[arin-ppml] GUA vs ULA vs ?

David Farmer farmer at umn.edu
Tue Mar 30 16:53:38 EDT 2010

michael.dillon at bt.com wrote:
>>> 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.

You are probably right, but I started the conversation with that term 
because that is what it was called in ARIN's IPv4 policy.  Not 
necessarily a good reason, but a reason.

>>> - 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

Sorry, I'd swear that said "Global Unicast Address" when I read it, but 
you are correct.

>> 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.

See, my other post;

>>> - 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.

I'll admit I didn't look that closely, but when I Googled it (Cymru 
ipv6) I got the following;


FC00::/7 is listed under 3-1-1-1-2 for ingress packet filter and 
3-1-2-1-2 ingress prefix filter.  You are right that they don't have the 
old 6Bone in the filter though.

>> 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?

No, write me up a definitive style sheet for PPML post and I'll follow 
it. :)

> --Michael Dillon
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David Farmer               Email:farmer at umn.edu
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