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!

Searchable, convenient, complete TCP/IP information.
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 Messaging and Message, Resource Record and Master File Formats

Previous Topic/Section
DNS Message Processing and General Message Format
Previous Page
Pages in Current Topic/Section
1
2
Next Page
 DNS Message Resource Record Field Formats
Next Topic/Section

DNS Message Header and Question Section Format
(Page 2 of 2)

DNS Question Section Format

DNS queries always contain at least one entry in the Question section that specifies what the client in the exchange is trying to find out. These entries are copied to the response message unchanged, for reference on the part of the client if needed. Table 170 and Figure 249 show the format used for each entry in the Question section of a DNS message.


Figure 249: DNS Message Question Section Format

 


Table 170: DNS Message Question Section Format

Field Name

Size (bytes)

Description

QName

Variable

Question Name: Contains the object, domain or zone name that is the subject of the query, encoded using standard DNS name notation.

QType

2

 

QClass

2

Question Class: Specifies the class of the resource record being requested, normally the value 1 for Internet (“IN”). See the topic on classes and resource record types for an explanation. In addition, the QClass value 255 is defined to have the special meaning “any class”.

Previous Topic/Section
DNS Message Processing and General Message Format
Previous Page
Pages in Current Topic/Section
1
2
Next Page
 DNS Message Resource Record Field Formats
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.