The shaping is done on the cell rate. People coming up with the calculations
are trying to provide end users/customers with IP performance equal to the
contracted rate so they are giving more ATM cell rate than it reads on the
contract.
Pete
----- Original Message -----
From: "Martin, Christian" <CMartin@mercury.balink.com>
To: <cisco-nsp@puck.nether.net>
Sent: Thursday, June 08, 2000 10:24 AM
Subject: [nsp] ATM PVC Shaping Question
> Folks,
>
> OK, I need an answer to this once an for all. Can someone stake their
> reputation on answering the following question:
>
> Does a Cisco router using PA-A3 hardware (or NPM-ATM) shape vbr-nrt
traffic
> based on the cell rate or the payload rate? I hear so many people saying
> that it is done based on payload, and they break out these little
> calculations to 'account' for the overhead. I cannot fathom that this is
> done before SAR. As I see it, the GCRA algorithm is cell-based,
therefore,
> leaky bucket operations are most efficiently done at a cell boundary.
Given
> varying lengths of CPCS PDU sizes, I would think that shaping would have
to
> be done in software were it done based on payload, which obviously would
be
> a huge performance hit. Unless the SAR chipset does this first? Call me
> crazy...
>
> ./chris
>
>
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