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Some Studies of H.323 VideoConference Traffic on LANs and WANs

Some Studies of H.323 VideoConference Traffic on LANs and WANs. Studies done for PPNCG & PIPVIC2 Lab Tests of H.323 kit Comparison with Mbone tools (SHRIMP++) Considerations for use on the WAN Some data from WAN measurements Much of the work is preliminary!.

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Some Studies of H.323 VideoConference Traffic on LANs and WANs

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  1. Some Studies of H.323 VideoConference Traffic on LANs and WANs Studies done for PPNCG & PIPVIC2 Lab Tests of H.323 kit Comparison with Mbone tools (SHRIMP++) Considerations for use on the WAN Some data from WAN measurements Much of the work is preliminary! R. Hughes-Jones Video_TAG Meeting Oct 1999

  2. Lab Measurements of H.323 on the LAN 10Mbit Ethernet LAN Analyzer Linux PC No. packets/s Kbit/s tcpdump • Simulate a VC on a private LAN • Two 350 MHz Pentium II Windows NT v4.0 _ service pack 4 • The VCON Escort 25 pro PCI cards and Philips camera ( 350 MHz Pentium II + 128 Mbytes mem ensure CPU power / memory not issues) • Two way Video of same subject - data rates for 1 Video stream • One way Audio or muted R. Hughes-Jones Video_TAG Meeting Oct 1999

  3. The Lab Test Conditions • Camera pointing at a static view of a coloured poster on a wall with no movement of the subject – similar to viewing a slide or picture in a talk • Camera observing a subject sitting very still – an approximation to a person listening at a VC as people always wriggle in real life! • Camera observing the head and shoulders of a person talking – probably more like real people in a real VC than the above. • Camera observing a subject making fast constant movement or violent movement, like clapping or waving arms. VCON ‘MeetingPoint’ software used • Video resolution CIF • Max. frame rate 30 f/s • Max. bandwidth 385 kbit/s R. Hughes-Jones Video_TAG Meeting Oct 1999

  4. Just touch the mouse ! Subject sitting VERY still Subject talking head as in a VC Subject Making violent movement Clap hands Mute video • Packet rate & kbit/s depend on movement • CIF12cm & 20 cm pictures good H.323 on the LAN The Network load from VCON for various movment scenarios - 386 kbit/s R. Hughes-Jones Video_TAG Meeting Oct 1999

  5. H.323 on the LAN The Network Load generated due to External Effects. The effect of Room Lighting. R. Hughes-Jones Video_TAG Meeting Oct 1999

  6. Action :Static talking head rub eye talking clap talking Frames/ 16 20 20 30 30 • Packet rate & kbit/s depend on movement • CIF ie ~10cm video pictures Mbone vic on the LAN The Network load from vic for various movment scenarios - no rate limits R. Hughes-Jones Video_TAG Meeting Oct 1999

  7. H.323 - Traffic Characterisation R. Hughes-Jones Video_TAG Meeting Oct 1999

  8. WAN Considerations • Bandwidth: The no. bits/s carried over the network. • Determines audio quality, video frame/s • Latency: The time for a packet to traverse the network. • Vital to audio exchanges, context switches • Jitter: The difference between the inter-packet arrival times • Critical to current H.323, good video, audio • (Mbone rat packets carry redundant data) • Network ‘configuration’ measurements: • Packet misordering • Packet loss • Latency & Jitter have distributions and dependencies: • time, location, bandwidth, scale, traffic types • Considerations apply to unicast and multicast traffic R. Hughes-Jones Video_TAG Meeting Oct 1999

  9. Packet size distributions from Mbone tools vic & rat R. Hughes-Jones Video_TAG Meeting Oct 1999

  10. Variation in packet arrival times Variation in the arrival times for packts in a multicast audio stream How the variation changes with the real time through the VC R. Hughes-Jones Video_TAG Meeting Oct 1999

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