Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

RE: Clock Tolerance and WAN PHY

I enter here with great trepidation. I would like to offer a couple of
thoughts, based on our current draft (I am intentionally calling this by
number) and what I remember reading on the reflector.

1. A 20 ppm clock or any other ppm less than or equal to 100 ppm would be
compliant with the standard and would interoperate with all compliant

2. I do not remember seeing any data regarding the cost ratio offered
between a 20 ppm clock and a 100 ppm clock. ($$ not allowed in comparison).

3. I do not remember seeing any data regarding the volume ratio of WAN to
LAN PHYs expected in the market place.

4. I do not remember seeing any data regarding the cost ratio of an ELTE
that has to support input of 100 ppm clock rates as compared to one that has
to support 20 ppm (or other).

5. Based on 2, 3, 4, I cannot therefore make even the simplest calculation
regarding a global optimization.

6. Based on 1, and 5, I don't see anything broken and I see no supporting
evidence that a change is beneficial (or, would provide incentive for 75% of
the voters to change this specification).


A. I don't see any reason why a LAN PHY can't source data at the OC-192 rate
and still be considered compliant to the standard and fully interoperable
with other LAN PHYs.

B. From an implementation standpoint, it is quite reasonable to think of
building an ELTE with the defined WIS and use a LAN PHY as the connection
between the Ethernet equipment and the ELTE running the mode specified above
in A.

C. The equipment ELTE built in B could easily translate between the two
clock domains (100 ppm and anything less than 100 ppm).

D. All that I describe above, I believe, would be compliant to the proposed
IEEE 802.3ae draft standard.

Therefore, what is the problem? It seems to me that any of you can implement
whatever you want and still be okay. I don't think that I am hearing issue
with our draft. I think that I am hearing implementation questions/issues.
What am I missing?