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RE: Re-Updated Draft Liaison to Q6/15
It does not look good to me. Please revise the paragraph in question to
"However, if a service provider chooses to measure optical link
impairments on an out of service basis and this can be achieved within
ITU-T standards , then this should not be
prohibited by the CCAMP protocol mechanisms, and the
communication of the information collected should be
accommodated within GMPLS"
There are no ITU standards for in service measurement
From: email@example.com [mailto:firstname.lastname@example.org] On
Behalf Of Greg Bernstein
Sent: Tuesday, March 10, 2009 12:46 PM
To: Adrian Farrel
Subject: Re: Re-Updated Draft Liaison to Q6/15
Looks good to me!
Adrian Farrel wrote:
> Continuing to try to reach some sort of grudging consensus...
> Dear Peter,
> CCAMP experts are looking forward to our joint meeting with Q6/5 on
> March 20th to discuss optical impairments and the control plane
> operation of wavelength switched optical networks (WSONs).
> This liaison is to summarise the activity within CCAMP on this subject
> so far and to set out our objectives for this work.
> As you will be aware, the GMPLS control plane is designed to provide a
> dynamic control plane for a variety of switching technologies. Amongst
> these is the "lambda switch capable" data plane where devices are
> OEOs, ROADMs, and photonic cross-connects (PXCs). In fact, lambda
> switching was the technology that led to the development of GMPLS from
> the packet switching MPLS control plane.
> The IETF's CCAMP working group is the design authority for all
> extensions to the GMPLS family of protocols.
> The original work on lambda switching networks within CCAMP recognised
> that there is a subset of optical networks in which it is possible to
> disregard optical impairments and where the number of regeneration
> points is high. In these environments, path computation can be
> performed on a reachability graph, and lambda conversion can be
> performed as necessary within the network.
> As PXCs were introduced into WSONs, it remained the case that optical
> impairments could be disregarded by the control plane. Where
> necessary, optimal impairment-aware paths could be computed off-line
> and supplied to the control plane, leaving the control plane to handle
> establishment of connections and recovery after failure. Failure
> recovery scenarios might lead to contention for wavelengths or
> suboptimal optical paths, but these could be handled by crankback
> within the signaling protocol.
> More recent work on WSONs indicates that the proportion of pure
> optical devices (ROADMs and PXCs) is increasing. This means that it is
> necessary to compute paths that offer end-to-end lambda continuity.
> This problem (called the routing and wavelength assignment (RWA)
> problem) must be solved, and may be compounded by devices with limited
> cross-connect capabilities (for example, with glass-through, a limited
> OEO matrix, or restricted port-to-port capabilities). In approaching
> this problem it is convenient if there is a common identification
> scheme for wavelengths across the whole network (previously,
> wavelength identification was a local matter between the nodes at the
> ends of each link). To aid with this, the CCAMP working group has
> that provides a protocol-independent encoding for wavelengths in a way
> that is compliant with G.694. Further work on this problem space can
> be seen in the following CCAMP documents:
> "Framework for GMPLS and PCE Control of Wavelength Switched Optical
> Networks (WSON)"
> "Routing and Wavelength Assignment Information Model for Wavelength
> Switched Optical Networks"
> "Routing and Wavelength Assignment Information Encoding for Wavelength
> Switched Optical Networks"
> CCAMP participants have further identified cases where they believe it
> would be helpful to consider optical impairments during the control
> plane operation of a WSON. This gives rise to four distinct deployment
> 1. No concern for impairments or lambda continuity
> because there is sufficent margin in all impairments.
> (Original GMPLS)
> 2. No concern for impairments (again because there is
> sufficient margin), but lambda continuity is important.
> (The RWA problem)
> 3. Networks in which it is necessary to consider impairments,
> but there is sufficient margin such that approximate
> impairment estimation (using "simple" computation of the
> accumulation) could be used and still have a high
> probability that the optical path would be viable and would
> not perturb any existing paths.
> 4. Networks in which detailed impairment validation is
> necessary to perform a full computation of the accumulation
> of impairments including the impact on existing paths.
> In focusing on the third of these categories, CCAMP intends to base
> its work on G.680 and related recommendations with the following
> - G.680 (et al.) provides the definitions of optical impairments,
> optical parameters, and insights into their use
> - Where G.680 refers to "single vendor" domains, it does not
> mean single manufacturer, but rather "single system integrator".
> That is, the equipment is not "plug and play", but has been
> tested to interoperate and the network has been planned.
> - There is no requirement to measure impairments.
> - Many networks are engineered such that configured
> impairment values are enough information
> - Measuring can often produce ambiguous values
> - Equipment to perform measurement may be expensive
> However, if an implementer chooses to measure impairments
> on their device, and this can be achieved within the mechanisms
> and definitions defined by the ITU-T, then this should not be
> prohibited by the CCAMP protocol mechanisms, and the
> communication of the information collected should be
> accommodated within GMPLS.
> With this in mind, CCAMP is looking to Q6/15 to work as a partner in
> - The complete list of impairments suitable for this type of network,
> and the complete list of Recommendations to use as references
> - The rules by which such impairments are accumulated along a path.
> That is, that CCAMP is looking for the rules by which the end-to-
> end impairments of a path may be determined from a knowldedge
> of paramters of the path and impairments on the path segments.
> - Generic encodings and ranges of values for the impairments
> For reference, some early work on impairment-aware GMPLS is listed
> below. This work is not yet adopted as CCAMP work, but is likely to
> form the basis of such work once we have discussed the way forward
> with Q6/15.
> "A Framework for the Control of Wavelength Switched Optical Networks
> (WSON) with Impairments"
> "Information Model for Impaired Optical Path Validation"
> Looking forward to a profitable meeting,
> Deborah Brungard and Adrian Farrel
> CCAMP Working Group Co-Chairs
Dr Greg Bernstein, Grotto Networking (510) 573-2237