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Re: [DNSOP] Anycast and DNS questions

Joe Abley <jabley@hopcount.ca> Wed, 03 September 2014 20:33 UTC

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From: Joe Abley <jabley@hopcount.ca>
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Date: Wed, 03 Sep 2014 16:32:47 -0400
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References: <20140806114759.GF5546@cisco.com>, <25907D96-0076-417A-8DB9-41A5A178D479@ianai.net>, <20140806123205.GG5546@cisco.com>, <2014082716115865363718@cnnic.cn>, <BAF35D7F-D6BA-45F3-B57E-BAF25F940355@virtualized.org>, <5405718F.5010007@sidn.nl> <2014090312002502171843@cnnic.cn>, <5406DD50.5040502@necom830.hpcl.titech.ac.jp> <2014090323421459684126@cnnic.cn> <1704A9DF-C082-451F-9962-69AC20495313@virtualized.org> <54074E19.4010202@bogus.com>
To: joel jaeggli <joelja@bogus.com>
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Archived-At: http://mailarchive.ietf.org/arch/msg/dnsop/l-ggyTdbmmbo5lzYakQPrpD2gZ4
Cc: "dnsop@ietf.org" <dnsop@ietf.org>, Guangqing Deng <dengguangqing@cnnic.cn>, David Conrad <drc@virtualized.org>
Subject: Re: [DNSOP] Anycast and DNS questions
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On 3 Sep 2014, at 13:21, joel jaeggli <joelja@bogus.com> wrote:

> On 9/3/14 10:01 AM, David Conrad wrote:
> 
>> On Sep 3, 2014, at 8:42 AM, Guangqing Deng <dengguangqing@cnnic.cn>
>> wrote:
>>> From RFC1034 section 4.1, it seems that the way used for improving
>>> the redundancy and resilience of DNS system is to increase DNS
>>> servers. I agree that for the performance of the DNS system, the
>>> redundancy and resilience are the first goal and low latency is the
>>> second goal. Usually, the first goal mainly depends on the DNS
>>> server deployment policy (such as the total number and geographical
>>> distribution of DNS severs) and the second goal relates to not only
>>> the DNS server deployment policy but also the method used for DNS
>>> clients selecting the best DNS server like any cast.
> 
> anycast is not a selection mechanism employed by a client. it is the
> network that determines the catchment area served by a given anycast
> instance.

RFC4786 may be a useful reference.

(and I remember when that document was progressing through the IESG there was confusion over the word "catchment"; we inserted a definition to make the use of that word clearer, pasted here since Joel used it too.)

  Catchment:  in physical geography, an area drained by a river, also
      known as a drainage basin.  By analogy, as used in this document,
      the topological region of a network within which packets directed
      at an Anycast Address are routed to one particular node.


Joe

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