i believe that the terms "client" and "server" are inadequate to describe
the roles of the various protocol agents in DNS, and as in RFC 2136, i
suggest the terms "initiator" and "responder" instead. the the parts of
RFC 2181 which you've quoted here, "client" really means "initiator". the
DNS protocol specification must be understood in terms of messages --
their format and meaning. two messages make up a transaction, and each
transaction is initiated by some protocol agent and responded to by others.

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