Priscilla Oppenheimer wrote:
> It appears from further research that both process and fast switching
> interrupt the CPU. The difference is that with process switching, during
the
> interrupt, the CPU determines the type of packet and copies it into
> processor memory if necessary (this decision is platform dependent).
> Finally, the processor places the packet on the appropriate process' input
> queue and the interrupt is released.
>
> The next time the scheduler runs, it notes the packet in the input queue of
> ip_input (assuming it was an IP packet), and schedules this process to run.
>
> With fast switching, the CPU is interrupted, and the packet is actually
> switched at that time.
Yup, that's how I understood it as well. The CPU must be interrupted in
all cases, because otherwise, how could it know a packet had arrived?
Unless you're doing distributed switching of some kind, of course; in
that case, the receive interrupt needn't be seen by the main CPU at all.
> However, I wasn't able to glean an answer to the original question about
the
> second part of the statisitic when you do a show interface. Do you think
the
> second part (the interrupt part) is just refering to the second situation
> (switching the packet during the CPU interrupt)?
That's how I always understood it anyway.
I'll take a peek at 'Inside Cisco IOS Software Architecture' when I'm at
work.
Regards,
Marco.
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