Re: draft-bourbaki-6man-classless-ipv6-00

[Job Snijders <[e-mail]>]

Dear Lorenzo,

On Fri, Jun 02, 2017 at 11:33:41PM +0900, Lorenzo Colitti wrote:
> Do not support. A few reasons:
> 
>    - The /64 boundary is beneficial for many reasons. See RFC 7421 and RFC 7934.

>From our brief hallway conversation at IETF 98 I was under the
impression that you have a strong personal preference for the /64
boundary because you believe there to be '64 bits for the network' and
'64 bits for the end-user' - however I do not share your (simplistic?)
view of the world.

Depending on the context, there may be more then 2 parties: an end-user
might be a network provider themselves, and these functions can be
recursive. What if someone resells a service to someone else? Without
flexibility on the /64 boundary one can't cut up the assigned space in
smaller pieces. 

It's been mentioned a couple of times before: any fixed boundary
(including /64) is detrimental to permissionless expansion at the edge
of the network.

>    - The document lists no compelling use cases of what you can do
>    with less than 2^64 addresses per link than you can't do with a
>    2^64 addresses per link.

This is not true. The security section for instance shows: "In such
cases, the use of smaller subnets forces an operational limit on such
data structures, thus helping mitigate some pathological behaviors (such
as Neighbor Cache Exhaustion attacks)." 

>    - The only technical motivation in this draft seems to be "classful
>    addressing was a bad idea in IPv4". That's not a valid argument in IPv6
>    because the address space is completely different. A /64 is *four billion
>    times* bigger than the IPv4 internet. That's 10,000 times more than the
>    difference between a grain of sand and the whole planet we live on. Such a
>    huge scaling difference pretty much invalidates any argument that solutions
>    that worked well in IPv4 will work well in IPv6.

Would be a shame to throw away lessons learned from IPv4.

>    - Routing on any prefix length is already required by the standards -
>    see BCP 198.

Yes, RFC7608 is referenced as suggested reading.

> Please stop trying to make IPv6 be the same as IPv4. That will take
> away our ability to make the Internet better once IPv4 is gone.

I believe there to be tangible merit in making IPv6 feel and look more
like IPv4. Perhaps this becomes more apparent when one shifts the
innovation focus from layer-3 to higher layers.

Making IPv6 look more like IPv4 (for instance through broader adoption
of DHCPv6 w/ routing options, and classlessness like in IPv4) will
positively impact IPv6 deployment.

Kind regards,

Job