ISP customer assignments

Wed Oct 14 14:06:32 UTC 2009

In message <E752070A-9081-4B36-8FB9-F60E0E420F88 at daork.net>, Nathan Ward writes
:
> 
> On 14/10/2009, at 7:23 PM, Mark Andrews wrote:
> 
> > DS-Lite is there for when the ISP runs out of IPv4 addresses to
> > hand one to each customer.  Many customers don't need a unique IPv4
> > address, these are the ones you switch to DS-Lite.  Those that do
> > require a unique IPv4 you leave on full dual stack for as long as
> > you can.
>
> The authors of DS-lite say it's because running a dual stack network  
> is hard.

It is harder.

> You clearly don't share that view, so in your view what's wrong with  
> dual stack with IPv4 for everyone then, whether they need a unique  
> address or not?

Dual stack for everyone was feasible 5 years ago.  It isn't anymore,
that transition plan has sailed and almost no one got on board.

Because there aren't enough addresses to go around and there hasn't
been for years.  PNAT is a kludge to work around that fact.  When
you can't give every customer their own IPv4 address yet you still
need to provide IPv4 connectivity you need to work out how to share
those addresses you have efficiently.  Given double PNAT or DS-Lite
I know which one I prefer.

DS-Lite allows lots of the tricks used with PNAT to continue to
work.  Those tricks will just stop working with double PNAT.

> DS-lite requires CGN, so does dual stack without enough IPv4 addresses.
> 
> This is probably the wrong forum for a DS-lite debate. I'm sure people  
> have a use for it, they actually might have gear that can only do IPv4  
> OR IPv6 but not both or something.
> My problem with it is that it's being seen as a solution for a whole  
> lot of people, when in reality it's a solution for a small number of  
> people.

It's not the only solution.  There are others and customers and
ISP's will need to work out what is best for their collective
requirements.

It is a reasonable fit for residentual ISP's as the CPE PNAT is
really very inefficient at conserving addresses and by splitting
the PNAT across 2 co-operating boxes you can get the address
utilisation efficency we now need in IPv4 to cover all the short
sightedness that has got us to the place where we need things other
than dual stack.

> Thanks for the point about the tunnel brokers though, I missed that,  
> I'll update this tomorrow with any suggestions I get before then.
> 
> --
> Nathan Ward
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org