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Re: [802.3ae] XAUI Rj TR comment


Your presentation is a very nice summary, particularly of the issues 
regarding jitter tolerance.  Thanks.

If you don't mind, I would like to make a comment and ask a question:  

 * With regard to your method #2 for RJ testing ("adding noise to 
   clock"), I suspect that very reasonable bandwidth limitations 
   on the Gaussian noise would avoid any unintended zero crossings.
   The available bit rate clocks seem to have more than adequate 
   amplitude control and spectral purity to make this amplitude-to-
   phase conversion very reliable and repeatable.

 * This is more of a question.  My background is with the Fibre
   Channel jitter working group which evolved this methodology.
   The implicit assumption behind allowing RJ =< TJmax - DJ(actual)
   was that the worst case was DJ=DJmax.  Random jitter was assumed
   to be more benign than DJ.  Hence, testing is required only for
   DJ=DJmax.  I would appreciate hearing any argument to rebut that

Mike Jenkins

"Howard A. Baumer" wrote:
> To all concerned,
>      I put in a TR Comment against D3.1 stating the desire to put a
> maximum
> limit on the TX Rj.  This comment was rejected and left unresolved.
> There was fairly wide agreement that having a max limit on TX Rj should
> be done but that we should first get a broader input on what this limit
> should be.  I took on the action item to start a reflector discussion to
> determine this limit.
>      The current draft sets a limit for Tj and a limit for Dj and then
> defines Rj aa Rj = Tj(max) - Dj(actual).  The TR comment proposes that a
> limit be set for Tj, Rj and Dj and that Rj(actual) + Dj(actual) <
> Tj(max). There is a presentation that we are developing that
> attempts to figure out a limit for Rj.  It can be found at
> Please review and comment.
>      This presentation also brings out a problem with the current Jitter
> Tolerance test technique.
> Howard Baumer

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