Re: [DNSOP] BCP on rrset ordering for round-robin? Also head's up on bind 9.12 bug (sorting rrsets by default)
Erik Nygren <erik+ietf@nygren.org> Fri, 15 June 2018 20:17 UTC
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From: Erik Nygren <erik+ietf@nygren.org>
Date: Fri, 15 Jun 2018 16:17:00 -0400
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To: Mukund Sivaraman <muks@mukund.org>
Cc: Bob Harold <rharolde@umich.edu>, IETF DNSOP WG <dnsop@ietf.org>, Andrew Sullivan <ajs@anvilwalrusden.com>
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Subject: Re: [DNSOP] BCP on rrset ordering for round-robin? Also head's up on bind 9.12 bug (sorting rrsets by default)
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On Fri, Jun 15, 2018 at 3:52 PM, Mukund Sivaraman <muks@mukund.org> wrote: > On Fri, Jun 15, 2018 at 02:38:00PM -0400, Bob Harold wrote: > > Round-robin is a documented feature that many applications use. Removing > > it from DNS resolvers, and then having to add it to a much larger number > of > > applications, does not seem like a good trade-off. > > The _default_ in BIND 9.12 was changed from order random to order > none. It seems to be missing from the release notes by mistake, but the > administrator manual mentions what the default is > We have many years of software that relies on emergent behaviors from the current default. While pedantically it may be true that these should be treated as unordered sets and that applications or stub resolver libraries should do some permutations or randomized selection, that doesn't match the current reality for widely used software (eg, curl and ssh, which I'm sure is just the tip of the iceberg). Software should have safe defaults that matches common expectations. Those common expectations, as demonstrated by the configuration of all of the large public resolvers I've tested, as well as by how common software behaves, is that the order of results is NOT consistent. In many environments, this lack of consistency is relied upon for systems to work properly. Switching to consistent order is no big deal on a small scale, but a widespread shift (eg, as would happen due to a change in default in popular software) would almost certainly have significant operational impact and is something that warrants significant discussion about the practical implications. This ambiguity in the current specifications results in this mismatch between the pedantic (rrsets are explicitly unordered, and a consistent order is a subset of that) and the current reality (applications and services rely on resolvers-at-scale to be explicitly inconsistent in the ordering of rrsets) is why I started off by proposing that we may need a BCP or informational RFC that describes the currently assumed defaults and best-practices (ie, round-robin is assumed in many places so don't consistently order at-scale by default). Erik
- Re: [DNSOP] BCP on rrset ordering for round-robin… Shumon Huque
- Re: [DNSOP] BCP on rrset ordering for round-robin… Shumon Huque
- Re: [DNSOP] BCP on rrset ordering for round-robin… 神明達哉
- Re: [DNSOP] BCP on rrset ordering for round-robin… Paul Vixie
- Re: [DNSOP] ?==?utf-8?q? BCP on rrset ordering fo… Petr Spacek
- Re: [DNSOP] BCP on rrset ordering for round-robin… Shumon Huque
- Re: [DNSOP] BCP on rrset ordering for round-robin… Darcy Kevin (FCA)
- Re: [DNSOP] BCP on rrset ordering for round-robin… Shumon Huque
- Re: [DNSOP] BCP on rrset ordering for round-robin… Florian Weimer
- Re: [DNSOP] BCP on rrset ordering for round-robin… Paul Vixie
- Re: [DNSOP] BCP on rrset ordering for round-robin… Andrew Sullivan
- Re: [DNSOP] BCP on rrset ordering for round-robin… Florian Weimer
- Re: [DNSOP] DoH interaction, sortlist Re: BCP on … Philip Homburg
- Re: [DNSOP] BCP on rrset ordering for round-robin… Peter van Dijk
- [DNSOP] DoH interaction, sortlist Re: BCP on rrse… bert hubert
- Re: [DNSOP] BCP on rrset ordering for round-robin… Erik Nygren
- Re: [DNSOP] BCP on rrset ordering for round-robin… Shumon Huque
- Re: [DNSOP] BCP on rrset ordering for round-robin… Shumon Huque
- Re: [DNSOP] BCP on rrset ordering for round-robin… Colm MacCárthaigh
- Re: [DNSOP] BCP on rrset ordering for round-robin… Shumon Huque
- Re: [DNSOP] BCP on rrset ordering for round-robin… Mark Andrews
- Re: [DNSOP] BCP on rrset ordering for round-robin… Colm MacCárthaigh
- Re: [DNSOP] BCP on rrset ordering for round-robin… Paul Vixie
- Re: [DNSOP] BCP on rrset ordering for round-robin… Mukund Sivaraman
- Re: [DNSOP] BCP on rrset ordering for round-robin… Erik Nygren
- Re: [DNSOP] BCP on rrset ordering for round-robin… Mukund Sivaraman
- Re: [DNSOP] BCP on rrset ordering for round-robin… Jared Mauch
- Re: [DNSOP] BCP on rrset ordering for round-robin… Bob Harold
- Re: [DNSOP] BCP on rrset ordering for round-robin… Shumon Huque
- Re: [DNSOP] BCP on rrset ordering for round-robin… Peter van Dijk
- Re: [DNSOP] BCP on rrset ordering for round-robin… Paul Vixie
- Re: [DNSOP] BCP on rrset ordering for round-robin… Andrew Sullivan
- Re: [DNSOP] BCP on rrset ordering for round-robin… Tony Finch
- Re: [DNSOP] BCP on rrset ordering for round-robin… Jared Mauch
- [DNSOP] BCP on rrset ordering for round-robin? Al… Erik Nygren