Subject: RE: I-D ACTION:draft-savola-ipv6-127-prefixlen-00.txt (fwd)

From: "Michel Py" <[email-masked]>
Date: Sun, 10 Feb 2002 21:24:22 -0800

Pekka,

> What do others think -- is this something worth noting?

Overall, I find the text excellent.

I oppose solutions 2,3 and 4 because they bring extra
complexity to solve a problem that does not exist. The problem
that does not exist is the need to subnet a /64.

The reason /127 subnets have become popular is simply because
of the old IPv4 habit of using a /30 for a point to point
link. We collectively have to unlearn that.

In other words, if operators are breaking RFC 2373 because of
old working habits, the solution is to aquire new working
habits, which is using a /64 for point-to-point links and
stay in complicance with RFC2373, solution 1.

It is clear that you were reading another thread on this same
list, "IPv6 Addr/Prefix clarification". There are no reported
RIR issues, and I still fail to see a valid reason to subnet
a /64 when one should have used a /48 and subnet using the SLA
bits. IPv6 is not widely deployed, why can't we just configure
it right?

I disagree with the phrasing that solution 1 is a workaround.
Solution 1 is the way it is supposed to be. Solution 2 is a
workaround, and not a very good one, IMHO. If an operator has
to renumber point-to-point links configured with a /126, it
makes a lot more sense to me to catch the opportunity to
comply with RFC 2373 and give it a /64 instead.

Michel.

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From: Pekka Savola <[email-masked]>
Date: Wed, 13 Feb 2002 10:24:02 +0200 (EET)

> that does not exist is the need to subnet a /64.

IMO, 2) adds no complexity.  3 might be remotely sensible, but 3 and 4 
both cannot be relied on.. so if you want to be sure, you always have to 
do either 1) or 2).

I hope I made the problems with at least 4) sufficiently clear.

> link. We collectively have to unlearn that.

Well, and then there is also RFC3021, "Using 31-Bit Prefixes on IPv4 
Point-to-Point Links" which is more of the equivalent..

> bits. IPv6 is not widely deployed, why can't we just configure

At least at one time, Randy Bush advocated /64's for IX's because they 
didn't need more..

If IX's get /48, this is no problem.

Anyway, I see why people see /126 and such as lucrative: they need to
assign only _one_ /64 for all point-to-point links.  There might be e.g. a
couple of hundred of them, and even though 200 of them could fit fine to 
2^16 subnets, you'd still have to define the addressing a bit more 
carefully.
  
> comply with RFC 2373 and give it a /64 instead.

I didn't see the problem with the wording, but I'll change the text 
slighly to reflect to this.

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords