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What is H.323?

H.323 Beacon: An H.323 Application Related End-to-End Performance Troubleshooting Tool Prasad Calyam, OARnet/The Ohio State University ACM SIGCOMM NetTs 2004 Weiping Mandrawa, Mukundan Sridharan, Arif Khan, Paul Schopis. What is H.323?. What is H.323?.

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What is H.323?

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  1. H.323 Beacon:An H.323 Application Related End-to-End Performance Troubleshooting ToolPrasad Calyam, OARnet/The Ohio State UniversityACM SIGCOMM NetTs 2004Weiping Mandrawa, Mukundan Sridharan, Arif Khan, Paul Schopis

  2. What is H.323?

  3. What is H.323? • An umbrella standard that defines how real-time multimedia communications such as Videoconferencing can be supported on packet switched networks (Internet) • Codecs: H.261, H.263, G.711, G.723.1 • Signaling: H.225, H.245 • Transport Mechanisms: TCP, UDP, RTP and RTCP • Data collaboration: T.120

  4. H.323 Protocol Stack

  5. Three ways to Videoconference over the Internet…

  6. Three ways to Videoconference over the Internet … 1. Point-to-Point

  7. Three ways to Videoconference over the Internet … 2. Multi-Point Star Topology

  8. Three ways to Videoconference over the Internet … 3. Multi-Point Multi-Star Topology

  9. Scenario I: A Researcher and an Industry professional want to Videoconference

  10. Case1:Researcher is unable to make a call!

  11. There was a mis-configured firewall blocking necessary ports…

  12. Case2: Industry professional is unable to make a call!

  13. His LAN’s Internet connectivity was non-functional at that time…

  14. Case3: They connected, but of them experienced bad audio & video!

  15. There was congestion at one of the intermediate routers along the path…

  16. There was congestion at one of the intermediate routers along the path…

  17. There was congestion at one of the intermediate routers along the path…

  18. The performance problem can be anywhere in the E2E Path!!!

  19. Good News! ISPs are instrumenting their networks…

  20. Scenario II: In a Multi-point setting…

  21. Scenario II: In a Multi-point setting…

  22. Scenario II: In a Multi-point setting…

  23. Topics of Discussion • H.323 Beacon Overview • Why not use the other existing tools? • Tool Features • Two Case-studies • Conclusion

  24. H.323 Beacon Overview • An application-specific measurement tool • To monitor and qualify the performance of an H.323 Videoconferencing sessions at the host and in the network (end-to-end) • Useful to an end-user/conference operator/network engineer • Uses OpenH323 and J323Engine libraries • Easy to install and use! • Open source

  25. Comparison with other existing tools… • H.323 protocol has many idiosyncrasies • ICMP and UDP based tools fail to capture the performance issues faced by actual voice and video traffic at the host and in the network • ping, traceroute, Iperf, pathrate, … • Commercial tools are VERY expensive! • NetIQ Chariot, Spirent Smartbits, Telchemy VQMon,…

  26. Initial call setup failures and haphazard disconnections… • Test Status • In-Session, Normal Close, Exception Close • Exception Close Alarms • “Possible Firewall/NAT presence obstruction” • “No Internet connectivity” • “Incompatible codec being used” • “Insufficient bandwidth” • “Remote H.323 Beacon Server not online”

  27. Initial call setup failures and haphazard disconnections…

  28. Network Health Status… • Delay, Jitter and Loss data • Real-time, offline raw data and test session summary

  29. Network Health Plots… • Watermarks for “Good”, “Acceptable” and “Poor” grade of quality as experienced by end-user • Delay: (0-150)ms, (150-300)ms, > 300ms • Jitter: (0-20)ms, (20-50)ms, > 50ms • Loss: (0-0.5)%, (0.5-1.5)%, >1.5% • Levels obtained from our PAM 2004 paper Poor Acceptable Good

  30. Audio and Video Quality Assessments • Audio and video loopback feature • E-Model-based objective MOS ranking • Slider-based subjective MOS ranking

  31. Customization of tests… • Test results data folder, TCP/UDP/RTP port settings, H.225 and H.245 parameters, preferred codec, watermarks for delay, jitter, loss, …

  32. Use-case I • Problem report • Intermittent frame freezing • Lot of pixilation • No significant audio problems • Sudden disconnections Effect of a mis-configured firewall on a video stream

  33. Use-case I (contd.) • MCU Software • ~15 fps for 384Kbps call and ~0.6% packet loss • ~30 fps for 128Kbps call and ~0% packet loss • H.323 Beacon • Sluggish call-setup • Delayed packet-events • Initial jitter variations in poor range Jitter variations indicated by H.323 Beacon client-to-server test Increasing the rate-limit and firewall re-configuration solved the problem!

  34. Use-case II • Problem report • Poor audio and video reception at the site of user • Problem only in the streams from Campus A to Campus B • MCU Software • Packet loss (~1%) • Packet re-ordering • H.323 Beacon • Jitter values consistently in poor range • Traceroute and Reverse-Traceroute showed an asymmetric route • E-Model results • Campus A to Campus B: 3.78 • Campus B to Campus A: 4.37

  35. Use-case II (contd.) Fig. 1 Time-plot of Equipment Impairment Factor Fig. 2 Time-plot of Delay Fig. 3 Time-plot of Loss Fig. 4 Time-plot of Mean Opinion Score Ranking Problem was solved by contacting the neighboring ISP who was suspected to be experiencing problems!

  36. Future Work • Porting the software to Linux • Fixing bugs of past releases • Server-to-Server module to support routine monitoring in ISP backbones • Video and E-Model integration into C++ client

  37. Questions? http://www.itecohio.org/beacon

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