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 What happens if it doesnt sound good. Telephony tools support production lab testing LAN, packet network tools dont capture voice QOS problems Result hurts: Market penetration Network Managers ability to support Carriers ability to assure quality Manufacturers ability to defend products Gateway Packet Network PSTN Office Network GatewayPBX Gateway PBX Phone PC IP phone PC Call server NMS BB modem Phone EP P VoIP System Elements Router 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 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 Quality Degradation: Delay, Jitter Variations in Packet Inter-arrival Rate Changes in Network Load Variations in Routing Paths Variable queuing delays Playout Buffer Gateway Product Packet Network Delay guideline: ITU-T G.114 Quality Degradation: Packet Loss, Out of Order Playout Buffer Gateway Product Packet Network Lost Potential Causes of Lost Packets: Network Congestion/Performance Network Architecture Improper Jitter Buffer Size Software Not Designed for Peak Load Potential Causes of Packet Reordering: Network Congestion/Performance Network Architecture Gateway Packet Network PSTN Office Network GatewayPBX Gateway PBX Phone PC IP phone PC Call server NMS BB modem Phone EP P Quality Vulnerabilities Router 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 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 - ITUT P.862: Recent standard for assessing voice quality Adds to PSQM and PAMS algorithms 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 Monitoring Options Active Monitoring Intrusive Metrics calculation on test calls Passive Monitoring Non-Intrusive Metrics calculation on live calls Active Monitoring QoS Monitoring Station Simulated traffic Reporting protocol Simulated VoIP traffic injected Endpoints are PCs or servers Active Monitoring VQT Call Server/SIP Proxy Switch Analog RTP SIP IP Phone Phone Gateway Pre-recorded audio injected, compared to receive Gateway Packet Network PSTN Office Network Gateway PBX Gateway PBX Phone PC IP phone PC Call server NMS BB modem Phone SIM EP SIM Reports SIM traffic Active Monitoring Passive Monitoring Options Port Mirroring Switch IP Phone Probe Switch/Router Inline Insertion Probe IP Phone Phone Switch Gateway Phone Gateway 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 RTCP XR 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 Passive Monitoring - Embedded Solutions QoS Domain QoS Domain Jitter Buffer Emulator VoIP End-Point QOS Monitor Embedded Software IP Network CODEC Embedded Software CODEC IP Network 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 Annex E Gateway Packet Network PSTN Office Network Gateway PBX Gateway PBX Phone PC IP phone PC Call server NMS BB modem Phone EP SIM EP SIM Reports RTP Passive Monitoring QOS Management System Central QoS Manager Console VoIP Network Packet monitoring RTCP SNMP ALARM 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