Re: A common problem with SLAAC in "renumbering" scenarios

[Tom Herbert <[e-mail]>]

On Mon, Feb 18, 2019 at 10:33 AM Lee Howard <[e-mail]> wrote:
>
>
> On 2/15/19 4:20 PM, Sander Steffann wrote:
> > Hi Lee,
> >
> >> Seems to me several operators have offered their opinions here. If you want more opinions, maybe ask a group of operators?
> > Not a very helpful comment... I think the underlying problem here is that there is no technical solution available that solves stable IPv6 address delegation at residential scale in an acceptable way.
>
> The question was, "Would operators support this solution?" To that
> question, asking a group of operators seems to me to be a pretty sound
> suggestion.
>
> I disagree that the problem to be solved is "stable IPv6 address
> delegation," and said so repeatedly and loudly when we worked on
> RIPE-690, along with the only other large operator involved in editing
> that document.
>
> The problem to be solved is stale address state. Stable prefix
> delegation would be one solution. Better dynamic renumbering would be
> another, which could be handled in ways Fernando describes in his draft
> (draft-gont-6man-slaac-renum-00 in case anyone's forgotten), or several
> others
>
>
> >
> > - For stable address delegation the routing inside the ISP becomes a mess, especially when it can't be guaranteed that a customer consistently ends up at the same BNG.
> > - To keep ISP networks scalable, prefixes are aggregated to (roughly) BNG level, making it impossible to keep prefix delegation stable at the customer's end
> >
> > With IPv4 this didn't cause massive problems because NAT disconnected the LAN addresses from the WAN side at the customer's end. With IPv6 this is no longer the case and it does cause problems.
> >
> > Stability at one end causes instability at the other end, and vice versa.
> > And as can be seen from this discussion it's still an unsolved problem...
>
> That's a good summary. Similar to Nick Hilliard's description of where
> the network state information lives.
>
> We can try to solve this with locator-ID splits, but that solution space
> has been sitting around for a while, and I'm not sure it ultimately
> solves the problem. We can always add a layer of indirection (put a
> mapping somewhere) but it doesn't help the stub hosts.

Lee,

That's already being done in mobile networks where stub hosts are
mobile devices. Grant it, that is done for mobility not necessarily
for dynamic prefixes or privacy. Nevertheless, it does demonstrate the
mapping model necessary if addressing and topological routing are
disassociated (aka identifier-locator split).

Tom


>
> Lee
>
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