V6 still not supported

Pascal Thubert (pthubert) pthubert at cisco.com
Fri Mar 25 20:39:53 UTC 2022

Hello Phil

The only far ressemblance with 6to4 is the thing that was actually nice in the design, the automatic word in automatic tunnel. Which for the rest of us means stateless. Compared to CGNATs that is huge.

Beyond that the proposal is not a tunnel and more akin to a nat64 since it allows v6 nodes to talk to v4 nodes. The network can be pure v4 or pure v6 if the method is implemented as a bump in the stack at the wrong end.

Your response is also missing the capability to extend the IPv4 network a million times. Or drop it completely while maintaining IPv4 applications.

6to4 was meant for early v6 to interconnect islands. A solution for a problem that never really existed. Solutions without a problem aren’t usually popular.

Apparently here there’s a real world problem to be solved. Sophisms are of no help.



> Le 25 mars 2022 à 19:40, Philip Homburg <pch-nanog-2 at u-1.phicoh.com> a écrit :
>> A host in the Internet that wants to talk to a host in China would require an 
>> update to parse new DNS double-A (realm, address) records to encapsulate the p
>> acket IP-in-IP, outer src= outer dest= The router that ser
>> ves the shaft at level 1 attracts within realm 1 and routes up the
>> elevator for more specific (host) routes within that prefix. The router that 
>> serves the shaft at level 2 attracts inside the shaft; upon the s
>> aid packet it would swap the inner and outer destination and the packet would 
>> reach the Chinese address with classical routing within realm 2. 
>> Routers serving the shaft need an update, but then, only those do. Obviously t
>> he host in China can only reply if its stack is updated to understand the form
>> at. But all the other hosts and routers in China can be classical IPv4 as we k
>> now them long as their traffic stays in China. To migrate to IPv6 what you can
>> do is map the elevator shaft prefix in, say, 400::/3 (sadly cannot use F00/3 
>> that would map 240 neatly but is already assigned). 
>> The current internet would own 400:1::/32, China would own 400:2::/32, etc... 
>> You encode the double-A of the host in the prefix, reserve a well known suffix
>> for IPv4 mapped double-A, and you have an IPv6 address that can be mapped bot
>> h ways statelessly. When migrating to v6, each IPv4 node that owns a public IP
>> v4 address in one realm gets a full IPv6 /64 for free.
>> "
> Somehow this sounds a lot like 6to4: packets get routed to special devices
> in the network and ISPs have little control over this. Not a popular
> architecture.
> Or another way to look at it is the resemblance with the ill fated 
> 'Provider-Based Global Unicast Addresses' (RFC 1884, Section 2.4.7). This
> was not very popular either.

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