RE: [802.3ae_Serial] Support for 10GFC
Pat -
Aside from the editor's note, here is what is really happening in the
Fibre channel PMDs.
1. Per decisions made in the August FC meetings, the hope was that there
was sufficient margin in the PMDs so that changes would NOT be required
in the cable plant. We did NOT want to change distance, losses, or other
specs.
2. Because of my involvement with both committees, I was designated by
FC as the one to review the spreadsheet tool for the FC rate.
3. In running the analysis, some of the margins showed negative. Since
this was not what we hoped for, we have to make some decisions. Obvious
options are:
a. Increase the budget (the email).
b. Reduce distance.
c. Reduce other losses.
d. Spec non-standard fibers, etc.
e. Ignore the negative margin as modeling conservatism.
If option "a" is accepted by the PMD suppliers, then all is done. Option
"e" may be difficult for system integrators to accept. The other options
are the very ones we don't want to change.
Tom
-----Original Message-----
From: THALER,PAT (A-Roseville,ex1) [mailto:pat_thaler@xxxxxxxxxxx]
Sent: Tuesday, December 18, 2001 11:09 AM
To: Vipul Bhatt; 802. 3ae Serial PMD (E-mail)
Subject: RE: [802.3ae_Serial] Support for 10GFC
Vipul and Tom,
The 10GFC draft says in an editor's note at the start of the specs for
the
PMDs they have borrowed from Ethernet:
The 10GFC project intends to compensate for the higher speed by making
compensating adjustments in specifications relating to cable length and
optical link budgets.
They are aware of the issue and have decided to deal with it by
adjusting
the link rather than the transceiver.
If you look at the specs for XGXS and PCS in 802.3ae, they actually do
include requirements to properly handle the reserved codes of K28.2 and
K28.6 (see Tables 48-2, 48-3, and 49-1). There was a brief period when
one
of the tables in 48 indicated otherwise, but I submitted a comment to
correct that which was accepted. The physical layer components defined
in
802.3ae will handle the FC encodings. However, I think your statement is
partially incorrect as K28.6 is listed as reserved in the 10GFC draft. I
believe that K28.2 is the only code additional that 10GFC uses.
I am in the process of reviewing the specs in 10GFC to see if there are
any
deviations that would interfere with using the same transceiver or XGXS
for
both standards. I encourage others to do the same.
Regards,
Pat
-----Original Message-----
From: Vipul Bhatt [mailto:vipul.bhatt@xxxxxxxxxxx]
Sent: Tuesday, December 18, 2001 10:06 AM
To: 802. 3ae Serial PMD (E-mail)
Subject: RE: [802.3ae_Serial] Support for 10GFC
Tom,
Good idea. From the standpoint of return on development efforts,
10GFC is a low hanging fruit. The increase in power budget is
relatively small.
I hope the designers of XGXS and PCS will do a similar exercise. My
(unreliable) recollection is that apart from the increased 2% speed,
the only thing a designer has to make sure is that K28.2 and K28.6
are supported. Support for these two characters is required in
10GFC, but not in 802.3ae.
Regards,
Vipul
=================
-----Original Message-----
From: owner-stds-802-3-hssg-serialpmd@xxxxxxxxxxxxxxxxxx
[mailto:owner-stds-802-3-hssg-serialpmd@xxxxxxxxxxxxxxxxxx]On Behalf
Of Lindsay, Tom
Sent: Monday, December 17, 2001 4:01 PM
To: 802. 3ae Serial PMD (E-mail)
Subject: [802.3ae_Serial] Support for 10GFC
Folks - 10G Fibre channel intends to use 10G Ethernet PMDs but for a
rate that is 2% faster. For serial, this would mean 10.51875 Gbd;
for LX4, this would mean 3.1875 Gbd per lane.
As a modeling approximation, I modified cell C4 in
10GEPBud3_1_16a.xls to the FC rates. Margins stay positive for
all -S variants, but go negative for:
-0.05 dB for 1310 serial
-0.21 dB for LX4
Possibly any of these are within spreadsheet margin for error, but
is there willingness to increase the power budget to drive these
margins back positive?
Tom
Stratos NW
425/672-8035 x105