[arin-discuss] IPv6 End User Assignments

[Eric Windisch]

On May 6, 2009, at 11:05 AM, Mike Berger wrote:

> I would expect a North American ISP to allocate a single IPv6 address
> and charge a huge fee for a subnet for their residential ADSL  
> customers.

The minimum reasonable size would be a /64 (a single address would be  
a /128).  It should be noted that a /64 doesn't entirely exclude  
customers from subnetting, but it will cause problems with router  
advertisement and other features.  I don't think that anyone with  
experience deploying IPv6 would argue for subnets smaller than a /64,  
so its not worth discussing further.

Another thought I have: what about routing?  Right now, while you  
might not see a lot of users configuring subnets at home, there is a  
much larger number of "power users" that configure their own routers  
and firewalls for purposes besides simply running NAT.   With IPv6, if  
an ISP only provides a bridged /64, customer's machines will connect  
directly to the ISP and will not pass through any customer-premises  
routing equipment.  At best, customers could configure a layer-3  
switch or bridging firewall.

To me, the logical deployment seems to provide a /128 address, and  
route a /64, /56, or /48 into that.  My fear is that this will be  
hidden inside a cable modem or other CPE that the customer won't have  
direct access to, similar to how it is currently, except that  
currently we at least have NAT and can avoid proper routing.  A /128  
address should be given directly to the customer for routing their  
subnet through their own devices.


Regards,
Eric Windisch