Development, Access and Information Service of Internet

Internet, once translated as Internet, is now called Internet. It is based on ANSNET in the United States, and the backbones of other countries and regions are connected with the Internet by accessing the Internet backbone, thus forming a global Internet. Internet is to connect all kinds of existing wide area networks and local area networks around the world to form a huge Internet that crosses national boundaries. It is not actually a network, but connects thousands of different types of networks, so it is called "the network of computer networks".

Second, the emergence and development of the Internet.

1. The embryonic form of the Internet-the birth of ARPANET

Internet, such a great project in human history, has different opinions on when it was born. The popular view is that it was born on 1969129 October, with the first node of ARPA (Advanced Research Projects Agency) and UCLA (University of California, Los Angeles) connected with the second node of SRI (Stanford Research Institute) on ARPAnet to realize long-distance communication of packet switching technology as a symbol of its formal birth. At first, only four computers distributed in four universities were connected to the Internet. To 1972, there are more than 40 points on the ARPANET.

From the mid-1970s to the early 1980s, with the development of ARPAnet, TCP/IP protocol was successfully designed, which solved the interconnection of heterogeneous networks. To 1983, ARPAnet is divided into ARPAnet (civil network) and MIL NET (military network). This separates the public part from the military part of ARPAnet. Starting from June 65438+ 10/in the same year, in ARPAnet, the NCP protocol was completely terminated, and all the networks participating in ARPAnet turned to TCP/IP protocol. At that time, the Internet was defined as a network connected to ARPAnet based on TCP/IP protocol.

The formation of 2.2. NSFNET

1985, the National Science Foundation (NSF for short) first connected five supercomputing centers in the United States with communication trunk lines. 1986, NSFNET backbone network was built, which gradually became the largest TCP/IP network in the United States, thus replacing ARPAnet as the backbone network of the Internet.

3. The formation of the domestic Internet in the United States

Before 1990, NSF network was mainly used for education and scientific research. With the emergence and development of WWW, computer networks have developed rapidly in the financial and commercial fields, and the US government has been unable to provide huge funds to support the Internet backbone.

At the same time that ARPAnet stopped running on 1990, three companies, IBM, MCI and MERIT, formed an ANS (Advanced Network and Service) company, built a faster ANSnet backbone network, and gradually replaced NSFNET (officially stopped running on1April 30, 995) as the current Internet backbone network.

4. Globalization. internet

From 65438 to 0995, ANSnet was transformed into a private company, which was called the Year of the Internet.

Because of the openness of the Internet and its powerful ability to share and exchange information resources, it has attracted many users since its formation. At present, according to incomplete statistics, 2 14 countries and regions in the world have access to the internet, and by the end of 2005, the number of people online in the world has exceeded 65,438 billion.

The development of 5.5. Internet in China

The development of Internet in China has roughly gone through the following two stages:

The first stage (1987-1993) is to connect to the internet by e-mail.

On September 4th, 1987, Professor Qian sent China's first e-mail, "Crossing the Great Wall, we can reach every corner of the world", which opened the curtain for China people to use the Internet.

Since then, Tsinghua University, Institute of High Energy Physics of Chinese Academy of Sciences and other units have successively realized the interconnection between e-mail and the Internet.

The second stage (1994 up to now) is a fully functional TCP/IP connection with the Internet.

1In April, 1994, computer network information center connected to the United States through a 64 Kbps international private line, and opened a router, marking the official full-featured access of China to the Internet. Since China officially joined the Internet in early April 1994 and became a member of 7 1, the number of Internet users has increased rapidly. According to the online survey published by CNNIC of China Internet Network Information Center, by the end of June 2006, the number of Internet users in China had reached1370,000.

China has built a domestic Internet, and there are currently ten network backbones. Among them, there are four non-profit organizations: cstnet, China Education and Research Computer Network, China International Economic and Trade Internet and China Great Wall Internet. These ten Internet companies all have independent international exports, with a total international export bandwidth of 256,696, and connected countries include the United States, Russia, France, Britain, Germany, Japan, South Korea and Singapore. The international export bandwidth of each backbone network (the following data comes from the online survey released by CNNIC) is shown in Table 6-2.

Third, the working mode and characteristics of the Internet

The Internet is like a freight center. When the internet transmits data or information, it will first load the container list (TCP protocol) into the goods, then decompose it, and then load a single sheet (IP protocol) into each package. The first "intersection" that the decomposed goods pass through is the router, whose function is to check these items and make sure that they are correct before letting these packages take different paths. On the way, they sent it to the recipient's address according to the name and address (IP protocol) recorded on the list. When all the packets are sent, they are reassembled according to the container list (TCP protocol) and the file transfer is completed. If part of it is lost in transmission, it will retransmit that part of the data according to TCP protocol, thus ensuring the security of the data. Internet works at high speed and high efficiency under the coordination of TCP/IP protocol.

Table 6-2 International Export Bandwidth of Main Backbone Networks in China

Note: "Bandwidth" in the table refers to the speed of network transmission, usually in units of "bps" (bit percentage seconds), that is, how many binary bits per second; For example, 56Kbps means 56 kilobits per second. And "bps" (percentage of bytes per second) usually refers to how many bytes per second.

The operation of the Internet has the following characteristics:

(1) adopts the most popular client-server mode in distributed networks. When users use various information services on the Internet, they can make requests through client programs installed on their own hosts and communicate with hosts with corresponding server programs to obtain the required information. Each host can choose to run different client programs and server programs according to its own conditions and needs. All hosts with server programs can provide information services to other hosts; All hosts installed with client programs can obtain information services provided by other hosts.

(2) Adopt TCP/IP protocol, that is, transmission control protocol/Internet protocol.

(3) Flexible and diverse access methods, which is an important reason for the rapid development of the Internet. As long as the TCP/IP protocol is used to communicate with any host in the Internet, any computer can become a part of the Internet.

(4) The integration of network technology, multimedia technology and hypertext technology reflects the development trend of the integration of various contemporary information technologies.

(5) The fees are low, and the development of the Internet benefits from the government's strong support for the information network. The current Internet is unofficial, and it is completely managed and operated by non-governmental organizations.

(6) Rich information resources, most of which are free.

Fourth, Internet access.

Internet is an open system. Any computer that wants to access the Internet can access the resources on the Internet by connecting a host that has been connected to the Internet in some way.

1. Internet access mode

(1) The main process of dial-up access is shown in Figure 6-4.

Figure 6-4 Dial-in Network

In the way of telephone dial-up, it can be divided into analog terminal mode and SLIP/PPP mode.

① Analog terminal mode: This mode connects the user's computer to the modem, and connects with the Internet through the public switched telephone network PSTN telephone dial-up login service system. A simulation terminal software supporting serial communication is needed on the user computer. When communicating, his computer acts as a remote terminal of the Internet host. End users don't have an IP address, so this method is rarely used in China.

②SLIP/PPP mode: This mode uses telephone dial-up to access the Internet, which is simple, low in Internet access cost, but slow, and suitable for users with less information transmission. At present, most users in China have switched from dial-up Internet access to broadband Internet access, and broadband Internet access has become the most important way to access the Internet. However, nearly one-third of users still use this dialing method to access the Internet.

When surfing the Internet in this way, the serial port of the user's computer is simulated as a network communication card through communication protocol software, so that the user's computer can directly communicate with other host systems on the Internet.

SLIP (Serial Line Internet Protocol) and PPP (Point-to-Point Transmission Protocol) are basically the same in function. Slip is the most original method developed for TCP/IP communication on serial telephone lines. PPP is developed from SLIP. Which method to choose depends on which method the user's ISP (Internet Access Provider) can provide, but for individual users, domestic ISPs provide more PPP methods.

In the SLIP/PPP mode, there are two types of IP address allocation for network users: static and dynamic, and most SLIP connections have static IP addresses. For PPP connection, the remote host system can assign a dynamic IP address to the user when dialing in, until you disconnect from the Internet, the host recovers IP resources, and reassign one for you when you dial in next time. To access the Internet in this way, you need to apply for IP address (if dynamic allocation is adopted, you don't need to apply), user name and password in advance, and you must enter the correct user name and password to connect successfully.

(2) The main process of private line access is shown in Figure 6-5.

Generally suitable for LAN access. Computer users in the local area network can surf the Internet through this dedicated line, which is faster but more expensive. There are two popular methods of private line access:

(1) DDN private line access: DDN is a kind of optical fiber digital circuit with a speed from 128 Kbps to 2 Mbps, which is suitable for enterprises with large data transmission (such as banks and securities companies). Fast speed, stable performance and high price, mainly for group enterprises.

Figure 6-5 Special Line Access

② Optical fiber access: At present, the transmission rate of this mode can reach1000 Mbps ~1000 Mbps, with high reliability, low loss and smooth communication.

(3) Broadband Access At present, broadband access has become the most important way to access the Internet. According to CNNIC, nearly two-thirds of users use broadband access. Broadband access methods can be divided into the following three types:

(1) ADSL private line access: ADSL technology, namely asymmetric digital subscriber line, provides users with asymmetric uplink and downlink transmission rates by using a pair of telephone copper wires. Uplink transmission can reach 1.5 Mbps, and downlink transmission can reach 8 Mbps. However, the use area is limited, and the client must be within 3 kilometers of the local office. At present, ADSL has been opened in most cities in China, gradually replacing telephone dial-up Internet access and becoming the first choice for users to access the Internet.

(2) HFC private line connection: This is the most competitive broadband access with ADSL at present, and the price is equivalent to ADSL. It is a Cable modem technology based on cable TV network, and it is a HFC technology, which can access and access the Internet in the frequency band without affecting cable TV broadcasting. Downlink transmission can reach 5 12 Kbps to 36 Mbps, and uplink transmission can reach 565438. At present, HFC networks have been built in major cities in China.

(3) residential broadband (FTTx+LAN): The switches and terminal switches in the cell are connected by optical fiber, and the cell is integrated with optical fiber and twisted pair. The theoretical internet access rate of users can reach 10/ 100 Mbps. This access mode has the characteristics of high reliability, good stability and flexible charging. It is an ideal way for home users to surf the Internet at present.

Verb (abbreviation for verb) Information service on the Internet.

1. Email (email)

E-mail is one of the most important services on the Internet. According to relevant data, the usage rate of e-mail is the highest, and it is a fast, simple and economical way of communication and information exchange provided by the Internet. You can write, send, read, reply and forward letters without paper. You can also transmit multimedia information such as videos, images and sounds, subscribe to various electronic magazines and participate in academic discussions.

2. Remote login Telnet

Remote login is the earliest and most basic service function of the Internet. It logs on to another host on the network through the Internet and shares the resources and services provided by the host. At this time, the user computer acts as the terminal of the remote computer.

For example, a large computer on the Internet can handle massive data of users through remote login.

3. File transfer FTP

There are many valuable information, materials and public free software on the Internet, allowing users to copy them for free. The FTP service for file transfer allows users to copy files from one computer to another. It is different from email. E-mail is particularly useful for the delivery of short messages, which is generally limited to the communication between two people.

For example, download the latest driver software, free software, and upload web pages with FTP.

4. Global Information Network

World Wide Web WWW is the most popular and popular information browsing service on the Internet. It is an information query tool based on hypertext. Users can conveniently and intuitively query and obtain the information of thousands of WWW servers distributed around the world through the "what you see is what you get" interface of WWW browser. Besides browsing hypertext information, you can also browse multimedia information.

WWW is a service that appeared in the early 1990s. Its appearance is regarded as an important milestone on the Internet, which has greatly promoted the development of the Internet.

5. Newsgroups Newsgroups (also known as newsgroups)

Newsgroup is an international forum for special discussion using the Internet. So far, newsgroup is still the largest online newsgroup. Users can receive and read information sent by others to the newsgroup server, and also express their opinions to the newsgroup server. In domestic universities, research institutes and abroad, a large number of users use newsgroups to discuss problems.

6.BBS (bulletin board system)

Bulletin board system is also one of the common service functions on the Internet, and it is another service similar to newsgroups. Users can use BBS service to chat with netizens, organize salons, get help, discuss problems and provide services for others. A large number of users in China use BBS to discuss issues. Before many people use the Internet, BBS has trained a large number of netizens for our country. Typical BBS sites include "Shui Mu Station in Tsinghua" in Tsinghua University and "Siyuan Drinking Water Station" in Shanghai Jiaotong University.

7. Other services

In addition to the above services, there are many other services on the Internet, such as Gopher service, Archie service, Finger service, WAIS service, online paging, online stock trading, Internet phone (IP phone), online games, video on demand (VOD), Internet TV, e-commerce (online shopping, online auction) and so on. ), online chat, online medical care, distance education (.

Intransitive verb internet network address

Any computer connected to the Internet has a unique network address. In the process of using the Internet, you usually encounter IP addresses and domain names. Know the physical address first, then know the IP address and domain name address.

1. physical address

Each host in the network has an identifiable real physical address, which is usually an unchangeable address code made by the network card manufacturer on the network card. Due to different network technologies and standards, the format of network card address coding is also different. For example, an Ethernet card uses a 48-bit binary number code as the physical address of the network card.

2. Internet address of the Internet.

If the physical address is directly used as the unified address of the Internet, it will be inconvenient to manage and difficult to communicate across networks. Therefore, the Internet adopts the method that the network layer (IP layer) "unifies" the physical address through the upper software. IP protocol provides a unified address format for the whole network, and assigns addresses under unified management to ensure that an address corresponds to a host on the Internet, and this address is unique in the whole Internet.

IP address adopts hierarchical structure and logically consists of two parts, namely network identification (Netid) and host identification (Hostid). Each IP address consists of a 32-bit binary number (4 bytes). In order to make it easier for users to understand and remember, a notation called "dotted decimal system" is adopted, that is, the binary value of 4 bytes is converted into 4 decimal values, each value is less than 255, and the values are separated by ".". For example:

Binary IP address:1101111101.

Expressed in dotted decimal system: 222.438+078.38+080.24.

Each IP address is divided into five categories: A, B, C, D and E according to the size and application of the network where the node computer is located. The first three categories are commonly used, and the rest are reserved for backup and testing. Table 6-3 lists the types and sizes of IP addresses.

Table 6-3 A, B and C IP address spaces

3. Domain name address

Because the IP address is just a string of numbers and has no meaning, it is difficult for users to remember. Just like in daily life, it is more convenient to identify a person with a first name. Therefore, the Internet introduced the domain name service system DNS (Domain Name System), which is responsible for converting domain names into IP addresses. Hosts on the Internet can only recognize IP addresses.

Domain name system adopts hierarchical unified management and is a tree directory structure. The format of domain name address is as follows:

Host name, company name, network name and top-level domain name of the host.

A domain name can also be less than or more than four parts.

Top-level domain names are rigidly stipulated by international standards and are divided into two modes: organizational mode and regional mode. The first seven fields correspond to the organization mode and consist of three letters. The remaining domains correspond to geographical patterns. These domain names represent countries or regions and consist of two letters. As shown in Table 6-4.

Table 6-4 Top-level Domain Code and Its Significance

In order to strengthen domain name management and alleviate the shortage of domain name resources, ICANN, the global top-level domain name management organization, made a resolution in 2006 10, and established the domain name management system in the traditional seven (com, net, org, edu, gov,. mil, int). Add seven top-level domains:. Business. Information, Name,. Dear, Aviation. coop，。 Museums. Among them, the first four are unrestricted domains and the last three are restricted domains. For example, Aero needs to be registered as an airline. Museums need to be registered as museums. Coop needs to be registered as a collective enterprise (not controlled by investors and not maximizing profits). The first four usages are as follows:

. Biz- the top-level domain name used for replacement. Com, suitable for commercial companies; (note: biz is the abbreviation of business);

. Info- the top-level domain name used for substitution. Com, which is suitable for enterprises providing information services;

. Name-a top-level domain name dedicated to individuals;

. Pro- a top-level domain name dedicated to doctors, lawyers, accountants and other professionals. (Note: pro is the abbreviation of professional)

The network name is a second-level domain name, which indicates the type of the host unit and also represents the administrative region of China. If it represents an administrative region, it consists of two letters. For example: bj (Beijing), cq (Chongqing), sh (Shanghai), ha (Henan) and so on.

The name of the company to which the host belongs generally indicates the domain or company to which it belongs. For example, Tsinghua represents Tsinghua University, Peking University represents Peking University, Sina represents Sina.com, and Southwest Normal University represents Southwest Normal University.

The following is an example of domain name and IP address comparison:

The domain name address of China Education and Research Network is www.edu.cn, and the IP address is 202. 1 12.0.36, which belongs to Class C.

The domain name address of Peking University is www.pku.edu.cn, and the IP address is162.105.129.12, which belongs to Class B.

Tsinghua University's domain name address is www.tsinghua.edu.cn, and its IP address is166.11.4.100, which belongs to Class B.

The domain name address of the University of Michigan is www.msu.edu, and the IP address is 35.9.2. 152, which belongs to Class A. ..

Formally, a host's domain name is much like an IP address, separated by three periods and four decimal digits, while the domain name address is represented by a string separated by several periods, but each part of the domain name has nothing to do with each part of the IP address.