RE: [EFM] P2MP -> P2P migration path
Jonathan, I had the same interpretation so I await Carlos' answer.
I would also like to clarify the overall point, as I interpret it anyway. I
would summarize it like this:
A TDMA-PON can only truly claim to be upgradeable to WDM if the original
definition of the TDMA PON defines the upgrade path at least in terms of the
wavelength plan. An arbitrarily loose wavelength definition at the first
step limits the possibilities at the upgrade step since the upgrade may
interfere with the original, in the lambda domain.
Another issue is that there are different ways to upgrade to WDM. For
example, it may be individual wavelengths that still utilize TDMA within a
given wavelength, or it may go to dedicated, single-user wavelengths.
Another possibility is time-multiplexed 10G and 1G bursts, across several
wavelengths. In any case, if an AWG is used for wavelength routing, even
though it is a passive device it would still require power for the
temperature compensation portion that is necessary today to meet industrial
temp range. That makes for an undesirable situation of providing power to a
previously all-passive outside enclosure. It may also require a change in
size to this outside enclosure. If an AWG is not used, then
wavelength-selective filtering is needed for ONU receivers, and these need a
grid and a range.
The easy answer for the lambda spacing is make it as wide as possible.
However, this limits the number of lambdas you can stack in the future.
Spacing that is too tight is not cost-effective. What is a "just right"
spacing for several years out? 200GHz over temperature? Maybe. A grid
defined on 50GHz spacing can still be used as a 200GHz grid when the time
comes, but allows flexibility in the future outcomes. Any thoughts?
From: Jonathan Thatcher [mailto:Jonathan.Thatcher@xxxxxxxxxxxxxxxxxxxx]
Sent: Wednesday, July 18, 2001 12:23 PM
To: 'Carlos Ribeiro'; John Pickens; Dolors Sala
Subject: RE: [EFM] P2MP -> P2P migration path
I think that I am understanding what you are saying here. I would like to
change some of the wording/acronyms/semantics and see if I understand.
What you are looking for is a migration path from P2MP to a VIRTUAL P2P
(VP2P). This VP2P would use the P2MP infrastructure but provide a P2P
functionality. The intent would be for each VP2P (or each VP2MP) link to
utilize an independent wavelength.
The implication is that EFM would have to provide a wavelength and budget
plan that supported this upgrade path.
Is that it?
> -----Original Message-----
> From: Carlos Ribeiro [mailto:cribeiro@xxxxxxxxxxxxxxxx]
> Sent: Wednesday, July 18, 2001 4:35 AM
> To: John Pickens; Dolors Sala
> Cc: email@example.com
> Subject: Re: [EFM] P2MP -> P2P migration path
> At 09:48 17/07/01 -0700, John Pickens wrote:
> >One school of thought is that EPON is just a simple
> transition technology
> >on the way toward PTP, so (upstream) efficiency is no
> >consideration. Heck, 10-20% of available link capacity would be
> >great. Heck, why not just divide up the bandwidth
> statically and give
> >each ONU 1/16th of the raw link bandwidth. It's a lot simpler that
> >way. Plus the EFM operator will just switchover to PTP
> anyway once the
> >traffic gets to a significant level.
> >Another school of thought is that EPON is an enduring
> technology which (in
> >order to compete with other enduring shared technologies,
> e.g. copper and
> >vaporized-copper) must dynamically maximize the utilization
> of the link
> >bandwidth up to 100% utilization. Furthermore latency
> sensitive traffic
> >must be capable of seeing minimum latency (e.g. 0 ms for a
> constant bit
> >rate stream) on the uplink.
> >So the question is which extreme model (or intermediate model) is
> >required. The model chosen will determine the functionality
> >of the MAC/PHY.
> I could not have put it better. That's where my wavelength allocation
> request comes into play. As we don't know (as of now) which
> model is going
> to be the winner, I believe that we have to reserve space for the P2P
> migration path. A carefully designed wavelength allocation
> scheme may allow
> this discussion be be tackled later. For now, we can work out
> the P2MP EPON
> standard, knowing that we will have room for P2P in the future.
> Carlos Ribeiro
> CTBC Telecom