Re: [v6ops] About Req for Comments - "Transition to IPv6"

[Owen DeLong <[e-mail]>]

> On Mar 5, 2020, at 6:02 AM, Alexandre Petrescu <[e-mail]> wrote:
> 
> Thank you very much for the pointer.  In it I could spot
> the following footnote: "[4] IPv6-Only refers to network environments in
> which use of the IPv4 protocol has been eliminated.”

No.

IPv6-Only refers to network environments which are not using IPv4. That could be a network where IPv4 has been eliminated (rare at this time, though Facebook is a significant example) or it could be a greenfield deployment where IPv4 was never deployed.

> 
> In my humble opinion,
> 
> I think, if I am not wrong, that there are no such networks in which
> IPv4 protocol has been eliminated.  On one hand, a network is made of
> computers, and IPv4 stacks are still present in almost all computers.
> On another hand, there might be some ptp links (not networks, but
> individual links) that run IPv6 only.

You are wrong… There are examples at various levels of IPv6-only networks. Many mobile carriers are IPv6-only in the US, though they do provide some apparent IPv4 capability to the end user through mechanisms such as 464XLAT and/or NAT64.

Another significant example is Facebook where they are essentially IPv6-only throughout their network and provide minimal IPv4 translation shim at the edge to cope with end users that lack IPv6 capability.

> That is why it is hard to agree on the assumption of IPv4 being eliminated somewhere.  Worse, it makes look as if the goal of that 'IPv6-only' is to arrive at that same situation which in fact does use IPv4.

As a general rule, once IPv6 is ubiquitously deployed in a network, the preservation of IPv4 in the majority of that network becomes an unnecessary cost factor and a security risk (increased attack surface, if nothing else). As such, I think you will see an increasing number of organizations follow on to the way Facebook has managed their transition and start eliminating IPv4 wherever possible and replacing it with translation shims as far out towards the border as practical.

Owen