The NOTIFY mechanism (was Re: short ttl and servermmirroring)

[Cricket Liu]

>     john> I was hoping for a 1- or 2-second value for this feature to
>     john> kick in.  These timings are key to enable rapid failover to
>     john> back-up servers.
>
> I think you are mistaken. The NOTIFY mechanism allows for fast
> propagation of fresh zone data. This has nothing to do with "rapid
> failover to back-up servers". What if the master server dies while a
> zone transfer is in progress to one of your so-called back-up servers?
> A faster NOTIFY is pointless once that happens. It doesn't matter how
> many seconds after the load that the transfer started: it still
> happens when the server crashes. BTW the DNS protocol says that name
> servers automatically try the other NS records for some zone if the
> first one they use doesn't respond.

I think what John may have been alluding to is the need for changes to zones
to propagate quickly if, say, your web server fails and you need to change
the
A RR pointing to it to point to a backup web server.  In cases like that,
convergence time between your zone's primary master name server and your
slaves is a real concern.

cricket

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