Shulou(Shulou.com)11/24 Report--

Have you seen the popular movie "wandering Earth 2" recently?

One of the most thrilling clips is "restarting the Internet".

In the film "restart the Internet", it restarts the Internet root servers in China, Japan and the United States, restoring the global Internet and ensuring the successful connection of thousands of planetary engines scattered around the world.

Even the editor of 5G surfing has a lot of questions when he sees the paragraph "restart the Internet" and "root server".

Passionate second brush finally understood, here the editor answers questions for everyone.

What is the root server? In reality, the full name of the root server is the root domain name server (root name server), which is mainly used to manage the home directory of the Internet and provide top-level domain name resolution services.

If the global Internet is a super-large library, then the root server is the query system that manages the books of the whole library. Through the root server, we can quickly find the novel "wandering the Earth" in the vast sea of books.

At present, there are 13 IPv4 root servers in the world, one is the primary root server in the United States, and the other 12 are secondary root servers, of which 9 are in the United States and 3 are in the United Kingdom, Sweden and Japan.

Every day, the list of primary root servers is replicated to 12 secondary root servers distributed around the world.

Tips

Usually we understand that the server is a host, but in fact, these 13 root servers refer to the IP addresses of 13 root servers. When we visit a root server, we do not access a specific host, but multiple servers with the same IP address and synchronized updates are distributed around the world.

By consulting the information about the setting of the world outlook in the film, the root server in the movie does not refer to the root domain name server alone, but a collection of root domain name server function and backbone router function.

How does the root server work? How does the query system of this huge "library" work?

The vast sea of books, how to quickly find a "wandering Earth"?

Let's start with the Domain name system (DNS,Domain Name System). When computers communicate on the network, they can only recognize IP addresses (for example: 123.123.123.123). There are about 4.3 billion IPv4 addresses in the world. We certainly can't remember so many IP addresses.

So we associate the hard-to-remember IP address to a set of meaningful and easy-to-remember characters, which are called domain names.

We use a database to manage the correspondence between domain names and IP addresses, which is the Domain name system (DNS).

When we surf the Internet, DNS automatically "translates" our domain name into the corresponding IP address. The translation process between domain name and IP address is called domain name resolution. For more information on DNS, please mark "what is DNS?" ".

DNS has a multi-level structure, which is divided as follows:

Domain name DNS

Server description root domain name

The top layer of the server domain name system.

When a lower-level DNS server is unable to resolve a domain name, look down from the root domain server layer by layer, and you will be able to find the corresponding IP address. Top-level domain

The server is managed by the Internet Domain name and address Authority (ICANN), the type of name used by a country or organization. For example:

Domain name DNS

Server description root domain root domain name

The top layer of the server domain name system.

When a lower-level DNS server is unable to resolve a domain name, look down from the root domain server layer by layer, and you will be able to find the corresponding IP address. Top-level domain

The server is managed by the Internet Domain name and address Authority (ICANN), the type of name used by a country or organization.

For example:

National top-level domain name: .uk: UK. JP: Japan. CN: China. International top-level domain name: .com: enterprise, .edu: educational institution .gov: government agency .mil: military department .net: network operation service .org: non-profit organization second-level domain authority domain name

The domain name under the server's top-level domain name. Under the international top-level domain name, indicates the online name of the domain name registrant, such as .zte, .163. Under the national top-level domain name, a symbol that represents the category of registered enterprises, such as .com, .edu, .gov, .net. Subdomain name

(third-level domain and superior domain) / belongs to the secondary domain. It does not need to be registered through the organization that manages the domain name and can be used to represent the services provided by the secondary domain administrator. .www: ordinary website.mail: mailbox. After reading these professional terms, is it still a little confused?

The editor should use the library to "lift the chestnut".

The root domain server manages the Chinese area, English area and other areas of the library.

The top-level domain server manages the sci-fi area, history area and other areas in the Chinese area.

The authoritative domain name server manages all the books on the shelves in the fantasy area of the department.

When I connect to the Internet with my computer, the Internet Service provider (ISP,Internet Service Provider) assigns the IP address of a local domain name DNS server to my computer.

This DNS server does not belong to the above structure, but can forward my DNS requests to the hierarchy described above.

When I browse the web, my computer will first send a DNS request to the local domain name server. if the target IP address is not found, the local domain name server will ask the root domain server to iteratively query the target IP address.

For example, I'm going to borrow a copy of wandering the Earth in the library.

If I had ever borrowed it, I would have known where the book was in the library. I went to the library to find it and read it happily.

If I haven't borrowed it, I don't know where the book is. After arriving at the library, I can find the location of the → "wandering Earth" in the science fiction area of → in turn through the query system in the library, and finally read it happily.

Is there a root server in our country? At this point, smart friends may have questions: as mentioned earlier, there are 13 root servers in the world, and the only primary root server is in the United States.

However, there are three root servers in the movie and they are distributed in China, Japan and the United States, which can't be compared with reality.

Don't worry, let me talk about it in detail.

Internet communication is inseparable from the IP protocol. At present, the widely used IP protocol is IPv4. As an address with a length of 32bit, the editor calculates that IPv4 can have up to 4.3 billion different addresses.

There seems to be a lot of IPv4 addresses, but in fact, they have been used up as early as 2019. In order to solve the problem of the number of network address resources, IPv6, the next generation IP protocol to replace IPv4, is being implemented.

The snowman project, a global next generation Internet (IPv6) root server test and operation pilot project based on the new technology architecture, was officially launched on June 23, 2015.

The "Snowman Project" is led by China's next Generation Internet Engineering Center. On November 28, 2017, on the basis of full compatibility with the existing IPv4 root server architecture, 25 IPv6 root servers have been installed worldwide. The distribution of IPv6 root servers is shown in the table below.

National main root server auxiliary root server China 13 Japan 10 India 03 France 03 Germany 02 Russia 01 Italy 01 Spain 01 Austria 01 Chile 01 South Africa 01 Australia 01 Switzerland 01 Netherlands 01 coincidentally, according to the "snowman project", three IPv6 main root servers are set up in China, the United States, Japan, what a science fiction movie!

So "wandering Earth 2" is currently a science fiction film, in the next few decades, the global IPv6 network popularity, IPv6 root server testing and operation experiments have been successfully completed, we will find that "wandering Earth 2" is actually a documentary, hee hee ~!

What exactly does "restart the Internet" mean to restart? According to the settings in the film, restarting the Internet should be a restart of similar network data center hubs, but in reality the Internet is distributed and decentralized.

In order to achieve network interconnection between the two places, there are many transit schemes that can be implemented (for example, from Beijing to Guangzhou, you can not only connect directly, but also transfer from Wuhan or Chengdu).

If a device in the backbone network breaks down and only affects the local network, it will not affect the entire Internet in the film.

And the root server only provides domain name resolution service, which is a part of the Internet, not the entire Internet as set in the movie. The location of DNS in the GPRS network is shown in the following figure.

So in reality, there can be "restart the root server" but not "restart the Internet".

Hit the point! In reality, the root server refers to the root domain name server.

The DNS server is like a phone book for end users. It is convenient to record contact information and can surf the Internet without a root server.

There are currently 13 IPv4 root servers around the world, of which one IPv4 primary root server is in the United States.

In the future, there will be 25 IPv6 root servers around the world, of which 3 IPv6 main root servers are in China, the United States and Japan.

Well, a little question about wandering Earth 2, the editor has figured it out.

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc)

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