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

Selecting PHY Solutions


It appears to me, having followed a number of streams over the last two
weeks, that there appears to be an unusual amount of chest-beating regarding
the potentials for different PHY implementations. As best as I can
determine, most of the proposed solutions (sans parallel), appear to be
closer to a research phase than they do to production. I have no doubt that
most supporters will say this is true for the competitive solutions, but not
theirs! :-)

Might I suggest that while posturing is something that we always have to put
up with, at this point in time it is more important for us to focus on the
criteria by which PHY decisions will be judged. We appear to be burning up a
lot of MIPS on the wrong issues. 

Might I suggest that there are key issues that will affect what PHYs are
ultimately selected/supported for which we still have no apparent consensus.
Some examples:

o Must we, like with 802.3z, attempt to support the fiber infrastructure as
it exists (e.g. 62.5 micron fiber at 550 meters) in order to accomplish
Criteria 1: Broad Market Potential? If so, I am POSITIVE we can find a
solution. It would be a stretch for me to believe that it will be least
expensive solution. Will it therefore impact the ability to achieve Criteria
5: Economic Feasibility (especially, "Reasonable cost for performance

o If not, is there a sub-portion that we must support in the existing
infrastructure? For instance: the horizontal space (100 meters)?

o If not, are we implying no support for the current building
infrastructure? If so, will we propose a new building infrastructure?

o What distances are we going to support outside the building? What is in
the 802.3z objectives; what is in the 802.3z standard (1000BASE-LX); or what
we are currently shipping in our boxes (A variety of 1000BASE-LX that
supports the Fibre Channel 10 km specification but runs at 1.25 GBd)?

o If we cannot resolve these objectives, can we ignore them?

I would suggest that these are primarily marketing questions. What do the
end customers need in the short term (next 2 to 5 years) and what will they
need after that? Is 10 Gig ever be a to-the-desktop application? If so, will
it be this 802.3 effort or some subsequent effort that meets that need? If
the marketing people say that the price needs to be 3x the equivalent 802.3z
price at entry to the market and needs to support all of the existing
infrastructure, what are we going to tell them?

While I am pounding on the podium, I will note one other thing: There have
been a large number of bits burned on the reflector regarding WAN
requirements. But, as far as I know, we are still lacking a concise list of
specific requirements.

Jonathan Thatcher "jonathan@xxxxxxxxxxxxx"