Hi TJ,
Thanks for your good follow-up comments and questions.
I will need to consult with George and others regarding the delay contribution from connectors since none of the other IEEE 802.3 clauses that specify a maximum link segment delay mention them.
Regarding alternative cable types:
- As noted in my contribution, the TF needs input regarding which types of twisted pairs should be considered. The velocity factor among those specified
in other 802.3 clauses ranges between 0.532 and 0.611. Since Scott and I have been focused on coaxial cable, I would defer to others regarding the proper choices of twisted pair cables to consider.
- For alternative coax cables, my investigation when preparing the contribution indicated that all the alternatives had a faster velocity factor of at
least the 0.66 of CX31 and CX174, with several types being >0.8. That’s why I was comfortable recommending 76 ns for the cable delay. Per my concluding bullets, I welcome input from cable experts regarding how much delay overhead should be added.
Thanks, and best regards,
Steve
Steve Gorshe, Ph.D., IEEE Life Fellow
Associate Fellow-Architecture
---------------------------------------------------------------------
Microchip Technology
MS-1F
21015 SE Stark Street
Gresham, OR 97030
+1 503 669 6171
From: TJ Houck <thouck@xxxxxxxxxxx>
Sent: Friday, May 2, 2025 8:25 AM
To: STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx
Subject: [802.3_ISAAC] Link Propagation Delay
EXTERNAL EMAIL:
Do not click links or open attachments unless you know the content is safe
Hi Steve,
Thanks for the presentation yesterday—it was very informative.
I have a follow-up question regarding the 76 ns propagation delay proposal. You referenced CX31 and CX174 as example cable types, assuming a 15-meter length. However, the proposal did not factor in the four inline connectors that have been
referenced in other task force discussions. From past measurements, these can contribute roughly 1–2 ns, which would bring the total closer to 80–84 ns in practice.
Given this, I was curious about your thoughts on:
- Including inline connector delay explicitly in the budget, mainly as most real-world systems include them.
- Allowing room for alternate cable types that may have slightly different velocity factors outside of CX31 and CX174 you referenced.
Best Regards,
TJ Houck
System Architect, Detroit
Mobile: +1-765-426-9832 | thouck@xxxxxxxxxxx
To unsubscribe from the STDS-802-3-ISAAC list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-ISAAC&A=1
To unsubscribe from the STDS-802-3-ISAAC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-ISAAC&A=1