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RE: Clock tolerance

Hi Devendra and all,

I think that is not enough to reduce the clock tolerance to 50ppm.

As far as I know, ITU-T is going to approve (February 2001) a new 
recommendation (G.709) that defines OTN (Optical Transport Network).
Future optical backbones over long distances will likely to be realized 
using G.709 and this will happen before 10 GbE final approval.

In G.709, among the others, a CBR10G client signal is defined as "a 
constant bit rate signal of 9953280 kbit/s +/-20 ppm" (for example an 
OC-192/STM-64 signal and then, in principle, also a 10 GbE WAN signal).

So, in my opinion, at least for a 10 GbE WAN signal, the clock 
tolerance should be 20ppm.

Best regards,
      \/                        Luigi Ronchetti
A L C A T E L  via Trento, 30 - 20059 Vimercate (MI) Italy
   TND R&D     phone: +39-039-686.4793 (Alcanet 2-210-(3)4793)
               fax:   +39-039-686.3590 (Alcanet 2-210-(3)3590) 

> -----Original Message-----
> From: tripathi@xxxxxxxxxxxx [mailto:tripathi@xxxxxxxxxxxx]
> Sent: Tuesday, January 09, 2001 10:50 PM
> To: stds-802-3-hssg@xxxxxxxx
> Cc: tripathi@xxxxxxxxxxxx
> Subject: Clock tolerance
> Hi,
> Right now we are specifying the clock tolerance of 100 ppm. Currently
> in-expensive
> oscillators are available with tolerance value less than 50 
> ppm. Just like
> we are moving
> voltage levels, it is time we revise the tolerance value too. 
> The elastic
> buffer
> requirements get simplified by this assumption. I propose 
> that we reduce it
> to 50 ppm.
> Regards,
> Devendra Tripathi
> VidyaWeb, Inc