogin): Provides a remote login function, a computer user can log in to a remote computer, such as in the remote host to operate directly.

2.

2, FTP (FileTransferProtocol): remote file transfer protocol, allowing users to copy files from a remote host to their own computers.

3, SMTP (SimpleMailtransferProtocol): Simple Mail Transfer Protocol, used to transfer e-mail.

4, NFS (NetworkFileServer): network file server that allows multiple computers to transparently access each other’s directories.

5, UDP (UserDatagramProtocol): user data packet protocol, it and TCP as located in the transport layer, and the IP protocol used in conjunction with the transmission of data in the transmission of packet header is omitted, but it can not provide packet retransmission, so suitable for the transmission of shorter files.

Introduction to the HTTP protocol

HTTP is an object-oriented protocol belonging to the application layer and is suitable for distributed hypermedia information systems because of its simplicity and speed. It was proposed in 1990 and has been continuously improved and extended through several years of use and development. The sixth version of HTTP/1.0 is currently used in the WWW, the normalization of HTTP/1.1 is in progress, and the proposal of HTTP-NG (NextGenerationofHTTP) has been put forward.

The main features of the HTTP protocol can be summarized as follows:

1. Support for client/server model.

2. Simple and fast: when a client requests a service from a server, only the request method and path are transmitted. Commonly used request methods are GET, HEAD, and POST. each method specifies a different type of client-server contact.

Because of the simplicity of the HTTP protocol, it makes the HTTP server’s program small in size, and thus the communication is fast.

3. Flexibility: HTTP allows the transmission of any type of data object. The type being transmitted is labeled by Content-Type.

4. Connectionless: Connectionless means limiting the processing of only one request per connection. After the server has processed the client’s request and received the client’s answer, it disconnects. Using this method saves transmission time.

5. Stateless: The HTTP protocol is stateless. Stateless means that the protocol has no memory capability for transaction processing. The lack of state means that if the previous information is needed for subsequent processing, it must be retransmitted, which may lead to an increase in the amount of data transmitted per connection. On the other hand, the server responds faster when it does not need previous information.

Computer Network Knowledge

The computer network course is characterized by the combination of computer technology and communication technology, and teachers engaged in teaching computer network courses should have a background in computer network construction, management and research. Here is some relevant information I have compiled about the introductory knowledge of computer networks for your reference.

Computer network knowledge

First, the foundation of computer networks

The understanding and definition of the concept of “computer network”, with the development of the computer network itself, people put forward a variety of different points of view.

Early computer systems were highly centralized, with all the equipment installed in separate large rooms, then batch and time-sharing systems appeared, and multiple terminals connected to the time-sharing system had to be immediately adjacent to the main computer.

In the mid-to-late 1950s, many systems connected geographically dispersed terminals to a central computer via communication lines, which led to the emergence of the first generation of computer networks. .

The first generation of computer networks were remote on-line systems centered on a single computer. A typical application was an airplane ticketing system consisting of a single computer and more than 2,000 terminals throughout the United States.

Terminal: one computer with external devices including a CRT controller and keyboard, no GPU memory.

With the increase in the number of remote terminals, in front of the host machine to increase the front-end machine FEP At that time, people defined the computer network as “the purpose of transmitting information and connected to realize the remote information processing or a step closer to achieving the resource sharing system”, but such a communication system has the prototype of communication.

The second generation of computer networks is to interconnect multiple hosts through communication lines to provide services to users, emerged in the late 1960s, typically represented by the U.S. Department of Defense Advanced Research Projects Agency to assist in the development of ARPAnet.

Hosts are not directly connected to the line, but the interface message processor IMP after the transfer of the interconnection. The IMP, along with the communication lines that are interconnected between them, is responsible for the communication tasks between the hosts and constitutes the communication subnet. The hosts interconnected by the communication subnet are responsible for running programs and providing resource sharing, forming a resource subnet.

When communicating between two hosts, the understanding of the content of the transmitted message, the form of the message representation, and the answer signals in various cases must comply with a common agreement, called a protocol.

In an ARPA network, the protocols are divided into layers by function, and the sum of how they are layered and the specific protocols used in each layer is called the network architecture, which is an abstract concept whose concrete implementation is accomplished by specific hardware and software.

The second generation of networks developed rapidly from the 1970s to the mid-1980s.

The second generation of networks centered on communication subnets. In this period, the concept of network is “a collection of computers with independent functions interconnected for the purpose of being able to share resources with each other”, which formed the basic concept of computer networks.

The third generation of computer networks is an open and standardized network with a unified network architecture and following international standards.

IS0 promulgated 0SI/RM in 1984, which is divided into seven levels, also known as the 0SI seven-layer model, recognized as the basis for a new generation of computer network architecture. It laid the foundation for the popularization of LANs. (^60090922a^1)

After the 1970s, due to the emergence of large-scale integrated circuits, local area networks (LANs) were widely used and developed rapidly due to their low investment, convenience and flexibility. Compared with wide area networks (WANs), they have commonalities, such as layered architecture, and different characteristics, such as LANs that do not use store-and-forward for cost savings, but are connected by a single broadcast channel to the The first is that it is a single broadcast channel that connects computers on the network.

The fourth generation of computer networks began in the late 1980s, the development of LAN technology has matured, the emergence of fiber optic and high-speed network technology, multimedia, intelligent networks, the entire network is like a large computer system transparent to the user, the development of the Internet as the representative of the Internet.

Computer network: multiple computer systems with the ability to work independently through the communication equipment and lines by a well-functioning network software to achieve resource sharing and data communication system.

From the definition of the three aspects involved:

(1) at least two computers interconnected.

(2) Communication equipment and line media.

(3) Network software, communication protocols and NOS

Second, the classification of computer networks

There are many standards used to categorize computer networks, such as topology, application protocols and so on. But these standards can only reflect the characteristics of a certain aspect of the network, the most reflective of the essential characteristics of the network technology classification criteria is the distribution distance, according to the distribution distance is divided into LAN, MAN, WAN, Internet.

1. Local Area Networks (LANs)

A few meters – 10 kilometers. Small machines, microcomputers developed after a large number of promotion, easy to configure, high rate, 4Mbps ~ 2GbpS. Located in a building or a unit, there is no pathfinding problem, does not include the network layer.

2. Metropolitan Network

10 kilometers – 100 kilometers. LAN interconnection to a city, using the IEEE802.6 standard, 50Kbps ~ l00Kbps, located in a city.

3. Wide Area Network

Also known as remote network, hundreds of kilometers – thousands of kilometers. Earlier development, leased lines, through the IMP and lines connected to form a mesh structure, to solve the problem of path, the rate of 9.6Kbps ~ 45Mbps such as: Ministry of Posts and Telecommunications of the CHINANET, CHINAPAC, and CHINADDN network.

4. The Internet

is not a specific network technology, it is a high-level technology that unifies different physical network technologies according to a certain protocol.

Third, the characteristics of the local area network

LAN distribution range is small, less investment, simple configuration, etc., has the following characteristics:

(1) high transmission rate: generally 1Mbps – 20Mbps, fiber-optic high-speed network up to 100Mbps, 1000MbpS

(2) support for a wide variety of transmission media.

(3) Communication processing is generally done by the network card.

(4) Good transmission quality and low BER.

(5) There is a regular topology.

Fourth, the composition of the LAN

LAN is generally composed of four parts: servers, workstations, network cards and transmission media.

1. Server

Runs the network 0S, provides hard disk, file data and printer sharing and other service functions, is the core of the network control.

From the application of the higher configuration of the ordinary 486 or more compatible machines can be used for file servers, but from the overall performance of the network to improve the system stability, especially from the network, it is appropriate to choose a dedicated server.

At present, the common NOS main Netware, Unix and WindowsNT three.

(1) Netware:

Popular version V3.12, V4.11, V5.0, low hardware requirements, the application environment is similar to that of DOS, the technology is perfect, reliable, support a variety of workstations and protocols, suitable for LAN operating systems, as a file server, print server performance.

(2) Unix:

A typical 32-bit multi-user NOS, mainly used in super-compact machines, mainframes, the current commonly used version of UnixSUR4.0. Support for network file system services, to provide data and other applications, powerful, not easy to master, the command is complex, launched by AT& T and SCO.

(3) WindowsNTServer4.0:

A complete platform system for distributed graphical applications, the interface is similar to Win95, easy to install and manage, and integrated Internet network management tools, a bright future.

The server is divided into file servers, print servers, database servers, and on the Internet, there are Web, FTP, E-mail and other servers.

Network 0S toward the direction of supporting a variety of communication protocols, a variety of network cards and workstations.

2. Workstation

Can have their own 0S, independent work; through the operation of the workstation network software, access to Server shared resources, common DOS workstations, Windows95 workstations.

3. NIC

The workstation servers connected to the network to achieve resource sharing and mutual communication, data conversion and electrical signal matching.

Network card (NTC) classification:

(1) Rate: 10Mbps, 100Mbps

(2) Bus type: ISA/PCI

(3) Transmission media interfaces:

Single-port: BNC (thin cable) or RJ-45 (twisted pair). (^60090922b^2)

4. Transmission Media

Currently the commonly used transmission media are twisted pair, coaxial cable, optical fiber and so on.

(1) Twisted Pair (TP):

More than one pair of twisted pair of wires encapsulated in an insulating jacket, in order to reduce interference, each pair of twisted each other and become. Divided into unshielded twisted pair (UTP) and shielded twisted pair (STP). LAN UTP is divided into four categories: Category 3, Category 4, Category 5 and Super Category 5.

Take AMP as an example:

Category 3: 10Mbps, thin skin, “cat3” on the skin, “category 3” on the box, 305 meters / box, 400 yuan / box.

Category 4: not much used in the network.

Category 5: (Super Category 5) 100Mbps, 10Mbps, thick skin, turns dense, the skin on the note “cat5”, the box on the note category 5, 305 meters / box, 600-700 yuan / box (each section of 100 meters, connected to four repeaters, the maximum 500 meters).

Wiring order:

Normal: White Orange Orange White Green Blue White Blue Green White Brown Brown

(corresponds to)12345678

Collective Union: White Green White Orange Orange Brown White Brown Orange White Blue Blue

(corresponds to)12345678

STP: The same internal and UTP, the outsourcing of aluminum foil, Apple, IBM Network products require the use of STP twisted pair, high rate, expensive.

(2) coaxial cable:

consists of a hollow outer cylindrical conductor and an inner conductor located in the center axis of the composition of the two conductors separated by insulating material.

According to the diameter is divided into thick cable and thin cable.

Coarse cable: long transmission distance, high performance but high cost, used in large LAN trunks, the connection needs to be terminated at both ends.

A. Coarse cable is connected to external transceiver.

B. The transceiver is connected to the NIC with an AUI cable.

C. The NIC must have an AUI interface: 500 meters per segment, 100 users, up to 2500 meters for 4 repeaters, 2.5 meters minimum between transceivers, 50 meters maximum for transceiver cables.

Fine cable: short transmission distance, relatively inexpensive, with a T-type header, connected to the BNC card, both ends of the An 50-ohm terminating resistor.

185 meters per section, 4 repeaters, maximum 925 meters, 30 users per section, minimum 0.5 meters between T-heads. According to the transmission band is divided into baseband and broadband transmission.

Baseband: digital signal, the signal accounts for the entire channel, the same time can transmit a signal.

Wideband: transmitted ‘is a different frequency of the signal.

(3) optical fiber:

Application of optical principles, the light transmitter generates a light beam, the electrical signal into an optical signal, and then the optical signal into the optical fiber, at the other end of the optical receiver by the optical receiver to receive optical signals coming from the optical fiber, and change it into an electrical signal, after decoding and then processed. Divided into single-mode fiber and multi-mode fiber. Insulation confidentiality is good.

Single-mode fiber: the laser as a light source, only a light path, long transmission distance, more than 2 km.

Multimode fiber: light-emitting diode, low-speed short distance, within 2 km.

V. Several modes of operation of the LAN

1. Dedicated server structure (Server-Baseb)

Also known as the “workstation/file server” structure, consisting of a number of microcomputer workstations connected to one or more file servers through the communication lines. The workstations access the server files and share the storage device.

File servers naturally share disk files as their main purpose. It is sufficient for general data transfer, but when database systems and other complex and being used by an ever-increasing number of users of the arrival of applications, the server can no longer take on such a task, because with the increase in the number of users, the number of programs serving each user also increases, each program is a large file running independently of each other, giving the user the feeling of extreme slowness, and thus gave rise to the client/server model.

2. client/server mode (client/server)

One or more of the larger computers centralized shared database management and access, known as the server, and other application processing work is dispersed to other microcomputers in the network to go to do, constituting a distributed processing system, the server to control the management of the data by the ability to manage the file management mode up to the database management mode, therefore, the server to control the management of data from the file management mode to the database management mode, so that the user feels extremely slow. The ability of the server to control and manage data has risen from file management to database management, therefore, C/S by the server is also known as the database server, focusing on data definition and access security backup and restore, concurrency control and transaction management, such as selective retrieval and indexing sorting and other database management functions, which has sufficient capacity to do through its processing of the part of the data that the user needs instead of the entire file transmitted to the client through the network to reduce the transmission load on the network. C/S structure is the result of the development and widespread application of database technology combined with the development of LAN technology.

3. Peer-to-Peer network

In the topology with a dedicated Server and C/S is the same. In the peer-to-peer network structure, there is no dedicated server each workstation can play both the role of the client and the server.

Computer Networking Knowledge (Exploring Technology and Applications in the Internet Age)

In the age of the Internet, computer networking knowledge has become an indispensable part of people’s lives. For most people, computer networks have become an essential tool in their daily work and life. So, in this era of information technology, how should we learn and master computer network knowledge?

Ways to learn computer network knowledge

1. Understand computer basics

Before learning computer network knowledge, we need to understand computer basics. For example, the composition of the computer, the installation and use of the operating system, disk partitioning, file management and so on. These basics are the foundation of our knowledge of computer networks.

2. Learning network basics

Network basics include network protocols, IP addresses, subnet masks, gateways, DNS, and so on. Learning this knowledge allows us to better understand how the network works and lays the foundation for learning more in-depth network knowledge.

3. Learning about network security

Network security is a very important part of learning about computer networks. Learning about network security can help us better protect our computers and personal information. For example, learning how to set up a firewall, how to protect against viruses and Trojans, and so on.

Methods of mastering computer network knowledge

1. Practical operation

Learning computer network knowledge needs practical operation, only through practice, can better master the knowledge. For example, to learn how to set up a router, you can try to do it yourself.

2. Participate in training courses

Participating in professional training courses can help us learn and master computer networking knowledge faster. Through the training program, we can learn more in-depth, more practical knowledge.

3. Participate in network technology exchange meeting

Participating in network technology exchange meeting can let us know the latest network technology and application. In the conference, we can exchange experience and skills with other network technology enthusiasts, so as to better master the computer network knowledge.

How can ordinary people catch the wind of AI?

On November 30, 2022, OpenAI released an AI conversation product chatGPT. after only two months, registered users exceeded 100 million, becoming the fastest growing application in human history, the number of people using. Subsequently, Google, Baidu, Ali and other major global technology companies, have also released or previewed their own AI models. the rapid development of AI technology, AI era just quietly came ~

Now, most people know that the birth of AI, but most people are not ready, but also limited to exchange a chat to chat on the end of the day, so the real embrace of AI, or seize the wind mouth of the people are indeed very few and far between. It can also be said that the vast majority of ordinary people to seize the opportunity of this wind mouth is too difficult to see how the netizen said:

But the current situation is that you do not learn can not do, or else will be eliminated in the near future. Without further ado, on today’s topic, let’s talk about what ordinary people should do to catch the wind in the AI wave; why ordinary people should learn AI:

First start from the basics, as an ordinary person needs to first understand the field that AI will be involved in, which includes mathematics, computers, physics, psychology, philosophy and many other aspects. You can learn the basics in a variety of ways, such as: by attending online or offline AI courses, reading relevant books, joining online courses, videos and many other ways to learn.

By learning the basics of AI, we can better understand the principles and applications of AI, and better grasp the development trend and business opportunities of AI. Therefore, as a general population, you need to master the basic concepts, principles, methods and applications of AI, as well as related programming languages and tools of these basics.AI involves a wide range of technical areas, you can also target the areas in which in-depth study, proficiency in the corresponding technology, which is a prerequisite for learning AI. These skills are highly sought after in today’s market, and those who have mastered them are likely to be better able to capitalize on the windfall that is AI.

We should also pay attention to the latest AI news in general. As ordinary people, people can make themselves more knowledgeable about AI by understanding the cutting-edge technology and application areas of AI. The way to understand the media, platforms, forums and other channels, you can also pay attention to some well-known AI companies and organizations, these are good ways.

Finally you can try to create your own AI products or services, for example, you can develop an AI voice assistant, develop an AI smart home product, develop an AI medical product, and so on. It will also make you more confident.

Take a chestnut:

Developing a robot customer service: you can use AI technology to develop an intelligent customer service chatbot, which can be used to automatically answer users’ questions. Then, cooperate with a number of enterprises to provide intelligent customer service for enterprises, charging a certain consulting fee. Such a robot customer service can serve multiple industries such as e-commerce platforms and online education.

Truthfully ~ blah blah blah is easy to say, but it is indeed very, very difficult to do, as far as the basics are concerned, it will take more than a year for the average person to get started, right? So, in the whole learning process, need to have enough enthusiasm, enough courage and interest and enough ability and so on as a backing, only then may walk into the AI industry, only then there may be wind to catch.

Yes, sometimes we need to force ourselves a hand, because artificial intelligence has become the inevitable trend of today’s development, only mastered the relevant technology, you can make better use of the tools to enhance the strength to realize the value of, and, at present, many of China’s companies are trying to use the AI technology, so want to seize the wind, the most important thing is still to rely on their own continuous efforts and fight.

Just as the famous economist Dr. Ren Zeping mentioned:

“China’s economy depends on technology, and China’s technology depends on AI. “This is the assertion made by Dr. Ren Zeping, a famous economist, in his speech titled “AI Acceleration for China’s Economy” delivered at the 2022 Vientiane – Baidu Mobile Ecological Conference.

Dr. Ren Zeping shared in his speech the importance of new infrastructure for China’s new economic engine. He predicted that AI technology in the era of New Infrastructure 2.0 will be the most favorable hand to realize the new infrastructure “to use up”, and suggested that enterprises and individuals highly grasp the dividends of the times brought by AI technology, and predicted that Baidu APP will become the new AI infrastructure available to everyone, through the “Baidu set the stage, and everyone sings the play” mode, which will stimulate the development of the AI industry. “The Baidu APP will become the new AI infrastructure available to everyone.

Ren Zeping mentioned in his speech that there is no way out if you can’t catch the wind of AI at the moment, just like you couldn’t catch the trend of the Internet 20 years ago.

So even if you are an ordinary person, you want to adapt to the trend and keep pace with the development of society should learn AI, no matter how many years, no matter how difficult the road is, you have to learn it, otherwise you will be eliminated.

While everyone is saying that 2023 will be a year of recession, don’t forget that in every recession, there are emerging industries. So, AI is the next revolutionary windfall, and the fact that some companies are already laying off workers is, I think, no coincidence or alarmist talk.

According to relevant information, in the last year, the whole year, the major U.S. technology companies laid off about 150,000 people, but in the first month of this year, they have already laid off about 60,000 more. Bank of America has warned that the U.S. economy is expected to lose an average of 175,000 jobs a month starting in the first quarter of 2023.

So don’t believe me just yet, AI has now infiltrated every industry. For example, in the medical field, AI technology is utilized to help doctors make diagnoses. In the financial field, the use of AI technology to predict market trends, the retail industry can also use AI technology to optimize sales strategy, these application scenarios are the direction of the development of AI technology.

That is to say, in the future, the application scenarios of AI will be more extensive. See here, you still want to say, I do not learn?

Said so much, let’s go into detail about the basic knowledge points that ordinary people need to master to learn AI:

There are a lot of basic knowledge to be learned, doing AI development involves Python programming knowledge, Linux knowledge, the visual aspect of image processing, OpenCV, etc., and at the same time, we also need to have a certain mathematical foundation.

Specifically:

1, basic mathematical knowledge: linear algebra, probability theory, statistics, graph theory;

2, basic computer knowledge: operating system, linux, network, compilation principle, data structure, database;

3, programming language basics: C/C++, Python, Java;

4 Artificial Intelligence basics: ID3, C4.5, logistic regression, SVM, classifiers and other algorithms such as characteristics, properties and other algorithms compared to the difference between the content;

5, tools basics: opencv, matlab, caffe and so on.

In short, I would say that if you want to catch the wave, be prepared to meet the challenge, because artificial intelligence will become more and more complex, and the development speed will be very fast. So, it’s better to be well prepared mentally, go for it~