1. SureCall: Towards Glitch-Free Real-Time Audio/Video Conferencing Amit Mondal, Northwestern University Ross Cutler, Microsoft Corporation Cheng Huang, Microsoft Research Jin Li, Microsoft Research Aleksandar Kuzmanovic, Northwestern University

2. Attending meeting in person is nice, but the overhead due to travel is high & unpredictable Unified Communications promise – VoIP service double in next 4 years, with an annual growth rate of 26% ( Infonetics Research, 2008 ) ScheduledActual Seattle  Cape Town24 hrs42 hrs Shanghai  Beijing2 hrs10 hrs Physical Presence or United Communications? not being there, but better than being there 2

3. Gradually being adopted by enterprises – Cisco acquired WebEx – Google announced acquisition of GIPS, which powers – Microsoft Unified Communications Booming of Unified Communications Widely validated in the consumer world 3

4. Contributions SureCall platform – A distributed measurement and experiment platform for audio/video conferencing Quantitatively analyze the impact of network over a wide variety of scenarios in fine granularity Validate new solutions 4

5. SureCall Platform A distributed measurement and experiment platform – SureCall agents installed on volunteers’ machines – Measurements & experiments driven by a master controller – Packet-level traces collected & analyzed – Agents upgradeable without user intervention Available from http://research.microsoft.com/~chengh/SureCall/SureCall.htm http://research.microsoft.com/~chengh/SureCall/SureCall.htm 5

6. SureCall Measurements Emulated bidirectional audio/video sessions using UDP – 5-minute session per hour – Audio bitrate : 24 kbps – Video bitrate: 192 kbps – STUN NAT traversal protocol for home users Network connectivity close to the clients – ICMP packet pair with TTL = 2 Traceroute to at the beginning and end of each session Environmental details on client machines – CPU load, network interface type 6

7. SureCall Deployment Microsoft global enterprise network & many residential networks Current deployment status – 80 unique machines Enterprise - 32 Home – 20 Both – 28 Enterprise trace and Home trace – two separate master controllers (within the enterprise network and on the Internet) 7

8. 4,800 hours of packet traces – 4,100 from enterprise – 700 from home 1,968 unique IP addresses – Enterprise - 1212 – Home -756 Trace classification and stratification – Intra-continental vs. inter- continental – Wired vs. wireless – Audio-only vs. audio+video Trace preprocessing – Clock skew removal 8 Clock skew in wild 8 SureCall Data Set

9. Jitter in Enterprise and Home Networks 9 US-US, wired traces Inter-continental, wired traces Home networks have significantly higher jitter compared to enterprise networks and affected greatly by inter- continental links.

10. Correlation between Loss Burst Length and Jitter 10 1.End-to-end jitter increases significantly before loss events in both enterprise and home networks (~ 80%) 2.Increase in end-to-end jitter is not a great indicator of loss burst length in enterprise networks. 1.End-to-end jitter increases significantly before loss events in both enterprise and home networks (~ 80%) 2.Increase in end-to-end jitter is not a great indicator of loss burst length in enterprise networks. Enterprise Home

11. Network Audio Diagnostics Concealed: percent of packets interpolated or extrapolated due to unrecovered packet loss Stretched: percent of packets stretched via time compression Classifier operates as follows Supervised training with ground-truth objectively determined by PESQ score 11

12. Audio Classifier Performance 12 The classifier achieves a true positive rate >80% and false positive rate < 1% for T1=T2=0.07.

13. WiFi Relay Wireless connections experience significantly more packet losses than wired connections Heavy replication is a effective manner to hide packet losses in wireless channel WiFi relay solution 13

14. Evaluated on SureCall platform Simultaneous direct and overlay VoIP call – An apple-to-apple comparison WiFi relay greatly reduces packet loss and significantly improves VoIP quality for WiFi users 14 WiFi Relay

15. Conclusion SureCall, a distributed measurement and experimental platform, to address the challenges of audio/video communications. Characterized enterprise and residential networks over a wide variety of network scenarios Two applications of SureCall – Network audio diagnostics – WiFi Relay 15