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

Le 13/06/2017 à 09:51, Ola Thoresen a écrit :
> On 13. juni 2017 04:22, Manfredi, Albert E wrote:
> 
>> Why so, Brian? I've already described one easy technique: the host 
>> can create IIDs of any length, based on an algorithm that we might 
>> just be debating for a long time, but fundamentally can be quite 
>> straightforward. And then the host chooses the correct IID to use 
>> for SLAAC, based on the RA it just received.
> 
> 
> Some people argue in the DNS "tussle" that it might be a problem if 
> the host receives different DNS-info from eg. RAs and DHCP. And now 
> we are discussing if the host should create its LL prefix length 
> based on a variable in the RAs?
> 
> What if multiple routers in a network announces different prefix 
> lengths? This would cause MUCH greater problems

Please identify such a problem.

In my setting, I could put a /64 and a /65 PIOs in a same RA.

The kernel of the existing Host would self-configure an address out of
that /64 and ignore the /65.  The software-to-be-written in userspace
would consider only  the /65 and form a second address.

What do you think breaks in this casE?

> than just getting an invalid DNS-server and would require much more 
> work for the operators to keep consistent throughout a complex 
> network.
> 
> I can foresee scenarios here, where one router is deployed and 
> announcing prefix-lengths of /80 for its public prefix.  Then
> another router is added do the mix, that does not have the
> flexibility to change the prefix-length, so it will always use /64.

What breaks in this case?  Who complains?  I think the existing Host
simply ignores the /65.

> Then the operator would either have to renumber the first prefix to 
> /64 as well, or you would be stuck with two different prefixes 
> announced in the RAs, and the host constantly regenerating its LL.

But the LLs have a prefix and plen that is distinct from the PIOs.  It
is fe80::/10.

> Or you would be forever forced to always use the longest prefix for 
> all subnets,

No.  Let's make that into a requirement: the longet-prefix applies for
forwarding but MUST NOT apply for address auto-configuration.

> so as soon as I have deployed 2001:db8:1234:5678:9abc::/80 from one
> ISP, I can never use anything but a /80 on that link no matter what
> prefix size another ISP might give me.

Right above.

Alex

> 
> 
> Rgds.
> 
> Ola (T)
> 
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