RFC about 9.3.4 - first query to >=bind.3 caching server always gives sorted order for round robin set

Peter Koch pk at DENIC.DE
Wed Feb 7 15:04:10 UTC 2007

On Wed, Feb 07, 2007 at 01:31:27PM +0100, Stefan Schmidt wrote:

> I just sent the following to bind9-bugs and wondered whether there probably
> are contrary opinions on this that you might want to share with us/me.

> > IMO the best thing to do with round-robin sets is rotate them - even for the first
> > query - as there are many DNS caching implementations around that aparently do not
> > rotate round-robin sets themselves.

to me this seems more like DNS operational or protocol question than a BIND
specific issue.  Neither the stub resolver nor any intermediaries are
obliged to rotate the RRSet. The order is undefined and that doesn't
imply anything. The MTA, however, has to follow the order as it arrives.

Have you considered spreading the load across multiple MX RRs with equal
preference values (keeping an eye on DNS packet size), like, e.g., AOL does?
That is, if you have to use DNS based load distribution at all.


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