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Whats so difficult about ISSU



I apologize, I realized I forgot a critical word in my reply.

The new Cisco OSes are /NOT/ run to completion.

For IOS-XE we have Linux in charge of the scheduler with a
multi-threaded IOSd process responsible for the control plane.  I'm
not familiar with movements to put processes directly on top of the
kernel, but this would be a lot more like the NX-OS model where a
process like BGP can crash without taking down the system (or the
critical IOSd process for example). The down side of this model is
that control plane scaling, due to message passing, starts to have a
lot of overhead. You can see this in the fact that the NX-OS routing
scale is not where IOS-XE is.

-Pete

On Fri, Nov 9, 2012 at 8:27 AM, Saku Ytti <saku at ytti.fi> wrote:
> On (2012-11-09 08:02 -0500), Pete Lumbis wrote:
>
>> 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.
>
> Really? I thought IOS XE is Linux control-plane on top of where you have
> monolithic IOSd process?
> I had chat with Michael Beesley when ASR1k was coming up, and he said Cisco
> has plans to remove processes from IOS and directly on top of Linux in XE,
> starting with BGP. But I don't think that has materialized?
>
> To me JunOS and IOS XE look very much same, NIX control-plane and magic
> process with has its own memory management and cooperative
> multitasking/scheduling?
>
> --
>   ++ytti
>