Re: [v6ops] Stability and Resilience (was Re: A common...)

[Fernando Gont <[e-mail]>]

On 22/2/19 13:36, Lee Howard wrote:
> I think I have heard the following suggestions in this conversation. I
> hope that taken all together, rather than as individual spot solutions,
> they can be a consensus recommendation.
> 
> 
> ISPs should, as much as possible, reissue the same prefix to customers.

Actually, I think that we agreed on not to tell ISPs how to run their
networks!


> Some things ISPs can do to increase the chances of this:
[...]

Analysis of the tradeoffs between stable vs dynamic prefixes can be
valuable, as well as advice on how to achieve each of them. However,
that certainly doesn't solve the problem... and at the end of the day,
it's an ISP choice whether they do dynamic or stable prefixes. ANy such
advice should happen in a separate document.


>  3.
> 
>     Set DHCPv6 lease timers very low prior to grooming events. A short
>     interval during the maintenance window will increase load on the
>     DHCPv6 server until timers have been returned to normal values.

Please see the full discussion in our I-D. That said, as per RFC4862 you
cannot lower the Valid Lifetime any further than two hours. So this is,
unfortunately, mostly useless.



> Networks should, as much as possible, be resilient to prefix changes.
> Some things networks can do to improve resilience:
> 
>  1.
> 
>     Write a learned prefix to non-volatile memory and issue a DHCPv6
>     Renew for that prefix on reboot.

Ultimately, you can only improve resiliency by improving the host behaviour.



> In the case of failures, it cannot be assumed that sessions will stay
> active.

Of course.


> We try to build in redundancy and resilience where we can, but
> where there's a single point of failure (such as CE or PE), and it fails
> (such as an unplanned reboot), our expectations should be appropriate.
> 
> Is this a reasonable summary?

I don't think so. Please check Sections 3 and 5 of our document. mY
working copy is at:
https://github.com/fgont/draft-slaac-renum/blob/master/draft-gont-6man-slaac-renum-02.txt
. Our plan is to publish a rev soon.

Thanks!

Cheers,
-- 
Fernando Gont
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