On Tue, 3 May 2005, Paul G wrote:
There seems to be no possibility for anycast to be "completely coherent", so ultradns' anycast couldn't be "completely coherent" either. But Vixie mentions it to respond to comments by others about Ultradns'
----- Original Message ----- From: "Dean Anderson" <dean@av8.com> To: "Paul G" <paul@rusko.us> Cc: <nanog@merit.edu> Sent: Tuesday, May 03, 2005 8:35 PM Subject: Re: [dnsop] DNS Anycast revisited (fwd) particularly
pervasive use of anycast.
it may not be possible to make every service *consistent*, but it is perfectly possible to make it coherent (i'm talking about coherency of copies of a shared resource).
This seems to be a trivial interpretation of "coherent". It is assumed that the copies of DNS _zones_ are kept in sync regardless of whether the servers are to traditional replicas or to anycasted replicas. No one ever claimed that zone transfers between the copies would be affected by anycast. The "in-sync"-ness of the zone data is competely orthogonal to anycast. Roots are updated via back channels on non-anycast addresses, and not with AXFR.
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. i snipped the rest for obvious reasons. -p