Re: “DHCPv6, SLAAC, Static Day X - 17 year interoperability issue” 2nd issue

[Alexandre Petrescu <[e-mail]>]

Le 10/11/2020 à 03:29, Gyan Mishra a écrit :
> I was just giving an example of mixed hosts on the same subnet using 
> different IPv6 addresses methods.  So it can be any network or any
> scenario where you have mix of addressing methods with longer
> prefixes.

It could be even just one single smartphone.  In every single smartphone
there are at least two processors inside.  The use of virtual machines
is highly probable.  Each one would need an address.  They are on
different subnets.

This problem of virtual machines on a smartphone was mentioned by
somebody else earlier, I only repeat it.

There could be, and there are, what I call 'hacks'.  These hacks make it
possible to exclude a /64 from a /56 (prefix exlude options in DHCP or
in PMIP); they make possible to use 'proxy' ND; they make unwritten
assumptions of padding always with 0s; they make a host sending itself
an RA just for the purpose of forming an address; and there are more
hacks that I might not remember that quickly.

Alex

> 
> The problem is that SLAAC does not support >64 prefixes due to IID 64
> bit limitation and that prevents use of DHCPv6 stateful or static
> with >64 prefix subnets.
> 
> 
> On Mon, Nov 9, 2020 at 9:19 PM Joel M. Halpern <[e-mail]>
> wrote:
> 
>> Gyan, I apparently was not unclear. I was not asking who needs to
>> use longer prefixes.  I was asking why. Telling me that some data
>> enters want them does not tell me what problem the data center
>> needs to solve.
>> 
>> Can you explain what problem needs to be solved, for whichever
>> community it is that needs to deploy these longer prefixes?
>> 
>> I presume there is a real problem.  But I can not tell from your 
>> description what it is.
>> 
>> Thank you, Joel
>> 
>> On 11/9/2020 8:37 PM, Gyan Mishra wrote:
>>> This is a separate issue from 3GPP PDP handset segmentation issue
>>> to downstream devices.
>>> 
>>> This issue exists with any deployments where the operator would
>>> like to deploy >64 prefix length host subnets at data center or
>>> access layer and this could be an enterprise or service provider
>>> use case where the router infrastructure is statically configured
>>> so no PD here.
>>> 
>>> So in this case the operator would like to deploy >64 prefixes
>>> and has let’s say all servers are configured with static and all
>>> access hosts are configured with dhcpv6 stateful RFC 8415.  No
>>> PD here.   So we have both static and stateful hosts on the same
>>> subnet.
>>> 
>>> So now you have SLAAC hosts that get added to that same subnet
>>> that now don’t support static or DHCPv6 stateful let’s say
>>> Chromebook or could be any device type for example and now your
>>> are in trouble.
>>> 
>>> So now due to SLAAC not supporting longer prefixes that very real
>>> fear of host operating systems that may only support slaac you
>>> and up in an terrible interoperability situation that you have to
>>> change your prefix length for all devices back to /64 so that all
>>> devices types with the 3 different IPv6 address allocation scheme
>>> can operate on the same subnet