Hi Igor, see comments below.
Igor Bryskin wrote:
Greg,
I believe the draft is very useful.
--> Thanks!
I have a couple of questions comments:
1. Section : 4.4. Traffic Grooming: Combining WSON and Higher Layer Network
Optimization
How the problem of grooming of higher layer network traffic over
optical trails is any different from the problem of traffic grooming
in TDM (e.g. VC12 over VC4)? I mean this is a general problem of
inter-layer relationship. I suggest moving all higher layer network
considerations out of scope of the draft and focusing on specifics of
the OCh layer.
--> Some of my co-authors agree with you on moving this section out.
The reason that I put it in was that the optical "Traffic Grooming"
problem has received a fair amount of attention in the research and
general technical literature and is also a driver for the use of ROADMs
(optical bypass). I guess in general we've got the following
inter-related problems: (a) virtual network topology design, (b) lower
layer connection routing, (c) higher layer flow routing. In our case (b)
is the RWA problem, which is fairly difficult in its own right. I guess
I should look closely at the MLN/MRN work and see if a specific example
that includes RWA is mentioned. If so then I'd feel fine removing this
section from the document.
2. Considering wavelength conversion inevitably brings to the problem
of looped paths, which is a completely new ball game in path
computation, and I am surprised that the issue was never mentioned in
the draft.
--> How is this different from the "looping" that can occur with a TDM
multiplexer in a drop and continue mode? Also in these two circuit
cases (TDM, and optical) do we have the same danger as in the packet
case where looping traffic can greatly degrade other flows. Was there
some general looping concerns already published for GMPLS with respect
to circuits?
Cheers,
Igor
------------------------------------------------------------------------
*From:* Greg Bernstein [mailto:[EMAIL PROTECTED]
*Sent:* Wednesday, September 26, 2007 7:42 PM
*To:* ccamp; [EMAIL PROTECTED]
*Subject:* [Pce] Some key issues with Wavelength Switched Optical
Networks...
Hi folks, I haven't seen too many comments on our draft "Framework for
GMPLS and PCE Control of Wavelength Switched Optical Networks" (
http://www.ietf.org/internet-drafts/draft-bernstein-ccamp-wavelength-switched-01.txt).
So I figured I'd point out some potentially controversial issues that
the draft brings up.
(a) The draft brings up models for the following WDM network elements:
1. WDM links
2. Optical transmitters
3. Wavelength Converters and OEO regenerators
4. ROADMs, FOADMs, optical splitters and combiners.
For items (3) and (4) we are taking the modeling lead rather than
some other SDO. And for ROADMs, in particular, we going beyond the
classic ITU-T "fabric" model (M.3100) which has been the mainstay of
any connection oriented switch (TDM, ATM, MPLS).
(b) The draft brings up three (not one, not two, but three) different
computational models for RWA which can impact GMPLS and PCE protocols:
1. A single PCE computing both the path and wavelength
2. Two distinct PCEs, where one computes the path, and a different
PCE computes the wavelength assignment
3. A PCE computes the path and wavelength assignment is
accomplished in a distributed fashion via signaling (e.g., using
label set objects)
Do we really need all three models?
(c) G.709 includes the Optical Multiplex Section and Optical
Channels. RFC4238 was aimed at GMPLS extensions for G.709 (Optical
Transport Network) control. Weren't we finished with all this optical
stuff years ago?
I'd like to think the draft answers some of these questions. I also
think that network element models and the process models are important
enough to warrant this separate framework document. Your opinions are
solicited.
Regards
Greg B.
--
===================================================
Dr Greg Bernstein, Grotto Networking (510) 573-2237
--
===================================================
Dr Greg Bernstein, Grotto Networking (510) 573-2237
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