Yeah, DS Lite requires CPE support, so it�s a non-starter for most NZ providers. Last time I looked at it, which was a few years ago admittedly, there was no backwards compatibility - a provider had to transition all customers to DS-L, and IPv4-only service was no longer possible.
Its key benefit is to �eliminate� double IPv4 NAT, but, that isn�t important and it doesn�t actually achieve it.
I looked at some data with someone (who I won�t name but they might like to implicate themselves) that showed that something like 20% of outbound packets from a medium sized NZ ISP had a set of TTL values that indicated double-NAT (or an extra routing hop but that doesn�t seem that likely), in the customer premise.
Something like 3% had more than two.
That�s % of packets, not % of users. I�m unsure whether it�d be higher or lower if it were % of users.
Anyway, given that, it�s my view that an extra NAT hop isn�t going to negatively impact the majority of customers. Sure, it�s bad for the Internet etc. etc. but we�re already there and almost all applications deal with it already. If a customer needs a �port forward�, they�re not going to get that with DS-Lite any easier than they are with an extra NAT hop in the ISP.
The key problem with DS-Lite that I see is that it requires CPE config - it's just too much hassle. Seems to be easier to go for CGN (with all the problems that entails).
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