How does URL work?

Question

I have an URL that point to a specific page http://stackoverflow.com/questions/123. Assume that stackoverflow.com is 123.12.12.12. How does DNS map a specific URL to the specific page after identifying the IP?

score 4 · Answer 1 · answered Apr 23 '13 at 16:51

4

It doesn't. DNS just tells you what IP address to connect to. It's the web server's job to map the URL to the page.

answered Apr 23 '13 at 16:51

David Schwartz

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score 3 · Accepted Answer · answered Apr 23 '13 at 16:54

DNS does not map URLs to pages, it is used strictly to look up host/domain names. URLs map to pages through the routing integrated into the web server.

For example, the client computer has a URL and looks up the host name part in DNS, which returns the IP. The computer then connects to the IP on the protocol-specific port and sends the HTTP request over that connection. The server then internally processes the URL from the HTTP request and returns the appropriate content.

score 1 · Answer 3 · answered Apr 23 '13 at 16:59

The specific resource to access is given in the HTTP (in case of HTTP) request once you know the ip of the server.

Using the case in your example, a GET request would be something like this:

GET /questions/123 HTTP/1.1   <- Here you have the specific resource
Host: stackoverflow.com       <- Here you have the host

And the DNS transform the host stackoverflow.com to 123.12.12.12

How does URL work?

3 Answers3