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
Gzimmerman11@xxxxxxx
310-920-3860