Subj : ULA
To   : Michiel van der Vlist
From : Markus Reschke
Date : Thu Jul 21 2016 12:15:54

Hello Michiel!

Jul 21 00:09 2016, Michiel van der Vlist wrote to Markus Reschke:

 MvdV> The original idea was "Site Local Address". That was abandonned for 
 MvdV> not being able to define "Site". Now it is "Unique Local Address". 
 MvdV> The idea is ho have a local address with a scope somewhere between 
 MvdV> a Link Local Address" and A "Globally Unique Address". It is not 
 MvdV> supposed to be globally routed. But the idea is that it is globally 
 MvdV> unique with a high degree of probabality.

There's a nice algorithm depicted in RFC4193 for that purpose. The fc00::/8 block was originally meant for a global unique private prefix but didn't attrack much support. The idea was to have a NIC assigning prefixes out of fc00::/8 to make them unique. Now we have only fd00::/8 with some probability of overlapping ranges.

 MvdV> ULA is not used by SixXs to route between users. All SixXs does is 
 MvdV> to maintain a list of the /48 prefixes in use. To decrease the 
 MvdV> chance of duplication.

Are they using the algorithm in RFC4193?

 MvdV> It is not supposed to be globally routed, but it can be routed 
 MvdV> between (virtual) private networks. If one has routers supporting 
 MvdV> it. Mine doesn't.

It's simply RFC1918 for IPv6 ;)

Regards,
Markus

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