Re: A common problem with SLAAC in "renumbering" scenarios

[Lee Howard <[e-mail]>]

On 2/13/19 11:38 AM, Jan Zorz - Go6 wrote:
> On 13/02/2019 16:38, Fernando Gont wrote:
>
>
> However, CPE is also an important part of the game here. As said 
> before and as heard from Richard, some huge operators are already 
> deploying this "hack" where they write a PD to persistent storage and 
> compare prefixes after reboots and this solves a lot of problems. Why 
> not making this easy fix a recommended thing to do for everyone?
>
> When talking about the provisioning part - IETF can't tell operators 
> how to run networks (obviously), but what we can do here is to say 
> "when assigning IPv6 prefix to a customer, identified by the same 
> DUID, we must not assign a different prefix to the same DUID before 
> the lifetime of PD that we set doesn't expire, otherwise you are 
> breaking the protocol standards."
"you are breaking the protocol standards" only matters if it breaks 
interoperability. Otherwise you're trying to be protocol police.
>
> If somebody decides (for some bizzare reason) that it's a good idea to 
> make CPEs with randomized DUID after every reboot, then they shall 
> implement memorizing PDs in persistent storage across reboots and send 
> ICMP packets after reboot to deprecate old prefix(es)
Well, CPEs do get some strange ideas of what a DUID should look like. 
When I had the ability to influence CPE features, I told them how to 
build their DUID so it was predictable to me. (I forget which version I 
specified, but it included link layer address). Still didn't help with 
the mass of retail devices.
>
> I think that extending a scope of our I-D to this three "advices" 
> would bring at least some hope for improvement, as currently it can't 
> be worse. Of course, things are easy for huge operators with home-brew 
> CPEs and a lot of knowledge, but there are other, smaller and less 
> deep-tech educated ISPs that could benefit from improved defaults.

My perception is that lack of support for IPv6 at all, followed by lack 
of support for IPv6 transition mechanisms, is a much larger problem in 
CPE. This will simply become another RFC they aren't implementing.

Lee

>
> Cheers, Jan
>
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