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

[Mark Smith <[e-mail]>]

On 17 Jun. 2017 05:15, "Manfredi, Albert E" <[e-mail]>
wrote:

-----Original Message-----
From: ipv6 [mailto:[e-mail]] On Behalf Of Philip Homburg

> Job,
>
> I'm curious what use you have for SLAAC with prefixes longer than /64.

By no means attempting to answer for Job, my answer is simple. SLAAC is a
plug and play technique, and I see no reason why that plug and play
technique cannot be applied to other than /64 networks. There's no reason
to make non-/64 networks always an exception, only available for manual
configuration, or even only available with this DHCP-PD that isn't much
supported.

To expand a routed network at the edges easily, and allow subnetting in the
expanded network, and allow plug and play operation in the expanded part,
SLAAC should be one element of the solution. DHCP-PD recycles the same
technique used in IPv4, and it's a good additional option, especially
useful when the client addresses must be known to the network operator.



* DHCPv6 does not record addresses in use on a link. It will not record
link local addresses or manually configured addresses. It is only recording
hosts that asked to acquire addresses via DHCP.

* You're overlooking the cost and service impact of renumbering to increase
the size of the subnet if it isn't large enough. That can be a large cost
and large impact if many hosts are involved. So large, I've seen people
avoid paying it when there were in the order of 1000 hosts involved on an
IPv4 network - the hosts were spread across 4 x /24s on the same Ethernet
segment.




Given that variable length IID SLAAC is just not difficult to implement, in
a graceful, backward-compatible manner, I can only conclude that opposition
to it is opposition to allow for easily moving the 64-bit boundary.

> The most contentious point in draft-bourbaki-6man-classless-ipv6-00
> is that it tries to change the IID length used for SLAAC.

That should hardly be contentious, on technical grounds, because the
problem is not difficult to solve. It might be contentious only
tangentially, in the sense that it makes variable prefix lengths so easy to
contend with?

Bert


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