The Earliest Deadline First Scheduling for Real-Time Traffic in the Internet

1
The Earliest Deadline First Scheduling for
Real-Time Traffic in the Internet

• Danny H. K. Tsang, Xiaojun Hei
• July 10, 2001
• http//www.ee.ust.hk/eetsang/
• Department of Electrical and Electronic
  EngineeringHong Kong University of Science and
  Technology

2
Outline

• Introduction
• Hierarchical scheduling framework
• EDF with active buffer management
• Conclusion and future work

3
Network Convergence

• Telephone Networks
• Computer Networks
• Cable Television Networks
• Wireless Networks
• Convergence IP-centric networks

4
Next Generation Internet

• Broadband networks (WDM, 3G, 802.11, )
• Multimedia communication
• Quality of Service provision
• Integrated Services (IntServ)
• Differentiated Services (DiffServ)

5
Packet Scheduling

• Service Policies
• First Come First Serve
• Generalized Processor Sharing
• Earliest Deadline First
• Buffer Management
• Drop-Tail
• Random Early Detection

6
Real Time Traffic

• Requirements
• High bandwidth
• Time-sensitive
• Packet loss
• Transport candidates
• User Datagram Protocol (UDP)--aggressive
• Transmission Control Protocol (TCP)--cooperative

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Hierarchical Generalized Processor Sharing
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Hierarchical Scheduling Framework
Figure 1
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Hierarchical Scheduling Structure
Figure 2
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Queueing Model for the EDF-CHOKe Scheme
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RED
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CHOKe
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Network Topology
Figure 3
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UDP Throughput Comparison
Figure 4
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Per Flow Throughput Comparison
Figure 5
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Fairness Index
Ideal 1.0
FCFS-DropTail 0.0305
FCFS-RED 0.0309
FCFS-CHOKe 0.3744
EDF-DropTail 0.0304
EDF-RED 0.0304
EDF-CHOKe 0.2838

• Definition

Table 1
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Packet Delay Distribution of the TCP Connections
Figure 6
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Statistics about the Delay Distribution(sec)
TCP TCP UDP UDP
Avg Std Avg Std
FCFS-CHOKe 0.9378 0.1203 0.0859 0.2743
EDF-CHOKe 0.5665 0.0398 0.0476 0.1564
Table 2
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Power of the Network
Definition
TCP UDP
FCFS-CHOKe 2.45 x 104 3.44 x 106
EDF-CHOKe 3.78 x 104 7.65 x 106
Table 3
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Conclusion

• EDF Schedule real-time traffic
• Hierarchical Scheduling Structure
• Best-effort service together with realtime
  traffic
• EDF with active buffer management
• Good delay performance
• Fair bandwidth allocation between UDP and TCP
  flows

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Future Work

• Hierarchical scheduling framework
• More complex networking scenarios

22
QA