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74th IETF – San Francisco, CA, March 2009Page - 1
A Framework for the Control and Measurement of Wavelength Switched Optical Networks
(WSON) with Impairments
Greg Bernstein [email protected] Networking
Young Lee [email protected]
Huawei
Dan Li [email protected]
Huawei
Giovanni Martinelli [email protected]
Cisco
draft-bernstein-ccamp-wson-impairments-03.txt
74th IETF – San Francisco, CA, March 2009Page - 2
Contributors
• Ming Chen (Huawei)
• Gabriele Galimberti (Cisco)
• Rebecca Han (Huawei)
• Alberto Tanzi (Cisco)
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A Framework for WSONs with Impairments
• Merged previous two drafts: Grotto-Huawei, and Cisco into one draft
• 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
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Who defines optical impairments
• ITU-T has an extensive recommendations that include terminology, definitions, estimation, and measurement techniques.
• We use ITU-T definitions for optical impairments and do not define, specify, or otherwise intrude into this domain other than to ask questions and request assistance!
• Impairment information models and encodings will be based on ITU-T recommendations and solicit ITU-T feedback.
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Control Plane Related Applications
• Impairment Aware Path Computation and Control– Our focus here– Includes path establishment and teardown
• Control and Collection of Optical Measurements – Interesting potential application for control
plane but we don’t address this here.
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Impairment Aware Path Computation and Control
• Optical Requirements and Constraints– Impairment Estimation Level of Detail– Impairment Information Sharing Constraints– Impairment Validation (IV) Function
• IA-RWA Computing and Control Plane Architectures– Combined Routing, WA, and IV– Separate Routing, WA or IV– Routing + Distributed WA and/or IV
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Impairment Estimation Level of Detail
• Ignored Impairments– In certain networks of limited physical extent, topology,
or for other reasons impairments may be ignored. A common case is certain types of WDM rings.
• Approximate Impairment Estimation– Computation of quantities such as OSNR, Q-factor, rise
time budget based on a set of given impairment parameters.
• Detailed Impairment Estimation– Detailed simulation of BER, eye diagrams, etc… based
on a set of given impairment parameters.
Our initial concern
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Impairment Info Sharing Constraints
• Constrained impairment information sharing– Some vendors within a network may not want to share
impairment information concerning their equipment or may not be using standardized impairment models.
– Within limits the control plane can still function in this case and we’ll show how…
• Unconstrained impairment information sharing– Information concerning a network elements
impairments can be shared freely via the control plane (but not necessarily beyond the control plane).
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Impairment Validation Function
• Functional Blocks– Transmitter and signal characterization– Optical Path characterization (channel estimation)– Receiver characterization– Estimation of signal quality (BER, Q Factor)
+-----------------+ +------------+ +-----------+ | +------------+ | | | | | | | | | | Optical | | Optical | | | Optical | | | Interface |------->| Path |--->| | Channel | | | (Transmit/ | | | | | Estimation | | | Receive) | | | | | | | +------------+ +-----------+ | +------------+ | | || | | || | | Estimation | | || | | \/ | | +------------+ | | | BER / | | | | Q Factor | | | +------------+ | +-----------------+
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IA-RWA Process Alternatives
Routing
Impairment Validation
(distributed)
Wavelength Assignment(distributed)
Routing
Wavelength Assignment
Impairment Validation
(candidates)
(a) (b) (c)
Impairment Validation
(approximate)
Routing
Wavelength Assignment
Combined RWA&IV(works with info sharing constraints)
Candidates IV + RWA(works with info sharing constraints)
Routing + Distributed WA & IV
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Candidates IV + RWA via PCE
Tim
e
Path Computation Client (PCC)
Impairment Validation
(candidates) (PCE)
PCC requests an optical path and wavelength between nodes A and Z.
RWA PCE requests a set of possible impairment qualified optical paths along with any wavelength constraints between nodes A and Z.
IV PCE returns a set of impairment qualified optical paths along with wavelength constraints between nodes A and Z.
RWA PCE performs RWA computation based on inputs from IV PCE.RWA PCE returns path and
wavelength to PCC.
RWA andCoordinating
(PCE)
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Protocol Implications
• Routing, Signaling, PCEP, need for an information model…
+-------------------+----+----+----------+--------+ | IA-RWA Option |PCE |Sig |Info Model| Routing| +-------------------+----+----+----------+--------+ | Combined |Yes | No | Yes | Yes | | IV & RWA | | | | | +-------------------+----+----+----------+--------+- | IV-Candidates |Yes | No | Yes | Yes | | + RWA | | | | | +-------------------+----+----+----------+--------+ | Routing + |No | Yes| Yes | No | |Distributed IV, RWA| | | | | +-------------------+----+----+----------+--------+
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Next Steps/Issues
• Informational working group document?– All frameworks are informational– Gives us something to liaison with ITU-T
• Continue refining requirements, architectures and models– Discuss ITU-T “black link” model from
G.698.1 and G.698.2 and which of our architectures applies to this situation.
• Continue discussions with ITU-T
