Ethernet auto-negotiate time

No mistake, your numbers are right. Moreover, this is the *minimum* time for a successful negotiation; in the event that an FLP burst is corrupted, it may require more than 3 repetitions before acknowledgment (but this is considered a rare event).

Given that Auto-Negotiation occurs just once at link initialization, it is not considered a big deal to take a few hundred milliseconds. In practice, this time overlaps with other events, such as machine boot sequences, power-up self tests, etc., all of which take even longer.

By the way, the minimum negotiation time is less for lower data rates, since the Base Page alone conveys all the necessary information to negotiate 10/100 Mb/s operation.

-- Rich Seifert Networks and Communications Consulting 21885 Bear Creek Way (408) 395-5700 Los Gatos, CA 95033 (408) 395-1966 FAX

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Thank you. I was not sure about the calculated time and am glad to know that it is OK.

Gigabit Ethernet is now common in desktop computers and we find that NIC power consumption is about 4% ~ 5% of the overall idle power consumption of the computer. And with copper 10GigE NICs expected within a couple of years that percentage is expected to increase significantly. At the University of South Florida my advisor, Dr. Ken Christensen and myself are studying the feasibility of dynamically changing the link speed and hence reducing the power consumption of the NIC. And the time taken to change link speed is an important metric.

Thanks again for your kind response,

Chamara Gunaratne

I would think you could minimize the amount of circuitry that had to be clocked at full speed during idle time.

For battery powered devices, though, I agree you want it as low as reasonably possible.

-- glen