RE: (SSIG) Taking the winning route
Georgio,
I don't understand the technical issue that you are raising by the
following comment:
"So far I didn't see any convincing proof that WWDM can support 300m of
installed base MMF (as a matter of fact any distance of installed MMF). I
also expect that such proof if it will come, will require a significant
amount of work
as was the case for Gb Ethernet. It is in fact necessary to field test the
transceivers with a large sample of existing "fairly unknown" installed MMF.
A long painful process that potentially could delay the standard
ratification (sounds familiar?)."
The WWDM proposal is based on the work of the Gigabit Ethernet committee. In
common with all 10GbE proposals it has used the Gigabit Ethernet link model
as the basis for its link budget. The GbE link model is known to be very
conservative. This is evidenced by the obvious robustness of the large
number of Gigabit Ethernet links in operation today.
Also, the multimode fiber (MMF) environment of the installed base was
extensively investigated as part of the work of the Gigabit Ethernet
Standardization (see list of publications at end of e-mail). It is therefore
wrong to say that it is "fairly unknown". The MMF issue that required
significant work was Differential Modal Delay (DMD). For 1000BASE-LX the
standardized offset launch patch cord was proven to remove this as an issue
- that's why it became part of the standard.
So, given that the WWDM proposal is based on the work of Gigabit Ethernet
including the offset launch patch cord, as far as the installed base is
concerned, what new parameters need to be investigated?
Since you brought the issue up I have to question the following statement:
"So why eliminate a solution that is the only one proven (multi vendor
testing) to work to embrace an unproved solution that is recognized (I
believe you agree with this although we disagree on the amount) to be more
expensive?"
I assume you are speaking on behalf of the serial MMF proposal that will use
the newly developed MMF. I feel obliged to remind everyone of the following
technical points:
1) The new high bandwidth MMF is not yet a standard,
2) It's final standards-based performance is therefore undefined (only
target specifications are known),
3) The laser launch requirements to guarantee its performance are not yet
defined,
4) The effect of link connectors on the performance of the standards-based
version of the MMF fiber have yet to be specified.
Also, to address the cost issue please remember that the installation of new
fiber adds more cost to the user than can be saved by using lower cost short
wavelength based transceivers.
Points 1 - 4 are evidenced by the call for transceivers companies to engage
in a further round of testing with the new MMF that was recently broadcast
over this reflector. Given all of this it could be argued that proposals
based on the new MMF have the higher risk for 10GbE. Technically, until
points 1 - 4 have been addressed, by the standardization of the new MMF, the
worst case 10 GbE link performance with the new MMF cannot be finalized.
Furthermore, projects to write supplements to the IEEE 802.3 standard can be
proposed at almost any time. From an IEEE 802.3 Standards point of view it
might therefore be wise wait until the new MMF has been standardized.
David.
List of relevant publications
-------------------------------
"Evaluation of Gb/s laser based fibre LAN links: Review of the Gigabit
Ethernet model", Mark C. Nowell, David G. Cunningham, Delon C. (Del) Hanson
and Leonid Kazovsky, Opitical and Quantum Electronic, vol.32, pages 169-192,
2000.
"A statistical analysis of conditioned launch for gigabit ethernet links
using multimode fiber", Webster, M.,Raddatz, L.,White, I.H.,Cunningham,
D.G., Journal of Lightwave Technology, vol.17, no.9, pages 1532-41,Sept.
1999
"Influence of restricted mode excitation on bandwidth of multimode fiber
links",
Raddatz, L.,White, I.H.,Cunningham, D.G.,Nowell, C., IEEE Photonics
Technology Letters, vol.10, no.4, pages 534-6, April 1998.
"An experimental and theoretical study of the offset launch technique for
the enhancement of the bandwidth of multimode fiber links", Raddatz,
L.,White, I.H.,Cunningham, D.G.,Nowell, M.C. Journal of Lightwave Technology
vol.16, no.3, pages 324-31 March 1998
"The Gigabit Ethernet Modal Bandwidth Investigation", Chapter 10, Gigabit
Ethernet Networking, Macmillan Technical Publishing, 1999. ISBN:
1-57870-062-0
MBI group field test data can be found at:
http://grouper.ieee.org/groups/802/3/z/mbi/index.html
-----Original Message-----
From: Giorgio Giaretta [mailto:giorgio@xxxxxxxxxx]
Sent: Monday, April 10, 2000 11:32 AM
To: rtaborek@xxxxxxxxxxx; HSSG
Subject: Re: (SSIG) Taking the winning route
Rich,
even if we don't consider cost I would change your statement
"WWDM meets all HSSG MMF objectives as well as SMF objectives to 10km."
to WWDM POTENTIALLY meets (or WE HOPE WILL MEET) all HSSG MMF objectives as
well
as SMF objectives to 10 km.
So far I didn't see any convincing proof that WWDM can support 300m of
installed
base MMF (as a matter of fact
any distance of installed MMF). I also expect that such proof if it will
come, will
require a significant ammount of work
as was the case for Gb Ethernet. It is in fact necessary to field test the
transceivers with a large sample of existing
"fairly unknown" installed MMF. A long painful process that potentially
could delay
the standard ratification (sounds familiar?).
So why eliminate a solution that is the only one proven (multi vendor
testing) to
work to embrace an unproved solution that
is recognized (I believe you agree with this although we disagree on the
amount) to
be more expensive?
I believe this point has been raised from other members before but so far no
one
has answered.
Are you aware of any data that I didn't see?
Giorgio Giaretta
Rich Taborek wrote:
> Vipul, Rob,
>
> It should be pointed out that a Serial 850nm solution only partially meets
one
> HSSG distance/cable plant objective: 300m on MMF. However, this MMF must
be the
> new, enhanced MMF. The Serial 850nmsolution addresses no SMF objectives
>
> WWDM meets all HSSG MMF objectives as well as SMF objectives to 10km.
>
> I agree with Vipul's choice of 3 PMDs as the best possible PMD set to
address
> HSSG HSSG distance/cable plant objectives.
> Best Regards,
> Rich
>
> --
>
> Vipul Bhatt wrote:
> >
> > Rob,
> >
> > Rob Marsland wrote:
> > >
> > > Finally, I hate to be annoying, but this is the SERIAL sig. Since
when is
> > > WWDM a serial solution?
> > >
> >
> > There is nothing annoying about your question. I should answer. I
believe it
> > is in our (the Serial SIG's) best interest to rise above our Serial
focus and
> > recognize that an "all Serial" set of solutions that meets all the
distance
> > objectives is not something our customers are willing to sign up for. By
> > proposing a set of three solutions - two of which are Serial - I am
proposing
> > a set that has the highest chance of being accepted by our customers and
the
> > majority of 802.3ae members. I understand you disagree, and I respect
your
> > opinion.
> >
> > Vipul
>
> -------------------------------------------------------
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