Efficient QoS Support for Optical Burst Switched Networks

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Efficient QoS Support for Optical Burst Switched
Networks

• Pascal Acquaah
• Prof. H. Anthony Chan
• Department of Electrical Engineering
• University of Cape Town

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Outline

• Introduction and Burst Assembly in OBS
• QoS Issues in OBS
• Performance parameters in OBS
• Previous QoS proposals
• Emission and Discard Priority (EDP) scheme
• Burst Assembly with EDP scheme
• Optimizing Deflection Routing with EDP scheme
• Simulation Setup and Simulation Results
• Conclusion

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Introduction and Burst Assembly in OBS
O-O-O
CIRCUIT SWITCHING
BURST SWITCHING O-O-O/O-E-O
PACKET SWITCHING
O-E-O
O-O-O All Optical Switching O-E-O Optical
Electronic Optical Switching
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Introduction and Burst Assembly in OBS
Edge Router
Egress Node
Input Traffic
Output Traffic
Core Router
Ingress Node
DWDM Link
Input Traffic
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Introduction and Burst Assembly in OBS
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QoS Issues in OBS

• Burst Loss Rate is high
• Need for Highly Effective Contention Resolution
• Lack of QoS support in the Core Network
• Further Service Differentiation required in core
  network
• Lack of practical and simple methods to provide
  QoS
• Certain proposals to resolve contention are too
  complex to implement and may hinder network
  performance

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QoS Issues in OBS
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Performance Parameters in OBS

• Throughput (Mbps)
• Throughput (Bytes Received 8) / 106
• End-to-End Delay (ms)
• Tdelay Tassembly Toffset Tprop
  Tdisassembly Tswitch
• Tdisassembly and Tswitch are negligible
• Burst Loss Rate
• P (burst loss) 1 (Burst Recv / Burst Sent)
• Goodput
• Ratio of packets that reach destination within
  their delay requirements

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Previous QoS proposals

• Relative QoS based Solutions
• Performance of the network is not guaranteed in
  quantitative terms
• High priority burst loss lt low priority burst
  loss. All based on traffic load
• Easy implementation
• Absolute QoS based Solutions
• Performance of the network is guaranteed in
  quantitative terms (worst case scenario)
• Hard guarantee offers expected level of
  performance
• Complex implementation

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Emission and Discard Priority (EDP) Scheme

• We introduce the concept of Emission and Discard
  Priority (EDP) to provide QoS in the OBS network
• Emission Priority
• Provides Static QoS at the edge
• Based on delay tolerance of packets
• Discard Priority
• Extended service differentiation in the core
• Provides Dynamic QoS in the core
• Based delay tolerance and loss sensitivity of
  packets

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Burst Assembly with the EDP scheme
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Burst Assembly with EDP scheme
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Optimizing Deflection Routing with EDP scheme
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Optimizing Deflection Routing with EDP scheme
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Performance Objectives

• Improve Goodput of deflection routing in the OBS
  network
• Increase throughput
• Meet delay requirements
• Eliminate unnecessary deflections
• Validate the use of deflection routing in OBS

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Simulation Setup

• Simulation tools
• Ns2 Simulator
• OBS-0.9a module
• Assumptions
• No Wavelength Conversion
• JET used as reservation scheme
• LAUC-VF used for scheduling
• Uniform distribution of delay tolerance
• Aggregated Pareto traffic sources
• Variable-timer based assembly

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Network Topology
Edge Router
Core Router
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Simulation Setup
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Simulation Results
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Simulation Results
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Simulation Results
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Simulation Results
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Simulation Results
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Conclusion

• We implemented an EDP scheme for simple QoS
  support in OBS
• Deflection with EDP scheme improved the goodput
  of deflection routing
• Deflection with EDP scheme outperformed normal
  deflection at high loads
• High throughput was maintained while meeting
  delay requirements
• Deflection routing with the EDP scheme is
  suitable to support wavelength conversion for
  contention resolution in OBS networks

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Thank you

• Questions

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Simulation Results