Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide


NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

The whole site in one document for easy reference!
The TCP/IP Guide

Custom Search







Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  Name Systems and TCP/IP Name Registration and Name Resolution
           9  TCP/IP Name Systems: Host Tables and Domain Name System (DNS)
                9  TCP/IP Domain Name System (DNS)
                     9  DNS Name Servers and Name Resolution
                          9  DNS Resolution Concepts and Resolver Operations

Previous Topic/Section
DNS Resolver Functions and General Operation
Previous Page
Pages in Current Topic/Section
12
3
4
Next Page
DNS Name Resolution Efficiency Improvements: Caching and Local Resolution
Next Topic/Section

DNS Basic Name Resolution Techniques: Iterative and Recursive Resolution
(Page 3 of 4)

Recursive Resolution

When a client sends a recursive request to a name server, the server responds back with the answer if it has the information sought. If it doesn't, the server takes responsibility for finding the answer by becoming a client on behalf of the original client and sending new requests to other servers. The original client only sends one request, and eventually gets the information it wants (or an error message if it is not available). This technique is shown in Figure 244.


Figure 244: Recursive DNS Name Resolution

This is the same theoretical DNS resolution that I showed in Figure 243, but this time, the client asks for the name servers to perform recursive resolution and they agree to do so. As in the iterative case, the client sends its initial request to the root name server. That server doesn’t have the address of “C.B.A.”, but instead of merely returning to the client the address of the name server for “A.”, it sends a request to that server itself. That name server sends a request to the server for “B.A.”, which in turn sends a request to the server for “C.B.A.”. The address of “C.B.A.” is then carried back up the chain of requests, from the server of “C.B.A.” to that of “B.A.”, then “A.”, then the root, and then finally, back to the client.

 


Previous Topic/Section
DNS Resolver Functions and General Operation
Previous Page
Pages in Current Topic/Section
12
3
4
Next Page
DNS Name Resolution Efficiency Improvements: Caching and Local Resolution
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $



Home - Table Of Contents - Contact Us

The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005

© Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.