[j-nsp] flow sampling: what packets are chosen?

[Michael Loftis]

On Wed, Jul 24, 2013 at 10:10 AM, Phil Sykes <phil at atdot.at> wrote:

> Run-length appears to be unsupported on newer (e.g. MX3D MPC) hardware.
>
> Regards,
>
> Phil
>

ISTR reading that's because they're 1:1 hardware sampling inside Trio
instead of just punts to the LC CPU or RE CPU, at least for IPFIX on
Trio.  Probably from the O'Reilly Juniper MX ... yup found it.  (any
typos are mine as I'm retyping this)

"When using inline IPFIX the only valid rate is 1.  The option
run-length isn't configurable, because there's no need to sample data
from the perspective of the microcode in the Trio Lookup Block.  Every
packet will be inspected and is subject to flow export."

Which seems like a dumb/dense view of things since even Trio has
limits on the flow rates/etc and - while I haven't done the math at
all - I'd bet it's entirely possible to exceed those limits.

--

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