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Re: [DNSOP] Clarifying referrals (#35)

Tony Finch <dot@dotat.at> Wed, 29 November 2017 23:34 UTC

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From: Tony Finch <dot@dotat.at>
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Date: Wed, 29 Nov 2017 23:34:12 +0000
Cc: IETF DNSOP WG <dnsop@ietf.org>, Andrew Sullivan <ajs@anvilwalrusden.com>
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References: <20171112075445.tf2ut5dxzhhnqe7l@mx4.yitter.info> <20171128195025.ifzwsjk42wz7ard6@mx4.yitter.info> <FAA4A6D6-1454-4705-B87F-1FB96CC50658@isc.org> <20171129014436.sx546yjwvobepnyp@mx4.yitter.info> <8E36C30A-A7BC-4908-BE06-6D2B8B469006@isc.org> <20171129015303.kthpahbi6w6m645d@mx4.yitter.info> <AE976F3F-0270-4484-BCE4-FE0E9BF9D03E@isc.org> <20171129020347.b3zq3rcwsubmrlhh@mx4.yitter.info> <476FF2A7-DB80-40B6-917A-2675497DD6FC@isc.org> <20171129121706.4zh4kgx3wmtucmpc@mx4.yitter.info> <CAKW6Ri4T1h0n2r-Zp5xUUvW4n+u4oFPww2SDRnqwQMBF_wjY0g@mail.gmail.com> <8CA9C8EB-F117-4797-810F-DEF047F110BB@dotat.at>
To: Dick Franks <rwfranks@acm.org>
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Subject: Re: [DNSOP] Clarifying referrals (#35)
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> On 29 Nov 2017, at 23:13, Tony Finch <dot@dotat.at> wrote:
> ... you get an implicit referral from the cache (which can be upwards).

I just realised this might be a useful point.

Normal (downward) referrals come from authoritative data, and indicate the server is saying to the client, you need to ask here next; on the other hand these special kinds of referrals come from the cache. An implicit referral comes in a full-fat RD=1 RA=1 answer, and indicates the server is telling the client where the answer came from; if RD=0 or RA=0 you can get an upward referral, which indicates the server is telling the client where the server would ask next in order to fill its cache.

Normal (downward) referrals are instructions to iterative resolvers; implicit referrals and upward referrals are supposed to be cache-filling gossip (in the distributed systems sense of gossip protocols).

Tony.
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f.anthony.n.finch  <dot@dotat.at>  http://dotat.at

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