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RE: 240/4 unreservation (was RE: Last Call: <draft-weil-shared-transition-space-request-03.txt> (IANA Reserved IPv4 Prefix for Shared Transition Space) to Informational RFC)

2011-09-26 17:21:56
I will be a bit more direct than Keith.

There is no such thing as "no leakage." These addresses will leak, no matter 
how well you believe you are isolated. Indeed, the issues posed by similar 
leakage were one of the main argument developed in RFC 3879, "Deprecating Site 
Local Addresses."

We see here a proposal to create site local IPv4 addresses for Internet 
providers. The IETF previously expanded significant efforts to deprecate IPv6 
site local addresses. Why exactly do we believe that IPv4 site local addresses 
would be a good idea, when the consensus was that IPv6 site local addresses 
caused more harm than good?

From: ietf-bounces(_at_)ietf(_dot_)org 
[mailto:ietf-bounces(_at_)ietf(_dot_)org] On Behalf Of Keith Moore
Sent: Monday, September 26, 2011 1:16 PM
To: George, Wes
Cc: IETF Discussion
Subject: Re: 240/4 unreservation (was RE: Last Call: 
<draft-weil-shared-transition-space-request-03.txt> (IANA Reserved IPv4 Prefix 
for Shared Transition Space) to Informational RFC)

On Sep 26, 2011, at 2:15 PM, George, Wes wrote:


From: ietf-bounces(_at_)ietf(_dot_)org<mailto:ietf-bounces(_at_)ietf(_dot_)org> 
[mailto:ietf-bounces(_at_)ietf(_dot_)org]<mailto:[mailto:ietf-bounces(_at_)ietf(_dot_)org]>
 On Behalf Of Keith Moore
Sent: Friday, September 23, 2011 10:04 PM

The problem is in the zillions of systems in the field that have assumptions 
about 240/4 wired into them, most of which either have no automatic upgrade 
mechanism, aren't set up to use it, or aren't being maintained.
<snip>
Honestly I'd guess that if vendors started changing their code today, it would 
be 10 years before 240/4 could be widely used in the field.


WEG] See that's the point, I think we keep looking at this from a "boil the 
ocean" perspective. The question is not, "could we use 240/4 as more global 
unicast space?" as the ship sailed on that years ago when IETF apparently 
decided it was too hard to change and nothing should be done.
The question is, "if the space were unreserved, are there valid use cases where 
networks within a given administrative control might be able to make use of it?"

maybe.  But I personally don't believe that such addresses won't leak out.

I'd say if a network operator wants to make a case for it using 240/4, it can 
write up an Internet-Draft detailing how it would be used along with 
containment measures, and petition IETF to ask IANA to permit such use.

The last thing that's needed is to open up that space for general use for 
anybody who thinks it's a good idea.  And I sympathize with the notion that any 
use of the precious remaining reserved v4 space should somehow credibly promote 
IPv6 adoption.

Keith

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