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RE: [EFM] Clarification of Copper Objective


Thanks for this important clarification.

In my opinion, the reason for the confusion is simply due
to the poor wording of the statement of the objective. It 
is not, for example, because people are not used to the
historical 802.3-speak.

The following description of the objective (with alternative
phrases in brackets) may be more unambiguous and complete:

OBJECTIVE:  To specify a PHY, for single-pair non-loaded
            voice-grade copper, that "CAN achieve" [OR: "is
            CAPABLE of achieving"] >= 10 Mbps full-duplex
            for loop lengths "in the range 0 - 750m"
            [OR: "<= 750m].

This clearly indicates that the minimum objective is a 
"line segment" in the rate-reach space, i.e. the line
segment specified by "rate = 10 Mbps, 0 < reach <= 750m".

This also shows that a PHY is allowed to be deployed at
longer-than-750m loop reach, as long as it is CAPABLE of
meeting the above objective.

It still doesn't clarify the issue of the TYPE of loop at
a given reach (i.e. gauge, topology including bridged taps
Just my 2 Indian rupees' worth :-)

Sudhakar Kalluri, Ph.D.
Senior Design Engineer (Systems & Algorithms)
Advanced PHY Development Group
(CTO - Intel Communications Group)

Intel Corporation, MS LOC3-14
9750 Goethe Road, Sacramento, CA 95827-3500
(916) 854-1177 (TEL), (916) 854-2809 (FAX)

-----Original Message-----
From: Howard Frazier [mailto:millardo@xxxxxxxxxxxxxxxxxx]
Sent: Tuesday, June 11, 2002 9:23 AM
Subject: [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