Re: v6 subnet size for DSL & leased line customers

[Mark Smith <nanog () 85d5b20a518b8f6864949bd940457dc124746ddc nosense org>]

On Wed, 2 Jan 2008 00:42:59 -0500
"Christopher Morrow" <morrowc.lists () gmail com> wrote:

> On Jan 1, 2008 8:29 AM, Mark Smith
> <nanog () 85d5b20a518b8f6864949bd940457dc124746ddc nosense org> wrote:
> > On Tue, 1 Jan 2008 12:57:17 +0100
> > Iljitsch van Beijnum <iljitsch () muada com> wrote:
> >
> > > On 31 dec 2007, at 1:24, Mark Smith wrote:
> > >
> > > > Another idea would be to give each non-/48 customer the
> > > > first /56 out of each /48.
> > >
> > > Right, so you combine the downsides of both approaches.
> > >
> > > It doesn't work when ARIN does it:
> >
> > Well, ARIN aren't running the Internet route tables. If they were, I'd
> > assume they'd force AS6453 to do the right thing and aggregate their
> > address space.
>
> 11920 - cogeco who I presume (just guessing) is doing this either
> because they have not aggregated by mistake or have to shed load and
> load-balance). I don't think teleglobe (6453) is at fault here...
>
> out of curiousity how is this sort of thing supposed to be done in v6?
> (traffic engineering given the '1 prefix per ISP' standard mantra)
>
> > > *  24.122.32.0/20   4.68.1.166               0             0 3356 6453
> > > 11290 i
> >
> > Static assignments of /56 to customers make sense to me, and that's the
> > assumption I've made when suggesting the addressing scheme I proposed.
> > Once you go static with /56s, you may as well make it easy for both
> > yourself and the customer to move to a /48 that encompasses the
> > original /56 (or configure the whole /48 for them from the outset).
>
> I think the assumption most folks make with DSL/cable is that
> end-users get dynamic assignments from a local (to the PE device)
> pool, similar to ipv4.

IPv6 is different to IPv4, don't assume things are to be done the
same. Some things are, some things can be, somethings shouldn't be.

Why was dynamic addressing for residential customers in IPv4 put in in
the first place? Occasional dial up access would be my guess as to the
root reason - it was wasting IPv4 addresses if your infrastructure
couldn't handle all of your customers dialing up at once.

Broadband has of course changed that, when you sell a broadband service,
you have to assume that the customer will be connected 24x7, so you
need as many IPv4 addresses as you've got customers - and the same will
apply for IPv6. Why do dynamic when you don't need to? 

> I suppose you could do static assignments, but
> there's a management payment there that might not fit within the ISP's
> cost plan.  I presume that something accepting PD would be smart
> enough to let the end-hosts/lans know when their top 56 bits
> changed... and v6 includes auto-renumbering for 'free' right? So all
> solved?
>
> (yes some of that is joking... or at the very least pointing out a gotcha)
>
> -Chris


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