On Jan 19, 2014, at 7:30 PM, houguanghua <houguang...@hotmail.com> wrote: > Would you please tell me which RFC depicts the policy of 'additional > section'? and how bind server deals with 'additional section'? > > Sometimes the number of 'additional section' is more than numbe of > 'authority section'. I don't know how local bind server will do when > receiving these additional sections. > Local Bind server may: > -- pick one name server randomly > -- or use sophisticated policies that "score" name servers and pick more > often the ones that replied faster > > Which is right?
The additional section is filled in by the responding name server with whatever records it feels would help the querier in the near future. This could be, for example, the addresses of name servers listed in NS records. It appears you’re asking about specifically this case. This behavior is described in RFC 1034 or 1035, I believe. As for responding to this data by following up on a referral and asking a listed name server, the BIND name server uses the RTT (round trip time) algorithm. Basically, it tries to guess which remote server would respond fastest and queries that server. Regards, Chris Buxton
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