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!

Read offline with no ads or diagram watermarks!
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 Header and Question Section Format
Previous Page
Pages in Current Topic/Section
12
3
45
Next Page
DNS Name Notation and Message Compression Technique
Next Topic/Section

DNS Message Resource Record Field Formats
(Page 3 of 5)

RData Field Formats For Common Resource Records

The RData field consists of one or more subfields that carry the actual “payload” for the resource record. Below is a list of the most common resource record types. For each I have indicated the resource record text code, name, and Type value, provided a brief summary of the resource record’s use, and shown the structure of the RData field in a table:

A / Address Resource Record (Type Value 1)

This is the primary resource record type in DNS; it contains a 32-bit IP address associated with a domain name, as shown in Table 172.


Table 172: DNS Address Resource Record Data Format

Subfield Name

Size (bytes)

Description

Address

4

Address: The 32-bit IP address corresponding to this record's named object.


NS / Name Server Resource Record (Type Value 2)

In this record, the data field carries the domain Carries the domain name of a name server (Table 173).


Table 173: DNS Name Server Resource Record Data Format

Subfield Name

Size (bytes)

Description

NSDName

Variable

Name Server Domain Name: A variable-length name of a name server that should be authoritative for this record's named object. Like all names, this name is encoded using standard DNS name notation.

A request for this resource record type normally results in an A record for the name server specified also being returned in the Additional section of the response, if available.


CName / Canonical Name Resource Record (Type Value 5)

The data field contains the real name of an a named object that has been referenced using an alias (Table 174).


Table 174: DNS Canonical Name Resource Record Data Format

Subfield Name

Size (bytes)

Description

CName

Variable

Canonical Name: The canonical (real) name of the named object. This name is then resolved using the standard DNS resolution procedure to get the address for the originally-specified name.


Previous Topic/Section
DNS Message Header and Question Section Format
Previous Page
Pages in Current Topic/Section
12
3
45
Next Page
DNS Name Notation and Message Compression Technique
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.