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


Now this is somewhat different from the way the previous statement came out.
Mapping data to a fixed size TDM pipe may cause  latency variation as a function of
how much data is buffered. A small component in order of several microseconds is
due to SOENT/SDH 125us frame structure.

Regards, Siamack
ps I am not sure if we are supposed to talk company specific stuff in the WG or its
mailing list

Roy Bynum wrote:

> Siamack,
> 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.
> >
> >Roy,
> >
> >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
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