Question Regarding 09-268 SPL - STP Extended Buffer Support

Tim Symons Tim_Symons at pmc-sierra.com
Mon Nov 2 12:17:39 PST 2009


* From the T10 Reflector (t10 at t10.org), posted by:
* "Tim Symons" <Tim_Symons at pmc-sierra.com>
*
Pd (total cable assembly prop delay) needs to report the delay from one
electrical connector the other. 
For optical cables, the bridge to laser light and back to electrical
domain should be considered part of the "active component of the cable"
and must be included in the propagation delay value.
It would be useful to have some reference data for optical cables as
well as copper. Maybe 50m, 100m, 250m and 500m optical cables Pd values
would be useful.
Tim.
Tim Symons
Principal Engineer, PMC-Sierra Ltd.
Cell: 778 998 5025
E-mail Tim_Symons at pmc-sierra.com
-----Original Message-----
From: Olawsky, Barry [mailto:Barry.Olawsky at hp.com] 
Sent: Monday, November 02, 2009 12:08 PM
To: Tim Symons; McGrath, James
Cc: t10 at t10.org
Subject: RE: Question Regarding 09-268 SPL - STP Extended Buffer Support
Tim (Symons),
I'm working with some bulk cable suppliers to calculate my own numbers.
I'm not sure how to approach the optical configurations.
-----Original Message-----
From: Tim Symons [mailto:Tim_Symons at pmc-sierra.com] 
Sent: Monday, November 02, 2009 1:55 PM
To: McGrath, James; Olawsky, Barry
Cc: t10 at t10.org
Subject: RE: Question Regarding 09-268 SPL - STP Extended Buffer Support
At an earlier meeting, it was noted that optical cables and any cables
different transmission media may exhibit propagation delays that would
be significantly different from the 5nS per meter "rule-of-thumb" used
today.
Can anyone comment on the propagation delay ranges for cables made of
other materials in addition to Jim's 24AWG/30AWG copper gauge data.
Note that this data is for managed cables Mini-SAS HD and QSFP+
Regards
	Tim.
Tim Symons
Principal Engineer, PMC-Sierra Ltd.
Cell: 778 998 5025
E-mail Tim_Symons at pmc-sierra.com
-----Original Message-----
From: McGrath, James [mailto:jmcgrath at email.cinch.com] 
Sent: Monday, November 02, 2009 10:54 AM
To: Olawsky, Barry; Tim Symons
Cc: t10 at t10.org
Subject: RE: Question Regarding 09-268 SPL - STP Extended Buffer Support
Barry, Cinch has done some work to help answer this question. For
example, in a 3m cable there is less than 0.50nanosec difference in prop
delay from a 24AWG to a 30AWG cable. So length appears to be a practical
parameter to determine prop delay. I can show a few charts, if needed,
at the meeting next week. 
Jim McGrath
Cinch Connectors
1700 Finley Road
Lombard, IL 60148
office: 630-693-2040
mobile: 630-244-3872
-----Original Message-----
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Olawsky,
Barry
Sent: Monday, November 02, 2009 11:30 AM
To: Tim Symons
Cc: t10 at t10.org
Subject: Question Regarding 09-268 SPL - STP Extended Buffer Support
* From the T10 Reflector (t10 at t10.org), posted by:
* "Olawsky, Barry" <Barry.Olawsky at hp.com>
*
Tim (Symons),
During the SFF-8636/8449 conference call on October 22nd a question was
posed for which we need your assistance to answer. Tom Palkert of
Luxtera proposed using cable length to estimate the end-device to
end-device propagation delay. To determine if this is a feasible
technique, we need to know the maximum acceptable total propagation
delay error including resolution and accuracy errors. Since you propose
limits on this parameter in 09-268 we thought you might have valuable
input on this topic.
Barry Olawsky
Hewlett Packard
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