RE: Going the distance

[Jonathan Thatcher <jonathan@xxxxxxxxxxxxx>]

Just to make sure that everyone is keeping everything in perspective. The
tabled motion on distance that we will pick up in Montreal currently reads:

Adopt as objectives for the Higher Speed Study Group:

Provide a family of Physical Layer specifications which support a link
distance of:
a. At least 100 m on multimode fiber
b. At least 3 km on single mode fiber

Move: Bob Grow
Second: Tom Dineen

Rich Taborek, with Howard Frazier seconding, is proposing the following as
an amendment/replacement:

That the distance objective support the premises cabling plant distances as
specified in ISO/IEC 11801

      The distances supported in ISO/IEC 11801 are:

      100 m for horizontal cabling
      550 m for vertical cabling
      2-3 km for campus cabling

Compare these to the 802.3z (Nov 96) objectives:

11. Provide a family of Physical Layer specifications which support a link
distance of:

a. At least 25 m on copper (100 m preferred)

b. At least 500 on multimode fiber

c. At least 3 km on single mode fiber

and 


13. Support media selected from ISO/ IEC 11801

For those of you that weren't there for 802.3z, the gigabit standard met and
supports this last set of objectives! It wasn't particularly easy at times
(in fact, for those of us who lived through it, we quip and wonder why we
would ever want to do this again). In fact, had it not been for these
objectives, we might have -- no, we probably would have -- given up and
resolved on a much shorter set of distances. Howard Frazier, armed with this
set of objectives, somehow managed to keep us going until we got it done. I
do not think I am over stating this!

Everyone, please think long and hard about the implications of these
objectives on the future work of the HSSG. There are any number of
significant differences in these three sets. I will note only one: item "b"
of the original motion (same as the 802.3z objective 11c) meets all the
requirements of the amendment to it. 

Having worked in a number of standards activities, I have come to appreciate
the value of setting the objectives early in the process. These become a
guide, a challenge, and a metric by which much of the work is gauged. If
there is any ambiguity as to the intent of the objectives, we will be doing
nothing but postponing the difficult decisions. If ambiguity is the only way
we can achieve consensus, I am not optimistic we will succeed. This is a
difficult thing to do. It is worth doing right. Whatever the process we use,
let's make sure the end result is something that everyone can get behind.

jonathan

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