Re: [v6ops] I-D Action: draft-ietf-v6ops-unique-ipv6-prefix-per-host-07.txt

[Lorenzo Colitti <[e-mail]>]

On Thu, Aug 17, 2017 at 4:47 AM, Simon Hobson <[e-mail]>
wrote:

> > /64 gives you something that no longer prefix does: the ability to run
> SLAAC and connect unlimited devices behind the host.
>
> From previous discussions, I am led to believe that SLAAC will work with
> other (longer or shorter) prefixes. It is only the deprecated EUI64 method
> that *needs* 64 bits.
>

In practice it does not because every link layer specifies 64-bit IIDs.


> > No. Someone wrote code that gets a prefix via DHCPv6 PD, and blindly
> announces it in an RA.
>
> Are you suggesting that someone who realises that not everything is a /64
> would do that ? You've not really done anything to counter this being a
> case of "everything is /64" thinking and thus ignoring the potential for
> anything else. It may be a simple case of blindly re-announcing the prefix
> you got delegated - but it still comes down to not understanding that the
> prefix may be other than /64.
>

You could just as well answer that if someone thought that everything was
/64 they'd just reject non-/64 prefixes.


> > Already? 64 everywhere has been the standard for 20 almost years now. It
> predates pretty much every IPv6 network and every IPv6 implementation out
> there today.
>
> And that hardcodes in a restriction which IN THE REAL WORLD is known to
> cause issues. For example, you (incorrectly) only get a single /64 from
> upstream, but want to something other than a single host or very simple
> network. I agree that it shouldn't happen, but in the real world it does -
> you either stick with a simple basic network, or you run prefixes smaller
> than a /64.


If the ISP is well-intentioned, it will give you a /64. If the ISP not
well-intentioned, they will give you an allocation that is the minimum size
that clients are prepared to accept. So you will never be able to subnet
anyway - as soon as your device is willing to do SLAAC on a /80, that's
what your ISP will hand you. There's no point starting that arms race.