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Format of a DNS message

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The same format is used in the DNS for queries and responses (see figure 2).

Figure 2: Format of a DNS message


The individual sections of a DNS message have the following significance:

  • The header has a fixed length and contains metadata on the DNS message, including, among other things, the identification, the type of message (query or response) and the length of the following variable sections.

  • The Query section specifies the information to be found.

  • The Response section contains the found information in the form of a variable number of Resource Records.

  • The Authority section contains RRs with the names of other name servers in case the name server contacted earlier could not return a response.

  • The lowest section may include additional information in the form of RRs.