Re: [Pce] 答复: My Comment on draft-lee-pce-flexible-grid

[Dieter Beller <[e-mail]>]

Hi all,

the description of the available spectrum in draft-lee-pce-flexible-grid should in my opinion be consistent with the available spectrum
description in draft-ietf-ccamp-flexible-grid-ospf-ext. Please note that the available spectrum is advertised in terms of available central
frequencies!

A central frequency f_c is available only if the spectrum is available in the interval [f_c - f_minSlotWidth/2, fc + f_minSlotWidth/2]

If the flexgrid granularity is 6.25GHz and the minSlotWidth is 12.5GHz this means leads to: [f_c - 6.25GHz, f_c + 6.25 GHz]

This is different from advertising spectrum slots like for example [f_c_n-1, fc_n].

Please note that a modulated optical carrier occupies spectrum symmetrical around the central frequency.


Thanks,
Dieter

On 20.07.2017 11:04, Zhenghaomian wrote:

Hi, Julien and Young, 

I fully agree on that we should try our best on reusing the existing object/TLVs. FYI, when we are working on GMPLS extensions from fixed-grid (WSON) to flexi-grid, we have some TLVs in parallel (switching types) for fixed/flexi-grid. 

I assume this is exactly what we are doing in this draft, the split occurs when it is difficult to use existing TLV to represent the new features. In some cases, the meaning of flags/TLVs need to be changed to support different scenarios, so the similarity on object does not necessarily mean the equivalent on functionality. 

My 2 cents, 
Haomian

-----邮件原件-----
发件人: Pce [mailto:[e-mail]] 代表 Leeyoung
发送时间: 2017年7月20日 16:41
收件人: Julien Meuric; [e-mail]; [e-mail]
主题: Re: [Pce] My Comment on draft-lee-pce-flexible-grid

Hi Julien,

I agree. A New flag on the object header (WA Object, I assume that is what you are pointing to) where we have a flag to indicate if this is fixed (WSON) or flexi-grid is reasonable instead of creating a new object for a new Spectrum Assignment Object.

TLVs require a bit different encoding due to the nature of additional parameters for flexi-grid. So strict re-use of WSON TLV may not be sufficient for some cases in flexi-grid. 

Best regards,
Young

-----Original Message-----
From: Julien Meuric [mailto:[e-mail]] 
Sent: Thursday, July 20, 2017 10:28 AM
To: [e-mail]; [e-mail]
Subject: My Comment on draft-lee-pce-flexible-grid

Hi,

The discussion during the meeting suggests that I need to clarify my comment about draft-lee-pce-flexible-grid.

This I-D is very similar to draft-ietf-pce-wson-rwa-ext, which addresses the exact same problem over a slightly different WDM label space (running a side-by-side diff between them appears to be very practical).
This new I-D requests the creation of one object and 3 TLVs, which are identical to the ones created in the WSON.
As a result, I believe the latter should be reused as a starting popint.
Covering the flexi-grid case may just need to allocate new flag in the object header to identify the WDM type we're dealing with, and document the flexi-grid-specific assumptions (if any).

Thanks,

Julien

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--

Dieter Beller
Open Agent & Routing Project Manager
IP/Optical Networks, Optics, Nokia

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