1. 73rd IETF – Minneapolis, MN, November 2008
A Framework for the Control and Measurement of Wavelength Switched Optical Networks (WSON) with Impairments
draft-bernstein-ccamp-wson-impairments-01.txt
Greg Bernstein Grotto Networking
Young Lee
Huawei
Dan Li
73rd IETF – Minneapolis, MN, November 2008

2. 73rd IETF – Minneapolis, MN, November 2008
Contributors
Ming Chen (Huawei)
Rebecca Han (Huawei)
73rd IETF – Minneapolis, MN, November 2008

3. 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.
73rd IETF – Minneapolis, MN, November 2008

4. 73rd IETF – Minneapolis, MN, November 2008
ITU-T References
[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.
[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.
[G.652] ITU-T Recommendation G.652, Characteristics of a single-mode optical fibre and cable, June 2005.
[G.653] ITU-T Recommendation G.653, Characteristics of a dispersion-shifted single-mode optical fibre and cable, December 2006.
[G.654] ITU-T Recommendation G.654, Characteristics of a cut-off shifted single-mode optical fibre and cable, December 2006.
[G.655] ITU-T Recommendation G.655, Characteristics of a non-zero dispersion-shifted single-mode optical fibre and cable, March 2006.
[G.656] ITU-T Recommendation G.656, Characteristics of a fibre and cable with non-zero dispersion for wideband optical transport, December 2006.
[G.661] ITU-T Recommendation G.661, Definition and test methods for the relevant generic parameters of optical amplifier devices and subsystems, March 2006.
[G.662] ITU-T Recommendation G.662, Generic characteristics of optical amplifier devices and subsystems, July 2005.
[G.671] ITU-T Recommendation G.671, Transmission characteristics of optical components and subsystems, January 2005.
[G.680] ITU-T Recommendation G.680, Physical transfer functions of optical network elements, July 2007.
[G.691] ITU-T Recommendation G.691, Optical interfaces for multichannel systems with optical amplifiers, November 1998.
[G.692] ITU-T Recommendation G.692, Optical interfaces for single channel STM-64 and other SDH systems with optical amplifiers, March 2006.
[G.872] ITU-T Recommendation G.872, Architecture of optical transport networks, November 2001.
[G.957] ITU-T Recommendation G.957, Optical interfaces for equipments and systems relating to the synchronous digital hierarchy, March 2006.
[G.959.1] ITU-T Recommendation G.959.1, Optical Transport Network Physical Layer Interfaces, March 2006.
[G.694.1] ITU-T Recommendation G.694.1, Spectral grids for WDM applications: DWDM frequency grid, June 2002.
[G.694.2] ITU-T Recommendation G.694.2, Spectral grids for WDM applications: CWDM wavelength grid, December 2003.
[G.Sup39] ITU-T Series G Supplement 39, Optical system design and engineering considerations, February 2006.
73rd IETF – Minneapolis, MN, November 2008

5. 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 don’t address this here.
73rd IETF – Minneapolis, MN, November 2008

6. 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)
73rd IETF – Minneapolis, MN, November 2008

7. Approaches to Impairments in WSONs
ITU-T Question 12/15 Working Group List
Networks designed such that every possible path is conformant for all the signal types permitted on the network (“impairment free case”)
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)
Networks in which impairment effects can be estimated via approximation techniques (impairment info needed)
Networks in which impairment effects must be more accurately estimated. Typically via “simulation” (impairment info needed)
73rd IETF – Minneapolis, MN, November 2008

8. 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.
73rd IETF – Minneapolis, MN, November 2008

9. 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 doesn’t 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.
73rd IETF – Minneapolis, MN, November 2008

10. 73rd IETF – Minneapolis, MN, November 2008
R+WA+IV
R+WA+IV
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
73rd IETF – Minneapolis, MN, November 2008

11. 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.
73rd IETF – Minneapolis, MN, November 2008

12. 73rd IETF – Minneapolis, MN, November 2008
Next Steps/Issues
Assess interest in an Impairment Framework
Relation to other drafts?
Continue discussions with ITU-T
73rd IETF – Minneapolis, MN, November 2008