Re: Call for Votes (getaddrinfo)
On Sat, Dec 01, 2007 at 12:12:41PM +1000, Anthony Towns wrote:
> I don't see any reason to like the current behaviour, so parallel to that,
> I'd also say:
> [1] We should work out what a desirable prefix sorting behaviour
> is, that works the same way for IPv4 and IPv6, and propose it
> to supercede RFC3484.
> [2] We should pass on concrete reports of harm rule9 causes for IPv4
> round-robin servers to the IETF with encouragement for them to
> review the sorting rules.
> [3] We should do nothing but hope the IETF and upstream work something
> better out themselves and not follow the standard until that
> happens.
> [4] Further discussion
> I haven't seen any concrete reports we could pass on, or any indication
> we're likely to come up with a better mechanism, though, which leaves us
> as doing nothing by default.
I've previously argued that there are at least two mechanisms that would be
an improvement:
- drop rule 9 altogether, passing through the sorting supplied by the DNS
server (whether that's round-robin, or sorted by some other server-side
rule)
- apply rule 9 only in the case that the common prefix is longer than the
prefix length of the "natural" unit network for the address family (/32
for IPv6, /22 for IPv4)
Do you disagree with the proposition of one of these being preferable to the
current behavior?
> I could be convinced it's RC, but I've seen precious little *actual*
> impact -- certainly people are surprised by the change in behaviour,
> and it does change traffic characteristics, but ... that seems to be it,
> so far. Where's the actual damage and problems?
The changed traffic characteristics are certainly damaging, at least
potentially. It can have financial consequences for anyone that's invested
in infrastructure with the expectation that round robin will continue to
work, and find that they have to choose between completely revamping their
DNS infrastructure to feed clients targetted results, or renegotiating
hosting/bandwidth contracts to accomodate client selectivity that's outside
of the server's control. Obviously in the general case Debian doesn't have
enough market share to be able to fix this on our own, but that doesn't stop
us from ensuring that Debian behaves as a good citizen.
In terms of how the behavior of Debian clients makes a difference, Debian
systems are certainly the primary consumers of the Debian mirror network. I
think that losing a mirror sponsor due to the uneven load distribution, or
being unable to meet demand for mirror capacity because the sponsors who
have capacity have their servers in the "wrong" IP address range, are very
real possibilities that we should take into consideration -- and in advance,
not just once we've found that it's an imminent problem for us and our
users.
--
Steve Langasek Give me a lever long enough and a Free OS
Debian Developer to set it on, and I can move the world.
Ubuntu Developer http://www.debian.org/
slangasek@ubuntu.com vorlon@debian.org
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