Date: Wed, 4 May 2005 08:31:52 -0400 (EDT)
From: Susan Harris <srh@merit.edu>
To: Dean Anderson <dean@av8.com>
Cc: nanog-admin@merit.edu
Subject: Re: [dnsop] DNS Anycast  revisited (fwd)

Dean, your ad hominem comment below, sent despite my "last warning"
message to you yesterday, has prompted us to remove your posting
privileges from the NANOG list for a period of six months.  Your messages
have repeatedly violated the NANOG list AUP:

        http://www.nanog.org/aup.html

   --Susan Harris, for the NANOG list admin team


On Tue, 3 May 2005, Dean Anderson wrote:

>
> On Tue, 3 May 2005, Paul G wrote:
>
> > i'm terribly sorry, but i'm unable to extract any meaning at all from these
> > statements. when i parse them, they make no sense at all (not in terms of
> > being wrong, just not understandable). could you rephrase them?
> >
> > coherency and consistency are well-defined terms in systems engineering. we
> > are talking about dns queries and hence coherency of zone data (the shared
> > resource). i fail to see how this is open to any interpretation at all.
>
> Sorry, The original statement Vixie made is nonsense. Here is the original
> statement again:
>
> Vixe writes:
>    lest anyone be confused, ultradns's anycast for .ORG is completely
>    coherent and doesn't admit the possibility of giving out different
>    responses from different anycast nodes for policy reasons or any other
>    reason, and so it's an example of "good" anycast the way i count such
>    things.
>
> Vixie seems to be responding to concern raised for Ultradns' pervasive use
> of anycasting. This was the only issue raised involving Ultradns.
>
> During the anycast discussion on DNSOP, the subject of zone coherency (as
> normally used) was not an issue.  So there is no question of zone
> coherency for Ultradns' servers. We assumed (and did not dispute) that
> zone updates were unaffected by anycast. Zone updates happen over private
> secure channels on non-anycasted IP addreses. They ought to be as coherent
> as DNS gets. They ought not be affected by anycast.
>
> Vixie ends by saying essentially, that because of Ultradns' coherency, it
> is an example of "good anycast". But the two issues (coherency and
> anycast) have no relationship. There is no reason to conclude that
> coherency means anycast is either good or bad. Hence, his statement is
> nonsense.
>
> Alternately, one might read "coherency" as refering to the shared TCP
> state of the group of servers. The "shared TCP state" of a group of
> anycast servers is conceptual.  There is no actual coherency for this
> shared TCP state. So that is nonsense, too.
>
> I suspect the statement is just nonsense, that is hoped to sound good.
> Many people will not really read or parse his whole statement, but will
> remember 'Ultradns is an example of good anycast, according to Vixie'
>
> But, given that the original statement is nonsense, I can't really say
> that any of these are correct.
>
>               --Dean
>
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