Re: IPv6 fc00::/7 — Unique local addresses

Thu Oct 21 07:46:00 UTC 2010

>>> 
>> Which is part one of the three things that have to happen to make ULA
>> really bad for the internet.
>> 
>> Part 2 will be when the first provider accepts a large sum of money to
>> route it within their public network between multiple sites owned by
>> the same customer.
>> 
> 
> That same customer is also going to have enough global address
> space to be able to reach other global destinations, at least enough
> space for all nodes that are permitted to access the Internet, if not
> more. Proper global address space ensures that if a global destination
> is reachable, then there is a high probability of successfully reaching
> it. The scope of external ULA reachability, regardless of how much
> money is thrown at the problem, isn't going to be as good as proper
> global addresses.
> 
_IF_ they implement as intended and as documented. As you've
noted there's a lot of confusion and a lot of people not reading the
documents, latching onto ULA and deciding ti's good.

It's not a big leap for some company to do a huge ULA deployment
saying "this will never connect to the intarweb thingy" and 5-10 years
later not want to redeploy all their addressing, so, they start throwing
money at getting providers to do what they shouldn't instead of
readdressing their networks.

> For private site interconnect, I'd think it more likely that the
> provider would isolate the customers traffic and ULA address space via
> something like a VPN service e.g. MPLS, IPsec.
> 
One would hope, but, I bet laziness and misunderstanding trumps
reason and adherence to RFCs over the long term. Since ULA
won't get hard-coded into routers as unroutable (it can't), when
people do bad stuff with it, it will work and since it works, they won't
go read the documentation explaining that what works is a bad
idea.

>> Part 3 will be when that same provider (or some other provider in the
>> same boat) takes the next step and starts trading routes of ULA space
>> with other provider(s).
>> 
>> At that point, ULA = GUA without policy = very bad thing (tm).
>> 
>> Since feature creep of this form is kind of a given in internet history,
>> I have no reason to believe it won't happen eventually with ULA.
>> 
> 
> So I'm not sure I can see much benefit would be of paying a
> huge amount of money to have ULA address space put in only a
> limited part/domain of the global route table. The only way to
> have ULA = GUA is to pay everybody on the Internet to carry it, and
> that is assuming that everybody would be willing to accept the money
> in the first place. That'd be far more expensive than just using GUA
> addresses for global reachability.
> 

No... The way it will work is that use of ULA as pseudo-GUA will
spread slowly like cancer through the network.

When provider A and provider B both have customers throwing lots
of money at them to route their ULA, provider A and provider B will
swallow hard and agree to exchange those routes in both directions.

I wish I had your confidence in people doing the right thing, but,
there are enough examples of RFC-1918 space in the GRT that
I simply can't share your belief that it won't happen with ULA
which doesn't have the reliability problems that RFC-1918 had.

Owen