Re: GMPLS dynamics vs. issues with optical amplifiers

["Adrian Farrel" <adrian@olddog.co.uk>]

Hi Marco,

I think that Huub may over-simplify the question with his response.

The issues of cross-talk, amplification, etc. do impact on the selection
of lambdas to carry services of different lengths through the network, and
can become extremely important where transparent optical devices (for
example, PXCs) are used.

Suitable planning tools are available to make such decisions in real time,
but provisioning may be slower than "instant" because of the need to tune
power levels etc.

We should note that in lambda networks we are probably talking about
building transport connections. In general, such connections do not need
to be provisioned instantly and have relatively high latency. So a lot
depends on what you mean by "fast allocating."

With respect to what the IETF would or would not work on, we should
observe the following:

- The IETF does not generally do algorithms
   So the mechanism of computing suitable paths and choosing
   lambdas is out of scope. You would need to contact a specialist
   computation / NMS company for this sort of thing.
- There is (as far as I can see) no immediate impact on signaling.
   Once a path and a lambda have been selected, we already
   have the tools to establish the connections.
- There *might* be a future requirement to signal certain
   constraints, but we would need to see the requirements clearly
   stated.
- There is probably a need to enhance the advertisement of
   some key physical attributes of optical links and nodes in
   the IGPs. At the moment, however, this information
   appears to be gathered through inventory systems and
   there has been very little consideration of this requirement.
- As Huub says, the IETF does not work on defining
   physical properties of optical links, nor on specifying
   the interactions between such properties.

Regards,
Adrian

----- Original Message ----- 
From: "Huub van Helvoort" <hhelvoort@chello.nl>
To: "Marco Ruffini" <ruffinim@tcd.ie>
Cc: <ccamp@ops.ietf.org>
Sent: Monday, April 10, 2006 9:07 AM
Subject: Re: GMPLS dynamics vs. issues with optical amplifiers


> Hello Marco,
>
> You wrote:
>
> > I’m a PhD student on optical network and I’m following the
> > development of the GMPLS work.
> >
> > I had a recent discussion with people working on the optical
> > transport network who where telling me their concern about creating
> > dynamical path over trails including optical amplifiers.
> >
> > They say that cross-talk and gain fluctuation effects may limit the
> > capability of fast allocating new wavelengths over those trials.
>
> Cross-talk and gain are physical properties and not related
> to bandwidth management like GMPLS.
>
> IMO the concern is unjustified.
>
> > I just wanted to know what is your opinion about this and if is there
> > some working group within the IETF already trying to challenge this
> > problem.
>
> IMO for the physical properties you should turn to the ITU-T.
>
> Cheers, Huub.
>
> -- 
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> Always remember that you are unique...just like everyone else...
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>
>