This was brought up in another part of the thread. I'm copy-pasting my reply:
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From the RFC (emphasis added):
> The long term goal of the TUBA proposal involves transition to a worldwide Internet which operates much as the current Internet, but with CLNP replacing IP and with NSAP addresses replacing IP addresses.
[…]
In §3 Migration:
> Updated Internet hosts talk to old Internet hosts using the current Internet suite unchanged. Updated Internet hosts talk to other updated Internet hosts using (TCP or UDP over) CLNP. This implies that updated Internet hosts must be able to send either old-style packets (using IP), or new style packet (using CLNP). Which to send is determined via the normal name-to-address lookup.
So you're replacing IPv4 with something that is not-IPv4 on every router and every host. During the transition period everyone will have IPv4 and not-IPv4 addresses.
How is not-IPv4 being CLNP/NSAP any different that not-IPv4 being IPv6? What am I missing?
In §6 on DNS:
> TUBA requires that a new DNS resource record entry type ("long-address") be defined, to store longer Internet (i.e., NSAP) addresses.
Can you explain how it was compatible? That RFC says "Updated Internet hosts talk to old Internet hosts using the current Internet suite unchanged." which sounds exactly the same as the way v6 normally does it.
As far as I could tell from the RFC, if TUBA counts as v4-compatible then so does v6.
