[99433] in North American Network Operators' Group
Re: Going dual-stack, how do apps behave and what to do as an operator (Was: Apple Airport Extreme IPv6 problems?)
daemon@ATHENA.MIT.EDU (Iljitsch van Beijnum)
Fri Sep 21 14:53:11 2007
In-Reply-To: <2d106eb50709202254q6f4ea4b7v6beda6deee5f7143@mail.gmail.com>
Cc: "Jeroen Massar" <jeroen@unfix.org>, "Barrett Lyon" <blyon@blyon.com>,
nanog@merit.edu
From: Iljitsch van Beijnum <iljitsch@muada.com>
Date: Fri, 21 Sep 2007 20:34:05 +0200
To: Martin Hannigan <hannigan@gmail.com>
Errors-To: owner-nanog@merit.edu
On 21-sep-2007, at 7:54, Martin Hannigan wrote:
>> All applications are supposed to use getaddrinfo() which sorts
>> these addresses per the above specification, the app should then
>> connect() to them in order, fail/timeout and try the next one
> Since when is a timeout on the Internet ok? Haven't we moved beyond
> that? This is a controllable timeout. We don't have to do it, which is
> the point. What's the right way to do this?
I agree that it's not acceptable to engineer things such that
timeouts occur by design. However, things tend to break, and in those
situations it's important to recover as well as can be expected. So
the correct way to operate here is for the network designer to make
reasonably sure ("unreliable datagram" etc) that everything works,
for the stack designer to make sure that there is a good algorithm
for selecting the "best" combination of destination and source
addresses and for the application to cycle through all addresses if
the two former efforts weren't completely successful.
