Hi Brian,
That sort of became RFC4798, with focus on MPLS tunnellingExactly; the non-MPLS methods were thrown away, although they seem to be completely valid. Why isn't there an informationalor BCP RFC describing them?
I am not sure if they were thrown away. RFC4798 cames from L3VPN paradigm and is sort of additional plug in for interconnect IPv6 islands over IPv4 core.
And since it is very much based on 2547/4364 any transport which applies to this would also apply to 4798. For example draft-ietf-l3vpn-gre-ip-2547-05 defines IP tunneling support.
Of course some vendors support automated multipoint GRE technic where your encapsulation header is automatically learned from BGP next hops allowing for very easy IP tunneling. For those vendors the very same functionality could be used for RFC4798.
> It really seems like a gap.I agree with you 100%. Unfortunately for some people dreaming about world of MPLS only core routers which are not able to route/switch even single IP packet this would be not a gap but a great feature :).
Cheers, R.