Enter URL to return the entire process of the page

After a more comprehensive study of the computer network, we can talk about life often encountered a more classic problem, is to describe the input URL from the page to return the entire process.

1. We enter a domain name: www.baidu.com, then click Confirm;

2. The browser finds the IP address of the domain name. The lookup process is as follows:

First is the browser cache, the browser will cache DNS records for a period of time;

If the required records are not found in the browser cache, the browser makes a system call to get the records in the system cache;

Then is the router cache, the router generally will have its own cache;

If the former is not found, you need to start the DNS query from the local domain name server. Detailed DNS query procedures I talked about in how DNS works .

3. Now that the browser has found the IP address of the domain name, you need to establish a TCP connection to the Web server and then send the HTTP request. The TCP connection process I spoke about in TCP , the specific request process I spoke about in HTTP .

Well, let's combine DNS, TCP, and HTTP to say the whole process of entering a URL into a page return.

1. We enter a domain name:www.baidu.com

2. browser to find the browser cache, if there is a domain name of the IP address is returned, if not continue to find;

3. System Lookup System cache, if there is a domain name of the IP address is returned, if not continue to find;

4. The router looks for the router cache, if there is a domain name of the IP address is returned, if not continue to find;

5. The local domain name server uses the iterative query, it first queries to a root domain name server;

6. The ROOT name server tells The local domain name server, the next time should query the top-level name server dns.com IP address;

7. The local domain name server dns.com The top-level domain name server;

8. Top-level domain name server dns.com tells The local name server, the next time should be queried the right name server dns.baidu.com IP address;

9. The local domain name server dns.baidu.com to the right domain name server;

10. The domain name server dns.baidu.com tells The local name server, the queried host www.baidu.com IP address;

11. The local domain name server finally tells the host the query result;

12. After the host browser obtains the IP address of the Web server, establish a TCP connection with the server;

13. The client where the browser is located sends a connection request message to the server;

14. After receiving the message, the server agrees to establish a connection to send a confirmation message to the client;

15. After receiving the acknowledgement message, the client sends a message to the server to confirm that the acknowledgement message has been received;

16. The TCP connection between client and server is established, and communication is started;

17. The browser sends out the file command: GET;

18. The server gives a response, sends the specified file to the browser;

19. The browser releases the TCP connection;

20. The host of the browser sends a connection release message to the server and then stops sending the data;

21. The server receives the release message and sends out a confirmation message, then sends out the data that is not transmitted on the server;

22. After the server data transfer is complete, send the connection release message to the client;

23. After receiving the message, the client sends out a confirmation and then waits for a period of time to release the TCP connection;

24. The browser displays all the text on the page.

These are all the detailed procedures from the input URL to the page return.

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

Enter URL to return the entire process of the page