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[802.3_ISAAC] Half duplex and full duplex

Dear all, 

 

On page 13 of the slide shown during the ISAAC meeting on Wednesday August 16, suggestions for general objectives are listed (see https://www.ieee802.org/3/ISAAC/public/081623/PAR_CSD_OBJ_081623_01.pdf). I concur with the first five objectives listed under “general and automotive objectives”, but I would like to discuss and understand better the rationale behind the suggestion to limit the technical solutions to “support full duplex operation only”.

 

Following thoughts occur:

  • We already have full duplex (PHY and MAC) MGbps Automotive Ethernet solutions.
  • For highly asymmetric use cases, half duplex (PHY and/or MAC) may reduce complexity and the reduction of complexity is one of the concerns and motivations for the projects.
  • Half duplex PHYs would have a distinct identity (as said, full duplex PHYs already exist).
  • There is the precedent of 10BASE-T1S, with a mandatory half-duplex P2P operation (see https://www.ieee802.org/3/cg/objectives_3cg_0318.pdf).
  • Even 1000BASE-X/T have half duplex modes (Clauses 22.2.4.4.2.and 22.2.4.4.4).
  • Why/when would we need full duplex for the envisioned use, i.e. to allow the MAC to send whenever? In the second part of the project we are explicitly looking for “2) a protocol for interfacing a PHY with asymmetric peak data rate capabilities to the existing 802.3 MAC with media independent interfaces at existing 802.3 rates”. Having an objective for full duplex operation (PHY or MAC) is an unnecessary burden.

In consequence, I propose to explore the suitability of a half-duplex PHY at this point in time and to not have the constraint of supporting full duplex MAC.

I am happy to propose to immediately adopt the first five objectives in the list and to remove “support full duplex operation only” (similar to what was done for the original objectives for 10BASE-T1S, see https://www.ieee802.org/3/10SPE/objectives_10SPE_111016.pdf).

 

Kind regards,

 

Kirsten

 

 

 

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