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RE: Optical impairments in draft-ietf-mpls-generalized-signaling- 04
John,
wavelength availability and wavelength conversion are two different points in my view.
A optical corss-connect without wavelength conversion can be seen as a connection matrix with limited connectivity (e.g. only connections between inputand output ports with the same lambda are possible), while a corss-connect with wavelength conversion has full connectivity if no other constrains apply. This is a static information that doesn't change over time. It is detected during startup of the network and will not result in flooding traffic. The available connectivity of a connection matrix can be taken into account by the routing.
Wavelength availability is a second issue. If you want to annouce the used and unused wavelengths in real-time you end up with flooding traffic and race conditions, I agree. But this is independent of wavelength conversion availability. A label set helps in my view only if you have wavelength conversion as it allows you to select between different wavelengths. Without wavelength conversion you are stuck to a fixed wavelength. What you need is a cranck back mechanism if you detect that all possible wavelengths are occupied.
The availabiity of wavelength conversion and the connectivity of a connection matrix as such is a separate issue from PMD or OSNR.
Note that even in TDM systesm (SONET) you may have limited connectivity. Some SONET ADMs for example don'tsupport time slot interchange for the line-line connection. That results in the same connectivity restricitions as an Optical ADM without wavelength conversion between the line interfaces.
We should separate the issue of wavelength conversion (-> limited connectivity) and signal impairments.
Wavelength conversion usually has impact on signal parameters, but that can be modelled as a separate process wich can also exists without wavelength conversion.
Today wavelength conversion ist mostly based on o-e-o conversin with re-timing (3-R). The 3-R process resets the otpical signal parameters, but it influences timing parameters (jitte, wander).
Wavelength conversion based on o-e-o conversion with re-shaping (limiting amplifier), but without re-timing is also available (2-R). This has influence on other parameters.
Pure optical wavelength conversion will have other influences. We don't know exactly which today and it may depend on the specific process used.
Consideration of signal impairments in the routing process is a much more complex issue compared to limited connectivity if I look on the tools we use today to design an optical path.
Juergen
> -----Original Message-----
> From: John Drake [SMTP:jdrake@calient.net]
> Sent: Tuesday, June 26, 2001 11:58 PM
> To: 'Heiles Juergen'; 'Yangguang Xu'; Diego Caviglia
> Cc: Ayan Banerjee; ccamp@ops.ietf.org; Giovanni Fiaschi
> Subject: RE: Optical impairments in draft-ietf-mpls-generalized-signaling- 04
>
> Announcing wavelength availability information in routing doesn't work
> because of the flooding traffic it would generate, plus there are still race
> conditions that would have to be handled by signalling anyway. Label set
> was intended to support wavelength continuity issues.
>
> Also, in the short term, we're dealing with transponder based interfaces to
> the DWDM systems so this is a non-issue. In the longer term, this is just
> another issue like PMD and OSNR that will need to be dealt with.
>
> -----Original Message-----
> From: Heiles Juergen [mailto:Juergen.Heiles@icn.siemens.de]
> Sent: Tuesday, June 26, 2001 7:43 AM
> To: 'Yangguang Xu'; Diego Caviglia
> Cc: Ayan Banerjee; ccamp@ops.ietf.org; Giovanni Fiaschi
> Subject: RE: Optical impairments in
> draft-ietf-mpls-generalized-signaling- 04
>
>
> Yangguang,
>
> wavelength conversion is in my view an issue for path selection as you
> cannot select a certain path if the wavelength doesn't fit and you have no>
> wavelength conversion.>
>
> Regards
>
> Juergen
>
> > -----Original Message-----
> > From: Yangguang Xu [SMTP:xuyg@lucent.com]
> > Sent: Tuesday, June 26, 2001 3:13 PM
> > To: Diego Caviglia
> > Cc: Ayan Banerjee; ccamp@ops.ietf.org; Giovanni Fiaschi
> > Subject: Re: Optical impairments in
> draft-ietf-mpls-generalized-signaling-04
> >
> >
> > Diego,
> >
> > As indicated by the document that Ayan pointed to you, there are many
> constrains
> > for the optical networking. These constrains can be considered at network
> > planning time, path selection time (routing using OSPF-TE/ISIS-TE) or
> connection
> > setup time(GMPLS signaling). When a constrain is considered is an
> engineering
> > issue. We just have to figure out when and where is the best and cheapest
> to
> > consider a constrain. To wavelength conversion, GMPLS signaling is a good
> place
> > to handle.
> >
> > Thanks,
> >
> > Yangguang
> >
> > Diego Caviglia wrote:
> > >
> > > Ayan,
> > >
> > > Thanks for your answer but I don't understand why lambda
> conversion is
> > > a signalling problem and thus is covered in generalized signalling
> draft while
> > > others optical impairments are routing problem and are covered in a
> separate
> > > document.
> > >
> > > Moreover even if the document you quoted is a well written and very
> useful one
> > > it is an informative contribution that simply points out the
> physically
> > > impairments of an all optical network. It doesn't propose any
> extension to
> > > OSPF/IS-IS in order to support optical routing.
> > >
> > > Given that in an All Optical Network we have to cope with
> lots of new
> > > information, as you stated in your document, are we sure that OSPF,
> in this
> > > environment, scales?
> > >
> > > I mean if it doesn't scale for wavelength availability information
> distribution
> > > why it has to scales for other optical impairment distribution?
> > >
> > > ----------------------------------------------------------------
> > > Diego Caviglia
> > > Photonic Networks Design and Modelling
> > > E-mail: diego.caviglia@marconi.com
> > > Tel: +39 (0) 10 6003 808
> > > Via A. Negrone 1A 16153 Genoa (Italy)
> > > http://www.marconi.com
> > >
> > > Ayan Banerjee <abanerjee@calient.net> on 25/06/2001 22.26.02
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > To: Diego Caviglia/MAIN/MC1@MCMAIN,
> > > petera@nortelnetworks.con, ccamp@ops.ietf.org
> > >
> > > cc: Giovanni Fiaschi/MAIN/MC1@MCMAIN
> > >
> > >
> > >
> > > Subject: RE: Optical impairments in
> > > draft-ietf-mpls-generalized-signaling- 04
> > >
> > >
> > >
> ----------------------------------------------------------------------------
> ----
> > >
> > > Diego,
> > >
> > > Please see draft-ietf-ipo-impairments-00.txt for optical constraints.
> > >
> > > Thanks,
> > > Ayan
> > >
> > > -----Original Message-----
> > > From: Diego Caviglia [mailto:Diego.Caviglia@marconi.com]
> > > Sent: Monday, June 25, 2001 6:19 AM
> > > To: petera@nortelnetworks.con; ccamp@ops.ietf.org
> > > Cc: Giovanni Fiaschi
> > > Subject: Optical impairments in draft-ietf-mpls-generalized-signaling-04
> > >
> > > Peter ,all,
> > >
> > > a comment about draft-ietf-mpls-generalized-signaling-04.
> In
> > > the
> > > draft there is the label set object that is very useful in All optical
> > > networks
> > > with CI-incapable nodes but lambda conversion is only one of the
> > > problems
> > > related to path establishment in such networks. I mean what about
> OSNR
> > > and
> > > non-linear impairments? What about gain variation and power
> equalization?
> > > Where
> > > are covered these topic?
> > >
> > > If I can find a path feasible from the lambda continuity point of
> view
> > > who
> > > assure me that I have the needed Q at the end of the all optical path?
> > >
> > > Best regards.
> > >
> > > ---------------------------------------------------------------->
> > > Diego Caviglia>
> > > Photonic Networks Design and Modelling
> > > E-mail: diego.caviglia@marconi.com
> > > Tel: +39 (0) 10 6003 808
> > > Via A. Negrone 1A 16153 Genoa (Italy)
> > > http://www.marconi.com