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RE: [moonv6] /120 prefix length at UNH

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From: CATANZARITI Sergio / FTR&D / US (sergio.catanzariti@rd.francetelecom.com)
Date: 10/15/03


Hello Ben,

it is not my intention to go into the interpretations of the numbers in the RFC whatever, because first Nietzsche and then Heidegger debated enough about truth, interpretation and relationships with math, and also I come from a region where Pythagoras built its school around the hidden relationships between numbers and religion, and I pray enough already in my life.

Anyway, thanks Ben to ask FT, as a major service provider, to give an opinion on the matter, we really appreciate the effort that you are doing in keeping service providers in the loop.

At FT, we use on ptp links IPv6 prefixes of /64 to comply with the (most common) interpretation of RFC 3315, and because we assume the "almost infinite" nature of the numbers of IPv6 addresses. So, we decided to have this view on the research operational IPv6 network that FT runs in France serving universities, hospitals, etc.

BUT, the folks that run the commercial FT IPv6 operational network use /126 prefix on ptp links because they apply some of the IPv4 architectural principles, like addresses conservation.

So, what is the solution? I do not know, but whatever choice we will make, at least let us offer a rational to our observers, without giving the impressions that we do not care about good industry practices, and we are just blind believers of IETF docs, that by the way are not real standards, in the classical way. In this context, I share Jim's view about that we, as a strong adopters and promoters community of IPv6 (the first one in the US), need also to give real feedback and being "active" when we interact with IETF community, not passive readers.

On the contrary, considering the small scale of the Moonv6 network and the "trial/test bed" nature of Moonv6, we could decide to go for strict RFC compliance, but I do not object to any decision, in this case I let that people that do the real work to decide, I only gave FT IPv6 status quo, rather than our view.

Sergio

-----Original Message-----
From: Alain Durand [mailto:Alain.Durand@Sun.COM] Sent: Wednesday, October 15, 2003 10:17 AM To: Bound, Jim
Cc: schultz@io.iol.unh.edu; moonv6@iol.unh.edu Subject: Re: [moonv6] /120 prefix length at UNH

moonv6 post from Alain Durand <Alain.Durand@Sun.COM>

Bound, Jim wrote:

>With /120
>
>m = 8. n == variable depending on prefix format. this is aggregatable
>format. so the prefix stops at /64 and low order 64 is the EUI. meaning n
>MUST not be greater than 58. 58 + 8 == 64. So what I am saying is I
beleive
>/120 or /96 does not step on the EUI but a /8 does step on the EU and does
>break 3315?
>

   | n bits | m bits | 128-n-m bits | 

   +------------------------+-----------+----------------------------+
   | global routing prefix  | subnet ID |       interface ID         |
   +------------------------+-----------+----------------------------+

I think you might have been loonking at the picture right to left instead of left to right! (just kidding)

With /120, you have: 

   |                        120 bits                    |    8 bits  |
   +------------------------+-----------+----------------------------+
   |       global routing prefix  + subnet ID           |interface ID|
   +------------------------+-----------+----------------------------+

Ok? So your Interface ID is effectively 8 bit long. This breaks 3315 as the global routing prefix is not starting with 000/3.

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