Shulou(Shulou.com)06/01 Report--

This article mainly explains "what are the knowledge points of DNS protocol". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what are the knowledge points of DNS protocol".

DNS server

Everyone goes online, will visit the URL, will use DNS, so it is very important, but it is also a challenge to it. Because as long as it breaks down, the whole Internet will almost be paralyzed, because you can't access the URL.

In addition, Internet users are distributed all over the world, and if the DNS server is deployed in one place, the access time will be very long. In this way, the DNS server must be highly available, high concurrency and distributed to meet the demand.

Based on such requirements, there is a tree-like hierarchical structure.

DNS parsing process

DNS is needed for parsing all over the world, so in order to improve the parsing performance of DNS, many networks deploy DNS cache servers nearby, so how does it parse?

1. When you want to access www.google.com, your computer will send a DNS request asking what www.google.com is and send it to the local domain name server (local DNS). If it is configured through DHCP, then the local DNS is automatically allocated by your Internet service provider, such as Telecom, Mobile, etc.

2. After the local DNS receives the request from the client, it starts to look for it to see if it can find the www.google.com, and if it can, directly return the IP address corresponding to this URL. But if not, then it will ask a higher level. But its boss does not directly resolve the domain name, but gives a solution.

3, its boss found that the request is .com, that is to say that the URL is managed by the .com area, let me introduce it for you, you ask it.

4, the local DNS turned to the friend who was introduced by the boss and said, dude, can you tell me the IP address of www.google.com, but this guy is responsible for .com, you ask about google.com, it may not be here, and then reply, "I don't have it here, but I know who is in charge of google.com. Can you ask him?"

5. Next, the local DNS turned to the person in charge of google.com and asked, Hello, what is the corresponding IP address of www.google.com? My master wants to visit this website now.

6. After querying here, the responsible person tells the local DNS what the IP address of www.google.com is. At this time, the local DNS gets the IP address and returns it to the client, so that the client has established a connection with the target.

Load balancing

In the above introduction, it was a DNS recursive query process, and because the local DNS works exclusively for the client, all you have to do is sit and wait for the results. In fact, in addition to mapping names to IP addresses, DNS can also do another thing in this process, that is, load balancing.

What do you mean? For example, Ah Fan's favorite food is duck blood fans. Nanjing duck blood fans are super famous, but because of a business trip, I am currently in Beijing, so I can just find a restaurant in Beijing to eat. You are in Hangzhou. Then you can find a restaurant in Hangzhou. We don't have to go all the way to Nanjing to eat. This is load balancing (I seem to have exposed the nature of foodie.)

Project it onto DNS, and it can do the same.

DNS can do internal load balancing:

For example, if an application wants to access a database, we should configure it with the IP address of the data, but what should I do if the database goes down for some reason? You need to replace all the IP addresses that are used in this database.

If you use a domain name, it will be relatively simple. After this database goes down, no problem. I just need to map the domain name to a new IP address in the DNS server.

This process greatly reduces the cost of manpower and time.

DNS can be used for global load balancing:

Applications like Taobao, QQ and Wechat must be deployed in multiple computer rooms, each with its own IP address, in order to ensure high availability. When users want to buy something on Taobao, then this IP address can poll and visit multiple data centers. If a data center in Guangzhou dies for some reason, you just need to delete the IP address of the data center in the DNS server, and then you won't ask the data center again.

In addition, in order to make the customer experience better and the access speed faster, we must want users in Beijing to visit the data center in Beijing and users in Shanghai to visit the data center in Shanghai.

This is the concept of global load balancing.

Thank you for your reading, the above is the content of "what are the knowledge points of DNS protocol". After the study of this article, I believe you have a deeper understanding of what are the knowledge points of DNS protocol, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.