Subject: RE: (ION) Optical routing

From: Fred Baker <[email-masked]>
Date: Mon, 25 Sep 2000 11:06:34 +0200

At 04:44 PM 9/24/00 -0400, Manfredi, Albert E wrote:
>If wavelengths could be assigned on a packet-by-packet basis, or at least on
>an session-by-session basis (which isn't necessarily any easier to do,
>especially with short HTTP-like transactions), these schemes, and ATM, would
>be easier to use with IP packet switching philosophies, methinks.

Maybe I'm missing something; I often feel that I am. Placing 
electrically-represented packets into a queue appropriate to a lambda is no 
different than placing them into a queue by traffic class. So we most 
certainly can select wavelengths on some variation of a per-packet basis. 
What is difficult to do, with today's technology, is to arbitrarily select 
a packet out of a lambda and change its color to an arbitrary other color 
without capturing all of the packets in a lambda and throwing them into 
electrical queues.

But do we need to? If the packets in a given lambda are to be so selected 
and sent on in a purely photonic manner (without conversion to 
electronics), I'm not sure we need to at all. The packets that we want to 
select out of an ingress lambda and distribute to a set of output lambdas 
will be sequenced in time on the output links exactly as they are on the 
input link. If we re-represent the packet electrically and then retransmit, 
the temporal dimensions may be changed, but in essence we have a beam of 
light coming in, passing through the moral equivalent of a color filter, 
and passing out on an interface or a set of interfaces. the photons aren't 
going to speed up and slow down during that process because we find 
interleaved traffic unimportant on a certain link.

So it seems like we could just as easily replicate the light beam to 
various outputs and color them appropriately to their outputs. Downstream 
devices could then select out of their instance of the light beam the 
traffic appropriate to them and ignore the rest. I don't see any 
operational difference between the two.

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From: Keith Chow <[email-masked]>
Date: Mon, 25 Sep 2000 09:11:03 -0400

Fred,

I agree with you that putting MPLS over lambda is more a marketing hype and
probably will not improve performance at all. Perhaps, another perspective 
is to
look at it as an signalling mechanism (LDP). It may still be useful for 
creating
e2e light paths because today if you buy DWDM devices from LU, NT or CIEN, they
won't speak to each others.

 > operational difference between the two.

The outcomes might be similar, but the complexity of such fabric would be quite
different.

-- Keith.

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From: "James V. Luciani" <[email-masked]>
Date: Wed, 27 Sep 2000 10:20:58 -0400

I would have characterized it more like putting them into different logical
ports rather than traffic classes since there is no implication of treatment
of the packets or service disciplines applied to the queues and parallelism
certainly occurs in a WDM interface amongs the lambdas.

> certainly can select wavelengths on some variation of a per-packet basis.

The below tad misleading.  What is quite doable today is to break the lambda
down temporally (essentially channelizing along the axis of time as opposed
to wavelength or space) and extract only those time slots which you know are
of interest to you.  Note this does not require packet inspection prior to
an add/drop since you already know that this slot is of interest to you (I
did not say was for you since you might not be interested in everything in
that time slot) via signaling or manual config or whatever.

> without capturing all of the packets in a lambda and throwing them into

It is non-trivial (and expensive) to arbitrarily move a lambda on the grid
to another lambda without doing transduction to the electrical domain.   To
the best of my limited knowledge, "all optical" wavelength converters
(non-OEO) are still mostly in the lab and not ready for cost effective
production systems of the type being of interest here.

> operational difference between the two.

There are certainly boxes becoming available that are boasting much larger
wavelength count but many of the deployed boxes are 16 to 32 wavelengths in
number per WDM port.  Depending on your application, merely assigning a
lambda to a point to point connection between two boxes of some arbitrary
number of all optical hops apart would not seem to be the most effective use
of  available bandwidth at hand.