who gets a /32 [Re: IPV6 renumbering painless?]

Thu Nov 25 20:08:23 UTC 2004

Thus spake <bmanning at vacation.karoshi.com>
> > No connectivity to the internet? -> use ULA, quick, easy, cheap.
>
> ULA leaves a bad taste for a number of reasons, some of which
> have seen some discussion.  What has not occured, and seems to
> be a major tenent of the ULA zelots, is how conflict resolution
> is to be done.
>
> if ULA is sufficent, in and of itself, then why do we need to
> have all the rest of the 128bits of space?

You need some bits at the top to denote the ULA portion of the address
space, you need bits at the bottom for the host address, and you need bits
in the middle for internal network structure.  Consensus was that 40 bits
was enough for the "unique" portion of the prefix.

ULAs were not intended to solve all problems, just like neither link-local,
PA, or PI addresses do not solve all problems by themselves.

> if ULA users ever have a conflict (and yes, they will) how will
> the conflict be resolved?

There is negligible chance of conflict between any two parties thanks to the
40-bit prefix space, and the odds of collision are still neglibigble even
when hundreds of networks are interconnected.

Sure, sooner or later two networks will happen to generate the same prefix.
When that happens -- and assuming those networks want to talk to each other,
one of them simply generates a new prefix and renumbers.  This is a
significantly better situation than with RFC1918 (or SLAs) where a collision
is _guaranteed_.

> and then there is the nasty delusion of "Internet"...  protestations
> to the contrary, the VSNL view of the "Internet" is vastly different
> than the US DOD view of the "Internet", is vastly different than the
> GE view, is different than the AS 701 view, is different than the
> Chinese R&E Network (CERN) view....  which one(s) count?  Policy
> routing dictates that there is no such thing as a "global" routing
> table...

There are clearly many parts of the Internet that are "private" and one
large part in the middle that is clearly "public".  ULAs are intended to
only be used within the "private" parts or even totally disconnected IP
networks.

> For me, as long as I have IP reachability to those folks whom I want
> or need to talk to, I could care less about the "rest" of the folks
> using IP to move datagrams about ...

Exactly.  However, the scope of who you want/need to talk to dictates what
sort of addresses you need (with the current routing architecture) and where
you get them.

S

Stephen Sprunk        "Stupid people surround themselves with smart
CCIE #3723           people.  Smart people surround themselves with
K5SSS         smart people who disagree with them."  --Aaron Sorkin