DNs query

[johnyb98]

Hi dear members.

Please, I would like your help in the following wonder. . .

 

Let's say a user (via his/her browser) wants to find a web server, in order to fetch a web page. Via DNS service, DNS queries take place.

Let's assume desirable server and its IP is server "a" in the following sequential domain path: a.b.c.d.e.com.

 

As far as I have read and understood, in every query step, the answer is given to first web server that made the first query. And afterwards, the same thing happens until server's "a" IP is got. The one thing that I do not understand is, why in every step, ip that is found, should be send back to first web server, and this specific server make the query again and again to find the next layer server IP, and not each layer server does not make just one query to the next layer server, and the final ip sends back  to the first query web server, and finally to the user.

 

Thank you for your time !

[BSpendlove]

You want to look more into the DNS process with how dns namespace and delegation works but take an easier example with something like a.mywebsite.com

 

Consider the scenario where your DNS server doesn't cache any dns queries and that your upstream DNS eg. Let's make it easier and say a windows 2019 server running DNS called DNS01 

 

Firstly, as you mentioned the user tries to query for A.MYWEBSITE1.COM, it tries to query its own dns server (eg. A router we setup to forward dns queries we can't resolve onto DNS01) 

 

DNS01 receives this request but doesn't have a clue where even mywebsite.com is. Let's back up a tiny bit, the com is typically referred to as a 'top-level' domain and isn't managed by typical DNS providers. Remember that our DNS needs to propagate to the top level root DNS servers around the world blah blah blah. 

 

DNS is not designed to work as a kind of daisy chain where you query the root server, that server queries eg. A com server, which then manages to find an entry for mywebsite and then return it to you. That is not how DNS is designed and it doesn't work this way. 

 

Dns is quick, lightweight and to this day, has no problem making multiple queries to a few different servers to finally get a specific reply to send back to the original client. From a DNS architecture point of view, I can't comment much but I could see that allowing the one single server to query eg. A root server, then a top level com server would be much easier to implement on an operating system level and from a sockets point of view within how the network stack is implemented in the operating system. 

 

When you take an example of a deeper subdomain like:

 

a.b.c.mywebsite.com

 

It doesn't work how you mentioned in regards to dns queries and what I mentioned above as a rough example. Normally a.b.c would exist as an A record and you wouldn't need to make like 4 queries. From a DNS server that needs to contact a top level server would just query the com server and be done with a single query.