Gentlemen,
I agree that the APL
sublayer should ideally be defined in a very general way. That is to
say, in a perfect world, it would support aggregation of channels with various
(i.e. – mixed) bit rates. That being said, this raises some interesting
challenges. For example, the striping (or splitting) ratio across the
channels will not be uniform – for every ten bits (or bytes) sent down a 10G
channel, only one could be sent down a 1G channel. Is there any
precedent for managing something like this? If not, does anyone have any
idea whether this is even feasible?
Regards,
Jugnu
From: Myles
Kimmitt [mailto:mylesk@xxxxxxxxxxx]
Sent: Wednesday, August 09, 2006 9:58
PM
To:
STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [HSSG] Topics for
Consideration
My point was that the APL should
try to be broader than an nx10G sublayer (at least architecturally) because
there are applications that could take advantage of higher speed links,
especially over time. Try to get more mileage out of the
sublayer.
I wasn't proposing that
802.3 get involved in any WAN links - it was just an example of how
economics skew in different
markets.
All that you say about dispersion
is true but 25G dispersion would be 2.5 times better than 40G. Beauty is in
the eye of the beholder.
----- Original Message -----
Sent:
Wednesday, August 09, 2006 7:56 PM
Subject: Re:
[HSSG] Topics for Consideration
Myles,
I agree that there is a
cost to consuming wavelengths, and they should be used wisely. But a
system that has been engineered to support 10G rates cannot necessarily step
up to higher speeds, even if optically compatible with the existing DWDM
grid and power levels. The SM fiber's dispersion limited distance
drops as the square of the bit rate. For example, for externally
modulated sources, if the dispersion limited distance is 60 km at 10Gb/s,
then at 25 Gb/s it will be less than 10km. So channels that exceed
this distance would need to be dispersion compensated. Were you
thinking that the higher rates would be used only on shorter channels,
or were you thinking of dispersion compensation technologies as
work-arounds? If the former, then consider how it impacts the
objectives. If the latter, it opens up a whole set of issues.
Regards,
Paul
Kolesar
CommScope Enterprise® Solutions
1300 East Lookout Drive
Richardson, TX 75082
Phone:
972.792.3155
Fax: 972.792.3111
eMail:
pkolesar@xxxxxxxxxxxxx
|
Myles
Kimmitt <mylesk@xxxxxxxxxxx>
08/09/2006 05:05
PM
|
Please respond
to
Myles Kimmitt
<mylesk@xxxxxxxxxxx> |
|
|
To |
STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
|
|
cc |
|
|
Subject |
Re: [HSSG]
Topics for
Consideration |
|
I would expand on
the statement:
"Carrier want to leverage their existing DWDM layer which
mean
baudrate in the 9.95-12.5
Gig".
There are two layers
at which compatibility with existing DWDM systems
can
be achieved: the electrical
layer (which this statement implies) and the
photonic layer. Compatibility at the photonic layer means
interoperability
with existing
DWDM wavelengths, optical filters, power leveling, etc.
on
the same fiber. Is is likely
that 25G (+7% FEC) NRZ optical signals are
compatible with many existing 10G NRZ DWDM systems. There
is a premium to
using many
wavelengths in these systems and a 4x25G channel might well
be
cheaper and more wavelength
efficient (as measured by GB/s/nm)than a
10x10G channel.
Such details are probably beyond the scope of the SG but
I think it is
important to
architect below the MAC to allow link speeds faster than
10G
within the APL which make
sense in certain markets and will become more
economic and widespread over
time.
-Myles
>
> I
have listed dilemma we are facing:
> - Implementing 100 Gig in the near term means
Nx10Gig
> - Implementing
100Gig in few years the right answer might be
nx25Gig
> - Carrier want to
leverage their existing DWDM layer which mean
> baudrate in the 9.95-12.5 Gig - If LAG implemented
why not allow n to be 4?
>
- Operation with different width
> - Backward compatibility XAUI, LX4
?
> - Greatest bandwidth
demands (100+Gig) are on VSR links <50 m but
> the longer reach >10Km may be able to live with
4x10Gig.
>
> All
these means we should either define some sort of
scalable
> architecture or
just define LAG method and do not define any PMDs!
>
>
>
Thanks,
>
Ali
>
>
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