MX record ordering

[Kevin Darcy]

RFC 974 specifies randomization of connection attempts between MX targets of equal
preference. So if you're seeing significantly more traffic on server1 than
server2, it's because one or more of your mail partners is violating the RFC.
Round-robin technically has nothing to do with it, although sometimes round-robin
helps to *mask* this particular RFC violation...


-Kevin

Brad Knowles wrote:

> At 12:54 PM -0500 3/30/01, lawrence.a.kravets at us.arthurandersen.com wrote:
>
> >  We have recently upgrade to Bind 9.1.0 from Bind 4.9.3. Given the
> >  following, we have reason to believe that the order of response of the
> >  following has changed. We expect that it would split equally between server1
> >  and server2. Unfortunately we see more traffic on server1 than server2.
> >  Has something changed in Bind 9?
> >
> >  mailhosts      IN   MX   10   server1.zone.com.
> >  mailhosts      IN   MX   10   server2.zone.com.
> >  mailhosts      IN   MX   20   server3.zone.com.
> >  mailhosts      IN   MX   30   server4.zone.com.
>
>         In theory, you are right.  The load should be balanced across the
> first two machines.  In practice, there are still plenty of sites out
> there for whom their local nameserver doesn't properly round-robin
> records once they have been cached, so you will see a traffic
> imbalance.
>
>         The only way around this problem is to put something like a layer
> 4 load-balancing switch in front of the machines which can all
> perform the same function, and to get this kind of information out of
> the DNS entirely.
>
>         Sorry, guy.  Don't mean to burst your bubble, but this is just
> one of the many little weirdnesses about the DNS and Internet e-mail.
>
> --
> Brad Knowles, <brad.knowles at skynet.be>
>
> /*        efdtt.c  Author:  Charles M. Hannum <root at ihack.net>          */
> /*       Represented as 1045 digit prime number by Phil Carmody         */
> /*     Prime as DNS cname chain by Roy Arends and Walter Belgers        */
> /*                                                                      */
> /*     Usage is:  cat title-key scrambled.vob | efdtt >clear.vob        */
> /*   where title-key = "153 2 8 105 225" or other similar 5-byte key    */
>
> dig decss.friet.org|perl -ne'if(/^x/){s/[x.]//g;print pack(H124,$_)}'