Connected: An Internet Encyclopedia
4.3.1. Queries and responses

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4.3.1. Queries and responses

4.3.1. Queries and responses

The principal activity of name servers is to answer standard queries. Both the query and its response are carried in a standard message format which is described in [RFC-1035]. The query contains a QTYPE, QCLASS, and QNAME, which describe the types and classes of desired information and the name of interest.

The way that the name server answers the query depends upon whether it is operating in recursive mode or not:

Recursive service is helpful in several situations:

Non-recursive service is appropriate if the requester is capable of pursuing referrals and interested in information which will aid future requests.

The use of recursive mode is limited to cases where both the client and the name server agree to its use. The agreement is negotiated through the use of two bits in query and response messages:

The recursive mode occurs when a query with RD set arrives at a server which is willing to provide recursive service; the client can verify that recursive mode was used by checking that both RA and RD are set in the reply. Note that the name server should never perform recursive service unless asked via RD, since this interferes with trouble shooting of name servers and their databases.

If recursive service is requested and available, the recursive response to a query will be one of the following:

If recursive service is not requested or is not available, the non- recursive response will be one of the following:


Next: 4.3.2. Algorithm

Connected: An Internet Encyclopedia
4.3.1. Queries and responses