Traffic Characterization and Perceptual Quality Assessment for VoIP at Pakistan

Internet Exchange-PIE

M. Amir Mehmood

Outline

BackgroundPakistan Internet Exchange - PIEMotivationPreliminaries

Our Worki) Traffic Characterizationii) VoIP quality assessmentiii) Simulation Conclusions

The Pakistan Internet Exchange

RWP

LHR

SEA-ME-WE3/4

KHI High Speed optical fiber cablerunning under Sea from South East Asia Middle East tillWestern Europe

Logical Topology of PIE

ISP‘s havemultiple links of 2Mbps, 34Mbps,155Mbps

PIE Network 2005

Motivation

PIE

Traffic Prediction based on current trends is a useful indicator of the growth …

What flows?

How much Traffic?

Is it good enough?

Motivation – (2)

Internet

Multimedia Broadband Network

Similar QoS

What is theQoS level forreal time application?

Motivation – (3)

Who is to blame in case of poorQoS?

Backbone Service Provider

or

Access Service Provider

Traffic Capturing at oneRegional Node

Used port mirroring at the Gigabit Link between the regional gateway routerand the cisco catalyst 6506 Switch.Sniffer from Network General forstatistics collection.Statistics taken for the period of twomonths (15th March to 14th May 2005)

PIE Network 2005

Protocol Wise Break-up: What flows?

Packet Size Distribution

VoIP

{

•Voice Stream is sampled at fixed rate

•Directly filled these samples into packets orcompressed before filling these samples.

•Add IP/UDP/RTP Headers

Fixed Interpacket Delay Variable Inter packet Delay - Jitter

De-jitter Buffer

VoIP

{

•Different kind of delays (Fixed or Variable)

•Algorithmic Delay

•Processing Delay

•Packetization Delay

•Transmission Delay

•Propagation Delay

•Queuing Delay

Fixed Interpacket Delay Variable Inter packet Delay - Jitter

De-jitter Buffer

VoIP

{

•VoIP Speech Quality depends on

•End to End Delay

•Packet Loss

•Delay Jitter

Fixed Interpacket Delay Variable Inter packet Delay - Jitter

De-jitter Buffer

Voice Quality Is it good enough?

“Perceptual”Mean Opinion Scores (MOS)

Time Consuming and Expansive ProcessQuality Models

Simulate human rating behavior by correlating perceptual QoS with other quantifiable parameters

Perceptual Speech Quality Measure - PSQM (ITU-T P.861)Perceptual Evaluation of Speech Quality -PESQ (ITU-T P.862)Both models compare the reference and degradedspeech samples.

The E-model (ITU-T G.107)Transmission Planning Tool

The E-model (ITU-T G.107)Predict Speech Quality from M2E impairments

The E-modelTransmission Quality Rating, R-factor

AIIIRR effeds +−−−= −0

0R

sI

dI

effeI −

A

Signal to noise ratio

Simultaneous impairments

Delay impairments

Equipment impairments due to low bit rate codec and packet loss Advantage Factor

Voice Quality Classes

Satisfied

90 4.3

Some users dissatisfiedMany users dissatisfied

Nearly all users dissatisfied

80

70

60

4.0

3.6

3.1

Not recommended

50

0

2.6

1

Very Satisfied100

93.2

5

4.4

R MOSUser Satisfaction

Experiments

SIP Call Signaling

Scenario - A

Scenario – A (contd)

Experiments

Scenario - B

Experiments

Scenario - C

Experiments

Scenario - D

Perceptual quality assessment for VoIP for the PIE backbone

Results

In the 4 scenarios studied:The backbone links exhibit low mean jitter

Access links present congestion hot spots

A satisfactory QoS cannot be achieved on an end to end basis because of bottlenecks in the access links

Simulation of PIE IP Backbonein OPNET IT Guru

Simulation of two separate backbones for voice and data

Comparitive Analysis

Average end to end delay Graphs for G.711, G.723.1 and G.729

After measuring End to End one way delay we made all calculations for MOS

Limitations

OPNET IT Guru is a limited versionand does not allow more than 2Million Discrete events simulation.

QoS for VoIP can not be achieved unless End-to-End QoS architecture is deployed both at backbone and at the access links.

Conclusions

Future Work

Measeure voip QoS at the DTAG Network for DSL and Wireless Networks.IP-PALMInterprovider QoS

Thank you