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Hello George I tend to agree that the latency is the
central issue in the control network. If we specify the speed, and distance,
the latency is the 3rd definitive parameter. The exact language or number cannot be
fixed at this time though (or better to say I do not know a good number ). But e.g 40
ns or less ? Best
regards , Yakov
Belopolsky Manager
, R&D From: George Zimmerman
[mailto:gzimmerman11@xxxxxxx] 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 |