RE: Distance Objectives: 2nd motion

["Chang, Edward S" <Edward.Chang@xxxxxxxxxx>]

All:
 
So far we are proposing distance numbers which are basically reasonable
numbers we can pin down eventually.
 
The question is we have two speeds on the table; namely, 10 Gbps and 2.5
Gbps.    What speeds we have in mind for those distance proposals?   Since
two speeds are 1 to 4 ratio , a big difference, logically we should have two
groups of distance proposal, one for 2.5 Gbps and another for 10 Gbps.
Otherwise, it seems our strategy is to pick distance first, then fit
whatever technologies?
 
Ed Chang  
 
 
 
 
 
 

-----Original Message-----
From: Jonathan Thatcher [mailto:jonathan@xxxxxxxxxxxxx]
Sent: Friday, June 25, 1999 7:38 PM
To: stds-802-3-hssg-distance@xxxxxxxx
Subject: Distance Objectives: 2nd motion



All,

Assuming general agreement on my first proposed motion (or maybe even if
not): there are several, potential interesting distances that are candidates
(there may be more, but this seems to be an adequate list to start with):

1. 100 meters over MMF (850 and 1300)
2. 300 meters over MMF (850? and 1300?)
3. 500 (550) meters over MMF (850? and 1300?)
4. 3 km over SMF (1300)
5. 5 km over SMF (1300)
6. 10 km over SMF (1300)
7. 20-40 km over SMF (1300)
8. 80-120 km over SMF (1500)

To sort through these, I think we need to consider some of the "traditional"
assumptions/arguments/positions that were used in Gigabit Ethernet when
making decisions about fiber, wavelength, and distance:

a. We should support the existing infrastructure (meaning the existing cable
plants)
b. We should minimize the number of PHY choices
c. We should minimize the cost of implementation

There is a corollary to "a." (called a' = "a prime") which is: we should try
to go as far as we went at slower speeds over the same media.

Let me start with 4, 5, and 6. Since we currently specify 5 km in the
1000BASE-LX standard, according to "a.", we should support at least 5 km.
Using this assumption, we would eliminate 4. To the best of my knowledge,
all the LX solutions in existence support 10 km (these parts typically meet
the Fibre Channel 10 km solution while running at the GbE speed),
effectively making "a" a 10 km requirement

Debatable issue 1 is therefore: support the LX distance as specified or as
commonly implementable in the industry (5 or 6).

Questions about 7 are most interesting if the group picks 6 over 5 but could
be independent, I will assume the former. We are all aware that solutions to
the 10 km LX actually run at much greater distances because of the
conservatism of the standard. We therefore see practical applications that
achieve 20 to 40 km. These are not guaranteed to be interoperable.

Debatable issue 1a is therefore (assuming issue 1 selects 6 over 5): support
the LX distance as commonly implementable or as available in the industry (6
or 7).


Questions about 8 are similar to those of 7 when taken independently. Most
arguments supporting 7 would also apply to 8. The major rationale for doing
either would be to take what are now proprietary solutions and make them
interoperable. If members believe that the market for these solutions will
be significant for 10 gig, then there will be interest in making these
solutions interoperable (standards based). If not, this will continue to be
a custom space.

Debatable issue 2 is therefore: How interesting is this potential market
space. Is it sufficient to create a standard? 

1, 2, and 3 are significantly more difficult. Especially since we do not yet
know if we can support assumption "a." without significantly impacting "c."
(I can barely imagine the flurry of opinions on this topic). We also don't
know where the majority opinion will go with respect to specifying new fiber
types (e.g. high bandwidth MMF). In short, it might not be possible to
satisfy both "a" and "c" simultaneously to the convincing of 75% of the
members.

Debatable issue 3 is therefore: what gives first "a" or "c"?

There is more that can be said here, but I have a more important idea I
would like to convey.

I would recommend the following: first, conclude the 1st general motion on
space per my previous append. The second section on that motion will help to
the members to resolve what they are going to do about about the debatable
issues here. The third portion of that motion does not impact this
discussion, since connection to the WAN can be accomplished with any
distance solution.

Next, bring forward a main motion that is easily passable and covers the
least controversial components of 1 through 8. I recommend a selection of 4,
5, or 6. (assuming you think that only one of the three will be kept (see
"b")). Each can be placed in the motion text with the intent to select only
one. Votes can be taken from least to most likely to succeed to see where
the 75% vote can be achieved. 

Note: This technique is frequently used in discussions of allocation of
money: "We move to collect from the membership ($0, $100, $1000, $50,000,
$1,000,000) to be given to the HSSG chair to use at his discretion." You
vote starting with the $1,000,000 and continue down the list till you reach
75% consensus,  then stop. This is simpler and faster than picking a single
number and having it amended to death. The 0$ is, of course, silly here
because if something higher than or equal to $100 is not passed, the motion
failed anyway.

Then make a motion(s) to add a line(s) to the previous objective (now a
passed motion) that includes something about 1 through 3. Given the
diversity of the group, a more general motion has a greater chance of
success than a more restrictive motion. An overly general motion ("do the
best you can on MMF") has no chance. The same technique could be used as
above (support a distance of at least (100, 300, 550) meters over multimode
fiber). I am assuming here that the group will want to have some MMF
solution (see "a") and will therefore pass at least 100 meters. Note that
this motion would set the lower bound!

Make a motion to add to the previous objective a direction to investigate,
or not investigate the use of higher BW MMF.

Make a motion to add to the previous objective support of a 1550 nm
solution.

Make a motion to add to the previous objective support of a longer distance
1300 nm solution.

etc.

Explain the process and content of each motion to the group prior to
starting. This way the membership will understand when the appropriate time
is to discuss/amend the motion (i.e. per the above process, the chair would
consider out of order any amendment and/or discussion during the initial
motion on LW, SMF, that relates to MMF as this would be covered in a
subsequent motion). The only problem is, I think, that someone might think
that at this point of the process the HSSG should investigate more potential
solutions than should be supported in the end. If so, then add another
motion that adds a line to the objective to limit the number of solutions to
N in the final standard.

I am suggesting this process because I believe that we must exit the process
with an objective on distance, which is the mission of this ad-hoc. I am
optimistic that this or a similar procedure would accomplish that goal.
There are alternatives to this which would be simpler and quicker (for
instance, a single motion that contains the correct wording to allow it to
pass with 75% vote). The problem is, if that vote fails, we got nuthin' and
that ain't acceptable.

jonathan