From: ietf-bounces(_at_)ietf(_dot_)org
[mailto:ietf-bounces(_at_)ietf(_dot_)org] On Behalf Of Keith Moore
Sent: Friday, September 23, 2011 10:04 PM
To: Cameron Byrne
Cc: IETF Discussion
Subject: Re: Last Call: <draft-weil-shared-transition-space-request-03.txt>
(IANA Reserved IPv4 Prefix for Shared Transition Space) to Informational RFC
On Sep 23, 2011, at 9:53 PM, Cameron Byrne wrote:
So if there is going to be breakage, and folks are willing to fix it over time
because the good outweighs the bad (I personally do not believe this), then why
not dedicate 240/4 for this purpose? The 240/4 work has been shot down multiple
times ( I don't know the history ), are we now changing the rules for the end
run ?
It's hard to know for sure, but I believe there's greater risk associated with
use of 240/4 than with a /10 from existing public IPv4 space. That is, I
think more software would be needed to allow 240/4 to be used reliably.
WEG] you know, the more I think about this line of logic, the more I wonder
about it.
In essence, the 240/4 problem is that lots of host and router implementations
have one or more functions in their input validation code that says "240/4 ==
invalid" thus preventing you from configuring or using it. To my (admittedly
oversimplified) view, this is a simple matter of:
1) Search source code for "240"
2) Comment out any relevant code you find
3) Recompile, test (changes only), ship
I'd be happy for one or more folks who have some experience with the
appropriate bits of Windows, Linux, MacOS, IOS, JunOS source code would explain
where I'm oversimplifying.
Now, compare that with the discussion of adding a new set of non-unique address
space where you likely have to add code to catch this if you care about the
scope of the address that you've been assigned.
The authors (or at least one of them) of draft-bdgks maintain that they've
discussed this with vendors
(http://www.ietf.org/mail-archive/web/opsawg/current/msg01879.html, search for
Linksys to find the relevant section of the message) and the vendors seem
willing to make code changes in support of this, at least in new gear. Now this
doesn't represent a commitment nor a critical mass necessarily, but I'm
wondering why 240/4 is so much harder?
Also, I don't see why we don't use all of the tools in our toolkit. We're out
of IANA space, except for a whole /4, which keeps getting shot down due to the
perceived problems with getting global support, when there are probably
multiple use cases that absolutely don't require global support. Why haven't we
gone ahead and unreserved the space, and then let those interested in using it
beat on the appropriate folks to fix it, rather than not even trying? I think
that it would be fully possible to caveat use of the space appropriately so
that people know what the risks are, but right now it's essentially useless
even for those who might be able to try.
Seems wasteful, no?
I'm willing to write a draft about it if there are people willing to support
it, but I only have so many windmills that I can tilt at per cycle, so I'd like
to hear support either privately or publicly before I undertake it.
Wes George
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