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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

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DNS Message Processing and General Message Format
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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”.


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