George,
That makes sense to me.
Regards,
Peter
_______________________________________________________________
Peter Jones Distinguished Engineer,
Cisco Networking Hardware
Chair, Ethernet Alliance
Mobile: +1 408 315 8024
Email:
petejone@xxxxxxxxx
Web:
https://about.me/petergjones
Webex:
https://cisco.webex.com/meet/petejone
Book a call: Peter's
booking page
_______________________________________________________________
From: George Zimmerman <george@xxxxxxxxxxxxxxxxxxxx>
Sent: Wednesday, January 8, 2025 7:43 AM
To: STDS-802-3-SPMD@xxxxxxxxxxxxxxxxx
Subject: [802.3_SPMD] Comment 323
Comment 323 on the PLCA-Control state diagram seems to require some thought. I am now convinced that the proposed ACCEPT is a mistake, at least for the reason that the dplca variables used (dplca_aging and dplca_txop_table_upd) aren’t
in the PLCA Control state diagram and need to be communicated, or defined there. A secondary concern is that the change, I believe, would create issues when D-PLCA is not present, because the state variables used in the proposed remedy have no values. We
would at least need to allow for the case where dplca_en = FALSE.
The commenter points out a state diagram issue in PLCA Control, on the transition out of NEXT_TX_OPPORTUNITY. This looks problematic because the solution appears to replace the ‘ELSE’ branch with a conditional (see original below).
With the following suggested remedy:
Suggest that:
[1] The transition condition for the transition from the NEXT_TX_OPPORTUNITY state to the
RESYNC state in Figure 148–4 'PLCA Control state diagram, part b' is changed to:
((local_nodeID = 0) * (curID >= plca_node_count)) + (curID = 255) * (dplca_txop_table_upd +
dplca_aging = OFF)
[2] The transition condition for the transition from the NEXT_TX_OPPORTUNITY state to the
WAIT_TO state in Figure 148–4 'PLCA Control state diagram, part b' is changed to:
((local_nodeID != 0) + (curID < plca_node_count)) * (curID != 255) * (dplca_txop_table_upd +
dplca_aging = OFF)
Reading this, this seems to create a condition where the state diagram can get stuck in the NEXT_TX_OPPORTUNITY when dplca_txop_table_upd = FALSE and dplca_aging = ON – but that appears to be what the commenter is trying to achieve – a
momentary pause in NEXT_TX_OPPORTUNITY to eliminate the race condition with the D-PLCA Aging State Diagram.
At a minimum we need to change the first condition to:
[1] The transition condition for the transition from the NEXT_TX_OPPORTUNITY state to the RESYNC state in Figure 148–4 'PLCA Control state diagram, part b' is changed to:
((local_nodeID = 0) * (curID >= plca_node_count)) + (curID = 255) *
( (dplca_txop_table_upd + dplca_aging = OFF)
+ (! dplca_en) )
The second condition is a little trickier. Because replacing the “ELSE” with a conditional causes the pause that seems to be the intended effect, simply inverting the logic doesn’t work.
I think we should be just adding the ‘no D-PLCA’ case in…:
[2] The transition condition for the transition from the NEXT_TX_OPPORTUNITY state to the WAIT_TO state in Figure 148–4 'PLCA Control state diagram, part b' is changed to:
((local_nodeID != 0) + (curID < plca_node_count)) * (curID != 255) *
( (dplca_txop_table_upd + dplca_aging = OFF)
+ (!dplca_en) )
(then, of course, we need to add dplca_txop_table_upd and dplca_aging to the variables list, with descriptions, “See 148.4.7.2”.
Does this look right?
George Zimmerman, Ph.D.
President & Principal
CME Consulting, Inc.
Experts in Advanced PHYsical Communications
310-920-3860
To unsubscribe from the STDS-802-3-SPMD list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-SPMD&A=1
To unsubscribe from the STDS-802-3-SPMD list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-SPMD&A=1