[62424] in North American Network Operators' Group
Re: DNS anycast considered harmful (was: .ORG problems this evening)
daemon@ATHENA.MIT.EDU (Stephen J. Wilcox)
Thu Sep 18 09:18:56 2003
Date: Thu, 18 Sep 2003 13:16:10 +0000 (GMT)
From: "Stephen J. Wilcox" <steve@telecomplete.co.uk>
To: Todd Vierling <tv@duh.org>
Cc: Stephane Bortzmeyer <bortzmeyer@nic.fr>,
Iljitsch van Beijnum <iljitsch@muada.com>, <nanog@merit.edu>
In-Reply-To: <Pine.NEB.4.58.0309180837410.3593@server.duh.org>
Errors-To: owner-nanog-outgoing@merit.edu
On Thu, 18 Sep 2003, Todd Vierling wrote:
> 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.
Okay but
1. Only you were affected
2. Only you have both servers going to the same place
Theres a theme in this, perhaps indicating where the problem may have been :)
