Internet development, access and information services

I. What is Internet

Internet, once translated as "International Internet", "International Network", etc., and now we call it "Internet".

Internet was once translated as "International Internet", "International Network", etc. Now we call it "Internet", which is the backbone of the United States ANSNET, the backbone of other countries and regions through the access to the Internet backbone and connected to the Internet, thus constituting a global interconnection of the Internet. Internet is to connect various WANs and LANs existing in different parts of the world to form a huge interconnected network across national boundaries. It is not actually "a" network, but will be thousands of different types of networks connected, so there is a "computer network of the network" called.

Two, the emergence and development of the Internet

1. Internet prototype - the birth of ARPAnet

Internet, the history of mankind such a great project, in fact, was born at what time, the various sectors of the argument is different, the more popular is to say that it was born in the first half of the year, the Internet was born in the first half of the year, the Internet was born in the second half of the year. The popular saying is that it was born on October 29, 1969, to ARPA (Advanced Research Project Agency, the U.S. Department of Defense Advanced Research Projects Agency) funded the completion of the ARPAnet on the UCLA (University of California, Los Angeles) the first node and SRI (Stanford Research Institute) the second node of the connection, the realization of packet The first node of UCLA (University of California, Los Angeles) was connected to the second node of SRI (Stanford Research Institute) on the ARPAnet funded by the Department of Defense, and the realization of packet-switching technology for long-distance communication marked the official birth of the network. Initially only four computers distributed in four universities to access, by 1972, the number of points on the ARPAnet network has reached more than 40.

In the mid-1970s to early 1980s, with the development of ARPAnet, the TCP/IP protocol was successfully designed to solve the interconnection of heterogeneous networks. By 1983 ARPAnet was broken down into ARPAnet (civilian network) and MIL NET (military network). This separated the public portion of ARPAnet from its military portion, and as of January 1 of the same year, the NCP protocol was fully terminated in ARPAnet, and all networks participating in ARPAnet switched to the TCP/IP protocol. The Internet at that time was defined as a TCP/IP protocol-based network connected to ARPAnet.

2. Formation of NSFNET

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

3. The Formation of the U.S. Domestic Internet

Before 1990, the NSF network was mainly used for education and research. With the creation and development of the WWW, computer networks rapidly evolved into the financial and commercial sectors, and the U.S. government was no longer able to provide large sums of money to fund the Internet backbone.

In 1990, ARPAnet stopped operating at the same time, by IBM, MCI, MERIT three companies formed ANS (advanced network and services) company, built a faster ANSnet backbone, and gradually replaced the NSFNET (April 30, 1995, NSFNET) to become the current backbone. officially announced its discontinuation on April 30, 1995) as the current Internet backbone.

4. Globalization of the Internet

In 1995, ANSnet was turned into a private company, and the year was called the Year of the Internet.

Because of the openness of the Internet and its strong information resource **** enjoyment and exchange ability, it has attracted a lot of users from the day of its formation. At present, according to incomplete statistics, 214 countries and regions around the world are connected to the Internet, and by the end of 2005, there were more than 1 billion online users worldwide.

5. Development of Internet in China

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

The first stage (1987-1993) is to connect with Internet e-mail

On September 14, 1987, Professor Qian Tianbai sent China's first e-mail "Internet". On September 14, 1987, Prof. Qian Tianbai sent China's first e-mail, "Across the Great Wall we can reach every corner in the world." This was the prelude to the use of the Internet by Chinese people.

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

The second phase (1994 to the present) and the Internet's full-featured TCP/IP connection

April 1994, the Chinese Academy of Sciences Computer Network Information Center, through the 64 Kbps international private line connected to the United States, the opening of the router, marking China's official full-featured to join the Internet. since the beginning of April 1994, China's formal entry into the Since the beginning of April 1994, China's formal accession to the Internet, becoming the 71st member of the unit, the rapid growth of users into the network, according to the China Internet Network Information Center CNNIC published online survey, as of December 31, 2006, China's access to the Internet has reached 137 million users.

China has built a domestic Internet, currently built ten network backbone. Among them, there are four non-profit units: China Science and Technology Network, China Education and Research Computer Network, China International Economic and Trade Internet and the Great Wall of China Internet. These ten major Internet units have independent international exports, and their total international export bandwidth has reached 256,696 M. The countries connected are the United States, Russia, France, Britain, Germany, Japan, Korea, Singapore, etc., of which the international export bandwidths of each backbone (the following data are derived from the online survey released by CNNIC) are shown in Table 6-2.

Three, the Internet's working mode and characteristics

Internet is like a cargo center, when the Internet transmits data or information, it will first be loaded into the goods in the container list (TCP protocol), and then break them down, and loaded into each packet of a single strip (IP protocol). After the decomposition of the goods through the first "junction" is the router, its role is to check these single article, to determine the correctness of these packets to take a different road. After the road they are based on a single (IP protocol) recorded on the name and address of the recipient, to the recipient's address. When all the packets are sent, in accordance with the container single (TCP protocol), they are reorganized into the original model, the document transmission is completed. If a part of it is lost in transmission, it will resend that part of the data according to the TCP protocol, which ensures the security of the data.Internet is coordinated by the TCP/IP protocol, high-speed and effective work.

Table 6-2 International Outlet Bandwidth of China's Major Network Backbones

Note: The "bandwidth" in the table refers to the speed of network transmission, which is usually measured in "bits per second" (bps), i.e., how many binary bits per second? How many binary bits per second; e.g. 56Kbps means 56 kilobits per second. The term "Bps" (Byte percent second) usually refers to the number of bytes per second.

The operation of the Internet has the following characteristics:

(1) It adopts the most popular client-server model in the distributed network, and the users can make requests through the client program installed on their own hosts and communicate with the hosts equipped with the corresponding server program to obtain the required information. The user can use various information services on the Internet by sending requests through the client program installed on the host and communicating with the host equipped with the corresponding server program to obtain the required information. Each host can choose to run different client and server programs according to its own conditions and needs. Any host with a server program can provide information services to other hosts; any host with a client program can obtain information services provided by other hosts.

(2) The TCP/IP protocol, or Transmission Control Protocol/Internet Protocol, is used.

(3) Flexible and diversified ways to enter the network, which is an important reason for the rapid development of the Internet, any computer as long as the use of TCP/IP protocol to communicate with any host in the Internet can become part of the Internet.

(4) the network technology, multimedia technology and hypertext technology into one, reflecting the contemporary development trend of the integration of various information technologies.

(5) Low charges, the development of the Internet benefits from the government's strong support for information networks. Nowadays, the Internet is unofficial, managed and operated entirely by private organizations.

(6) There are extremely rich information resources, and most of them are free.

Four, Internet access

Internet is an open system, any computer to access the Internet, as long as a way to connect to the Internet has been connected to a host can access the resources on the Internet.

1. Internet access

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

Figure 6-4 Dial-in access

In the telephone dial-in access to the Internet method, it can be divided into the emulated terminal method and SLIP/PPP method.

①Emulation terminal method: This method connects the user's computer to a modem, and through the public switched telephone network (PSTN), the user logs on to the service system through telephone dial-up to realize the connection with the Internet. In the user's computer needs to support a serial communication emulation terminal software, when the communication, their own computer as a remote terminal of the Internet host. End users do not have an IP address, the current domestic Internet access has been rarely used in this way.

② SLIP/PPP method: this way to use the telephone dial-up Internet access, Internet access is simple, Internet access costs are low, but the speed is slow, suitable for transferring small amounts of information to the user. At present, most of the domestic users from dial-up Internet access to broadband Internet access, broadband Internet access has become the most important way to access the Internet.

When using this way of accessing the Internet, it is through the communication protocol software to the user's computer's serial port (Serial port) emulation into a network communication card, so that the user's computer can communicate directly with other host systems on the Internet.

Serial line internet protocol SLIP (Serial line internet protocol) and point-to-point protocol PPP (Point-topoint) are basically the same in terms of functionality. SLIP is the original method developed for TCP/IP communication over serial telephone lines; PPP was developed from SLIP. The choice depends on which method the user's ISP (Internet access provider) can offer, but for individual users, domestic ISPs offer the PPP method more often.

In the SLIP/PPP method, there are two types of IP address assignments for incoming users, static and dynamic, and most SLIP connections have static IP addresses. For PPP connections, a dynamic IP address can be assigned to the user by the remote host system while dialing up, until you disconnect from the Internet, the host recovers the IP resources, and reassigns one to you the next time you dial up. To access the Internet in this way, you need to apply in advance to the ISP of the organization that provides access to the IP address (if you use dynamic allocation, you don't need to apply for it), user name and password, etc., and you have to enter the correct user name and password when connecting in order to connect successfully.

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

Generally applicable to LAN access, LAN computer users can enter the Internet through this dedicated line, this way to access the Internet faster, but also more expensive. The more popular private line access methods are the following two:

①DDDN private line access: DDN is a fiber-optic digital circuit, the speed from 128 Kbps to 2 Mbps, suitable for a large number of data transmission enterprises (such as banks, securities companies, etc.) to use. The speed is fast, the performance is stable, and the price is also expensive, mainly for group enterprises.

Figure 6-5 leased line access

② fiber access: this way the transmission rate can now reach 100 Mbps ~ 1000 Mbps, and has a high degree of reliability, low loss, to ensure unimpeded communications.

(3) broadband access Currently, broadband Internet access has become the most important way of accessing the Internet, according to CNNIC's survey, nearly two-thirds of the users use broadband access. Broadband access can be divided into the following three types:

①ADSL leased line access: ADSL technology, namely, asymmetric digital subscriber line, is the use of a pair of telephone copper lines, providing users with upstream and downstream asymmetric transmission rate, the upper act of low-speed transmission, upstream transmission of up to 1.5 Mbps, downstream transmission of up to 8 Mbps, but there is a restriction on the use of the region, the client must be in the bureau end of the 3 km The client must be within 3 kilometers of the bureau. At present, most cities in China have opened ADSL, gradually replacing the telephone dial-up Internet access, becoming the preferred way of users to access the Internet.

② HFC leased line connection: this is currently the most competitive with ADSL a broadband access, the price is comparable to ADSL, it is the use of Cable modem technology, is based on a fiber optic - coaxial hybrid network (HFC) on the basis of a technology that does not affect the cable broadcasting band to achieve access to the Internet and access to the band, downlink transmission up to 10 Mbps, downlink transmission up to 10 Mbps. The downlink transmission can reach 10 Mbps to 36 Mbps, and the uplink can reach more than 512 Kbps. At present, China's major cities have built HFC network.

③Cell Broadband (FTTx+LAN): the switch and terminal switch in the district to fiber optic connection, the use of fiber optic cable + twisted pair of the way to the district for the integrated wiring, the user's theoretical Internet access rate of up to 10/100 Mbps. This access is characterized by its high reliability, stability, billing flexibility, etc., is the current speed and quality of Internet access for home users is more satisfactory an Internet access. The Internet is a way to access the Internet.

Fifth, the Internet's information services

1. E-mail E-mail (Electronic mail)

E-mail is one of the most important services of the Internet. According to relevant information, e-mail E-mail usage is the highest, is the Internet provides users with a fast, simple and economical method of communication and information exchange, without paper, you can write letters, send letters, read letters, back to the letter, forwarding letters. It can also transmit multimedia information such as video, image and sound, subscribe to various electronic magazines and participate in academic discussions.

2. Telnet

Telnet is the earliest and most basic service function of the Internet. It is through the Internet to log on to another host on the network, share the resources and services provided by the host, when the user's computer as the terminal of the remote computer.

For example, using a mainframe computer on the Internet to process massive amounts of user data by remote login.

3. File Transfer FTP

On the Internet there are many valuable information, data, public free software, etc., allowing users to copy without charge, file transfer FTP service allows users to copy files from one computer to another. It differs from e-mail in that e-mail is particularly useful for the transfer of brief messages and is generally limited to communication between two people.

For example, FTP is used to download the latest driver software, freeware, and upload web pages.

4. World Wide Web (World Wide Web)

The World Wide Web (WWW) is currently the most popular and favorite information browsing service on the Internet. It is a hypertext (Hyper Text) based information query tool, the user through the WWW browser "WYSIWYG" interface, easy and intuitive query and access to information distributed around the world thousands of WWW servers. In addition to browsing hypertext information, you can also browse multimedia information.

The WWW is a service that appeared in the early 1990s, and its appearance is considered to be an important milestone on the Internet, and it has played a huge role in promoting the development of the Internet.

5. Newsgroup Usenet (also known as Newsgroup)

Newsgroups are international forums that utilize the Internet to conduct topical discussions, and so far Usenet is still the largest network newsgroup. Users can receive and read the information sent to the newsgroup server, they can also publish their own opinions to the newsgroup server. In domestic colleges and universities, research institutes and abroad, there are a large number of users using newsgroups to discuss issues.

6. Electronic bulletin board BBS (Bulletin board system)

Electronic bulletin boards are also one of the more commonly used services on the Internet, is another service similar to newsgroups. Users can use BBS services to chat with Internet users, organize salons, get help, discuss problems and provide services for others. There are a large number of user groups in China who utilize BBS to discuss problems. In China, not many people use the Internet, BBS has cultivated a large number of Internet users for China. Typical BBS sites are Tsinghua University's "Shuimu Qinghua Station", Shanghai Jiaotong University's "Drinking Water Siyuan Station" and so on.

7. Other Services

In addition to the above, the Internet has many other services, such as Gopher services, Archie services, Finger services, WAIS services, online paging, online speculation, Internet telephony (IP telephony), online games, video-on-demand (VOD), Internet TV, e-commerce (online shopping, online auctions, etc.), online shopping, e-commerce, e-commerce, e-commerce, e-commerce, e-commerce, e-commerce, and so on. online shopping, online auction, etc.), online chat, online medical care, distance education (such as online school), etc.

Six, Internet network address

Any computer accessing the Internet has a unique network address. In the process of using the Internet, usually encounter IP addresses, domain name addresses. Before figuring out IP addresses and domain addresses, it is important to understand physical addresses.

1. Physical Addresses

Each host in a network has a recognizable, real physical address, usually an unchangeable address code made on the network card by the card's manufacturer. The format of the NIC address encoding varies due to different network technologies and standards; for example, Ethernet NICs use 48-bit binary number encoding for the NIC physical address.

2. IP address

If the physical address is used directly as the Internet unified address, it is inconvenient to manage and difficult to communicate across networks; therefore, the Internet adopts the method of "unified" physical address by the network layer (IP layer) through the upper layer software, and the IP protocol provides a network-wide unified address format. The IP protocol provides a uniform address format for the entire network, and address allocation under unified management ensures that an address corresponds to a host on the Internet, and that this address is unique across the Internet.

IP addresses have a hierarchical structure that logically consists of two parts, a network identifier (Netid) and a host identifier (Hostid). Each IP address consists of a 32-bit binary number (4 bytes), in order to facilitate the user to understand and remember, using a method called "point decimal" marking, that is, 4 bytes of binary values converted to four decimal values, each value is less than 255, the value of the middle of the "-" separated. " in between the values. For example:

Binary IP address: 11011110 10110010 10110100 00011000

Dot decimal representation: 222.178.180.24

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

Table 6-3 Class A, B, C IP address space

3. Domain Name Address

Because the IP address is just a string of numbers, there is no meaning, it is very difficult for the user to memorize, just like in daily life, rarely use the ID card number to identify a person, and it is more convenient to use the name. Therefore, the Internet introduced the domain name service system DNS (Domain Name System), which is responsible for converting domain name addresses to IP addresses, and hosts on the Internet can only recognize IP addresses.

The Domain Name System uses a hierarchical and unified management, which is a tree directory structure. The format of a domain name address is as follows:

Host name. Name of the organization to which the host belongs. Network name. Top-level domain name

The domain name can also have fewer or more than four parts.

Top-level domain names are hardwired by international standards, and the division is done in two modes, organizational and geographic, with the first seven domains corresponding to the organizational mode, which consists of three letters, and the rest of the domains corresponding to the geographic mode, where such domains represent countries or regions, and consist of two letters. As shown in Table 6-4.

Table 6-4 Top-Level Domain Codes and Meaning

In order to strengthen the management of domain names and alleviate the tension of domain name resources, ICANN, the highest governing body of domain names in the world, has made a resolution in November 2001 to add seven new top-level domains (com, net, org, edu, gov, .mil, int) in addition to the traditional seven top-level domains. top-level domains. The seven new TLDs are: .biz, .info, .name, .pro, .aero, .coop, and .museum, the first four of which are non-restricted domains, and the last three of which are restricted domains, e.g., .aero needs to be registered by a company in the aviation industry, .museum needs to be registered by a museum, and .coop needs to be registered by a collective enterprise (non-investor-controlled, not required to maximize profits). profit maximization) registration. The uses of the first four are as follows:

.biz - a top-level domain name used as a replacement for .com for commercial companies; (note: biz is the customary abbreviation for business);

.info - a top-level domain name used as a replacement for .com for commercial companies; (note: biz is the customary abbreviation for business);

.info - a top-level domain name used as a replacement for .com for commercial companies. - a top-level domain used to replace .com, for businesses that provide information services;

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

.pro - a top-level domain dedicated to top-level domains for professionals such as doctors, lawyers, accountants, etc. (Note: pro is an abbreviation for professional)

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

The name of the unit to which the host belongs generally indicates the domain or unit to which it belongs. For example: tsinghua means Tsinghua University, pku means Peking University, sina means Sina.com Inc. and swnu means Southwest Normal University.

The following is an example of a domain name compared with an IP address:

The domain name of China Education and Research Network is www.edu.cn, while the IP address is 202.112.0.36, which is class C. The domain name is www.edu.cn, and the IP address is 202.112.0.36.

The domain name of Peking University is www.pku.edu.cn, while the IP address is 162.105.129.12, which is in category B.

Tsinghua University's domain address is www.tsinghua.edu.cn and its IP address is 166.111.4.100, which is in Class B.

The domain address of Michigan State University is www.msu.edu, with an IP address of 35.9.2.152, which is in Class A.

Formally, a host's domain name looks a lot like an IP address; an IP address uses three periods to separate four decimal numbers, whereas a domain address is represented as a string separated by a few periods, but there is no relationship between each part of the domain name and each part of the IP address.