Re: [10GMMF] Coverage calculation for 10GBASE-LRM
David and all,
I agree with a respect the process for resolving these questions and assume
that the formal choice of coverage percentage will be decided by vote at a
future meeting. However, it seems rather unavoidable that in order to
calculate any link coverage percentage, we must consider both fibers in the
link. Since TP3 is formulating coverage related proposals over the next few
days I am re-iterating this point now to facilitate that work.
Previous 802.3 coverage calculations have accounted for bi-directional links
as such are relevant to the end user. For example, the 95% coverage per
fiber number that some support for LRM translates to 90% link coverage for
the end user. The 95% case should represent link coverage, which requires
97.5% coverage for each of the 2 fibers in the link.
Best Regards,
John George
Systems Engineering Mgr.
FTTP and Premises Applications
OFS Optical Fiber Division
770-798-2432
-----Original Message-----
From: David Cunningham [mailto:david_cunningham@AGILENT.COM]
Sent: Tuesday, April 19, 2005 4:50 AM
To: STDS-802-3-10GMMF@LISTSERV.IEEE.ORG
Subject: Re: [10GMMF] Coverage calculation for 10GBASE-LRM
John,
It is not I but the committee that you must convince. Whilst I understand
your arguments I must add that at our last meeting this was discussed both
in 10GBASE-LRM and IEEE 802.3 and there were members of both committees who
held equally strong but different views to yours.
Other views I observed were:
99% coverage is not an issue for LRM
95% coverage is perfectly acceptable for LRM
Coverage can be traded-off for reduced power and reduced size per the LRM
PAR
The installed base is unknowable and our fibre models can only ever give us
vision of the ~ 5% with statistical significance
I'm sure there were more views expressed.
Because of the range of strongly held views that I have observed I believe
this is an issue that needs to be resolved in comment resolution by a formal
vote.
Regards,
David
-----Original Message-----
From: owner-stds-802-3-10gmmf@IEEE.ORG
[mailto:owner-stds-802-3-10gmmf@IEEE.ORG]On Behalf Of George, John
(John)
Sent: 19 April 2005 06:42
To: STDS-802-3-10GMMF@LISTSERV.IEEE.ORG
Subject: Re: [10GMMF] Coverage calculation for 10GBASE-LRM
Hello David,
I suggest that all coverage calculations going forward should be based on a
bi-directional link, as opposed to one direction of the link as had been the
practive thus far in 802.3aq. For example, 95% link coverage would require
97.5 coverage for each of the two fibers in the link, and 99% link coverage
(the precedent for all other 1 and 10 Gigabit optical PMDs) would require
99.5% coverage for each of the two fibers in the link
I made the comment below against draft 1.1 that I also plan to make a
similar comment against draft 2.0 with a specific remedy. During our task
force discussion of this comment you unofficially agreed in principle with
using bi-directional coverage as the metric for assessing installed base
coverage of 10GBASE-LRM. I suggest that we begin doing this immediately in
TP3 and as a task force to more accurately assess the draft standard vs
coverage going forward.
The comment:
"The design philosophy used to date to calculate the parameters in clause 68
is intended to create a standard that assures 99% of installed fibers will
support 10GBASE-LRM to 300 meters based on relaxation of 1 parameter, in
this case PIE-D, to the 99% coverage level. However, the precedent of IEEE
worst case design philosophy is that at least 99% of installed LINKS will
support the standard to it's maximum rated reach, as was done in the
following: 1BASE5 99%, 10BASE-T 99%, 100BASE-T4 99%, 10GBASE-S over OM3
99.5% of fibers (0.995^2=99% of links). The current design philosophy of
10GBASE-LRM will only will only support 0.99 x 0.99 = 98% coverage.
For all modeling and affected parameters in clause 68, adjust the 99% PIE-D
values to assure 99% LINK coverage as required by IEEE worst case design
philosophy precedents (10BASE-T, 10GBASE-SR, .......), which thus requires
99.5% coverage for each of the two fibers in the duplex link. For example,
this will increase the PIE-D requirement by ~0.3dB for best launch according
MC67YY with connectors"
Best Regards,
John George
Systems Engineering Mgr.
FTTP and Premises Applications
OFS Optical Fiber Division
770-798-2432