Re: [v6ops] IPv6 mostly for DS-Lite

[Ondřej Caletka <[e-mail]>]

>
>
> DHCPv4 option 108 is tied to 464XLAT.  DS-Lite is already has per host
> support defined.  DS-Lite only needs an equivalent DHCPv4 option that
> specifies DS-Lite is supported by the node rather than 464XLAT as is
> indicated by 108.
>

I see the point here. I was about to point out that NAT64 stands out from
all other transition mechanisms because it allows unmodified hosts to work
on an IPv6-only network, while the rest of transition mechanisms require
some sort of software running in each host to support the transition
mechanism.

However, the practice shows us that running unmodified hosts on a NAT64
network is not sufficient anyway. Switching to 464XLAT with a piece of
software required to run on every single host eliminates this key feature
of NAT64. In that sense, 464XLAT is not in any way better or worse than
DS-Lite, MAP-* or anything else.

Network operators should be able to choose different IPv4aaS mechanisms to
use in IPv6-mostly networks. I think it would be nice if DHCP option 108
had a bit field with transition mechanisms supported by the network. Upon
receiving the option, the client would decide whether it supports that
particular transition mechanism and either stopped DHCP transaction, if the
offered transition mechanism is supported, or continued further with native
IPv4 otherwise.

We are probably too late to extend option 108 without interoperability
issues. What could be done though would be another option with just this
bitfield of supported IPv4aaS mechanisms.

Personally, I would really like to have IPv6-mostly with MAP-* so I could
get a proper public IPv4 address even when running IPv6-only :)

--
Ondřej Caletka