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Re: [EFM] RE: Pause frame usage in transport networks


The 125us that I was referring to was worst case under close to 100% 
utilization.  Not all frames had that much latency variance, even at that 
loading.  Some of the frames in the traffic stream had a latency variance 
that was closer to the bit time delta of the largest to smallest frames, 
which is closer to the inherent worst case latency variance of native 802.3 
Ethernet.  Some frames had very little, if any latency variance.

Under best case conditions, data traffic streams can have almost no latency 
variance, particularly when switching constant size frames.  This is true 
of almost all Ethernet only data switches.  I am not sure if it is true of 
IP/MPLS switches, but it could be under certain conditions.

I would interested in hearing more about the what your company is doing.

Thank you,
Roy Bynum

At 09:36 AM 3/5/2003 -0500, Siamack Ayandeh wrote:

>Roy Bynum wrote:
> > Regardless of the protocol that is used, all TDM transmission facilities
> > induce a 125us latency variance at the customer data link layer.  This is
> > because the transmission convergence mapping is based on a specific payload
> > window that occurs every 125us  in SONET framing.
>I don't think this statement is quite correct as not the entire 125us 
>frame needs
>to be mapped/switched at once. Current generation SONET/SDH framing/switching
>equipment have a latency variance that is an order of magnitude less than the
>125us frame interval.
>Regards, Siamack