Hi Natalie and all,
Currently the PLCA specification supports PLCA and CSMA/CD interop. Seeing the following PLCA and CSMA/CD interop issue and not sure anyone else saw similar issue. The spec may need update to clarify/fix this; this will also affect EPLCA.
The orange boxes highlight the issues.
- Normally, the first Tx transfer in PLCA always starts with collision and retry due to not having TO and FIFO getting full
- During PLCA Node’s 2nd retry transfer, a CSMA/CD device also transmits and collides, we are not setting packet-pending/CSR for this collision.
- Since we didn’t set CRS, the MAC retries 3rd time when we don’t have TO and this causes collision indication and we set packet-pending/CRS
- On the next PLCA cycle, when we have TO, we remove CRS. Because of multiple retries, the MAC retry timer has increased and it does not indicate any transfer even though we have the
TO. We clear packet-pending at the end of our TO and CRS is already cleared.
- The MAC now retries again 4th time when we don’t have TO and we indicate collision and we set packet-pending/CRS
- This can go on multiple times, and we can exhaust all 15 MAC level retries.
The following spec change could fix this:
- On media collision also we set packet-pending and CRS
- When the packet-pending/CRS are set previously and we have TO and MAC does not start any transfer, we continue to hold these till our next TO in the next PLCA cycle (do this up to
15 times?).
Thx,
Arvind.
From: Natalie Wienckowski <natalie@xxxxxxxxxxxxxxxxxxx>
Sent: Friday, October 9, 2026 1:32 PM
To: STDS-802-3-EPLCA@xxxxxxxxxxxxxxxxx
Subject: [802.3_EPLCA] IEEE 802.3 PLCA Enhancements upcoming meetings and due dates.
Dear Colleagues,
We have an ad hoc meeting scheduled on Thursday, October 22nd. The main goal for this meeting is to select a draft set of Objectives, to be reviewed, modified, and approved in November. This meeting can be found on the 802.3 Calendar
(https://ieee802.org/3/calendar.html). Please
note, this meeting has been changed to use my WebEx account instead of the previous Zoom meeting. If you had added this to your calendar manually, please update it.
If you would like to present at this meeting please observe the posted deadlines:
-
October
22, 2026 (Thursday)7 am PDT/USA, Presentation Request by Oct 16, presentation sent by Oct 20, 2026
We will meet during the November Plenary in Bangkok, Thailand. REGISTRATION and FEES apply.
We are scheduled to meet the morning of Wednesday, November 11th. This meeting can be found on the 802.3 Calendar.
If you would like to present at this meeting please observe the following deadlines:
- November 9-12, 2026 (Plenary) (Requests due AOE October 29, Presentations due AOE November 3)
Thanks,
Natalie Wienckowski
In-Vehicle Networking Solutions LLC
IEEE P802.3 EPLCA Chair Pro Tem
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