[arin-ppml] Draft Policy 2011-5: Shared Transition Space for IPv4 Address Extension - IAB comment

[Alain Durand]

On Jun 29, 2011, at 1:35 AM, Joel Jaeggli wrote:
> 
> no it isn't. there is a tangible difference between a scenario where something will not be configured and therefore will never fail and a, something which fires packets into the ether becuase it doesn't know any better. LSN is here, allocating a new prefix or squatting on public scope prefixes will break some fraction of old cpe (it does today) in worse way then allocating them out of private scope prefixes (for which they already have logic) until they age out of the network.

This is exactly the point. There is logic coded in many, many devices that understand what a private address [rfc1918] is and do different things accordingly.
Feeding those devices with what looks like a perfectly good global unicast address will inevitably creates breakage. The first that comes to mind is 6to4, another
one is SIP where there is some logic to do NAT traversal put in place, etc...

This breakage has to be compared to the level of breakage of the same CPEs that would be fed RFC1918 addresses, especially 172.16/12 and that might get
confused with what they have allocated internally.

   - Alain.