Analyze Assure Accelerate Standard IP Network Model for Comparing Voice Quality of IP Telephony Devices Dolby VoIP? How close are we to better than PSTN Sound? Jack Douglass, Spirent Chair TIA TR30.3

How close are we to better than PSTN Sound? An objective method of measuring and comparing the Audio Quality and Performance of IP Telephony Equipment in the presence of Network Impairments is needed – A Standard Network Model for Evaluating Multimedia Transmission Performance Over Internet Protocol – Audio Quality must be measured over time-varying network impairments that are statistically accurate – TIA TR30.3 is working with the ITU-T on a Statistically Based IP Network Model Will become TIA-921when released Submit to ITU-T for consideration as a Recommendation

Signaling Path Converged IP Telephony Network is Very Complex and has Many Impairments

Network Topologies that need be considered when testing Audio Quality over a Converged Network

Converged Network Reference Model Diagram TE A D LL Telco Switch Gateway IP Network R,G,S* Gateway L L Telco Switch TE D A

Parameters & Impairments that Need to be Considered when Simulating an IP Network Network Architecture Types of Access Links QoS controlled Edge Routing Route Flapping Link Failure Load Sharing Time Drift MTU Size Packet Loss Background Traffic (Congestion, Bandwidth, Utilization, Network Load) One Way Delay

Sources of IP Network Impairments

IP Network Model

Example of Test Profile with Time Variable Network Impairments Time Packet Delay

Time Varying Statistically Based IP Network Impairment Conditions (ICs) Each Impairment Condition is assigned a Likely-hood of Occurrence (LOO) based on real IP Network Statistics, Network Architecture, Classes of Service The goal is to have approximately 100 test combinations so that an automated run of the test suite completes in less than a day. IC1 LOO X% IC2 LOO X% IC100 LOO X% Time

Test Profiles Based on QoS Classes Test ProfilesQoS Class (Y.1541) Applications (Examples)Node MechanismsNetwork Techniques A (VoIP, MoIP, FoIP, ToIP) 0Real-Time, loss sensitive, Jitter sensitive, high interaction (VoIP, VTC) Strict QoS. Guaranteed no over subscription on links. Constrained Routing and Distance B (VoIP, MoIP, FoIP, ToIP) 1Real-Time, Jitter sensitive, interactive (VoIP, VTC). Separate Queue with preferential servicing, Traffic grooming Less constrained Routing and Distances C (FoIP only) 2Transaction Data, Highly Interactive (Signaling) Separate Queue, Drop priority Constrained Routing and Distance 3Transaction Data, InteractiveLess constrained Routing and Distances 4Low Loss Only (Short Transactions, Bulk Data, Video Streaming) Long Queue, Drop priorityAny route/path 5Traditional Applications of Default IP Networks Separate Queue (lowest priority)Any route/path Statistically based models can be created for different QoS Classes

Example of Network Model Coverage (NMC) Curve

Examples of Communication Equipment that can be tested over the Converged Network Model Plain Old Telephone Service (POTS) and IP telephones PSTN Video H320 and H324 IP Network Devices such as User Agents, Call Agents, Media Servers, Media Gateway Controllers, Gatekeepers, Application Servers, Edge Routers, Gateways, IP Phones, IAF (Internet Aware Fax) Voice-over-IP (VoIP) gateways T.38 facsimile devices and gateways V and voiceband data (VBD) modem-over-IP gateways TIA-1001 (and V.toip) textphone-over-IP gateways

TR30.3 Test Standards TIA/EIA 496A-1989: Interface Between Data Circuit Terminating Equipment (DCE) and the Public Switched Telephone Network – Included Network Model for Evaluating Modem Performance TIA/EIA TSB 37A-1994: Telephone Network Transmission Model for Evaluating Analog Modem Performance, which became ITU-T Recommendation V.56bis-1995 EIA/TIA TSB : Test Procedures for Evaluation of 2-Wire 4 Kilohertz Voice Band Duplex Modems, which became ITU-T Recommendation V.56ter-1996 ANSI/TIA/EIA : Telephone Network Transmission Model for Evaluating Analog Modem Performance ANSI/TIA/EIA : North American Telephone Network Transmission Model for Evaluating Analog Client and Digitally Connected Server Modems ANSI/TIA 876 – 2002: North American Network Access Transmission Model for Evaluating xDSL Modem Performance

Value of Converged Network Model Predicts product performance under statistically based network conditions Finds design weaknesses Find compatibility issues between network equipment Facilitates isolating and resolving field problems Assists in evaluating different technologies Competition for better performance over the Network Model drives the industry to create better quality products

Target Audience for Converged Network Model Operating Companies Service Providers Manufacturers Design Engineers Test houses Magazines and product reviewers

How will TIA-921 help the Industry Achieve Better than PSTN sound? PSTN quality sound on the IP Network has not yet been achieved The Network Model will provide a standard test bed – objectively compare the Audio Quality of various IP Telephony devices – Competition to perform better on the Network Model will help drive the Quality of IP Telephony sound to be better that PSTN sound