[EFM] Clarification of Copper Objective
We have noted with concern that there seems to be some
confusion regarding the interpretation of the IEEE P802.3ah
EFM Task Force copper PHY objective. Given that the objective
is terse, and provides room for interpretation, we offer the following
clarification. Please parse this clarification carefully.
The objective:
PHY for single pair non-loaded voice grade copper
distance >=750m and speed >=10Mbps full-duplex
The interpretation:
The 802.3ah task force has chosen an objective that specifies
a symmetric MINIMUM bit rate at a particular link distance.
It would be perfectly valid to build and deploy equipment that
provides an asymmetric service at that distance, provided that
the minimum is met in each direction.
Similarly, it would be perfectly valid to build and deploy equipment
that offers a different bit rate at a different link distance, provided
that for all link distances less than the distance specified in the
objective, the minimum bit rate is met in each direction.
The objective does not have to be met on all possible copper
loops of the specified length, nor does it have to be met in the
face of all possible impairments.
Howard Frazier
Chair, IEEE P802.3ah EFM Task Force
Robert Grow
Chair, IEEE 802.3 CSMA/CD Working Group