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Re: DNS anycast considered harmful (was: .ORG problems this evening)

  • From: Todd Vierling
  • Date: Thu Sep 18 08:50:00 2003

On Thu, 18 Sep 2003, Stephane Bortzmeyer wrote:

: > Still doesn't help .ORG, which is 100% anycast and thus has no DNS-based
: > redundancy
:
: Wrong since there are two IP addresses. They may fail at the same time
: (which apparently happened to you) but there is a least an element of
: non-BGP redundancy (I'm not aware of any TLD running with only one
: anycasted name server, although it would still have some redundancy).

Okay, let me qualify then:

"...no DNS-based redundancy when both routes point to the same place and
that particular place goes off the air while its BGP advertisements stay
up and running..."

DNS-based redundancy typically implies going to different servers at
different locations, regardless of what BGP says.  The fact that anycast
took me to the same place for both IPs, and that same place went down all at
once, means that I was effectively looking at a single point of failure with
no way for DNS to pick another place to look.

-- 
-- Todd Vierling <[email protected]> <[email protected]>