Subject: GMPLS dynamics vs. issues with optical amplifiers

From: "Marco Ruffini" <[email-masked]>
Date: Mon, 10 Apr 2006 08:43:45 +0100

Hi all,

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.

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.

Thank you for your attention

Best Regards,

Marco Ruffini.

CTVR, 

University of Dublin, Trinity College, 

Dublin 2,

Ireland.

Phone: +353-1-608 8441

---

From: Huub van Helvoort <[email-masked]>
Date: Mon, 10 Apr 2006 10:07:46 +0200

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.
> 

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.

-- 
================================================================
              http://members.chello.nl/hhelvoort/
================================================================
Always remember that you are unique...just like everyone else...

---

From: "Adrian Farrel" <[email-masked]>
Date: Mon, 10 Apr 2006 15:07:50 +0100

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

---

From: "Ash, Gerald R \(Jerry\), ALABS" <[email-masked]>
Date: Mon, 10 Apr 2006 09:13:39 -0500

Furthermore RFC 4054 http://www.ietf.org/rfc/rfc4054.txt deals with some
of these issues.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Adrian Farrel
Sent: Monday, April 10, 2006 10:08 AM
To: Huub van Helvoort; Marco Ruffini
Cc: [email-masked]
Subject: Re: GMPLS dynamics vs. issues with optical amplifiers

Hi Marco,

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.

Regards,
Adrian

----- Original Message ----- 
From: "Huub van Helvoort" <[email-masked]>
To: "Marco Ruffini" <[email-masked]>
Cc: <[email-masked]>
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

---

From: "Filippo Cugini" <[email-masked]>
Date: Mon, 10 Apr 2006 16:54:10 +0200

Hi all,

IMO the issue will have to be faced soon. Transparent network elements such 
as ROADM and PXC are beginning to be deployed in optical transport networks.
However, the current GMPLS does not provide any functionality to keep track 
of the signal quality degradation. Thus, transparent mesh networks must be 
statically designed, during the network planning, to guarantee that even the 
most impaired connection  (e.g., the longest path) is acceptable. Otherwise, 
because of the current GMPLS limits, connections can successfully be set up 
even if they do not comply with physical parameters constraints.
However, the worst case design approach heavily limits the size of the 
transparent networks.

  Filippo

----- Original Message ----- 
From: "Adrian Farrel"
>  [..]

---

From: Kireeti Kompella <[email-masked]>
Date: Mon, 10 Apr 2006 08:31:00 -0700 (PDT)

Hi Marco,

> capability of fast allocating new wavelengths over those trials.

We've talked on and off about these in CCAMP, and there have been 
drafts to describe some of the various optical impairments to consider.

In the GMPLS structure defined so far, there are link attributes (such 
as metrics and bandwidth), and typically, these can be combined simply 
to get a functioning path.  Thus, for metrics, the combining function 
is summation, and for bandwidth, the function is "min".

To accommodate attributes that are not carried as TE extensions today, 
we may have to add node attributes (say for dB loss across a mirror 
complex).  We may also have to linearize impairments, or define how 
they are composed across links and nodes; this is not always easy to do.

You say "fast allocating new wavelengths".  I would have thought that 
the issue is not how fast the allocation is, but whether the 
allocation and ultimately, the optical LSP setup, is successful taking 
into account optics and physics.

Kireeti.
-------

---

From: "Americo F. Muchanga" <[email-masked]>
Date: Mon, 10 Apr 2006 17:55:37 +0200

Huub,

It is true that GMPLS addresses bandwidth management as one of the primary  
concerns but GMPLS as such thus include information that is aimed at  
enabling end notes to establish and end-to-end light path. This being the  
case, the constraints regarding the quality of that path from physical  
properties perspective is crucial to be taken in consideration. Otherwise  
we might need to maintain a secondary system just to deal with these  
effects. So it is justified to start this discussion to see if GMPLS could  
be extended to also carry that information.

rgds, americo./

-- 
Americo F. Muchanga
Telecommunications Systems Lab (TSLAB/KTH)
School of Information and Communication Technology
The Royal Institute of Technology KTH
Stockholm, Sweden

---

From: "Marco Ruffini" <[email-masked]>
Date: Mon, 10 Apr 2006 17:12:20 +0100

Hi,
My understanding is that supposing that the optical path can be physically
allocated (e.g. none of the optical trails included in the path get blocked
for physical constraint reasons), there must be an adaptation in the
operative parameters of the optical amplifiers to avoid that the setup of a
new wavelength could disturb the signals brought by the other wavelengths in
the same fiber.

So on one hand GMPLS should consider if there is any blocking physical
constraint that may impair the allocating of a new wavelength on a specified
path.
On the other hand it should be considered how long it would take to the
transport layer to adapt all the physical parameter in the path to include a
new wavelength on the fiber without disturbing the existing signals (I
imagine this could be quite a lengthy process if more amplifiers are
cascaded, like in a long haul system for example). This issue I think would
put a lower limit to the reconfiguration-time of new optical paths.  

Marco

-----Original Message-----
From: Kireeti Kompella [mailto:[email-masked]] 
Sent: 10 April 2006 16:31
To: Marco Ruffini
Cc: [email-masked]
Subject: Re: GMPLS dynamics vs. issues with optical amplifiers 

Hi Marco,

Kireeti.
-------