Wavelength Reservation

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Wavelength Reservation Protection Threshold

• By
• Geetha Sanapala
• CSE, UNL

2
Introduction

• Heuristics for wavelength assignment
• Assumption Longer lightpaths have a higher
  probability of getting blocked than shorter paths
• Aim To protect longer paths
• How are they different from other schemes
• i) Specify under what conditions a wavelength
  can be assigned to a connection request
• ii) Attempt to reduce blocking probability for
  longer or multi-hop connections

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Working

• Wavelength Reservation (Rsv)
• One or more wavelengths are reserved on each
  link.
• Usually for a longer-hop route.
• Longer connection can use other wavelengths.
• Other connections not allowed to use reserved
  wavelengths.
• Threshold Protection (Thr)
• Shorter connections are assigned wavelengths
  only if available wavelengths is above a given
  threshold.
• Purpose is to provide available wavelengths for
  longer connections.

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Types of WRPs

• Forward Reservation Protocol
• SRC node sends a REQ packet to DEST
• REQ packet tries to reserve suitable
  wavelengths
• If succeeded, wavelength is reserved
• If failed, NACK is sent back to SRC reserved
  wavelengths are released
• Backward Reservation Protocol
• PROB packet is sent by SRC along the route to
  DEST
• PROB packet collects information about
  available wavelengths
• When PROB reaches DEST, it selects a suitable
  wavelength and sends a RESV packet

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Pros Cons

• Wavelength Reservation
• Blocking probability for longer connections is
  reduced
• Reduces wavelength utilization
• Threshold Protection
• Reduces blocking probability as well as set-up
  time for longer connections
• Reduced performance of shorter connections and
  overall network performance

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References

• Optical WDM Networks Concepts Design
  Principles by Jun Zheng, Hussein T.
• Review of Routing Wavelength Assignment
  Approaches for Wavelength-Routed Optical WDM
  Networks
• http//networks.cs.ucdavis.edu/mukherje/links/hu
  i_RWA_onm00.pdf