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

Naveen Kottapalli <> Thu, 31 October 2019 17:40 UTC

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From: Naveen Kottapalli <>
Date: Thu, 31 Oct 2019 23:09:44 +0530
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To: Mark Smith <>
Cc: Ole Troan <>, v6ops list <>
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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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The problem I feel is mainly because of the the middle boxes sitting
between the devices which are using the prefix and the one who delegated
the prefixes.  I believe in most of the deployed implementations like the
BNG or any DHC server will have a record of the prefixes being delegated
and lifetimes will be honored till lease time expires.  As a matter of fact
in the cases listed, prefixes are be valid for the given lifetimes at both
the device and the delegating router.  Just because the CPE got rebooted or
lost the context of the prefixes, the middle boxes deprecating or
suggesting a whole set of new prefixes towards the devices might not be the
solution to the actual problem.


On Thu, 31 Oct 2019 at 05:09, Mark Smith <> wrote:

> On Wed, 30 Oct 2019 at 22:02, Ole Troan <> wrote:
> >
> <snip>
> > In the case when a requesting router loses a prefix, it can of course
> signal that to the hosts as proposed in Fernando's draft. But that doesn't
> solve the general problem, and I'm skeptical to using addressing as a
> reachability signal. E.g. if the CPE's upstream link flaps, is that enough
> to trigger deprecation of the prefix? Of course it shouldn't.
> >
> Exactly. Transient network faults are supposed to be survived - that's
> why TCP makes quite a number of attempts at re-transmitting when
> packet loss occurs, rather than just immediately terminating the
> connection.
> When an ISP "flash renumbers" a customer what's really happening is
> that the customer's network layer point of attachment to the network
> is being changed - the customer is being abruptly disconnected, moved
> and re-connected. Possibly that is easy to overlook because the
> customers physical location and their physical link to the network
> doesn't change.
> 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.
> Regards,
> Mark.
> > Ole
> > _______________________________________________
> > v6ops mailing list
> >
> >
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