An Overlay Architecture for High Quality VoIP Streams

1. An Overlay Architecture for High Quality VoIPStreams IEEE Trans. on Multimedia 2006 R97725013 翁郁婷 R97725015 周克遠

2. AUTHORS David Hedqvist Chalmers, Sweden, Stud. Andreas Terzis IEEE Member Yair Amir Johns Hopkins, US Prof. ClaudiuDanilov Johns Hopkins, Assist. Stuart Goose IEEE Member

3. AGENDA • INTRODUCTION • FRAMEWORK • DEPLOYMENT • CONCLUSION

4. INTRODUCTION • VoIP • Quality of VoIP • Internet Loss Characters

5. VoIP All-IP Service Voice over IP Low Cost Low Quality > Characters of VoIP

6. QUALITY ISSUE INTERACTIVE • Delay CANNOT higher than 100-150 ms • Use UDP to deliver VoIP Packets LOW QUALITY: PACKET LOSS OR DROP • Loss during the Internet Routing • Delay and Drop Packet Note: Currently we allow short delay: Use a buffer on receiver side > The Cause Factors of VoIP Quality

7. INTERNET • Internet Loss Rate: 0.42% • Internet Burstiness Rate: 72%

8. FRAMEWORK • Overlay Network & Spines • Real-time Recovery Protocol • Real-time Routing for Audio

9. THE PROTOCOL Why use UNRELIABLE UDPprotocol? • No sufficient time to End-to-end Retransmission • How about BREAK the END-TO-END into HOP-TO-HOP > The Reason to Use Spines

10. OVERLAY NETWORK • Virtual Network with Limited Scope • Easy to Implement and Control • Overhead Signaling Message > What is Overlay?

11. THE SPINES Spines Daemon Applications • Open Source Overlay Network • Two-level Architecture • Each Spines Daemon (Node) is both SERVER and ROUTER > The Spines Architecture

12. RECOVERY PROTOCOL Real-time Recovery Protocol • Keep a buffer on each outgoing link • Intermediate nodes forward packets as they are received • Upon detecting loss, asks the upstream node for Retransmission. A Retransmission Request for a packet is only sent once. • When receives a Retransmission Request:If it has the packet, resends itIf not, ignore the request • Only the first instance will be forwarded > The Real-time Recovery Protocol

13. PACKET LOSS RATE on Link: p LOSS RATE CASE OF CANNOT RECOVERY Retransmission Request Lossp(1–p)p = p2 – p3 Retransmission Packet Lossp(1–p)(1–p)p = p2 – 2p3 + p4 Else – Negligible p One Overlay Link with Two Overlay Nodes Total Loss Probability: 2p2 – 3p3, approximately > Calculate the Loss Rate of the Real-time Recovery Protocol

14. THE ROUTING Real Time Routing For Audio • Adjust Overlay Routing to avoid Problematic Path • Two Parameter: Packet Loss Rate and Latency > Use a COST FUNCTION to handle the Two-metric Decision

15. COST FUNCTION THE COST: TRANSMISSION DELAY • PACKET LOSS RATE on Link: p • Maximum WAITING TIME: Tmax • ERROR DETECT TIME: Δ ALL CASES Success Transmit: (1 – p)T Recovery Transmit: (p – 2p2 + 3p3)(3T + Δ) Packet Loss: (2p2 – 3p3)Tmax The Cost FunctionTexp(1 – p)T + (p – 2p2 + 3p3)(3T + Δ) + (2p2 – 3p3) Tmax > Calculate the Cost Function of the Routing

16. DELAY DISTRIBUTION (2p2 - 3p3) Tmax (p – 2p2 + 3p3) (3T+Δ) (1–p) T ALWAYS CANNOT HANDLE • Delay distribution - 1 link, 5% loss

17. COMPARISON • Different Routing Metrics - 100 nodes

18. DEPLOYMENT • Performance on Loaded Computer • Test over PlanetLab

19. APPLICATION LOAD OVERLAY PROBLEM Affected on the LOADED COMPUTERS? INCREASE the PRIORITY > Overlay Loading Affected by Application Layer

20. PlanetLab US • Planetlab US - Percentage of Streams That Missed

21. CONCLUSIONS

22. CONCLUSION • Segment End-to-end into shorter Overlay Paths • Recovery Lost Packets with Limited Time • Avoid Problematic Path OVERLAY • Slightly Change the Overall Architecture • More Flexibility • Easy to Implement and Deployment ADVANTAGE DISADVANTAGE • Overhead • Diminish Margin Utility

23. THANK YOU FOR ATTENTION