RE: Unified PMD vs. Unified PHY
Jonathan:
I did have a couple of concerns regarding possible areas of potential bias
in the survey.
In the first place, I was uncomfortable with the fact that the UniPHY
occupied 4/7 (57%) of the option set for the first question. This has the
potential of creating an inherent "option bias" which could potentially skew
the results in the UniPHY direction.
Secondly, since the independently optimized LAN and WAN PHY was perhaps a
more realistic option than the WAN only or LAN only options it perhaps
should not have been sandwiched between these and the UniPHY series of
options for fear of the "orphan effect".
Perhaps the UniPHY series of options could have been shortened at, say ">20
%". In the same vein, maybe the independent optimized LAN/WAN PHY could have
had other options like "total cost equal to UniPHY cost" or perhaps "total
cost <=x% of UniPHY cost".
With regard to the second question, the options read to me like a ranked or
sorted set. To minimize the potential for bias it would perhaps had been
better to have randomized the options.
I have no sense of what the possible magnitude of bias in the survey results
is or even if it is significant enough to warrant undue concern.
Best Regards,
-Nevin Jones
System Architect
Lucent Microlectronics
908-582-5343
> ----------
> From: Jonathan
> Thatcher[SMTP:jonathan.thatcher@xxxxxxxxxxxxxxxxxxxx]
> Reply To: jonathan.thatcher@xxxxxxxxxxxxxxxxxxxx
> Sent: Tuesday, March 14, 2000 11:50 AM
> To: HSSG_reflector
> Subject: RE: Unified PMD vs. Unified PHY
>
>
> All,
>
> So far, I have received no negative feedback on the survey nor on the
> method. On the other hand, I haven't heard a great ground swell of postive
> feedback either.
>
> I welcome feedback from anyone that it interested. If you don't want to
> clog
> the reflector with traffic, send the feedback directly to me.
>
> On the assumption that the group felt the information was helpful and
> would
> like to drive down to lower levels, I would be happy to work on the next
> iteration.
>
> jonathan
>
> > -----Original Message-----
> > From: Roy Bynum [mailto:rabynum@xxxxxxxxxxxxxx]
> > Sent: Tuesday, March 14, 2000 8:40 AM
> > To: jonathan.thatcher@xxxxxxxxxxxxxxxxxxxx; stds-802-3-hssg@xxxxxxxx
> > Subject: Re: Unified PMD vs. Unified PHY
> >
> >
> > Jonathan,
> >
> > Thank you for the explaination. I am sure, given your justified desire
> to
> > reduce the number of PMDs that you will continue with the
> > iterations of the
> > survey at the next meeting.
> >
> > Thank you,
> > Roy Bynum
> >
> >
> > ----- Original Message -----
> > From: Jonathan Thatcher <jonathan.thatcher@xxxxxxxxxxxxxxxxxxxx>
> > To: <stds-802-3-hssg@xxxxxxxx>
> > Sent: Monday, March 13, 2000 5:04 PM
> > Subject: RE: Unified PMD vs. Unified PHY
> >
> >
> > >
> > > Roy,
> > >
> > > 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.
> > >
> > > jonathan
> > >
> > > > -----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
> > > >
> > > >
> > > >
> > >
> >
>