Regardless of the ease of implementing the change (which is quite simple in the linux case for example), the question is really what is the impact on existing systems? The presumption is they won't change until they age out of the network which is the same reason any a+p solution that requires host signalling or new private scope unicast ranges have negative implications for the support of legacy systems. By that measure 240/4 is unequivically not useful (for this purpose). It was also not useful 4 years ago (for this purpose). On 9/26/11 07:07 , George, Wes wrote: > > > *From:*ietf-bounces@xxxxxxxx [mailto:ietf-bounces@xxxxxxxx] *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 > > > ------------------------------------------------------------------------ > This E-mail and any of its attachments may contain Time Warner Cable > proprietary information, which is privileged, confidential, or subject > to copyright belonging to Time Warner Cable. This E-mail is intended > solely for the use of the individual or entity to which it is addressed. > If you are not the intended recipient of this E-mail, you are hereby > notified that any dissemination, distribution, copying, or action taken > in relation to the contents of and attachments to this E-mail is > strictly prohibited and may be unlawful. If you have received this > E-mail in error, please notify the sender immediately and permanently > delete the original and any copy of this E-mail and any printout. > > > _______________________________________________ > Ietf mailing list > Ietf@xxxxxxxx > https://www.ietf.org/mailman/listinfo/ietf _______________________________________________ Ietf mailing list Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf