RFC 2065:Domain Name System Security Extensions
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header bit


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... security non-aware. Two additional query header bits are defined for signaling between resolvers and servers. ...


... If header bits are falsely set by a server, there is little that can be done. However, it is possible to add transaction authentication ...


... The AD and CD Header Bits ...


... RRs, (5) recognize the CD query header bit and set the AD query ...
... AD query header bit, as appropriate, and (6) proper handling of the two NXT RRs ...
... CD query header bit on its queries. ...



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