Re: [v6ops] A broken promise - "You said PD Prefix Valid Lifetime is going to be X" (Re: SLAAC renum: Problem Statement & Operational workarounds)

Fernando Gont <fgont@si6networks.com> Fri, 08 November 2019 12:56 UTC

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To: Ole Troan <otroan@employees.org>
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From: Fernando Gont <fgont@si6networks.com>
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Date: Fri, 8 Nov 2019 09:55:49 -0300
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Subject: Re: [v6ops] A broken promise - "You said PD Prefix Valid Lifetime is going to be X" (Re: SLAAC renum: Problem Statement & Operational workarounds)
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On 8/11/19 09:47, Ole Troan wrote:
>>>>> I think Ole observed that this is contrary to what the PD 
>>>>> prefix's Valid Lifetime said would be the case. The ISP supplied 
>>>>> a PD Prefix with a Valid Lifetime of X seconds, and then broke 
>>>>> that promise by abruptly changing addressing before X seconds. 
>>>>> ISPs should be expected to live up to their Valid Lifetime 
>>>>> promises.
>>>>
>>>> "Hope" doesn't make networks run properly.
>>>
>>> This isn't "Hope", this is breaking promises, and that does break 
>>> networks. If you can't at least trust that promises are intended to 
>>> be kept then you have no network at all...
>>
>> They are intended to be kept, but at times s* happens e.g., CPE routers
>> don't crash and reboot on purpose.
> 
> This comment worries me.
> That a CE reboots is _not_ the problem, nor does it cause the problem.

Well, if the CPE did keep state, there would be no problem. (is there a
formal requirement for prefixes to be stable across crash & reboots?).

(just as a reminder, this is just one scenario. there have been at least
three operators that have noted that their setups experience renumbering
scenarios for other reasons... and slaac could certainly do much better
in those)

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492