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Re: SONET/Ethernet clock tolerance


I have discussed about jitter budget over the end-end SONET-framed link.  
As I understand, in a chain of SONET(-lite) regenerators, the link jitter 
budget should be specified for all the chain elements.  This means each 
regenerator should meet very stringent jitter-transfer specifications.  
I think this is not the issue of +/-100ppm or +/-4.6ppm.

It would be appreciated if you let me know about jitter-transfer spec. 
in "SONET-lite".

Also please let me know if you have any further information about 
"SONET-lite".  I have checked the T1.416 Standard Document approved 
last December, but I can not find any statement about "+/-100ppm".  
It seems to say just "be compliant to T1.105 (=SONET)".

My understanding at present is that there is no "SONET-lite" standard 
in ITU-T, T1, IETF, nor OIF.  Please correct me if I am wrong.

Best Regards,
Osamu Ishida

At 8:37 AM -0600 00.3.29, Roy Bynum wrote:
> The clock tolerances for regenerators (LRE) are very relaxed from those of
> line terminating equipment (LTE).  It is the LTE that does the multiplexing
> of the smaller TDM payloads into a full OC192 payload and puts the full
> SONET overhead on it, scrambles it,  and sends it out.  The regenerator does
> a line clock recovery, unscrambles the SONET frame, uses the section
> overhead information to determine performance and fault issues, rescrambles
> the SONET frame, and sends it out.  The regenerator re-times the signal
> using the recovered clock, not a Stratum clock.  In the process the
> regenerator removes any signal bit jitter that has been introduced by the
> various forms of dispersion that occur in optical fiber over any distance.
> Because it does not do the multiplexing and does not have the clock
> tolerance issues that the LTE has, a regenerator is a lot less expensive
> than an LTE.