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Whats so difficult about ISSU

I can't speak for JunOS, but none of the "new" IOS operating systems
are run to completion. This includes IOS-XE, XR and NX-OS.

On Fri, Nov 9, 2012 at 2:36 AM, Saku Ytti <saku at ytti.fi> wrote:
> When we start on that premise, we can do silly things like write
> run-to-completion operating systems like IOS and JunOS (rpd). Which means
> single guy making one bad judgement call, and whole OS is bad.
> Of course run-to-completion is most optimum way to execute code, if your
> code is flawless, but that ship has sailed. Possibly when IOS started CPU
> time was premium and it was cheaper to through code review money at the
> problem.
> But today it clearly is cheaper to add power to control plane and have
> levels of abstraction in control-plane which saves the system from bad
> code, i.e. design your control-plane assuming code you deliver isn't good.