Subject: RE: Next steps on Reserving bits in RFC 2473 Interface IDs?

From: "Michel Py" <[email-masked]>
Date: Tue, 12 Mar 2002 07:59:23 -0800

>> Alexandru Petrescu wrote:
>> I'm very curious if the suggested recommendation is really
>> "no more than 64" or is it "exactly 64"?

> kre wrote:
> It is currently probably exactly 64 - but there's no
> reason for that.

Actually, there are, but I will not get into that again.

"more than 64" is not even debatable.
"exactly 64" is today's status for most IPv6 addresses.
"no more than 64" has some good arguments for it, mostly the following one:
> A link layer that doesn't have a use for all 64 bits
> shouldn't be required to pad them for no reason
This is especially true with NBMA technologies such as frame relay, when using the MAC address of e0 on s0 is not always the best thing to do.

My take on it is:

IPv6 over ethernet: stick to exactly /64. Probably for TR and FDDI too.
IPv6 over foo: it might be desirable to get a lower value (make it fit on a nibble or byte boundary) _if_ accompanied by RFC2373 modifications or new text that define a fixed aggregation boundary for routing purposes. Subneting below /64 must have defined boundaries just like above /64.

Michel.

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From: Alexandru Petrescu<[email-masked]>
Date: 12 Mar 2002 17:27:06 +0100

"Michel Py" <[email-masked]> writes:
> IPv6 over foo: it might be desirable to get a lower value (make it
> fit on a nibble or byte boundary) _if_ accompanied by RFC2373
> modifications or new text that define a fixed aggregation boundary
> for routing purposes.

I like these, FWIW.  This would imply changes in the meanings of
Prefix 001 and Prefix 000.  I doubt the intended meaning can be to
have Ethernet under Prefix 001 and all other L2's under Prefix 000.

Alex