[arin-discuss] IPv6 End User Assignments

[Matthew Wilder]

I have a question about subnet size for end user sites (and a few thoughts as well).

What size of IPv6 subnet would you imagine an ADSL customer (consumer, not business) would get from their ISP?  The NRPM actually has nifty guidelines around subnet assignment here:

/64 when it is known that one and only one subnet is needed 
/56 for small sites, those expected to need only a few subnets over the next 5 years. 
/48 for larger sites 

I would assume that with the average Joe ADSL user, one subnet is enough.  Whether or not an ISP would make that assumption in their provisioning of the service might be another question.  Either way, I would bet that a /64 would suffice for 99% of users.

I can see value in assigning a /56 to every user so that they can subnet to their hearts' content to save any trouble of renumbering down the road, not that an average consumer would have a lot of renumbering to do.

That said, I was a little surprised to see on the slashdot article about the ARIN letter (http://tech.slashdot.org/article.pl?sid=09/04/30/2051235&art_pos=2) that a comment came out suggesting every household would have a /48 assigned to it.  What was more surprising is that no comments surfaced to correct this claim.

My understanding of /48 is along with the NRPM: that /48 subnets are for "larger sites".  Not many consumers would use much of their 65,536 /64 subnets in a /48 (at least in my estimation).

This got me to do some exploring.  I know that French telcos have already got IPv6 available for their ADSL customers.  So with the help of Google translation, I got the following page from a telco called Nerim:
http://translate.google.com/translate?hl=en&sl=fr&u=http://www.nerim.fr/ipv6&ei=iaEASrPINZritAPxjqX-BQ&sa=X&oi=translate&resnum=1&ct=result&prev=/search%3Fq%3Dnerim%2Bipv6%26hl%3Den%26rls%3Dcom.microsoft:en-US

If you read near the bottom of the translated text, you will see "For access, IPv6 allocation is a / 48..."  A /48 for a consumer?  

This made me curious to see what RIPE NCC says about end user assignments.  They have similar language about the /64 being the minimum, in the case that no subnetting is required.  They skip over /56 (which makes me appreciate the ARIN policy) directly to /48.  They leave it to the LIR and ISP to determine what size of assignments to make for end sites.

So, all this back to the original question:
What kind of IPv6 subnet would YOU expect a North American ISP to assign to their residential ADSL customer?

Kindly,
Matthew Wilder 
matthew.wilder at telus.com