[76520] in North American Network Operators' Group
Re: Anycast reliability (was: Re: verizon.net and other email grief)
daemon@ATHENA.MIT.EDU (Joe Abley)
Mon Dec 13 17:25:56 2004
In-Reply-To: <20041213114316.P78635@sprockets.gibbard.org>
Cc: Simon Waters <simonw@zynet.net>, nanog@nanog.org
From: Joe Abley <jabley@isc.org>
Date: Mon, 13 Dec 2004 17:24:54 -0500
To: Steve Gibbard <scg@gibbard.org>
Errors-To: owner-nanog-outgoing@merit.edu
On 13 Dec 2004, at 15:27, Steve Gibbard wrote:
> On Mon, 13 Dec 2004, Simon Waters wrote:
>
>> Inspection suggests that the anycast announcements in the UK were
>> pointing to a server that wasn't accepting email.
>>
>> I believe here the problem is using anycast, and not providing a
>> backup
>> system not using anycast. The previous case I'm aware of was when bits
>> of the NE USA lost ".org" because they only had anycast DNS servers
>> (and
>> still do AFAIK), and the announcement messed up.
>>
>> Whilst I plead ignorant of the technical details of anycast, strikes
>> me
>> that it is clearly more complex, and thus more prone to failure, and
>> these failures are potentially less obvious.
>
> (for anybody reading this who doesn't know, anycast is multiple
> servers in
> multiple locations announcing routes and accepting connections to the
> same
> IP address).
Distribution of a service (whether by anycast or by some other means)
is bound to introduce complexity over that incurred by a single
instance of a service running in just one place. In some cases, the
cost of that complexity is offset by reduced costs (or risk) elsewhere,
and anycast makes sense.
For a discussion of some of the issues surrounding service distribution
using anycast, see:
http://www.ietf.org/internet-drafts/draft-kurtis-anycast-bcp-00.txt
Flames and projectiles relating to that draft would be very gratefully
received (either directly or on the GROW list, but probably not on
NANOG).
Joe
