Re: [v6ops] I-D Action: draft-ietf-v6ops-ula-usage-recommendations-02.txt

[Lorenzo Colitti <[e-mail]>]

On Thu, Feb 20, 2014 at 10:52 AM, Brian E Carpenter <
[e-mail]> wrote:

> > 2. A piece of remarkably bad luck, rather less likely than
> >> winning any lottery I'm aware of.
>

Can you elaborate on exactly how bad this luck is as a function of how many
ULA prefixes you use your organization?

For example - if two large organizations that each use 200 ULA /48s (one
per site) merge, what is the chance that one of them will collide?

I don't feel it's satisfactory to say "the probability of a collision is
low" without saying how low it actually is. In fact, I think the draft
should not be published without giving a few examples of these numbers. If
*nobody* among the authors or on this list knows what the numbers actually
are, then we should not advocate using ULAs. It is not good engineering
practice to recommend something that you do not understand.

> You assume that people will actually follow the rules instead of saying
> > "let's just do this like IPv4, and use NAT at the border".
>
> If CERs do the right thing the ULA prefix will be generated
> correctly. But you're right, there will be a generation of
> old-time IPv4 operators who will do exactly that whatever we
> put in RFCs.
>

I'm not talking about home networks here, I'm talking about corporate IT
environments.