D. J. Bernstein <djb@cr.yp.to> schrieb/wrote: > A moment ago we were being told how vitally important it was for AXFR > clients to preserve all records received under all circumstances: > * ``An ACURATE [sic] copy of the zone is ESSENTIAL''; > * ``A modified zone is NOT a [sic] ACURATE [sic] copy. It's not > even a copy. It is a derived work''; Well, djb raises an intersting question here: Is that really necessary? Or, even one step further: Is it necessary that all authorative servers have the same SOA record for a zone, especially the serial number? I think the only requirement that's really essential is that the serial number changes whenever the data that would be returned by a zone transfer changes (even if that breaks database consistency for the SOA record's serial number). One strategy to implement this would be to keep an exact copy of a zone obtained from other servers for outgoing transfers (so you'll always use the original serial number), which is the BIND 9 strategy. Another strategy would be to just increment the serial number of a zone when it is actually changed by importing glue records from another zone. This would solve the synchronisation problem, too: If the parent zone is updated too early, the server might throw away the glue record. But it will update the parent zone and increase its the serial number when it gets an up-to-date copy of the child zone. Claus -- http://www.faerber.muc.de/