Re: v6 subnet size for DSL & leased line customers

On Jan 1, 2008 8:29 AM, Mark Smith
<nanog85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org&
gt; wrote:
>
> On Tue, 1 Jan 2008 12:57:17 +0100
> Iljitsch van Beijnum <iljitschmuada.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. 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

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

> 
> On Jan 1, 2008 8:29 AM, Mark Smith
> <nanog85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org&
gt; wrote:
> >
> > On Tue, 1 Jan 2008 12:57:17 +0100
> > Iljitsch van Beijnum <iljitschmuada.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


-- 

        "Sheep are slow and tasty, and therefore must
remain constantly
         alert."
                                   - Bruce Schneier,
"Beyond Fear"

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

> 
> On Jan 1, 2008 8:29 AM, Mark Smith
> <nanog85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org&
gt; wrote:
> >
> > On Tue, 1 Jan 2008 12:57:17 +0100
> > Iljitsch van Beijnum <iljitschmuada.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...

Yeah, you're right, I missed the line wrapped AS_PATH.

> 
> 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. 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


-- 

        "Sheep are slow and tasty, and therefore must
remain constantly
         alert."
                                   - Bruce Schneier,
"Beyond Fear"

On 2 jan 2008, at 6:42, Christopher Morrow wrote:

> 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)

AS path prepending, local preference, that kind of thing...

>> 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. I suppose you could do static
assignments, but
> there's a management payment there that might not fit
within the ISP's
> cost plan.

There is no "static" and "dynamic", only
points along a line...  
Obviously you don't want your customers to renumber every
day and  
twice on sunday, but you also don't want to keep
configurations  
specific for each customer. A good DHCP server will keep
giving you  
the same address until it's forced to give that address to
someone  
else when you're not using it, or until it loses its
assignment  
history. I assume something similar will happen here for
most customers.

> I presume that something accepting PD would be smart
> enough to let the end-hosts/lans know when their top 56
bits
> changed...

Cisco routers can change their RAs based on a new PD prefix
and even  
align the lifetimes so the renumbering happens very
smoothly.

> and v6 includes auto-renumbering for 'free' right?

Yes, that must be why IPv6-capable firewalls are still hard
to  
find.