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VoIP Monitoring and Analysis - Still Top of Mind in Network Performance Monitoring
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VoIP Monitoring and Analysis - Still Top of Mind in Network Performance Monitoring


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With over 10 years of deployment history, VoIP is the primary voice solution for just about every company in existence - large, medium, or small. But even with all that history, recent research from …

With over 10 years of deployment history, VoIP is the primary voice solution for just about every company in existence - large, medium, or small. But even with all that history, recent research from TRAC shows that VoIP is still the number one IT initiative impacting network performance. And with the growth of 802.11 and Wi-Fi enabled smart phones, the use of voice over Wi-Fi (VoFi) promises to increase the volume of VoIP traffic even more. Analyzing VoIP traffic alone is not enough. VoIP analysis must be part of your overall network performance analysis. After all, VoIP is just another data type on your network, and according to TRAC, it is impacting your network performance, so you must monitor and analyze the network as a whole, including voice and video over IP. Join us to see how easy it is to capture and analyze voice, video, and data traffic simultaneously, allowing you to pinpoint the impact of each data type on your overall network performance.

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  • 1.© WildPackets, Inc. VoIP – Still Top of Mind in Network Performance Monitoring
  • 2. © WildPackets, Inc.#wp_voip 2 TRAC NPM Research Demographics Sep 2013 406 participants Company type:  70% - Enterprise  28% - Service Providers Company size:  41% - Large organizations  38% - Medium  21% - Small Geography  56% - North America  24% - EMEA  14% - APAC
  • 3. © WildPackets, Inc.#wp_voip 3 Key IT Initiatives Impacting Network Performance 48% 54% 59% 65% 66% 69% 72% BYOD Public Cloud services Video conferencing Virtual desktops Enterprise Mobility Big Data VoIP
  • 4. © WildPackets, Inc.#wp_voip 4 36% 40% 41% 59% 64% Ability to improve performance for home office users Managing recreational traffic Increase in number of IP flows to be managed Managing bandwidth consumption per user/subscriber Managing real-time applications (VoIP, video, etc.) Key Challenges for Managing Network Traffic
  • 5. © WildPackets, Inc.#wp_voip 5 Key Challenges for Managing UC Performance 24% 31% 38% 44% 44% 52% Time spent on extracting session details Inability to correlate multiple network layers Visibility into bandwidth utilization Visibility into the quality of user experience Visibility into each session for UC technologies Visibility into the impact of UC deployments on other applications on the network
  • 6. © WildPackets, Inc.#wp_voip 6 And It’s Not Just VoIP … • Percentage of all forms of video (TV, VoD, Internet, and P2P) will be approximately 90 percent of global consumer traffic by 2015 • Internet video to TVs will increase 17-fold by 2015 s525/ns537/ns705/ns827/white_paper_c11-481360.pdf
  • 7.© WildPackets, Inc. VoIP/Video Is Just Different!
  • 8. © WildPackets, Inc.#wp_voip 8 VoIP/Video Is Just Different! • Packet delivery not guaranteed • Small and consistent packet sizes • Highly regular packet spacing • Reliable packet delivery • Large and variable packet sizes • Widely varying packet spacing VoIP Data
  • 9. © WildPackets, Inc.#wp_voip 9 Key RTP (VoIP/VoFi/Video) Issues CAMP IT Pinpointing the Problem 9 Packet Loss JitterLatency
  • 10. © WildPackets, Inc.#wp_voip 10 Latency Queue Latency & Decision Latency Network Propagation Delay Encoding / Decoding Compression / Decompression Jitter Buffer Latency 0 ms 100 ms 200 ms 300 ms 400 ms 500 ms 600 ms 700 ms 800 ms The ITU recommends a maximum one- way delay of 150 ms for VoIP
  • 11. © WildPackets, Inc.#wp_voip 11 Latency's Effects • Talkover ‒ Occurs when excessive latency delays audio – Conversation cadence is not natural or comfortable – Callers feel as if they must “push to talk” or say “over” to control the conversation • Echo ‒ The speaker’s voice feeds back into the listener’s microphone ‒ The speaker then hears his own voice returning from the listener’s end, but delayed due to latency ‒ Most callers find it difficult to maintain normal speech when echo delay is prolonged ‒ Some VoIP systems attempt to cancel echo, but are not always successful High latency may also cause additional troubles such as loss of synchronization between audio and video for multimedia sessions.
  • 12. © WildPackets, Inc.#wp_voip 12 Jitter • Jitter is the variance in packet delivery intervals to the listener • Jitter buffer adds additional delay to voice reaching the ear piece in case other packets need to catch up • Packets delayed too long in the network are not allowed to enter the jitter buffer Packets delayed more than the buffer delay (100 ms as an example) are dropped . . .. .. . . ........ ...... Packets are buffered and delayed at the Receiver The “jitter” buffer releases a G.711 packet every 20 ms A G.711 packet sent every 20 ms Packet jitter and drops 31 2 4
  • 13. © WildPackets, Inc.#wp_voip 13 Jitter's Effects • Jitter causes weird “sound effects” that vary with jitter severity and environmental factors • Examples include: ‒ Static ‒ Stuttering or uneven audio – abnormal speech rhythm ‒ For multimedia systems, video may be “jerky” or irregular • If jitter levels are high, packet loss can result ‒ In some cases, severe jitter may sound similar to packet loss, even if no packets are actually dropped
  • 14. © WildPackets, Inc.#wp_voip 14 Packet Loss • Packet dropped due to physical layer corruption • Congestion without adequate QoS provisions • Jitter buffer discards due to excessive latency
  • 15. © WildPackets, Inc.#wp_voip 15 Packet Loss Effects • Causes missing sounds, syllables, words, or phrases ‒ DSP algorithms may compensate for up to 30 ms of missing data ‒ More than 30 ms of missing audio is noticeable by listeners • An average person speaks at a rate of about 200 words per minute ‒ That’s 3.33 words/sec = 300 ms per word ‒ For G.711, we would need to lose 15 consecutive RTP packets to lose a whole word ‒ Dropping 15 packets/sec for G.711 would be a loss rate of 30% • But losing only a few packets can still be very noticeable ‒ Loss of more than 2 consecutive packets will be heard ‒ Loss rates ≥ 2% will have a strong impact on quality ‒ Losses of 5 – 10% make calls all but intolerable ‒ Bursty periods of packet loss are worse than more dispersed loss
  • 16. © WildPackets, Inc.#wp_voip 16 Measuring Key RTP Metrics
  • 17. © WildPackets, Inc.#wp_voip 17 Making Sense of the Metrics • A single value to reflect the user’s QoE (quality of experience) • Mean Opinion Score (MOS) – several flavors ‒ Algorithmic simulation of subjective audio assessment ‒ Most commonly used varieties are MOS-LQ (listening quality) and MOS-CQ (conversational quality) ‒ Possible range of 1 (poor) to 5 (excellent) ‒ Maximum possible MOS = 4.4 with G.711 ‒ Typical range in most networks is 3.5 – 4.2 • R-Factor – several flavors ‒ Based on latency, jitter, packet loss, bit rate, and signal-to-noise ratio, codec effects (for low bit-rate codecs) • The ITU algorithms consider about 20 quality inputs ‒ Possible range of 0 (poor) to 100 (excellent) ‒ Provides LQ, CQ, and other score variants
  • 18. © WildPackets, Inc.#wp_voip 18 Key Metrics So Far • Latency • Jitter • Packet Loss • MOS • R-Factor
  • 19. © WildPackets, Inc.#wp_voip 19 Measuring MOS and R-Factor
  • 20.© WildPackets, Inc. Can RTP and TCP Coexist?
  • 21. © WildPackets, Inc.#wp_voip 21 Coexistence Is Possible, But Challenging • While traditional network applications are very tolerant of jitter, latency, and even to some degree packet loss, VoIP/Video/VoFi is not • Tolerable levels of jitter, latency, and packet for TCP are devastating for RTP • Pre- and post-deployment network assessments are critical ‒ Pre-deployment: understanding your network’s ability to accommodate VoIP • Current latency, jitter, and packet loss • QoS capabilities • Current bandwidth utilization (is there any room for VoIP) • Mix of RTP vs. TCP • Is all RTP traffic equal? ‒ Post-deployment: maintain a constant vigil after deployment to watch for imminent troubles
  • 22. © WildPackets, Inc.#wp_voip 22 Network Traffic: Qualitative Analysis • The quality of your network traffic is potentially more important than its quantity when it comes to VoIP • Understanding the character of network traffic is key ‒ “Bursty” traffic - rapid, recurring traffic spikes that can occur over long periods of time ‒ Prolonged, slow rises in utilization may decrease the number of calls that can occur simultaneously over the course of a day ‒ Sharp spikes can cause very noticeable quality issues with ongoing calls • Your baseline monitoring should consider not only averages and long-term trends, but also the short- term peaks and dips that characterize your traffic flow
  • 23. © WildPackets, Inc.#wp_voip 23 Network Traffic: Quantitative Analysis • Most network engineers are concerned about the amount of traffic on their networks ‒ Utilization (percentage of bandwidth) ‒ Throughput (bits or bytes per second) • You also need to be concerned about individual utilization components ‒ How much bandwidth and throughput can be attributed to each application or process? • Clarifies which application traffic may need to be tuned or controlled ‒ How well or poorly will the baseline (trended) behavior of each application interact with VoIP • Don’t forget to also consider the reverse case – VoIP’s impact on existing applications
  • 24. © WildPackets, Inc.#wp_voip 24 The Impact of "Just One More Call" • Although a network link may be able to support a number of concurrent calls, one additional call is often enough to cause quality problems … x1113 x2111 x1112 x1111 1st Call 2nd Call 3rd Call x2112 x2113 Example: The WAN can support 2 simultaneous calls. What happens when a third call is attempted??? Call #3 Causes Poor Quality for ALL Calls
  • 25. © WildPackets, Inc.#wp_voip 25 Quality Score Trending • Isolated scores are useful for validating single call complaints, but overall VoIP health is best seen by graphing long-term trends Overlaying VoIP trends with network utilization, errors, or other metrics may reveal previously unseen performance relationships!
  • 26. © WildPackets, Inc.#wp_voip 26 Data Impacts on VoIP
  • 27. © WildPackets, Inc.#wp_voip 27 Got QoS? • One of the most potent weapons for fighting VoIP troubles is to provision Quality of Service (QoS) • QoS enables network devices to prioritize and give preference to packet streams that are sensitive to delay, packet loss, jitter, and other performance inhibitors • Standards-based QoS methods include: ‒ IP Differentiated Services (DiffServ) ‒ MAC Layer QoS with IEEE 802.1p ‒ VLANs • QoS may be obtained or supplemented via proprietary means, such as traffic shaping via various flow processing algorithms • Watch for too much differentiated traffic!
  • 28. © WildPackets, Inc.#wp_voip 28 Ready for QoS? • QoS provisions are based on the “weakest link” concept ‒ If any device in a data path does not support QoS, then media streams will not be afforded the preference they require for good performance • Pre-deployment assessment must ensure that ALL devices can recognize and respond to QoS parameters in packet headers ‒ Switches, routers, firewalls, proxies, and any other devices that touch RTP packets must be “VoIP-friendly”
  • 29. © WildPackets, Inc.#wp_voip 29 Monitoring QoS Configuration
  • 30.© WildPackets, Inc. Unique Challenges of VoFi
  • 31. © WildPackets, Inc.#wp_voip 31 Quantitative Interference Impacts on VoFi Source: Farpoint Group
  • 32. © WildPackets, Inc.#wp_voip 32 Quantitative Interference Impacts on VidFi Source: Farpoint Group
  • 33. © WildPackets, Inc.#wp_voip 33 Packet-by-Packet VoFi Call Wired VoIP Call
  • 34.© WildPackets, Inc. Troubleshooting RTP Issues
  • 35. © WildPackets, Inc.#wp_voip 35 VoIP Dashboard View
  • 36. © WildPackets, Inc.#wp_voip 36 Calls View
  • 37. © WildPackets, Inc.#wp_voip 37 Media View
  • 38. © WildPackets, Inc.#wp_voip 38 Down To The Details …
  • 39. © WildPackets, Inc.#wp_voip 39 Call Data Record (CDR) Provides comprehensive, real-time statistical and quality report for base- lining, and 100% visibility into calls
  • 40. © WildPackets, Inc.#wp_voip 40 Identifying Unauthorized RTP Traffic • Look for bandwidth hogs • Use filters and alarms
  • 41.© WildPackets, Inc. Q&A Show us your tweets! Use today’s webinar hashtag: #wp_voip with any questions, comments, or feedback. Follow us @wildpackets Follow us on SlideShare! Check out today’s slides on SlideShare
  • 42.© WildPackets, Inc. Thank You! WildPackets, Inc. 1340 Treat Boulevard, Suite 500 Walnut Creek, CA 94597 (925) 937-3200