VoIP Performance Management. Anthony Caiozzo

Transcription

1 VoIP Performance Management Anthony Caiozzo

2 Outline VoIP Performance Problems Embedded performance monitoring Data collection Application scenario

3 Packet Loss is strongly time varying mS Avge Packet Loss Rate Average packet loss rate = 2.1% Peak packet loss = 30% Time (seconds)

4 Jitter leads to time varying packet discards Delay (ms) Time (Seconds)

5 Impact on Voice Quality Bandwidth (kbit/s) MOS High jitter/ loss/ discard Voice Data Time

6 Impact of packet loss on modem/fax calls Lost packet triggers retrain Retrain sequence Data Data Losses here have no further impact Losses here can re-trigger retrain Bursty packet losses - modem/fax disconnects Widely dispersed packet losses - lose throughput but connection ok Hence - reliability and throughput depend strongly on packet loss distribution

7 Other key factors affecting performance Signal level Can be too high or too low Noise level Can be too high or too low Echo return loss Major problem if delay > 50ms Delay 50+ ms exacerbates echo problems 300+ ms causes conversational difficulty

8 Inside VQmon Discarded VQmon Jitter Buffer Emulator or actual Jitter Buffer Loss/ Discard events VQmon Markov Model Statistical Model Gather detailed packet loss info in real time Jitter buffer CODEC CODEC, Signal/ Noise/ Echo level Metrics calculation VQmon Core Metrics MOS-LQ / CQ R-LQ / CQ Modem/Fax - Reliability - Throughput

9 VQmon 2.0/2.1 computational model Burst loss rate Gap loss rate Ie mapping Perceptual model Calculate R/ MOS -LQ/ CQ Signal level Noise level Delay Echo Calculate Ro,Is,Id Burst/ Gap loss rate Codec type Datapump Model Calculate Modem metrics

10 Typical VoIP performance metrics Call Quality (NB/WB) -R-LQ -R-CQ -MOS-LQ -MOS-CQ - Modem/Fax Throughput - Modem/Fax Reliability Signal Metrics - Signal Level -Noise Level - Originating RERL - Terminating RERL Burst Metrics -Burst R - Burst Count - Burst Loss Rate - Burst Length (Packets) -Burst Length (ms) -Gap R -Gap Count - Gap Loss Rate - Gap Length (Packets) - Gap Length (ms) - Loss/Discard Rate -Loss Rate - Discard Rate Degradation factors - Due to Loss (%) - Due to Discard (%) - Due to Delay (%) - Due to Codec (%) - Due to Signal Level (%) - Due to Noise Level (%) - Due to Echo Level (%) - Due to Recency (%)

11 Subjective test results 50% VQmon: Mean Error % E Model: Mean Error Frequency 30% 20% 10% 0% Error vs Subjective MOS (MOS range 1-5) Source ITU, subjective test data from France Telecom, comparisons performed by the University of Bochum (Germany)

12 Objective test results VQmon MOS LQO PESQ test Vs results VQmon VQmon prediction Perfect MOS LQO PESQ Vs E-Model Using VqMon Discards E Model test results E-Model Prediction Perfect PESQ MOS LQO PESQ MOS LQO VQmon MOS E-Model MOS Tests performed according to P.564..ITU standard for testing the accuracy of MOS estimation algorithms against PESQ

13 Modem/Fax - Throughput Prediction Measured throughput Predicted throughput

14 VoIP Performance Management Model End of call SIP QoS report SIP QoS VQmon/EP RTCP XR RTCP XR VQmon/EP RTCP XR exchanged every 5-15 seconds during call VQmon/EP: 6k-30kbytes MIPS

15 VQmon/EP generation of RTCP XR messages Remote End System Delay Signal Level Residual Echo Return Loss RTCP XR VQmon/EP VQmon/EP incorporates some data from remote endpoint into call quality calculations made at this endpoint

16 SQmediator for call quality reporting SIP QoS reports analyzed in real-time and stored in SQL database SIP QoS SQmediator VQmon/EP SIP QoS report contains call quality data for receiving direction, and if RTCP XR is also used, for sending direction

17 SQprobe for mid-stream analysis/collection SQprobe - analyzes RTP streams directly, collects RTCP XR messages and integrates local measurements with endpoint reported data VQmon/EP RTCP XR RTCP XR VQmon/EP

18 Summary VQmon most widely used VoIP performance monitoring agent technology IP impairments are time varying Bursty loss Interferes with modem/ fax retrain process leads to low reliability & low throughput Causes transient voice quality problems VQmon + SQmediator provides Accurate voice quality metrics Modem/Fax performance and reliability metrics Scaleable data collection system

19 Telchemy Overview Leading provider of technology for Voice and Video Fault/ Performance Management VQmon technology economically measures call quality and captures diagnostic data at both endpoint and midstream on every voice or video over IP call/session used by 80 equipment vendors, 100+ different product lines, over 8 million units licensed, deployed in Carrier/Enterprise networks for 5 years Leading technical contributor for 9 key VoIP and IPTV management protocols in IETF, ITU, PacketCable, participant in ATIS IIF Close working relationships with many carriers and major enterprise, providing guidance on management architecture, SLA definition..