[arin-ppml] ULA-C

michael.dillon at bt.com michael.dillon at bt.com
Thu Apr 8 06:26:11 EDT 2010

> The real value of ULA-C (IMO) 
> is the understanding that it's not supposed to be globally 
> routed. Yes, that's enforced by convention only...but that's 
> no different then pretty much anything else on the internet.

Actually, ULA-C *IS* designed to be globally routed. But only
on private internetworks, not on the public Internet. 

Remember that the Internet Protocol suite and the IETF are 
not there to service the public Internet. They are there to
allow everyone to internetwork computers and other devices
in any way that is useful to them. This includes private
internetworks and it includes semi-connected regions of
the public Internet, as well as the so-called "global Public

I think that everyone understands what private internetworks
are whether they are COINs or just a company that connects
to a couple of key trading partners over some kind of VPN
service. But consider this possibility. A country like China
might choose to offer certain government services using
a few registered ULA-C ranges, and require all ISPs in China
to route those addresses, i.e. punch some /48 holes in their
FC00::/7 filters. The end result would be that within China,
those government sites are fully connected to the public Internet
but outside of China, those sites do not exist.

You might never want to do such a thing, but I can't think of
a good reason why you would want to prevent everybody on the
planet from doing such a thing. The IETF is there to create
possibilities, not to prescribe everything about how you 
must operate your networks.

Within ARIN we must remember that we are part of a larger picture,
and sometimes, public Internet operators need to step aside and
say, "this doesn't affect us because we filter FC00::/7" and let
other people do their thing. Other people includes enterprise 
network operators, Community Of Interest Network (COIN) operators,
and innovative thinkers who want to do something new.

This is a situation where even if the majority of PPML voices
are opposed to ULA-C addressing, the AC and Board of Trustees
should do the right thing and make it happen, in a reasonable
and orderly way. Remember that ULA-C addresses do exist today;
they just don't have any orderly processes surrounding them.
This is a vacuum that must be filled, before someone creates
a fait accompli type of solution.

--Michael Dillon

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