Subject: [CCAMP] A general question on the WSON Framework draft

From: Lou Berger <[email-masked]>
Date: Tue, 20 Oct 2009 18:02:51 -0400

Authors, (WG)

	I have a pretty basic question on the WSON framework document:  What is
the scope of the optical networks covered by this framework?

I think the document should be very clear on this.

Keep in mind that a framework (or even protocol) may allow for, i.e.,
not preclude, functions and aspects of an architecture or solution
without fully defining them.

To elaborate on my question:

A) It's clear that some portions of optical networks are in scope, such
as: "wavelength division multiplexed links, tunable laser transmitters,
reconfigurable optical add/drop multiplexers (ROADM) and wavelength
converters". But it is unclear if other portions are in or out; in
particular regenerators, OEO switches and, to some degree, OXCs.  All
are mentioned in the document, but the document is a bit vague on
whether they are part of the framework or not.  So what's included and
what's excluded?

My personal opinion is that the framework should allow for all aspects
of today's optical networks, but need not define support for each (e.g.,
impairment based RWA).

B) Are multiple signal types included or not?

The document seems to say that they are not, but then there is section
3.2.2.  It seems to me that it really doesn't take much to allow for
support of multiple signal types in this document.  Given that multiple
signal types are a reality in today's optical networks, I personally
think they belong in the framework.

I have a bunch of more minor comments on the document, but will hold
these until the above is closed.

Much thanks,
Lou

---

From: Young Lee <[email-masked]>
Date: Tue, 20 Oct 2009 18:14:35 -0500

Hi Lou, 

Thanks for your comments. Please see in-line for my response. 

In a nutshell, what the authors' intention of the WSON Framework was to stay
in the basic RWA issues (including Wavelength Converters and OXC); 

Having said that, any multi-signal related issues (we refer to this as
signal compatibility and processing constraints) that encompass Regenerators
and OEO switches is addressed in a separate document we just updated. 

Impairment has been addressed separately as you know. 

Perhaps, Greg can elaborate more from his perspective.

Regards,
Young

-----Original Message-----
From: Lou Berger [mailto:[email-masked]] 
Sent: Tuesday, October 20, 2009 5:03 PM
To: [email-masked]
Cc: CCAMP WG
Subject: A general question on the WSON Framework draft

Authors, (WG)

	I have a pretty basic question on the WSON framework document:  What
is
the scope of the optical networks covered by this framework?

YOUNG>> WSON RWA Framework includes wavelength division multiplexed links,
tunable laser transmitters, reconfigurable optical add/drop multiplexers
(ROADM) and wavelength converters and OXC. 

Regenerators and OEO switches are addressed in the context of signal
compatibility in a separate document. 

YOUNG>> I agree. The concern we have had was the document gets larger and
larger to the point that it is hard to read and edit. In the framework, we
added the document relationship across RWA, Impairment and Signal
Compatibility so that these are all included in the larger WSON scope than
the document is addressing. 

YOUNG>> No. 

YOUNG>> We thought we asked the WG chairs in Stockholm meeting. What we
thought we heard was a suggestion to separate "signal issues" from the basic
RWA issues. 

Much thanks,
Lou

---

From: Lou Berger <[email-masked]>
Date: Tue, 20 Oct 2009 19:56:17 -0400

Young,
	Please see below for in-line responses.

> in the basic RWA issues (including Wavelength Converters and OXC); 

doesn't really leave much out ;-)

> and OEO switches is addressed in a separate document we just updated. 

see below.

> Impairment has been addressed separately as you know. 

Right.  This fits with point of a function being allowed for in the
framework, but not being fully defined.

> larger to the point that it is hard to read and edit. 

The flip side of this is that you can end up with such a fragmented
document set that the base set isn't really usable (at least in
practical terms), and that the base can get significantly out of sync
with a critical component.  I fear this is where we're ending up with
the current work.

> In the framework, we

right now it reads to me as covering half the relevant problem space,
leaving out some very basic (and almost always used) functions.

> thought we heard was a suggestion to separate "signal issues" from the basic

I believe we ended this part of the discussion with "let's take it to
the list".  Albeit a bit delayed, here we are ;-)

More seriously, I think there's some concern about defining
attributes/functions that are currently not standardized in the ITU-T.
I think this is a point that we need to be sensitive to, particularly
when considering solutions drafts.  But this document is a framework
document and, in my personal opinion, the framework should cover (or
allow for) all aspects of a typical optical network.

Lou

---

From: Greg Bernstein <[email-masked]>
Date: Wed, 21 Oct 2009 09:51:51 -0700

Hi Lou, see comments below.  This is a key point and one that wasn't 
clear until we split off the compatibility draft from the framework and 
had some questions on the list.

Regards

Greg

> whether they are part of the framework or not.  So what's included and
--> This document extends the GMPLS control plane to include 
"asymmetric" switches. No matter how they are implemented.
It also includes models for shared wavelength converters and detailed 
link-wavelength usage. Such information is useful across many WSONs.
What it doesn't model or cover is signal constraints imposed by 
particular technology implementations such as an OEO wavelength converter.
It also would not be aware of regenerators since it doesn't understand 
differences among optical signals or impairments. We've moved such text out
to the compatibility and impairment drafts.
> B) Are multiple signal types included or not?
--> Yes. But no checking of signal compatibility is provided.
> think they belong in the framework.
--->  Hmm, we say in the abstract:
"nor does it address potential incompatibilities between some types of 
optical signals and some types of network elements and links"
This is a fairly general statement in line with the scope that we intend.

But confusingly we say in section 3.2.2:
"As pointed out in the introduction, for the purposes of this document 
we assume that all optical signals used in a WSON are compatible with 
all links, network elements, and receivers in that WSON."

This is too restrictive since it says all signals should be compatible 
with all links, elements, receivers all over the network. We should 
probably say something like:
As pointed out in the introduction, for the purposes of this document we 
assume that all optical signals used in a WSON are compatible with 
/*the*/ links, network elements, and receivers in that WSON */that they 
traverse or terminate on.

/*A "signal" may change its characteristics as it traverses a path, e.g. 
modulation format, or FEC, particularly at a regeneration point. For 
this draft we assume that the compatibility of signals and elements has 
been pre-planned and is not a control plane function to worry about. We 
split this off as the signal compatibility aspects grew and based on the 
chairs (Deborah's) comments in Stockholm. See the latest compatibility 
draft for more complete analysis of the compatibility issues with 
regenerators, OEOs and the like.

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