WF2Q : Worstcase Fair Weighted Fair Queueing

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WF2Q Worst-case Fair Weighted Fair Queueing

• Jon C.R. Bennett
• Hui Zhang
• IEEE Infocom 1996

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Agenda

• Introduction
• Related Work
• Generalized Processor Sharing (GPS)
• Weighted Fair Queueing (WFQ)
• Worst-case Fair Weighted Fair Queueing (WF2Q)
• Conclusion

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Introduction

• Wired network scheduler
• Fluid systems Packet systems

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Fluid Systems
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Packet Systems
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Introduction

• Approximating algorithm
• Approximate fluid systems by packet systems
• Packet Generalized Processor Sharing (PGPS)

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Related Work

• Self-Clocked Fair Queueing (SCFQ) 7
• Much larger delay bound
• Virtual Clock algorithm 19
• Large normalized Worst-case Fair Index

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Generalized Processor Sharing (GPS)

• Concept of fluid systems algorithm (Idelized)
• Serving N backlogged sessions simultaneously
• Property
• Provide end-to-end bounded-delay service to
  sessions which are leaky-bucket
• Ensure fair allocation of bandwidth among all
  backlogged sessions

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Notation
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GPS
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GPS

• Definition
• Service rate
• Emulating GPS service in packet systems

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Weighted Fair Queueing (WFQ)

• In 13 establishes relationship
• Fall behind within one maximum packet
• But can far ahead numbers of maximum packets

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WFQ
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Example

• Packet size 1
• Link speed 1
• Guarantee session rate
• Session 1 0.8
• Session 2 0.1
• Session 3 0.1
• All packets arrive at time 0

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WFQ
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Worst-case Fair Index (WFI)

• Definition
• Normalized
• Normalized Worst-case Fair Index

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WFI

• GPS
• WFQ

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Worst-case Fair Weighted Fair Queueing (WF2Q)

• Packet start later in packet system than in GPS
  system, but finish earilier
• Difference expand
• To minimize the difference, choose next
  transmission packet from started sessions

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WF2Q
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WF2Q
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WF2Q

• Property

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Conclusion

• Quantitative measurement WFI
• Proposed new PFQ algorithm WF2Q
• Future work
• Improve high computation of maintaining virtual
  time function