[arin-ppml] ARIN-prop-127: Shared Transition Space for IPv4 Address Extension

Jack Bates jbates at brightok.net
Mon Jan 24 13:53:48 EST 2011

On 1/24/2011 12:43 PM, George, Wes E [NTK] wrote:
> on an individual basis, the same problem exists. So it's not a surprise, but
> that's part of why I'm so adamant about using 1918 space for this if at all
> possible.

So your thought is that a CPE might have code which won't do 6to4 if 
there's RFC-1918 assigned to the WAN, but otherwise might use 6to4 and 

> Not to speak for Joel, but I think that the point he's making is that if
> this block isn't codified as an update/addition to RFC1918 space, it'll be
> treated incorrectly by applications which care about global uniqueness in
> addressing, regardless of where they live. Even if it is codified in that
> manner, it'll take the applications (host stack and otherwise) a while to
> catch up.

Using a specific block will allow these applications to catch up. Using 
RFC-1918 would be best, but there are so many possible conflicts that 
using it in large deployments would cause even more support issues. If 
the /10 isn't assigned for this purpose, organizations will use their 
own allocated space (not RFC-1918) and there will still be breakage, but 
the applications won't be able to rewrite their code to recognize the 

Given the high probability that RFC-1918 won't be used for LSN, 
assigning a new block is more application friendly than using random 


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