1. Performance Analysis for VoIP System B92902088 邱柏儒 B92902093 紀忠毅 B92902106 莊典融 B92902120 孟昭宏 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 ) 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 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 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. 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) ModelPhaseMeanComment Web traffic generator1.2 1.5 2 12(kB) 0.5(sec) 50,10(sec) “object size” “inter-object” “inter-page” HTTP reply traces1.04-1.14 FTP traffic1.1880(kB)Exponential session and burse inter-arrival time Published Pareto distribution parameters used in modeling internet data traffic. Choose appreciate environment Modeling data traffic

7. Modeling by Distribution(3) Run Simulator Analysis and diagnosis Delay Packet loss Jitters 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. 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 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 Latency Jitter Packet Loss Echo

13. Latency 1. Good: < 80ms Acceptable: 150~180ms (each way) 2. Must be addressed with VoIP protocols. Eg, SIP, H.323 3. Commonly associated with network congestion and poor bandwidth management. Not in LAN but at LAN/WAN boundary. 1. Good: < 80ms Acceptable: 150~180ms (each way) 2. Must be addressed with VoIP protocols. Eg, SIP, H.323 3. Commonly associated with network congestion and poor bandwidth management. Not in LAN but at LAN/WAN boundary.

14. Latency 4. 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. 4. 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 1. Tolerance range: 20~30ms 2. Possible solutions Jitter buffer Temporarily store Smooth out the delivery of voice packet Router queue 1. Tolerance range: 20~30ms 2. Possible solutions Jitter buffer Temporarily store Smooth out the delivery of voice packet Router queue

16. Jitter 3. 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 3. 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 1. Loss rate < 1%: OK 2. Loss rate > 3%: conversation seems “breaking up” 3. IP: best effort 4. Serious packet loss may cause dropped calls or even system failure 1. Loss rate < 1%: OK 2. Loss rate > 3%: conversation seems “breaking up” 3. IP: best effort 4. Serious packet loss may cause dropped calls or even system failure

18. Packet Loss 5. Prevent packet loss Apply more control IP: best effort predictable 5. 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 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 Testing coverage Testing environment Testing Equipment & Software REDCOM performer QPro MediaPro

21. Testing Coverage 1. Functionality e.g VoIP/PSTN call, QoS, SIP/Phone Setting 2. Performance e.g QoS/RTP measurement 3. Stress e.g VoIP call with data integration 1. Functionality e.g VoIP/PSTN call, QoS, SIP/Phone Setting 2. Performance e.g QoS/RTP measurement 3. Stress e.g VoIP call with data integration

22. Testing Coverage 4. Reliability e.g Long term VoIP / Continuous VoIP call 5. Interoperability e.g Cisco ATA/IP Phone/SoftPhone 4. Reliability e.g Long term VoIP / Continuous VoIP call 5. 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 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 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 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 Introduction VoIP Multiplex Multicast Scheme Capacity Analysis Conclusion

35. The Problems faced by WLAN System Capacity System capacity for voice can be quite low Other data traffic Data from traditional App can interfere with each other System Capacity System capacity for voice can be quite low Other data traffic Data 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 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 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 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 us 40 * 8 / 11 = 29 us Efficiency drops to less than 50% IP + UDP + RTP header = 40bytes VoIP payload ranging from 10 to 30 bytes The transmission time: 30 * 8 / 11 = 22 us 40 * 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% 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 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. 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. 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. 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 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. 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 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

51. Multiplex-Multicast Procedure The download link VoIP traffic first goes through a MUX in the voice gateway The MUX replaces the RTP, UDP, IP header of each packet with a compressed mini header In mini header, there is an ID used to identify the session of the VoIP packet The download link VoIP traffic first goes through a MUX in the voice gateway The MUX replaces the RTP, UDP, IP header of each packet with a compressed mini header In mini header, there is an ID used to identify the session of the VoIP packet

52. Multiplex-Multicast Procedure Then multicast the multiplexed packet to the WLAN through AP The DEMUX at the receiver restores the original RTP header and necessary information Then multicast the multiplexed packet to the WLAN through AP The DEMUX at the receiver restores the original RTP header and necessary information

53. Multiplex-Multicast Scheme HeaderData1 Header Data2 Data3 Header Minih + Data1 + Minih + Data2 …

54. Multiplex-Multicast Scheme

55. Advantages Reduce the number of VoIP streams in one BSS from 2n to 1 + n, where n is the number of VoIP sessions. Improve the bandwidth efficiency Reduce the number of VoIP streams in one BSS from 2n to 1 + n, where n is the number of VoIP sessions. Improve the bandwidth efficiency

56. Tradeoff The MUX sends out a multiplexed packet every T ms, which is equal to or shorter than the VoIP inter-packet interval. For GSM 6.10, the inter-packet interval is 20 ms. Larger value of T can improve bandwidth efficiency The MUX sends out a multiplexed packet every T ms, which is equal to or shorter than the VoIP inter-packet interval. For GSM 6.10, the inter-packet interval is 20 ms. Larger value of T can improve bandwidth efficiency

57. Tradeoff (cont.) But the larger T will cause more delay One can control the tradeoff between bandwidth efficiency and delay by adjusting T But the larger T will cause more delay One can control the tradeoff between bandwidth efficiency and delay by adjusting T

58. Multiplex-Multicast Scheme

59. Should be solved by encrypting the voice packet

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

61. CSMA/CA Algorithm

62. Capacity Analysis n : maximum number of sessions that can be supported T down & T up : transmission times for downlink and uplink packets T avg : average time between the transmissions of two consecutive packets in a WLAN N P : number of packets sent by one stream in one second 1/T avg = number of streams * N P n : maximum number of sessions that can be supported T down & T up : transmission times for downlink and uplink packets T avg : average time between the transmissions of two consecutive packets in a WLAN N P : number of packets sent by one stream in one second 1/T avg = number of streams * N P

63. Capacity of Ordinary VoIP OH hdr = H RTP + H UDP + H IP + H MAC OH sender = DIFS + averageCW + PHY if unicast packet: OH receiver = SIFS + ACK T down = T up = (Payload +OH hdr ) * 8 / dataRate + OH sender + OH receiver OH hdr = H RTP + H UDP + H IP + H MAC OH sender = DIFS + averageCW + PHY if unicast packet: OH receiver = SIFS + ACK T down = T up = (Payload +OH hdr ) * 8 / dataRate + OH sender + OH receiver

64. Capacity of Ordinary VoIP n downlink and n uplink unicast streams T avg = (T down + T up ) / 2 1/T avg = 2n *N p n = 11 n downlink and n uplink unicast streams T avg = (T down + T up ) / 2 1/T avg = 2n *N p n = 11

65. Capacity of M-M Scheme the RTP, UDP and IP header of each packet is compressed to 2 bytes T down = [(Payload + 2) *n + H UDP + H IP + H MAC ] * 8 / dataRate + OH sender T avg = (T down + n *T up ) / (n + 1) 1/T avg = (n + 1) *N p n = 21.2 the RTP, UDP and IP header of each packet is compressed to 2 bytes T down = [(Payload + 2) *n + H UDP + H IP + H MAC ] * 8 / dataRate + OH sender T avg = (T down + n *T up ) / (n + 1) 1/T avg = (n + 1) *N p n = 21.2

66. Capacities assuming Different Codecs CodecsOrdinary VoIP Multiplex-Multicast Scheme GSM 6.1011.221.2 G.71110.217.7 G.723.117.233.2 G.726-3210.819.8 G.72911.421.7

67. Simulations increase the number of VoIP sessions until the per stream packet loss rate exceeds 1% system capacity = max number of sessions assume that the retry limit for each packet is 3 increase the number of VoIP sessions until the per stream packet loss rate exceeds 1% system capacity = max number of sessions assume that the retry limit for each packet is 3

68. Simulations For ordinary VoIP over WLAN, the system capacity is 12 Exceeding the system capacity leads to a large surge in packet losses for the downlink streams For ordinary VoIP over WLAN, the system capacity is 12 Exceeding the system capacity leads to a large surge in packet losses for the downlink streams

69. Analysis V.S. Simulation Different SchemesAnalysisSimulation Original VoIP11.212 Multiplex-Multicast Scheme 21.222

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

71. Conclusions M-M scheme can reduce the large overhead when VoIP traffic is delivered over WLAN it requires no changes to the MAC protocol at the wireless end stations more readily deployable over the existing network infrastructure. it makes the voice capacity nearly 100% higher than ordinary VoIP M-M scheme can reduce the large overhead when VoIP traffic is delivered over WLAN it requires no changes to the MAC protocol at the wireless end stations more readily deployable over the existing network infrastructure. it makes the voice capacity nearly 100% higher than ordinary VoIP

72. 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 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

73. Summary(1/2) Mathematical modeling - Queuing theory Poisson distribution Pareto distribution - Inaccuracy Industrial testing method Performance in various environments - Ethernet - Wireless Mathematical modeling - Queuing theory Poisson distribution Pareto distribution - Inaccuracy Industrial testing method Performance in various environments - Ethernet - Wireless

74. Summary(2/2) Improvement - e.g. priority queue, jitter absorption, loss concealment. - QoS absolute QoS level relative QoS level e.g. Expedited Forwarding, Assured Forwarding.

75. Reference P.M. Fiorini: Voice over IP for Enterprise Networks: Performance Implications & Traffic Models E. Noel & K.W. Tang: Performance Analysis of a VoIP Access Architecture Wei Wang: Solutions To Performance Problems In VoIP Over A 802.11 Wireless LAN P.M. Fiorini: Voice over IP for Enterprise Networks: Performance Implications & Traffic Models E. Noel & K.W. Tang: Performance Analysis of a VoIP Access Architecture Wei Wang: Solutions To Performance Problems In VoIP Over A 802.11 Wireless LAN

76. Q & A

77. Thanks for your listening…