Sliding weighted fair queueing scheme for realtime applications

1
Sliding weighted fair queueing scheme for
real-time applications

• Source IEE Proceedings-Communications, vol. 152,
  Issue 3, 3 June 2005, pp. 320 - 326
• Author Yen, Y.-S., Chen, W., Zhhuang, J.-C. and
  Chao, H.-C.
• SCI (2004) 82.8 (173/209, Impact Factor 0.195)
• Report Chao-Yu Kuo (???)
• Date 2005/11/18

2
Outline

• Introduction
• Sliding weighted fair queueing (SWFQ)
• Simulations
• Conclusions
• Comments

3
Key Words

• WFQ (Weighted Fair Queue)
• PWFQ (Priority based Weighted Fair Queue)
• Sliding Window

4
Introduction

• The priority-driven scheduling
• It serves the higher priority packets first
• It can starve the lower priority packets
• Example PQ (Priority Queue) etc

5
Introduction

• The share-driven scheduling
• It guarantees bandwidth
• It has the delay bound
• High service sharing has a lower delay bound
• Example WFQ (Weighted Fair Queue) etc

6
Introduction

• The priority-driven scheduling and WFQ are used
  at the same time
• The bandwidth and bounded delay guarantee could
  not be preserved

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Introduction

• PWFQ (Priority based Weighted Fair Queueing)
• The method to integrate WFQ and the
  priority-driven scheme is to use a sliding
  windows
• In order to determine which packet should be set
  out first within the window, fixed priority is
  used

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Introduction

• PWFQ (Priority based Weighted Fair Queueing)

Service sharing order 1, 2, 3 Priority order
3, 2 ,1
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Introduction

• SWFQ (Sliding Weighted Fair Queueing)
• It combines WFQ and a sliding window
• It decouples the effect of the service sharing
  limit in WFQ
• Example a session with low sharing but with a
  high priority

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Sliding weighted fair queueing (SWFQ)
Service sharing order 1, 2, 3 Priority order
3, 2 ,1
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Sliding weighted fair queueing (SWFQ)
Flow chart for SWFQ W window size Fik virtual
finish time for the kth packet of session i
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Simulations

• Simulation tool Delphi
• Simulation system parameters

si the bucket size of session i ?i the token
rate of session i gi the guaranteed service rate
of session i ?i the service share of session i
13
Simulations

• The network topology

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Simulations
The worst-case queueing delay for three sessions
using PWFQ
The worst-case queueing delay for three sessions
using SWFQ
15
Conclusions

• SWFQ combins priority-driven and share-driven
  scheduling for a real-time IPv6 network
• The performance of SWFQ was better than the PWFQ
  performance
• The SWFQ fairness is controlled by the size of
  the sliding window

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Conclusions

• The SWFQ window scheme can be applied to most
  fair queueing algorithms, such as WF2Q, SCFQ, etc

WF2Q (Worst-case Fair Weighted Fair
Queueing) SCFQ (Self-Clocked Fair Queueing)
17
Comments

• Is the leaky Bucket necessary?
• The traffic is shaped
• Calculating virtual finish time isnt fact
• In order to guarantee delay bound

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Questions

• Which is priority-driven scheduling?
• 1) WFQ 2) PQ 3) FCFS 4) the above is not all
• Which is share-driven scheduling?
• 1) WFQ 2) PQ 3) FCFS 4) the above is not all

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Questions

• Which picture is SWFQ?
• 1)
• 2)