The Department of Work and Pensions, UK has an entire /8

Mark Andrews marka at
Sat Sep 22 10:21:44 UTC 2012

In message <505CDD21.4080103 at>, Nick Hilliard writes:
> On 21/09/2012 19:23, Tony Hain wrote:
> > App developers have never wanted to be aware of the network.
> By not sitting down and thinking about the user experience of a
> dual-stacked network, we have now forced them to be aware of the network
> and that's not a good thing because they are as clued out about networking
> as most network operators are about programming.  If we had designed a
> portable and consistent happy-eyeballs API 10 years ago, it would be widely
> available for use now.  But we didn't do that because we were thinking
> about the network rather than the users.  So now, each dual stack developer
> is going to have to sit down and reimplement happy eyeballs for themselves.
>  What a waste.

RFC 1123 told app developers that they needed to support multihomed
servers.  That was over 2 decades ago.  HE would not have been
needed if app developers had followed that advice.

> > As far as they
> > are concerned it is the network managers job to get bits from the endpoint
> > they are on to the endpoint they want to get to. Making them do contortions
> > to figure out that they need to, and then how to, tell the network to do
> > that adds complexity to their development and support. This is not an IPv6
> > issue, it is historic reality.
> No, it's a current reality for early venturers into ipv6.  It may become a
> future reality in the mainstream if ipv6 takes off in a way that I can't
> foresee at the moment.  One day in the future, maybe, it will become less
> of an issue if people go back to a single-stack endpoint system.

IPv6 will still be multi-homed.  Dual stack is just a example of multi-homed.
> > And something that is easy to fix by simply deploying a 6to4 relay in each
> > AS and announcing the correct IPv6 prefix set to make it symmetric. 
> In theory yes.  In practice no.
> > event. Those that are doing so intentionally, while providing the long term
> > path in parallel, can be described as weaning their customers off the
> > legacy. Those that are doing so inadvertently, because they don't care abou
> t
> > anything but their tiny part of the overall system, will lose customers to
> > the provider offering the long term path.
> So long as the cost of that is less than the cost of deploying ipv6 and
> pushing people in that direction, it's a good business plan in the short
> term.  Which is what most people care about.  I'm with you that it's a
> hopeless long term business plan, but that's not the world we live in.
> Nick
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at

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