Re: [v6ops] I-D Action: draft-ietf-v6ops-unique-ipv6-prefix-per-host-07.txt

[Mark Smith <[e-mail]>]

I give up. Do what you like, treat sand like diamonds.

On 5 August 2017 at 19:58, Simon Hobson <[e-mail]> wrote:
> Mark Smith <[e-mail]> wrote:
>
>>> Is this prohibited by this document? Or is ‘/64’ mentioned in the document only an example?
>>
>> No. /64s as the subnet size as been the common edge subnet/IID
>> boundary for almost 20 years since RFC2373.
>
>> Analysis of the 64-bit Boundary in IPv6 Addressing
>> https://tools.ietf.org/rfc/rfc7421.txt
>
> I'll make an observation that one of the primary reasons given is the now deprecated EUI64 addressing model for SLAAC.
> Also there is mention of "but there sooooo many addresses, we can't possibly run out". I don't have a crystal ball, in much the same way that all those decades ago, those designing IPv4 didn't have a crystal ball.


> So it appears to me that the basis of a fixed /64 comes down to :
>
> 1) A now deprecated addressing method requires it
> 2) Based on what we know now we can't see things ever running out
> 3) If any but /64 is used, then some things (implementations) may break.
>
> So isn't the logical route to say that all implementations must support arbitrary prefix lengths - that avoids breakage when (and I suspect in the real world it will be when, rather than if) they meet something other than /64 ?
> Something that handles arbitrary prefix lengths can handle 64+64, the reverse isn't true if it expects 64+64 and is thrown something else.
>
> That and removing references to fixed 64 bit boundaries where they aren't necessary. Noting that allowing plenty of space for randomisation for security by obscurity isn't a technical limitation as such - it's merely a best practice.
>
> And finally. There has been mention in here in the past about not preventing flexibility in the future with things no-one has yet thought of. Yes the numbers are huge, but as I said, I don't have a crystal ball.
>
> And the argument about not having to work out prefixes/masks/etc is only partly true - and assumes that no-one would ever have to work with anything but /64. It could well lead to people who CANNOT work with anything else, in the same way that many people cannot work with anything but /24 in the IPv4 world.
>
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