Fair enough. I think given the magnitude of address space, wastage becomes a secondary concern.

I guess when you have 281,474,976,710,656 number of /48 subnets available, you can probably afford to not care too much about being wasteful....

This may be a correct assumption so long as the current architectures of subnets residing behind a physical router device continue to hold - because the real surge would occur if virtualized hosts themselves become router devices and further require subnets to reside behind them.

If the above becomes the case, we could have problems...


From: Alastair Johnson <aj@sneep.net>
To: sig-policy@lists.apnic.net
Sent: Sunday, 18 September 2011 9:51 PM
Subject: Re: [sig-policy] Need to understand logic behind assigning /64 IPv6 addresses

On 9/18/2011 4:25 AM, Usman Latif wrote:
> So when folks say that "we need atleast /64 subnets for all sites
> (including residential single-user customers) because SLAAC would fail"
> then we should ask ourselves the question:
>
> - Do we have alternatives to SLAAC?
> I'd say yes we do (DHCPv6 and ND)...
>
> - Is SLAAC the reason we are wasting 18446744073709551616 worth of
> address space for residential sites?
> I'd say this is not a good enough reason...

In turn these questions have to be reframed as 'But can we afford to be
prescriptive about how our customers want to address their networks, and
what IPv6 stacks they will have to have in their home?'

While the /64 approach is driven by SLAAC, it's driven because of
established devices and stacks, and that SLAAC was seen as a good
approach for simple home networking.

By removing the ability for your customers to deploy their internal
networks in a way that allows SLAAC to function, you are likely going to
annoy them.

"Why does my gaming device not work when I use ISP-A but does when I
take it to my friend who uses ISP-B?"

> But without going into an endless debate on this subject, I think we all
> have our own perspectives of looking at things and when I initially
> started my query "Need to understand logic behind /64 IPv6 addresses" -
> I can only say that I am only partially convinced and cannot convince
> myself with the reasoning provided so far that its worth wasting that
> much address space using a one-size-fit-all approach of /64 - especially
> as I said in the case of home-user CPEs etc.

I think you will find many people are only partially convinced by /64s
(and SLAAC), however it's not really practical to change things. It's
been a long and hard road to get DHCPv6 operationally deployable.

aj
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