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Traffic Characterization and Perceptual Quality Assessment for VoIP at Pakistan Internet Exchange-PIE M. Amir Mehmood
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
