SureCall: Towards Glitch-Free Real-Time Audio/Video Conferencing

1
SureCall Towards Glitch-FreeReal-Time
Audio/Video Conferencing

• Amit Mondal, Northwestern University
• Ross Cutler, Microsoft Corporation
• Cheng Huang, Microsoft Research
• Jin Li, Microsoft Research
• Aleksandar Kuzmanovic, Northwestern University

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Physical Presence or United Communications?

• 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)

Scheduled Actual
Seattle ? Cape Town 24 hrs 42 hrs
Shanghai ? Beijing 2 hrs 10 hrs
not being there, but better than being there
3
Booming of Unified Communications

• Widely validated in the consumer world

• Gradually being adopted by enterprises
• Cisco acquired WebEx
• Google announced acquisition of GIPS, which
  powers
• Microsoft Unified Communications

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

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/che
  ngh/SureCall/SureCall.htm

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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

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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)

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SureCall Data Set

• 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. audiovideo
• Trace preprocessing
• Clock skew removal

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Clock skew in wild
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Jitter in Enterprise and Home Networks
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.
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Correlation between Loss Burst Length and Jitter
Home
Enterprise

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.

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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

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Audio Classifier Performance
The classifier achieves a true positive rate gt80
and false positive rate lt 1 for T1T20.07.
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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

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WiFi Relay

• 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
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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