Re: IPv6 Anycast has been killed by LINUX patch in 2016 - who cares?
Warren Kumari <warren@kumari.net> Mon, 09 August 2021 18:55 UTC
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From: Warren Kumari <warren@kumari.net>
Date: Mon, 09 Aug 2021 14:54:40 -0400
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Subject: Re: IPv6 Anycast has been killed by LINUX patch in 2016 - who cares?
To: Tom Herbert <tom@herbertland.com>
Cc: Töma Gavrichenkov <ximaera@gmail.com>, 6man WG <ipv6@ietf.org>, Phillip Hallam-Baker <phill@hallambaker.com>, Theodore Ts'o <tytso@mit.edu>, IETF discussion list <ietf@ietf.org>
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On Mon, Aug 9, 2021 at 2:24 PM Tom Herbert <tom@herbertland.com> wrote: > On Mon, Aug 9, 2021 at 11:09 AM Warren Kumari <warren@kumari.net> wrote: > > > > > > > > On Mon, Aug 9, 2021 at 1:08 PM Töma Gavrichenkov <ximaera@gmail.com> > wrote: > >> > >> Peace, > >> > >> On Mon, Aug 9, 2021, 7:47 PM Phillip Hallam-Baker < > phill@hallambaker.com> wrote: > >>> > >>> We have people vigorously asserting that Linux broke IPv6 TCP over > Anycast five years ago and this is serious. > >>> > >>> And We have people vigorously asserting that TCP over Anycast works > absolutely perfectly and there are no issues. > >>> > >>> And they are the same people. > >> > >> > >> a) they're not really the same people, > >> > >> b) no one said that TCP works _perfectly_ over anycast per se, because > it's understood that perfectionism just doesn't belong in the area or > engineering. > >> What's been actually said is that it works just fine in a number of > applications, including almost every popular application, and these > applications use it this way on purpose, > > > > > > ... including a number of content providers. > > As examples (many aren't really documented), Fastly ( > https://docs.fastly.com/en/guides/using-fastly-with-apex-domains) and > CloudFlare ( > https://www.cloudflare.com/learning/cdn/glossary/anycast-network/, > https://blog.cloudflare.com/cloudflares-architecture-eliminating-single-p/) > have offered this. > > Fastly and CloudFlare both have some really smart people working for > them, and they collect and analyze lots of transport level stats. I suspect > that they'd be surprised to hear that what they've built doesn't work > reliably... > > > > I'm often surprised just how often we end up in discussions in the IETF > where people make an assertion like "Foo will never work. Can't be done, no > way, no how.", and then someone else points at a bunch of existing > implementations. This feels like another instance of this. > > Warren, > > That logic works both ways. The fact that these patches in question > are over five years old and no one has reported a production issue > with them is inconsistent with some of the dire proclamations in this > thread that anycast is broken. Yes.... No..... Maybe.... I cannot tell if we are in violent agreement here or not. There are dire proclamations that IPv6 TCP anycast cannot work.... And yet there are a bunch of existing implementations where it is clearly working, and people have built their business models around it, showing that it is working fine. I think that we are in violent agreement; the bit that gave me pause was the "that logic works both ways", which made me think that you thought I was using it to argue the other side? Note that the concerns were raised by a > researcher not by any production data, and also note that the authors > of the patches were from Google and Facebook which obviously have a > vested interest in not creating problems on the Internet. Yup. Nod. Fully agree. We've actually had a really similar discussion back in 2016 -- https://mailarchive.ietf.org/arch/msg/v6ops/NLb9D5HBWDubS52EoNrdK8gqzqI/ In that thread you said: "The flow label for a connection may change if the connection is failing in hopes of finding a better route-- either the networking stack detects a bad route (i.e. TCP is retransmitting) or userspace can request a route change if it has information about path quality. So flow labels are not necessarily persistent which probably makes flow label filtering a bad idea at least if persistence for the lifetime of a connection is required for that" It's clear what the intent was (it's described in the patch as well). > In fact, > these points are likely to be counter arguments brought up on LKML if > we try to change the Linux behavior, Linux maintainers are often > loathe to change a deployed default without a strong rationale that > there's a real problem in deployment. > Indeed. 'tis been working like this for many years, and the Internet is not on fire. Ok, so, we *are* in violent agreement :-) W > > Tom > > > > > W > > > >> > >> > >> c) also, the impact of IPv6 deployment and performance issues is > perfectly limited by the current poor scale of IPv6 deployment. > >> And, when the existing behaviour of applications working just fine in > IPv4 breaks during transition to IPv6, that's not really going to speed the > transition up. > >> > >> -- > >> Töma > > > > > > > > -- > > The computing scientist’s main challenge is not to get confused by the > > complexities of his own making. > > -- E. W. Dijkstra > > -------------------------------------------------------------------- > > IETF IPv6 working group mailing list > > ipv6@ietf.org > > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > > -------------------------------------------------------------------- > -- The computing scientist’s main challenge is not to get confused by the complexities of his own making. -- E. W. Dijkstra
- Re: IPv6 Anycast has been killed by LINUX patch i… Toerless Eckert
- Re: IPv6 Anycast has been killed by LINUX patch i… Mark Smith
- Re: IPv6 Anycast has been killed by LINUX patch i… Jeff Tantsura
- Re: IPv6 Anycast has been killed by LINUX patch i… Mark Smith
- Re: IPv6 Anycast has been killed by LINUX patch i… Toerless Eckert
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Toerless Eckert
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Tom Herbert
- Re: IPv6 Anycast has been killed by LINUX patch i… Brian E Carpenter
- Re: IPv6 Anycast has been killed by LINUX patch i… Michael Tuexen
- Re: IPv6 Anycast has been killed by LINUX patch i… Tom Herbert
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Robert Raszuk
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Robert Raszuk
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Robert Raszuk
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Tom Herbert
- Re: IPv6 Anycast has been killed by LINUX patch i… Tom Herbert
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Tom Herbert
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Robert Raszuk
- Re: IPv6 Anycast has been killed by LINUX patch i… Simon Hobson
- Re: IPv6 Anycast has been killed by LINUX patch i… Tom Herbert
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Tom Herbert
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… David Farmer
- Re: IPv6 Anycast has been killed by LINUX patch i… Tom Herbert
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Theodore Ts'o
- Re: IPv6 Anycast has been killed by LINUX patch i… Nick Hilliard
- Re: IPv6 Anycast has been killed by LINUX patch i… Brian E Carpenter
- Re: IPv6 Anycast has been killed by LINUX patch i… Tom Herbert
- Re: IPv6 Anycast has been killed by LINUX patch i… Tom Herbert
- Re: IPv6 Anycast has been killed by LINUX patch i… Jen Linkova
- Re: IPv6 Anycast has been killed by LINUX patch i… Patrik Fältström
- Re: IPv6 Anycast has been killed by LINUX patch i… Ole Troan
- Re: IPv6 Anycast has been killed by LINUX patch i… Patrik Fältström
- RE: IPv6 Anycast has been killed by LINUX patch i… Vasilenko Eduard
- RE: IPv6 Anycast has been killed by LINUX patch i… Vasilenko Eduard
- Re: IPv6 Anycast has been killed by LINUX patch i… Michael Tuexen
- Re: IPv6 Anycast has been killed by LINUX patch i… Michael Tuexen
- Re: IPv6 Anycast has been killed by LINUX patch i… Brian Carpenter
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Nick Hilliard
- Re: IPv6 Anycast has been killed by LINUX patch i… Templin (US), Fred L
- Re: IPv6 Anycast has been killed by LINUX patch i… Phillip Hallam-Baker
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- Re: IPv6 Anycast has been killed by LINUX patch i… Warren Kumari
- Re: IPv6 Anycast has been killed by LINUX patch i… Tom Herbert
- RE: IPv6 Anycast has been killed by LINUX patch i… Vasilenko Eduard
- Re: IPv6 Anycast has been killed by LINUX patch i… Tom Herbert
- Re: IPv6 Anycast has been killed by LINUX patch i… Phillip Hallam-Baker
- Re: IPv6 Anycast has been killed by LINUX patch i… Phillip Hallam-Baker
- Re: IPv6 Anycast has been killed by LINUX patch i… Warren Kumari
- Re: IPv6 Anycast has been killed by LINUX patch i… Christian Huitema
- Re: IPv6 Anycast has been killed by LINUX patch i… Robert Raszuk
- Re: IPv6 Anycast has been killed by LINUX patch i… Warren Kumari
- Re: IPv6 Anycast has been killed by LINUX patch i… Warren Kumari
- Re: IPv6 Anycast has been killed by LINUX patch i… Theodore Ts'o
- Re: IPv6 Anycast has been killed by LINUX patch i… Gyan Mishra
- RE: IPv6 Anycast has been killed by LINUX patch i… Vasilenko Eduard
- Re: IPv6 Anycast has been killed by LINUX patch i… Töma Gavrichenkov
- RE: IPv6 Anycast has been killed by LINUX patch i… Vasilenko Eduard
- Re: IPv6 Anycast has been killed by LINUX patch i… Gyan Mishra
- RE: IPv6 Anycast has been killed by LINUX patch i… Vasilenko Eduard
- Re: IPv6 Anycast has been killed by LINUX patch i… Gyan Mishra
- RE: IPv6 Anycast has been killed by LINUX patch i… Vasilenko Eduard
- Re: IPv6 Anycast has been killed by LINUX patch i… Gyan Mishra
- Driver for SRV6 [Re: IPv6 Anycast has been killed… Brian E Carpenter
- Re: Driver for SRV6 [Re: IPv6 Anycast has been ki… Gyan Mishra
- RE: Driver for SRV6 [Re: IPv6 Anycast has been ki… Vasilenko Eduard
- Re: Driver for SRV6 [Re: IPv6 Anycast has been ki… Stefano Salsano
- RE: Driver for SRV6 [Re: IPv6 Anycast has been ki… Vasilenko Eduard
- Re: Driver for SRV6 [Re: IPv6 Anycast has been ki… Gyan Mishra