A Framework for the Control and Measurement of Wavelength Switched Optical Networks (WSON) with Impairments

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A Framework for the Control and Measurement of
Wavelength Switched Optical Networks (WSON) with
Impairments
draft-bernstein-ccamp-wson-impairments-01.txt
Greg Bernstein gregb_at_grotto-networking.com Grott
o Networking Young Lee ylee_at_huawei.com Huawei
Dan Li danli_at_huawei.com Huawei
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Contributors

• Ming Chen (Huawei)
• Rebecca Han (Huawei)

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A Framework for WSONs with Impairments

• What are impairments and how do they relate to
  routing
• Physical processes that can alter an optical
  signal during transmission or other processing
  such as switching
• RFC4054 gives an overview
• Who defines optical impairments?
• ITU-T has an extensive recommendations that
  include terminology, definitions and measurement
  techniques.

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ITU-T References

1. G.650.1 ITU-T Recommendation G.650.1,
   Definitions and test methods for linear,
   deterministic attributes of single-mode fibre and
   cable, June 2004.
2. 650.2 ITU-T Recommendation G.650.2, Definitions
   and test methods for statistical and non-linear
   related attributes of single-mode fibre and
   cable, July 2007.
3. G.652 ITU-T Recommendation G.652,
   Characteristics of a single-mode optical fibre
   and cable, June 2005.
4. G.653 ITU-T Recommendation G.653,
   Characteristics of a dispersion-shifted
   single-mode optical fibre and cable, December
   2006.
5. G.654 ITU-T Recommendation G.654,
   Characteristics of a cut-off shifted single-mode
   optical fibre and cable, December 2006.
6. G.655 ITU-T Recommendation G.655,
   Characteristics of a non-zero dispersion-shifted
   single-mode optical fibre and cable, March 2006.
7. G.656 ITU-T Recommendation G.656,
   Characteristics of a fibre and cable with
   non-zero dispersion for wideband optical
   transport, December 2006.
8. G.661 ITU-T Recommendation G.661, Definition
   and test methods for the relevant generic
   parameters of optical amplifier devices and
   subsystems, March 2006.
9. G.662 ITU-T Recommendation G.662, Generic
   characteristics of optical amplifier devices and
   subsystems, July 2005.
10. G.671 ITU-T Recommendation G.671, Transmission
    characteristics of optical components and
    subsystems, January 2005.
11. G.680 ITU-T Recommendation G.680, Physical
    transfer functions of optical network elements,
    July 2007.
12. G.691 ITU-T Recommendation G.691, Optical
    interfaces for multichannel systems with optical
    amplifiers, November 1998.
13. G.692 ITU-T Recommendation G.692, Optical
    interfaces for single channel STM-64 and other
    SDH systems with optical amplifiers, March 2006.
14. G.872 ITU-T Recommendation G.872, Architecture
    of optical transport networks, November 2001.
15. G.957 ITU-T Recommendation G.957, Optical
    interfaces for equipments and systems relating to
    the synchronous digital hierarchy, March 2006.
16. G.959.1 ITU-T Recommendation G.959.1, Optical
    Transport Network Physical Layer Interfaces,
    March 2006.
17. G.694.1 ITU-T Recommendation G.694.1, Spectral
    grids for WDM applications DWDM frequency grid,
    June 2002.
18. G.694.2 ITU-T Recommendation G.694.2, Spectral
    grids for WDM applications CWDM wavelength grid,
    December 2003.
19. G.Sup39 ITU-T Series G Supplement 39, Optical
    system design and engineering considerations,
    February 2006.

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Control Plane related Applications

• Impairment Aware Path Computation and Control
• Our focus here
• Includes path establishment and teardown
• Measurement of Optical Connection Quality
• Interesting potential application of control
  plane but we dont address this here.

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Impairment Framework Goals

• Relate the application area to the GMPLS and PCE
  control plane (also see Giovanni)
• Decompose and classify various reasonable
  approaches -- Very important to get folks on the
  same page--
• Identify, define and classify terminology,
  nomenclature, parameters -- Here we reference
  ITU-T, but more classification for control plane
  purposes is useful (see Imp-Info and Giovanni)
• Look for commonality and difference among
  approaches with respect to (a) shared
  information, (b) procedures, (c) actors (entities
  involved)

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Approaches to Impairments in WSONs
ITU-T Question 12/15 Working Group List

1. Networks designed such that every possible path
   is conformant for all the signal types permitted
   on the network (impairment free case)
2. Networks in which a limited number of
   pre-calculated paths are conformant for each type
   of signal permitted in the network. (no knowledge
   of impairments in the control plane)
3. Networks in which impairment effects can be
   estimated via approximation techniques
   (impairment info needed)
4. Networks in which impairment effects must be more
   accurately estimated. Typically via simulation
   (impairment info needed)

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Impairment Aware RWA Computation

• Three conceptual functions
• Routing (WSON Framework)
• Finding one or more paths from source to
  destination
• Wavelength Assignment (WSON Framework)
• Selecting a wavelength/wavelengths to use along a
  path
• Impairment Validation (IV) -- new
• Determining if the impairments encountered by a
  specific signal on this selected path and
  wavelength result in unacceptable degradation in
  received signal quality.

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Architectural Alternatives

• Combined Routing, WA, and IV
• Routing (R), Wavelength Assignment (WA) and
  Impairment Validation (IV) performed on a single
  entity, e.g., PCE. This doesnt specify
  algorithms or procedures. Does need some type of
  impairment information (cases 3 4)
• Routing WA IV
• Splitting all or any of these functions amongst
  different entities.
• Routing Distributed WA/IV
• Performing either WA or IV or both in a
  distributed fashion via a signaling protocol.

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RWAIV

• RWAIV
• separate routing, wavelength assignment, and
  impairment validation
• R (WA IV)
• routing separate from a combined wavelength
  assignment and impairment validation process.
  Note that impairment validation is typically
  wavelength dependent hence combining WA with IV
  can lead to efficiencies.
• (RWA)IV
• combined routing and wavelength assignment with a
  separate impairment validation process.

Control plane implications getting required
information to computational entities and
communications between entities, does not require
additional signaling modifications
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Routing and Distributed WA/IV
Valid for Case 3 Approximate Impairment
computation

• RWA Distributed IV
• Does IV for only a particular wavelength
• R Distributed WA IV
• Needs to perform IV for each potential wavelength
  and carry this information as long as the
  potential wavelength is under consideration.

Control plane implications modification of
signaling protocols, does not require impairment
information distribution.
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Next Steps/Issues

• Assess interest in an Impairment Framework
• Relation to other drafts?
• Continue discussions with ITU-T