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Re: 20 ppm clock tolerance for WIS


When you compared the the two clock sources did the +/-20 oscillator met over the 
temperature (0-70 deg. C) and 10 years of life.  I have noticed the price of the +/-20ppm
oscillators varies significantly if you can limit your temperature range and don't require 
10 years absolute accuracy.


Ali Ghiasi
Sun Microsystems

> Date: Mon, 5 Jun 2000 15:26:02 -0700 (PDT)
> From: Howard Frazier <hfrazier@xxxxxxxxx>
> To: stds-802-3-hssg@xxxxxxxx
> Subject: Re: 20 ppm clock tolerance for WIS
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> Praveen,
> I appologize for the delay in responding to your question.  I wanted to
> be absolutely sure of the facts before I replied.
> I have sent out 5 requests for quotes for oscillators, and thus far I
> have received three responses.
> The first two responses indicated a less than 10% price premium for a
> 20 ppm 155.52 MHz oscillator versus a 100 ppm oscillator with otherwise
> identical specs.  I can't talk about absolute price on this reflector,
> but I can say that the price difference is very small.  Truly, it is
> lost in the noise as far as the overall cost for a 10 Gigabit interface
> is concerned.
> The third quote I received indicated a more substantial cost
> difference.  The 20 ppm oscillator cost twice as much as the 100 ppm.
> However, the lead time for the 100 ppm oscillator was 20 weeks, whereas
> the 20 ppm oscillator is available immediately.  Once again, the
> absolute price difference is a very small percentage of the overall
> cost for a 10 Gigabit adapter.
> My conclusion remains the same.  Specifying 20 ppm is the right way to
> go.  The cost difference does not justify changing to 100 ppm, because
> this change probably will compromise compatibility with existing OC-192
> transponders and regenerators.
> As to the jitter specifications, it is my understanding that the WAN
> PHY proponents want to use all of the same optical components that are
> being specified for the LAN applications of 10 Gigabit Ethernet.  I
> believe that the SONET jitter specifications do impose additional cost
> on the optical components.  It is unreasonable to burden the LAN
> applications with the cost of meeting the SONET jitter specifications.
> Therefore, while I am keeping an open mind on the topic, and I am
> willing to consider other points of view, I believe that we should not
> impose the SONET jitter specifications on the 802.3ae PMDs, and I don't
> think that this will compromise compatibility with OC-192 transponders
> and regenerators.
> If I get any additional responses to my requests for quotes, I will
> be happy to share them on the reflector.
> Howard Frazier
> Cisco Systems, Inc.
> ----- Begin Included Message -----
> From praveen@xxxxxxxxxxx Tue May 30 15:38:01 2000
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> Date: Tue, 30 May 2000 15:56:05 -0700
> To: gnicholl@xxxxxxxxx, hfrazier@xxxxxxxxx, stds-802-3-hssg@xxxxxxxx
> From: Praveen Kumar <praveen@xxxxxxxxxxx>
> Subject: 20 ppm clock tolerance for WIS
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> Gary, Howard:
> 	For the benefit of those who could not make it to your presentation in 
> Ottawa,  could you clarify some of the issues that you raise.
> You mention that the "cost difference between +/-20ppm and +/-100ppm 
> oscillators is a tiny fraction of the total cost of a 10GigE  interface".
> Could you perhaps substantiate this statement with quantitative input (some 
> real numbers).  My understanding is that the +-100ppm tolerance was 
> specified only to keep the cost down (as the cost differential between a 
> 20ppm solution and 100ppm solution is perceived to be significant).
> You recommend using "LAN PHY jitter specs".  This makes the WIS 
> incompatible with installed base SONET . This doesn't seem to meet your 
> goal of being compatible with installed OC-192 SONET 
> infrastructure.  Please clarify.
> -Praveen
> ----- End Included Message -----