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RE: Unified PMD vs. Unified PHY


There are a rather large number of reasons why I did not extend the
selection set in the first question. Primarily, it has to do with the fact
that a 2-dimensional question like the one I asked is already significantly
challenging. To have made this a 3-dimensional question would have made it,
in my mind, unanswerable. There are ways to take 3-dimensional questions and
reduce them to 2-dimensions, but to do this correctly requires several
iterations of questions to confirm the many assumptions that are made to do
so. Without having the time to go through these iterations would have forced
me to impose my own interpretation upon the question, thus breaking all the
rules of conducting this type of survey.


> -----Original Message-----
> From: owner-stds-802-3-hssg@xxxxxxxx
> [mailto:owner-stds-802-3-hssg@xxxxxxxx]On Behalf Of Roy Bynum
> Sent: Sunday, March 12, 2000 11:50 AM
> To: Jonathan Thatcher
> Cc: stds-802-3-hssg@xxxxxxxx
> Subject: Unified PMD vs. Unified PHY
> Johnathan,
> I was intending to ask you why you did not ask about unified PMDs
> separate from a unified PHY as part of your survey but did not get a
> chance.  At the 10GEA technical meeting you were very adamant about
> getting consensus for a small set of PMDs.  I agree that having a small
> group of PMDs is preferable.  Having a unified PHY in order to have a
> small set of PMDs may not be preferable.
> The cost of the unified PHY, as presented, so far has been very high in
> the form of lost transfer rate.  As it is, the unified PHY, as
> presented, does not meet the objective to have a 10.000 Gigabit MAC
> data transfer rate (Gb-Mtr).  Separate PHYs, LAN and WAN do meet the
> objectives.  Additionally, one of the scramble encoded WAN PHY
> presentations was able to achieve an average 10.000 Gb-Mtr transfer rate
> by using IPG compression, which can be inferred to meet the 10.000
> Gb-Mtr objective in addition to the 9.548 Gb-Mtr objective.
> A unified PMD set can support the block encoded LAN PHY and the scramble
> encoded WAN PHY, allowing both to meet the 10.000 Gb-Mtr objective.
> This will allow the PMD people to concentrate on the technologies of the
> PMDs with the consideration of a signaling range to support both PHYs.
> It will also simplify the marketing of 10GbE by reducing the confusion
> about distances and fiber types.
> As was demonstrated in some of the previous presentations (SUPI and OIF
> SERDES), it is possible to have unified PMDs without having a unified
> PHY.  If the question had been asked, would it have made a difference to
> separate the issues?  If they are separate issues, as a I believe they
> are, then should the survey be redone with that segregation?  Would this
> have put less pressure on group to have a unified PHY and changed the
> scaling of the responses?
> Thank you,
> Roy Bynum