1. Do Twin Clouds Make Smoothness for Transoceanic Video Telephony ? Jian Li Tsinghua University Zhenhua Li Tsinghua University Yao Liu Binghamton University Zhi-Li Zhang University of Minnesota upton@tsinghua.edu.cn Sep. 2nd, 2015

2. 2 Outline ① Background & Motivation ② Objective & Metric ③ Dataset & Testbed ④ Results & Analysis ■ Summary of Contribution

3. Video Telephony Services 3 Anywhere Any device Anytime

4. Massive Popularity Over 300M users 1PB data per day 200M users in its first two years 4 Over 500M users Over 3 PB data …

5. 5 Transoceanic Video Telephony (TVT) Overseas study Global trade Online Learning

6. 6 Challenges Challenges of transoceanic video telephony (TVT): high-rate (>500kbps) low-delay (<350ms) users sensitive to voice/video quality degradation longer round-trip delay larger number of relay hops higher packet loss rate

7. 7 ② Objective & Metric

8. 8 Objective Examine how today ’ s commercial service providers achieve smoothness for TVT? Proprietary protocols Encrypted data and signaling Little info about design choices

9. 9 A Novel Metric quantifysmoothness To quantify the smoothness of video telephony services L: Packet Loss Rate R: Packet Recovery Rate Smoothness = 1 - L*(1-R), delay<1s Bandwidth? RTT?

10. 10 ③ Dataset & Testbed

11. 11 Dataset A real-world data trace of four popular video telephony services AppLocationTimestampHops Loss rateRound-trip delay and jitterRecovery rate Video Smoothness File attributes recorded in our collected trace

12. 12 Testbed Internet Sent Packets Received Packets Domestic video call Transoceanic video call

13. 13 ④ Results & Analysis

14. 14 Trasoceanic Video Telephony In TVT experiments, there are three data transmission paths. The upper, blue path is used by Skype, Facetime, and QQ The middle path is used by WeChat The lowermost is the detour path of WeChat

15. 15 Twin Clouds WeChat's Video/Voice Data Delivery Infrastructure.

16. 16 Transoceanic Video Telephony Relay hops WeChat decreases the number of hops from 21 to 11.

17. 17 Transoceanic Video Telephony Round-trip delay and jitter RTT of WeChat is decreasing from 1200msec to 360msec. Jitter of WeChat is decreasing from 252msec to 90msec.

18. 18 Transoceanic Video Telephony ISP awareness WeChat develops the ISP-aware cloud server selection mechanism WeChat

19. 19 Transoceanic Video Telephony Packet loss rate WeChat decreases the packet loss rate from 11%, 13%, 11.6% to 7%. Packet recovery rate WeChat adopts aggressive retransmission strategy. (16%, 43%, 24%  56%) Retrans traffic increase rate(2.7%, 5.9%, 3.5%  8.5%).

20. 20 Tranoceanic Video Telephony Video telephony smoothness TVT smoothness of WeChat is 97% on average (94.9%-98.6%) TVT smoothness of Skype, Facetime, and QQ is 90.8%, 92.6%, and 91.2%. WeChat outperforms the others in both the absolute value and the stability.

21. 21 Are there any drawbacks of twin clouds?

22. 22 Tranoceanic Video Telephony Shortage of Twin Clouds’ Capacity WeChat uses an alternative cloud located at Shenzhen (China) to take over the data delivery. Performance degradation!

23. 23 Tranoceanic Video Telephony Startup time TVT video startup delay of WeChat is ~ 10s. VS

24. 24 ■ Summary of Contribution Objective: Examine how today ’ s commercial service providers achieve smoothness for transoceanic video telephony (TVT) ? Metric: Video Telephony Smoothness WeChat has the smoothest video which results from fewer network hops, lower loss rate and RTT, and more aggressive retransmissions. Twin clouds’ shortcomings: shortage of resource capacity, longer video startup time.

25. The End Thank you!

26. 26 Domestic Video Telephony In DVT experiments, there are two different data transmission paths. The upper, yellow path is used by skype, facetime, and QQ The lower, circuitous path is used by WeChat

27. 27 Domestic Video Telephony Relay hops WeChat decreases the number of relay hops from 12 to 9.

28. 28 Domestic Video Telephony Round-trip delay and jitter RTT of WeChat is decreasing from 252msec to 135msec. Jitter of WeChat is decreasing from 110msec to 50msec

29. 29 Domestic Video Telephony Packet loss rate WeChat decreases the packet loss rate from 7.3%, 7.6%, 6.8% to 4.3%.

30. 30 Domestic Video Telephony Packet recovery rate WeChat adopts aggressive retransmission strategy. (22%, 45%, 29%  62%) Retrans traffic increase rate. (1.9%, 3.8%, 2.3%  7.4%)

31. 31 Domestic Video Telephony Video telephony smoothness DVT smoothness of WeChat is excellent: 98.4% DVT smoothness of Skype, Facetime, and QQ is 94.3%, 95.8%, and 95.2%. WeChat outperforms the others in both the absolute value and the stability.