Subject: RE: [Pce] New draft on wavelength switched optical networks

From: "MEURIC Julien RD-CORE-LAN" <[email-masked]>
Date: Fri, 13 Jul 2007 16:20:43 +0200

Hi Greg.

I'm really interested in this topic, but I think I've missed some points when reading your ID.

For instance, I don't get why you consider the signal modulation format. I don't believe a single-vendor environment would require a negociation on modulation for a specific bandwidth, and I don't think modulation information would be enough for 2 different implementations to interwork on (analog) optical line.

Anyway, this work is a good start to highlight GMPLS and PCE lack to handle the different kinds of optical networks.

Regards,

Julien

-----Original Message-----
From: Greg Bernstein [mailto:[email-masked]] 

Hi CCAMPer's and PCEr's, we have just published a new draft on the 
"Applicability of GMPLS and PCE to Wavelength Switched Optical 
Networks"  
http://www.ietf.org/internet-drafts/draft-bernstein-ccamp-wavelength-switched-00.txt 
.

This draft looks at optical networks that include tunable lasers and 
ROADM (reconfigurable optical add/drop multiplexers) with no or limited 
wavelength conversion capability (these components are defined in the 
draft). 
These limitations lead to the RWA (routing and wavelength assignment) 
problem which is a bit more demanding in terms of input information and 
computation than other constrained path computation problems.  In the 
draft we look at the implications for GMPLS signaling, GMPLS routing, 
and PCE protocols and suggest some potential extensions to better 
accommodate this application.

We'd appreciate feedback/collaboration on (a) overall interest in this 
application, (b) requirements discussions, and (c) solution/extension 
discussions.

Cheers

Greg B.

-- 
===================================================
Dr Greg Bernstein, Grotto Networking (510) 573-2237

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Pce mailing list
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---

From: Greg Bernstein <[email-masked]>
Date: Fri, 13 Jul 2007 11:14:21 -0700

Hi Julien, good questions.  See comments below. 

Regards

Greg B.

MEURIC Julien RD-CORE-LAN wrote:
> For instance, I don't get why you consider the signal modulation format. I don't believe a single-vendor environment would require a negociation on modulation for a specific bandwidth, 
--> In the optical case as it is currently implemented I tend to agree 
with you here.  However in other systems negotiation of modulation 
format and such is more common.
> and I don't think modulation information would be enough for 2 different implementations to interwork on (analog) optical line.
>   
I was thinking along the lines of the relatively new ITU-T optical 
signal designations such as NRZ 2.5G, and RZ 40G defined in G.959.1.
I'm also, like most of the ITU-T recommendations, restricting the focus 
to digital signals over fiber. Not including impairment information for 
now, this should give us adequate information to understand the signals 
spectral characteristics for compatibility with wavelength selective 
switching elements and such.  At least this was the part of the point of 
the physical layers interfaces defined G.959.1. 

One thing that we might have not hit well enough is the compatibility of 
the end systems where the optical signals are demodulated. Its one thing 
to be able to switch the lambdas its another to demodulate them. Would 
we need more information or would this be covered in the PID?  For 
example if the PID indicates that the carried signal is a particular 
flavor of10G Ethernet that would be sufficient.  I'll review the current 
PID stuff as applied to lambda switching.

---

From: "Bardalai, Snigdho" <[email-masked]>
Date: Sat, 14 Jul 2007 08:10:09 -0500

Hi Greg,

I believe your ID has presented some of the key points regarding wavelength routing.

I think we are still missing a few other issues that may have to be considered.
1. Constraints related to the configuration of the ROADM switching elements. For
   example, transponders could be pre-wired to a specific port on the ROADM, and hence
   restricting the wavelengths that could be routed to that transponder.
2. When considering wavelength routing it may be important to consider
   if regeneration of the signal is required. Also, it may be equally important to
   be able to specify, if and where reqeneration would be required during signaling
   (assuming an external entity such as a PCE can determine where the regeneration can
   be done).
   
It would be of much interest to me to learn what is your (and others) opinion on these
issues.

Regards,
Snigdho

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On
Behalf Of Greg Bernstein
Sent: Wednesday, June 27, 2007 12:39 PM
To: ccamp; [email-masked]
Cc: Young Lee
Subject: New draft on wavelength switched optical networks

Cheers

Greg B.

---

From: Greg Bernstein <[email-masked]>
Date: Sat, 14 Jul 2007 08:46:11 -0700

Hi Snigdho, good points and questions.  See comments below.

Regards

Greg B.

>    restricting the wavelengths that could be routed to that transponder.
--> Yes. We touched on this only a bit but this is very important. There 
is a new draft (July 9, 2007) by Wataru. Imajuku, "Routing Extensions to 
Support Network Elements with Switching Constraint", 
draft-imajuku-ccamp-rtg-switching-constraint-02.txt. Which also hits 
some of these issues.  But this is an area that needs further 
requirements analysis.
It seems like we have at least:
(a) Internal switching topology constraints.  Such as you can't get to 
that port from this port. Illustrated in Wataru's draft.
(b) "Colored" interface related constraints where specific lambdas 
ingressing on a port will egress on a fixed port (not configurable). 
Like what you mention above.
(c) Wavelength converter based constraints such as we mention in our draft.
(d) ... Others? Or a better taxonomy than the above?
>    if regeneration of the signal is required. 
--> This kind of work was started by John Strand and Angela Chiu in 
RFC4054 on optical impairments related to routing.  Now since the 
publication the ITU-T has made a lot of progress in defining and 
characterizing various optical impairments so the time maybe about right 
to related some of this data plane work to the control plane. We 
originally were looking at this then saw some other gaps that needed 
filling.
> Also, it may be equally important to
--> Yes.  We need regeneration capability information with our topology 
information which affects routing. Don't know that we'd need extensions 
to signaling, since once you've specified in the ERO to go through a 
regenerator element then you're done. At least for the fixed 
regenerators and those implicit in OEO switches.

---

From: "Bardalai, Snigdho" <[email-masked]>
Date: Sat, 14 Jul 2007 23:23:01 -0500

Hi Greg,

Some more comments.....

Snigdho

-----Original Message-----
From: Greg Bernstein [mailto:[email-masked]]
Sent: Saturday, July 14, 2007 10:46 AM
To: Bardalai, Snigdho
Cc: ccamp; Young Lee; [email-masked]
Subject: Re: New draft on wavelength switched optical networks

Regards

Greg B.

[Snigdho] With O-E-O wavelength convertors additional constraints wrt to 
          the signal rate (2.5G or 10G) and other attributes related to the
          electrical signal will have to be taken into account.

[Snigdho] I tend to agree with your view on this. Could you elaborate on "gaps" ?

[Snigdho] I think it is possible to have per wavelength O-E-O regeneration as well.
          Using this mode of operation, the selection of the regeneration site could
          become more flexible. So routing could pick a site that is suitable considering
          the optical impairment parameters whereas signaling could actually require
          a specific type of regeneration module to be existing at the site.

---

From: Young Lee <[email-masked]>
Date: Mon, 16 Jul 2007 11:14:29 -0500

Hi Snigdho,

Please see in-line for my comments.  Thanks.

Young

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of Greg Bernstein
Sent: Saturday, July 14, 2007 10:46 AM
To: Bardalai, Snigdho
Cc: ccamp; Young Lee; [email-masked]
Subject: Re: New draft on wavelength switched optical networks

Regards

Greg B.

[Young] Agree with Greg. Wataru draft addressed the need to differentiate
interface types: (i) colored vs. (ii) colorless. 

[Young] The approach we have taken in regards to impairment issues in
wavelength optical switched network was to put on hold for now until we have
received enough interest in the current work. We (Greg and I) judged that
basic signaling and routing of the wavelengths should get kicked off before
we address optical impairment issues. 

But as you indicated, optical impairment issue is one of the key routing
constraints especially in the transparent optical network. We have not
forgotten this issue; but at this juncture, we'd like to pursue the issues
around the basic RWA issue first. Once this work is accepted in the
community, then we should pursue impairment issue. 

[Young]  One thing we should be careful, though, is routing scalability.
Previous attempts in this work have failed due to routing scalability issues
associated with the sheer amount of data that need to be advertised. But now
due to advancement of PCE, some of the information can be made available in
PCE (not necessarily via IGP) and PCE would handle path computation
constraints associated with regeneration and other optical impairment data. 

But before we jump into architectural alternatives, we should reach to an
agreement on the scope of essential data required to enable RWA. 

> "Applicability of GMPLS and PCE to Wavelength Switched Optical 
http://www.ietf.org/internet-drafts/draft-bernstein-ccamp-wavelength-switche
d-00.txt

---

From: <[email-masked]>
Date: Sun, 29 Jul 2007 14:15:03 +0200

Hi Greg,

this is a timely topic to be tackled for both the PCE and GMPLS WGs, and
well worth supporting. I would like to highlight that the renewed
interest in this work by carriers is sparked by the fact that there is
new optical equipment moving into the network, both in the core as well
as in the metro/aggregation area which needs management and
configuration. There is no intention to implement fast optical switching
at large scale, except during failure recovery and for planned
maintenance etc which would affect the IGP stability. Dimitri's remark
during the GMPLS WG meeting showed me that it might be necessary to
emphasize that position.

Regards,

Michael

-----Original Message-----

Hi CCAMPer's and PCEr's, we have just published a new draft on the 
"Applicability of GMPLS and PCE to Wavelength Switched Optical 
Networks"  
http://www.ietf.org/internet-drafts/draft-bernstein-ccamp-wavelength-swi
tched-00.txt 
.

Cheers

Greg B.