[CUWiN-Dev] Re: RFC4193: Unique Local IPv6 Unicast Addresses

[Sascha Meinrath]

> On Fri, Dec 02, 2005 at 01:04:41AM -0600, David Young wrote:
> 
>>I am going to use RFC4193 "unique local addresses" (ULAs) to
>>replace the deprecated IPv6 "site local" addresses on CUWiN routers.
>>See <http://ip-doc.com/rfc/rfc4193> for the definition of a ULA.

Just read through the RFC.  This is nice -- and pretty much eliminates the need 
to go through the process of obtaining IPv6 space.  Not to mention having a 
really nice (low) collision probability:

P = 1 - exp(-N**2 / 2**(L+1))

[Basically, for a 10,000-node network the chance of duplication is 4.54*10^-05]

The non-global routability is a problem only if there's no coordination among 
networks utilizing this numbering regime.  I wonder if this is something that 
should be brought up on the "meta" list for discussion.  With a 16-bit Subnet ID 
available, it would be easy to set up some sort of FreeNetworks routability.

If nothing else, it would be good to get more people thinking about this.

Nice catch!

--Sascha

>>I made CUWiN a ULA prefix, fdb4:542d:dc11::/48, using a CGI script
>>by one Shinsuke SUZUKI.  I have installed a copy of the script at
>><http://chambana.net/~dyoung/gen-ula.html>.
>>
>>I will put the ULA prefix in /etc/myula, and adapt /sbin/eth6ip to
>>use the prefix in /etc/myula, instead of fec0/48.  Other sites should
>>probably create their own ULA, and modify /etc/myula to suit.
>>
>>Since ULAs are unique and self-assigned, they are IMO a sensible choice
>>for IPv6 community wireless networks that are without "native" IPv6
>>connectivity, but nevertheless want to tunnel to other IPv6 CWNs around
>>the globe.
>>
>>Dave
>>
>>-- 
>>David Young             OJC Technologies
>>dyoung at ojctech.com      Urbana, IL * (217) 278-3933

-- 
Sascha Meinrath
Policy Analyst    *  Project Coordinator  *  President
Free Press       *** CUWiN               *** Acorn Active Media
www.freepress.net *  www.cuwireless.net   *  www.acornactivemedia.com