In message <E752070A-9081-4B36-8FB9-F60E0E420F88@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@isc.org