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Quality of Service for Real-Time Network Management

Quality of Service for Real-Time Network Management. Debbie Greenstreet Product Management Director Texas Instruments. Agenda. Overview of VoIP QOS QOS system level elements QOS measurement metrics QOS monitoring techniques Solutions. VoIP Quality Monitoring.

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Quality of Service for Real-Time Network Management

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  1. Quality of Service for Real-Time Network Management Debbie Greenstreet Product Management Director Texas Instruments

  2. Agenda • Overview of VoIP QOS • QOS system level elements • QOS measurement metrics • QOS monitoring techniques • Solutions

  3. VoIP Quality Monitoring • What happens if it doesn’t sound good…. • Telephony tools support production lab testing • LAN, packet network tools don’t capture voice QOS problems • Result hurts: • Market penetration • Network Manager’s ability to support • Carrier’s ability to assure quality • Manufacturer’s ability to defend products

  4. PSTN Router VoIP System Elements Phone PBX Phone Gateway EP OfficeNetwork Gateway PC IP phone PacketNetwork Phone PBX Gateway NMS P Phone BB modem Call server OfficeNetwork PC IP phone

  5. Causes of Degradation - Implementation • End point Implementation - Delay – processing, accumulation - Echo – robust canceller design - Jitter – proper buffer sizing - Packet loss – jitter buffer sizing • System Implementation - Delay – network performance - Echo – proper loss plan, cancellation - Jitter – network behavior - Packet loss – network performance

  6. Causes of Degradation – Operational • System Operation • Outages, failures • Infrastructure: switch, router, bridge, etc • VoIP elements: call server, SIP server, gateways, terminal endpoints. • System Performance • Increase in traffic • Affects delay, jitter, loss • Increase in system complexity • Changes delay, potential for failure

  7. Quality Degradation: Delay, Jitter Delay guideline: ITU-T G.114 GatewayProduct PacketNetwork GatewayProduct PlayoutBuffer • Variations in Packet Inter-arrival Rate • Changes in Network Load • Variations in Routing Paths • Variable queuing delays

  8. Quality Degradation: Packet Loss, Out of Order • Potential Causes of Lost Packets: • Network Congestion/Performance • Network Architecture • Improper Jitter Buffer Size • Software Not Designed for Peak Load GatewayProduct PacketNetwork GatewayProduct 5 4 2 1 PlayoutBuffer 6 3 Lost Lost • Potential Causes of Packet Reordering: • Network Congestion/Performance • Network Architecture

  9. PSTN Router Quality Vulnerabilities Phone PBX Phone Gateway EP OfficeNetwork Gateway PC IP phone PacketNetwork Phone PBX Gateway NMS P Phone BB modem Call server OfficeNetwork PC IP phone

  10. VoIP QOS Metrics - Implementation • MOS (Mean Opinion Score): - Subjective measurement of voice quality - Group rates 1 – 5 • PSQM - ITU-T P.861 (Perceptual Speech Quality Measurement): - Automated scoring system - Designed for circuit-switched network

  11. VoIP QOS Metrics – System level • PAMS (Perceptual Analysis and Measurement System): • Intrusive speech quality assessment tool • End to End degradation analysis of injected signal • PESQ - ITU–T P.862: • Recent standard for assessing voice quality • Adds to PSQM and PAMS algorithms

  12. Existing QOS Related Standards • ITU-T • G.107: E-Model network design guide • G.114:Delay guidelines • P.800: Subjective MOS techniques • P.862: PESQ, replaces P.861 (PSQM) • P.562:Call-clarity Index (CCI) • non-invasive measurements to estimate conversational quality

  13. Monitoring Options • Active Monitoring • Intrusive • Metrics calculation on “test” calls • Passive Monitoring • Non-Intrusive • Metrics calculation on live calls

  14. Simulated VoIP traffic injected Endpoints are PCs or servers Active Monitoring QoS Monitoring Station Reporting protocol Simulated traffic

  15. VQT Gateway Analog Analog IP Phone RTP RTP Switch SIP SIP Phone Call Server/SIP Proxy Active Monitoring • Pre-recorded audio injected, compared to receive

  16. PSTN SIM Active Monitoring Reports Phone SIM traffic PBX Phone Gateway OfficeNetwork Gateway PC IP phone PacketNetwork SIM Phone PBX Gateway EP NMS Gateway Phone BB modem Call server OfficeNetwork PC IP phone SIM

  17. Passive Monitoring Options Port Mirroring Inline Insertion Switch/Router Probe Probe Switch Switch Gateway IP Phone Gateway IP Phone Phone Phone

  18. Other Measurement Tools • E Model: R-Factor • “R” = Ro - Is - Id - Ie + A • “Mouth to ear”, 0 – 100 rating • RTCP • IETF RFC 3550 – significant change to RTP, mostly RTCP • Use to report far end performance

  19. Extended Reports VoIP Metrics Block Packet loss and discard Physical level signal metrics Signal level Noise level RERL – Residual Echo Return Loss Call Quality Metrics User and Network R Factor MOS – LQ (listening quality) MOS – CQ (conversational quality) Gap Threshold Receiver configuration RTCP XR

  20. IP Network IP Network Passive Monitoring -Embedded Solutions QOS Monitor QoS Domain QoS Domain VoIP End-Point CODEC EmbeddedSoftware Jitter Buffer Emulator CODEC EmbeddedSoftware

  21. New QOS Measurement Standards • IETF • RTCP Reporting Extensions (XR) • SIP using RTCP • ITU • Extensions to Megaco, H.323 • P.VTQ, P.SEAM, P.AAM • G.113 • TIA • VoIP CPE Performance Management requirements • ETSI • TS 101 329-5 Annex E

  22. PSTN SIM Passive Monitoring Reports Phone RTP PBX Phone Gateway EP OfficeNetwork Gateway EP PC IP phone PacketNetwork SIM Phone PBX Gateway EP NMS EP Gateway Phone BB modem Call server OfficeNetwork PC IP phone SIM

  23. Packet monitoring ALARM SNMP RTCP QOS Management System Central QoS Manager Console VoIP Network

  24. Summary • Comprehensive QOS monitoring and management required for VoIP • Techniques and standards exist • VoIP equipment needs to include monitoring and measurement elements • QOS management tools need to be deployed

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