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Seeing Brad’s note about the energy efficiency discussion reminded me that one of the reasons to consider not necessarily going directly with 802.3az at the face-to-face was that it would be desirable to use the network as a control network, and hence, packet latency would be an issue. This got me thinking, should we have a latency objective? Signal processing latency is probably not a PHY problem for normal modes, but could influence coding strategies for dealing with an impulsive EMC environment, and, would likely influence any transitions out of low-power states for energy efficiency. It would be good to get the group’s minds thinking about what fundamental parameters we may have left out (of the kind that are specified in interface standards – e.g., not absolute power or complexity, but yes to reduced power modes, latency, speed, distance, media, duplexing, compatibility with environment & other signals, autonegotiation, etc.) Here’s my list of what I think we’ve covered thus far: - Speed (fixed in the CFI – 1000Mb/s at MAC/PLS interface wording to be approved) - Media (fixed in the CFI – twisted pair copper, wording to be worked) - 802.3 framing (agreed) - 802.3 frame sizes (agreed) - Distance and/or channel loss, (still working the exact language) - Topology (3 connectors proposed, – to be approved) - EMC (still working the language) - BER performance (prelim agreed) - Training time from cold start (needs work and agreement, still) - Optional energy efficient operations (proposed – to be approved at this general level, may need further definition) Questions on other issues that that have been raised, which, depending on the resolution, may be objectives: - Do we support clause 28 (or other) autonegotiation, even optionally? - Support or even compatibility with Clause 33 DTE Power over MDI (existing poe)? - Minimum latency (normal and especially for transitions out of low power mode) -george George Zimmerman Principal, CME Consulting Experts in Advanced PHYsical Communications Technology 310-920-3860 |