[802.3_ISAAC] Link Propagation Delay

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To: STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx

Subject: [802.3_ISAAC] Link Propagation Delay

From: TJ Houck <thouck@xxxxxxxxxxx>

Date: Fri, 2 May 2025 15:24:32 +0000

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Reply-to: TJ Houck <thouck@xxxxxxxxxxx>

Thread-index: Adu7deX5Rysu8ws7TRKDDoKyvWI8Xg==

Thread-topic: Link Propagation Delay

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

www.marvell.com

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