[arin-ppml] GUA vs ULA vs ?

michael.dillon at bt.com michael.dillon at bt.com
Tue Mar 30 04:55:56 EDT 2010

> > I am overwhelmed with the number of posts regarding the whole 
> > 'Non-connected networks', so I'll admit freely that I haven't been 
> > able to keep up.

What on earth are non-connected networks? The very essence of
a network is connectivity. This phrase should be erased from 
our discussions because it is confusing and an oxymoron.

> > - I'm a bit behind the curve on some of the abbreviations, but I 
> > believe that this is correct:
> > --- ULA == Unique Local Address
> > --- GUA == Global Unique Address
> > 
> > If that is the case, here is how I feel...
> That is how I have been using them and I believe others are 
> using them to mean that too.

A simple Google search would show that the IETF folks
use GUA to mean Global Unicast Addresses.
The ULA-C addresses that we are discussing would be
globally unique addresses but are clearly not GUA
because they are not from FC00::/7

> Personally, I'd like to have the IETF define FC00::/8 for 
> this purpose, and delegate it to IANA to allocate to the RIRs 

RFC 4193 is very muddy when it comes to laying out how the
FC00::/7 addresss are defined. First of all, the FC00 part
is hexadecimal, so each letter refers to 4 bits of the 
address. Given the /7 part, this means that only the F and
3 bits from the C, are fixed. The L bit, which determines
whether it is ULA-C or ULA-RANDOM (called ULA-L by IETF folk)
is part of that C digit. This means that addresses beginning
with FD, are ULA-L (ULA-RANDOM). Addresses beginning with
FC are currently in limbo because they are defined by the
RFC, but not yet assigned to IANA.

So, FD00::/8 are the ULA-L randomly assigned unique unicast
addresses intended for local use.

And FC00::/8 are indeed the ULA-C addresses that need another
RFC in order to instruct IANA to allocate them to RIRs.

> for assignment to organizations using process similar to 
> those used for GUA today and using policies designated by the 
> RIRs.

This risks people doing things like blocking ULA-C addresses
from other RIR regions but routing them openly in one region.
The current thinking has been to allocate them randomly so
that they cannot be aggregated either by network or by region.

> > - So that the maintainers of BOGON lists (eg: Team Cymru) 
> can hold one 
> Agreed.  And, FC00::/7 is already in their BOGON list.

Sadly, no. Nor are the old 6bone addresses in their bogon list.
Not even SIXXS <http://www.sixxs.net/tools/grh/bogons/> includes
these as bogons.

> Your /32 presumably is a GUA-PA provider allocation not an 
> GUA-PI end-user assignment. 

Do we really need to change PA and PI to have a GUA prefix?

--Michael Dillon

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