Re: Thoughts on draft-otani-ccamp-gmpls-lambda-labels-00.txt

[Dan Li <danli@huawei.com>]

Hi,

If the wavelength label only has the local significance, then the routing 
problem needs to be addressed only at the level of the TE link choice, 
and wavelength assignment can be resolved locally by the switches on 
a hop-by-hop basis.

But if we can have the "global semantic" labels, we can run into the 
wavelength level to choose the path.

I also agree with Adrian on the definition of the "global semantic" label,
current the 160 wavelengths per fiber WDM system is deployed by 
some carriers, and the 320 wavelengths per fiber is under developed. 
The 640 wavelengths per fiber is expected in the near future. So the
"n" field is better to be expanded, and leave some room for the new 
technologies. 

Regards,

Dan

----- Original Message ----- 
From: "Greg Bernstein" <gregb@grotto-networking.com>
To: "Adrian Farrel" <adrian@olddog.co.uk>
Cc: <ccamp@ops.ietf.org>; "Tomohiro Otani" <otani@kddilabs.jp>; <ho-guo@kddilabs.jp>; "K. Miyazaki" <miyazaki.keiji@jp.fujitsu.com>; "Diego Caviglia (GO/MCI)" <diego.caviglia@ericsson.com>
Sent: Thursday, October 04, 2007 1:46 AM
Subject: Re: Thoughts on draft-otani-ccamp-gmpls-lambda-labels-00.txt


> Hi folks, I agree with Adrian that this draft is very valuable for LSC 
> networks. In addition, it seems that  these "global semantic" labels can 
> be very useful in characterizing optical subsystems and that information 
> can feed into a PCE performing the routing and wavelength assignment 
> problem.
> 
> For example a single wavelength drop port on a ROADM may be either a 
> fixed lambda, or a range of lambda. So I'd like to characterize  this 
> port with either one of your globally defined labels or via a range 
> specified by by two of your nicely defined lambdas.
> 
> Note that in ultra high capacity systems multiple optical bands could be 
> used. In 
> http://www.ietf.org/internet-drafts/draft-bernstein-ccamp-wavelength-switched-01.txt 
> we estimated that to cover a wide band fiber at the narrowest channel 
> spacing currently defined (12.5GHz) would require 4800 labels. Hence 
> with advances in modulation formats and narrower channel spacing 
> Adrian's suggestion of 16 bits for the "n" field below allows us to 
> fully characterize a wide band fiber with room to grow.
> 
> Regards
> 
> Greg B.
> 
> Adrian Farrel wrote:
> > Hi,
> >
> > I think this draft is introducing a useful feature for LSC networks by 
> > allowing lambda labels to have a global semantic.
> >
> > Although this work is functionally not an absolute requirement (it is 
> > always possible to map lambdas on a hop-by-hop basis) it is clearly a 
> > simplification to have a common semantic just as in the TDM label case.
> ---snip---
> > ===
> > Section 5.2
> > It looks like you have already almost run out of Channel Spacing bits 
> > in the CS field. Given that technology developments are likely to find 
> > ways of decreasing the channel spacing, I would suggest allocating 
> > another bit to the CS field.
> > Similarly, n is limited to 511 (if my bit counting is right), and it 
> > seems to me that the potential for more than 500 lambdas on a fiber is 
> > not so improbable.
> > So, how about...
> >       0                   1                   2                   3
> >       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
> >      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> >      |Grid |  C.S. |S|    Reserved   |               n               |
> >      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> > ===
> >
> --snip--
> > The two things you do need in this section are:
> > 1. How do I use a new Lambda Label?
> >   Answer: in all of the places that an existing Generalized
> >   Label can be used.
> > 2. How do I tell when a new Lambda Label is being used
> >   and when an existing Generalized Label is being used?
> >   Does this remain a link local issue (as it always has done)
> >   or do you propose to define a new field value in the
> >   Generalized label Request or a new C-Type for the
> >   Generalized Label Object?
> > ===
> > Section 6.2
> > As mentioned before, I think that discussion of advertising lambda 
> > availability is best removed from this I-D.
> > ===
> > Section 7
> > You might like to consider that the use of a global semantic makes the 
> > control plane signaling information slightly more vulnerable to 
> > snooping and external control. I don't think this changes the security 
> > model, but you should mention the fact.
> > ===
> > Section 10
> > I think [G.694.1] and [G.694.2] are probably normative references.
> > ===
> >
> > Cheers,
> > Adrian
> >
> >
> >
> 
> -- 
> ===================================================
> Dr Greg Bernstein, Grotto Networking (510) 573-2237
> 
> 
>