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.

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 DL LTelco Switch Gateway IP Network

R,G,S*

R,G,S* R,G,S* GatewayGateway L L

Gateway 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

Core IP NetworkLAN A

Local AccessB

1000BaseX* 100BaseT Switch100BaseT Hub10BaseT* WLAN (~4 Mbit/s)----------------------Occupancy levelPacket loss

64 kbit/s*128 kbit/s256 kbit/s*384 kbit/s512 kbit/s*768 kbit/s

*T1 (1.536 kbit/s)E1 (1.920 kbit/s)E3 (34 Mbit/s)*T3 (44 Mbit/s)

ADSL (~256 kbit/s)*Cable (~256 kbit/s)Fiber (1-10 Gbit/s)

--------------------Occupancy levelQoS edge router

LAN B

Route flappingOne-way delay

JitterPacket loss

DestinationDevice B

Local AccessA

64 kbit/s*128 kbit/s256 kbit/s*384 kbit/s512 kbit/s*768 kbit/s

*T1 (1.536 kbit/s)E1 (1.920 kbit/s)E3 (34 Mbit/s)*T3 (44 Mbit/s)

ADSL (~2 Mbit/s)*Cable (~3 Mbit/s)Fiber (1-10 Gbit/s)

--------------------Occupancy levelQoS edge router

SourceDevice A

* Case used in impairment tables

1000BaseX* 100BaseT Switch100BaseT Hub10BaseT* WLAN (~4 Mbit/s)----------------------Occupancy levelPacket loss

Example of Test Profile with Time Variable Network Impairments

Time

Pac

ket

Del

ay

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 ClassesTest Profiles QoS Class

(Y.1541)Applications (Examples) Node Mechanisms Network Techniques

A(VoIP, MoIP, FoIP, ToIP)

0 Real-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)

1 Real-Time, Jitter sensitive, interactive (VoIP, VTC). Separate Queue with preferential

servicing, Traffic grooming

Less constrained Routing and Distances

C(FoIP only)

2 Transaction Data, Highly Interactive (Signaling)

Separate Queue, Drop priority

Constrained Routing and Distance

3 Transaction Data, Interactive Less constrained Routing and Distances

4 Low Loss Only (Short Transactions, Bulk Data, Video Streaming)

Long Queue, Drop priority Any route/path

5 Traditional 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

Parameter X Vs Network Model Coverage Percentage

0

0 10 20 30 40 50 60 70 80 90 100

Percentage of Network Coverage

Device ADevice BDevice C

PE

SQ

, P

SQ

M,

MO

S,

R-F

act

or,

Th

rou

gh

pu

t, C

on

ne

ct R

ate

, e

tc.

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.150.1 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 38-1994: Test Procedures for Evaluation of 2-Wire 4 Kilohertz Voice Band Duplex Modems, which became ITU-T Recommendation V.56ter-1996

• ANSI/TIA/EIA 3700-1999: Telephone Network Transmission Model for Evaluating Analog Modem Performance

• ANSI/TIA/EIA 793 -2000: 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