The stupidity of trying to "fix" DHCPv6

Nick Hilliard nick at
Tue Jun 14 16:15:34 UTC 2011

On 14/06/2011 16:12, Ray Soucy wrote:
> The point was you shouldn't base protocol design around the
> possibility that someone might tell it to do something you don't want
> it to do; otherwise you'll end up with a one-size-fits-all protocol
> that has zero flexibility (and might not even be functional at all).

sensible engineering dictates that design should aim to be fail-safe.  I.e. 
not "failsafe" in the common usage of the term (= doesn't fail), but rather 
cogniscent of the fact that all systems fail from time to time, and when 
they do, they ought to fail in such a way that the collateral damage is 
minimised.  This principal is recodified in various ways ("be liberal in 
what you accept", etc), but the underlying idea is the same.

In IPv6-land, we appear not to have learned the lessons from ipv4 history, 
and our vendors aren't yet shipping switches with native RA- and DHCPv6- 
guard (yes, there are some exceptions to the former).


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