RFC 883                                                    November 1983
                         Domain Names - Implementation and Specification


   The contents of standard queries and responses

      When a name server processes a standard query, it first determines
      whether it is an authority for the domain name specified in the
      query.

      If the name server is an authority, it returns either:

         1. the specified resource information

         2. an indication that the specified name does not exist

         3. an indication that the requested resource information does
            not exist

      If the name server is not an authority for the specified name, it
      returns whatever relevant resource information it has along with
      resource records that the requesting resolver can use to locate an
      authoritative name server.

   Standard query and response example

      The overall structure of a query for retrieving information for
      Internet mail for domain F.ISI.ARPA is shown below:

                          +-----------------------------------------+
            Header        |          OPCODE=QUERY, ID=2304          |
                          +-----------------------------------------+
           Question       |QTYPE=MAILA, QCLASS=IN, QNAME=F.ISI.ARPA |
                          +-----------------------------------------+
            Answer        |                                  |
                          +-----------------------------------------+
           Authority      |                                  |
                          +-----------------------------------------+
          Additional      |                                  |
                          +-----------------------------------------+

      The header includes an opcode field that specifies that this
      datagram is a query, and an ID field that will be used to
      associate replies with the original query.  (Some additional
      header fields have been omitted for clarity.)  The question
      section specifies that the type of the query is for mail agent
      information, that only ARPA Internet information is to be
      considered, and that the domain name of interest is F.ISI.ARPA.
      The remaining sections are empty, and would not use any octets in
      a real query.






 

RFC 883                                                    November 1983
                         Domain Names - Implementation and Specification


      One possible response to this query might be:

                          +-----------------------------------------+
            Header        |        OPCODE=RESPONSE, ID=2304         |
                          +-----------------------------------------+
           Question       |QTYPE=MAILA, QCLASS=IN, QNAME=F.ISI.ARPA |
                          +-----------------------------------------+
            Answer        |                                  |
                          +-----------------------------------------+