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Performance Analysis for VoIP System

Explore VoIP system analysis, modeling, and solutions for Ethernet and Wireless LAN. Address latency, jitter, packet loss challenges with effective strategies, and technologies.

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Performance Analysis for VoIP System

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  1. PerformanceAnalysis for VoIP System B92902088 邱柏儒 B92902093 紀忠毅 B92902106 莊典融 B92902120 孟昭宏

  2. Agenda • Modeling VoIP (莊典融) • VoIP in Ethernet (紀忠毅) • An Example in Performance Analysis • VoIP in Wireless LAN (孟昭宏) • Solutions to Performance Problems in VoIP over a 802.11 Wireless LAN • Summary (邱柏儒)

  3. Agenda • Modeling VoIP • VoIP in Ethernet • An Example in Performance Analysis • VoIP in Wireless LAN • Solutions to Performance Problems in VoIP over a 802.11 Wireless LAN • Summary

  4. Modeling VoIP • How to model VoIP traffic • Modeling by distribution • Modeling by state diagram • Pros and Cons

  5. Modeling by Distribution(1) • Modeling data traffic • The data size distribution of Internet traffic which uses the TCP (many smaller files, few larger ones) seen as approximately Pareto-distributed.

  6. Modeling by Distribution(2) • Modeling data traffic • Choose appreciate environment

  7. Modeling by Distribution(3) • Run Simulator • Analysis and diagnosis • Delay • Packet loss • Jitters

  8. Modeling by State Diagram(1) • Modeling speech process

  9. Modeling by State Diagram(2) • Modeling speech process

  10. Pros and Cons • Inaccurate on modeling • Variant and complex • Simulator is different from real world • Unexpected problems on hardware • Low cost • We can implement solution after getting good simulation.

  11. Agenda • Modeling VoIP • VoIP in Ethernet • An Example in Performance Analysis • VoIP in Wireless Lan • Solutions to Performance Problems in VoIP over a 802.11 Wireless Lan • Summary

  12. Critical VoIP Performance Challenges • Latency • Jitter • Packet Loss • Echo

  13. Latency • Good: < 80ms Acceptable: 150~180ms (each way) • Must be addressed with VoIP protocols. Eg, SIP, H.323 • Commonly associated with network congestion and poor bandwidth management. Not in LAN but at LAN/WAN boundary.

  14. Latency • Minimize delay/latency • Queuing techniques • Eq, DiffServ, 802.1p/q • Voice packet priority over other traffic • More stringent, intelligent bandwidth management/QoS • Guaranteed amount of bandwidth to each traffic type.

  15. Jitter • Tolerance range: 20~30ms • Possible solutions • Jitter buffer • Temporarily store • Smooth out the delivery of voice packet • Router queue

  16. Jitter • Prevent jitter • TCP rate control (for data traffic) • UDP rate control (for voice traffic) • Eq, Packeteer’s Application Traffic Management System • Policy-based bandwidth management or QoS strategy

  17. Packet Loss • Loss rate < 1%: OK • Loss rate > 3%: conversation seems “breaking up” • IP: best effort • Serious packet loss may cause dropped calls or even system failure

  18. Packet Loss • Prevent packet loss • Apply more control • IP: best effort predictable

  19. Solution to Improve Quality • PLC (Packet Lost Concealment)  Packet Lost • Dynamic Jitter Buffer  Jitter • Bandwidth Reservation / Packet Priorities / Queuing  Delay • G.168 Echo cancellation  Echo • VAD (Voice Active Detection)  Save Bandwidth

  20. An Example in Performance Analysis • Testing coverage • Testing environment • Testing Equipment & Software • REDCOM performer • QPro • MediaPro

  21. Testing Coverage • Functionality • e.g VoIP/PSTN call, QoS, SIP/Phone Setting • Performance • e.g QoS/RTP measurement • Stress • e.g VoIP call with data integration

  22. Testing Coverage • Reliability • e.g Long term VoIP / Continuous VoIP call • Interoperability • e.g Cisco ATA/IP Phone/SoftPhone

  23. Testing Environment (1/2)

  24. Testing Environment (2/2) • Pure Environment • Direct connection • Congestion Environment • Smart-bit tools

  25. Testing Equipment & Software EXCEL 9000 • PSTN simulator RADCOM Performer • QPro –Voice quality measurement • MediaPro – VoIP protocol analysis ProLAB • SIP Proxy server / H.323 Gateway • SIP UA simulator / H.323 Client VoIP Phone • Cisco 7940 IP Phone • XTEN / Windows Messenger Analysis Tool • Ethereal / CoolEdit

  26. REDCOM Performer • QPro • Provide voice quality measurement • MediaPro • Provide VoIP protocol flow analysis

  27. QPro – Line Configuration

  28. QPro – Phone Configuration

  29. QPro – Call Setting

  30. QPro – Test Result (1/2)

  31. QPro – Test Result (2/2)

  32. QPro - Summary

  33. Agenda • Modeling VoIP • VoIP in Ethernet • A Case Study in Performance Analysis • VoIP in Wireless LAN • Solutions to Performance Problems in VoIP over a 802.11 Wireless LAN • Summary

  34. VoIP in Wireless LAN - outline • Introduction • VoIP Multiplex Multicast Scheme • Capacity Analysis • Conclusion

  35. The Problems faced by WLAN • System CapacitySystem capacity for voice can be quite low • Other data trafficData from traditional App can interfere with each other

  36. VoIP in 802.11b • VoIP in WLAN can potentially support more than 500 sessions in theory • In practice, only 12 are supported due to various overhead

  37. VoIP in 802.11b • Support data rate up to 11Mb/s • A VoIP stream typically requires less than 10kb/s • The number of simultaneous VoIP streams that can be supported by an 802.11b in theory is around 11M/10K = 1100 • About 550 VoIP sessions

  38. VoIP in 802.11b • In practice, no more than a few VoIP sessions • If GSM 6.10 codec is used, the maximum is 12 • The result is mainly due to added packet header overheads as well as the inefficiency inherent in the WLAN MAC

  39. VoIP in 802.11b • IP + UDP + RTP header = 40bytes • VoIP payload ranging from 10 to 30 bytes • The transmission time:30 * 8 / 11 = 22 us40 * 8 / 11 = 29 us • Efficiency drops to less than 50%

  40. VoIP in 802.11b • Physical layer have additional overhead more than 800 us • Attributed to the Physical preamble, MAC header, MAC backoff time, MAC ACK, Inter-transmission time • Overall efficiency drops to less than 3%

  41. VoIP in 802.11b • TCP connection will cause unacceptably large increase in the delay and packet loss rate of VoIP traffic

  42. VoIP in Wireless LAN - outline • Introduction • VoIP Multiplex Multicast Scheme • Capacity Analysis • Conclusion

  43. Multiplex-Multicast Scheme • An 802.11 WLAN is referred to as the basic service set (BSS) in the standard specification • There are two types of BSSs: Independent BSS and Infrastructure BSS.

  44. Ad Hoc (Independent) BSS

  45. Infrastructure BSS

  46. Multiplex-Multicast Scheme • Focus on infrastructure BSS • Assume that all voice streams are between stations in different BSS • Each AP has two interfaces, an 802.11 interface, and an Ethernet interface which is connected to the voice gateway.

  47. Multiplex-Multicast Scheme

  48. Multiplex-Multicast Scheme • Within a BSS, there are two streams for each VoIP session. • M-M Scheme idea : Combine the data from several downlink streams into a single packet for multicast over the WLAN to their destinations

  49. Multiplex-Multicast Scheme

  50. Multiplex-Multicast Scheme • The voice multiplexer resides in the voice gateway for H.323 • The MUX can also resides in a specially designed AP or a server between the voice gateway and AP

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