performance analysis of a call center interface …system description • the call center monitoring...
TRANSCRIPT
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Performance Analysis of a Call Center
Telecommunications InterfaceCS672 Spring 2004
Mohamed BenalayatRaymond Jordan
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Overview• Call center monitoring and recording systems allow corporations to
monitor the performance of their agents by providing the ability to record and retrieve telephone conversations in real time.
• Monitoring systems usually require an interface between the Call Center Monitor/Recorder and the telecommunications infrastructure.
• The following paper is a study of the performance characteristics of such a call center telecommunications interface.
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Project Goals• Determine the maximum workload that can be placed on the Call Center
Telecom Interface.
• Determine how to improve the Call Center Telecom Interface in order to achieve 100 or more simultaneous input lines.
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System Description• The call center monitoring system under study can be described as
being composed of 2 functional components:
•A front-end telecommunications interface component, which functions as a call-processing unit. It is responsible for real time reception of digitized telephony data, processing the received data, converting to a recognized audio format, and forwarding to recording unit.
•A back end recording component which functions as a digital recording unit. It is responsible for recording and file management.
Call CenterPBX
Telecominterface 10BASE-T
interface
CPU/Disk
Recording unit
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System DiagramCall Center Telecommunications Interface
CPU
Disk
NetworkOut to recording device
In from T-1 card
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Hardware Description• Intel 1.263 GHz CPU
• 1 GB RAM
• Seagate Barracuda ATA IV 60 GB Hard Drive
• Average Write Service Time = 14.3 msec
• 10/100 Ethernet Card
• 24-channel telecom interface card(T1)
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Workload Characterization• The system workload is a stream of digitized call conversations.
• Further monitoring of a production system, reviewing its logged data and discussions with the system architects, revealed the existence of 2 distinct traffic call classes.
• The first class, which we will call the PCM class, represents the call traffic digitized using the standard pulse code modulation techniques.
• The second class, which we will call VOIP class, represents the call traffic in the form of voice over IP calls. These calls may contain voice and data elements.
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Data Collection Method• Our performance data collection process involved the use of a
telephone call simulation tool.
• The simulation tool is capable of streaming digitized audio files thru a T1 connection. Provided with a set of audio files, the tool will randomly pick a group of files to streamline.
• We had available to us a total of 12 audio files. 6 were PCM class and 6 were VOIP class.
• The Call Center Telecommunications Interface is equipped with a 24 channel T1 card. The audio simulator was configured to concurrently transmit 24 audio streams.
• Permon, the Microsoft windows performance tools was used to gather the performance statistics during the load testing.
• Ran 1-hour load test with only a PCM workload and another 1-hour load test with only a VOIP workload.
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Queuing Network• The system can be represented by an Open Queuing Network. The
workload intensity is specified by the arrival rate of calls through the T1 interface.
• The number of calls simulated is limited only by the number of T1 interface cards installed in the unit.
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ClusteringDisk Transfers vs. CPU Time
Disk Transfers/sec vs. %CPU Time
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% CPU Time
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PCM VOIP
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ClusteringNetwork Bytes Sent vs. CPU Time
Network Bytes Sent/sec vs. %CPU Time
050,000
100,000150,000200,000250,000300,000350,000400,000450,000500,000
0 5 10 15 20 25 30 35 40 45 50 55 60 65
% CPU Time
Net
wor
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Sen
t/sec
PCM VOIP
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System Completions
ClassNumber of
Lines
Average Session Length
Recordings Generated
(minutes)PCM 24 5.31 271VOIP 24 4.62 312
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Basic Statistics for the PCM Service Workload
PCM% Processor
Time % Disk Time Disk Bytes/secNetwork Bytes
Sent/secU(cpu) U(disk) X(disk) X(net)
Mean 6.2 0.0 5,108.3 356,432.4Standard Deviation 2.7 0.1 8,641.0 27,385.6Sample Variance 7.5 0.0 74,666,318.7 749,970,852.6Coeff. Of Variance 0.4 1.6 1.7 0.1Minimum 0.0 0.0 2,355.2 0.0First Quartile (Q1) 4.3 0.0 3,481.6 347,264.7Median (Q2) 6.3 0.0 4,096.0 359,520.1Third Quartile (Q3) 8.1 0.0 4,480.0 375,268.4Maximum 14.3 0.6 110,863.5 376,915.5Range 14.3 0.6 108,508.3 376,915.5Largest 14.3 0.6 110,863.5 376,915.5Smallest 0.0 0.0 2,355.2 0.0Sum 1,489.6 7.5 1,225,990.2 85,543,779.9
Elapsed Time = 1 hour = 60 min. = 3600 secQ1
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PCM Box and Whisker Plots
2,355.2 110,863.54,480.04,096.03,481.6
Disk Bytes/Sec
Q1 Q2 Q3
Q1
0.0 14.38.16.34.3
% Processor Time
Q2 Q3
0.0 376,915.5375,268.4359,520.1347,264.7
Network Bytes Sent/Sec
Q1 Q2 Q3
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Basic Statistics for the VOIP Service Workload
VOIP% Processor
Time % Disk Time Disk Bytes/secNetwork Bytes
Sent/secU(cpu) U(disk) X(disk) X(net)
Mean 40.3 0.0 4,585.9 403,856.1Standard Deviation 7.9 0.1 3,113.5 30,635.0Sample Variance 62.7 0.0 9,693,663.1 938,501,610.0Coeff. Of Variance 0.2 2.0 0.7 0.1Minimum 3.1 0.0 2,455.0 182.7First Quartile (Q1) 35.1 0.0 3,583.9 398,367.6Median (Q2) 40.4 0.0 4,334.9 411,343.3Third Quartile (Q3) 45.2 0.0 4,889.6 411,796.1Maximum 58.5 0.8 44,762.1 447,753.4Range 55.4 0.7 42,307.0 447,570.8Largest 58.5 0.8 44,762.1 447,753.4Smallest 3.1 0.0 2,455.0 182.7Sum 9,676.4 11.1 1,100,614.4 96,925,454.6
Elapsed Time = 1 hour = 60 min. = 3600 sec
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VOIP Box and Whisker Plots
2,455.0 44,762.14,889.64,334.93,583.9
Disk Bytes/Sec
Q1 Q2 Q3
Q1
3.1 58.514.3
45.28.1
40.435.1
% Processor Time
Q2 Q3
182.7 447,753.4
411,796.1411,343.3398,367.6
Network Bytes Sent/Sec
Q1 Q2 Q3
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Service Demand CalculationsType Description Symbol PCM VOIP Units Formula Comment
Time Total Time T 3,600 3,600 sec Performance MonitorInput Lines 24 24 lines Test SimulatorCompleted Sessions System Arrivals/Completions A (Co) 271 312 sessions System Log
Average Time Per Session 318.82 276.92 secondsAverage Time Per Session 5.31 4.62 minutes
Throughput System Throughput Xo 0.075 0.087 sessions/sec = A / TCPU Utilization Ucpu 6.21% 40.32% % Performance Monitor
Busy Time Bcpu 223.44 1451.46 sec = Ui * TAverage Service Time Scpu 7.92E-10 7.92E-10 sec/transaction 1.263 Ghz processorService Completions Ccpu 282,199,242,017 1,833,195,030,583 transactions = Bi / SiThroughput Xcpu 78,388,678 509,220,842 transactions/sec = Ui / Si Utilization LawVisits to CPU Vcpu 1,041,325,616.3 5,875,625,098.0 = Ci / CoService Demand Dcpu 0.824 4.652 sec = Ui / Xo Service Demand Law
Disk Utilization Udisk 0.0311% 0.0462% % Performance MonitorBusy Time Bdisk 1.12 1.66 sec = Ui * TAverage Service Time Sdisk 0.014300000 0.014300000 sec/byte = Ui / Xi StorageReview.com Seagate Data SheetService Completions Cdisk 78.37 116.28 bytes = Bi / SiThroughput Xdisk 5,108.29 4,585.89 bytes/sec Performance MonitorVisits to Disk Vdisk 0.29 0.37 = Ci / CoService Demand Ddisk 0.004135392 0.005329316 sec = Ui / Xo
Network Interface Bytes Sent/sec 356,432.42 403,856.06 bytes/sec Performance MonitorTotal Bits/sec 2,851,459.33 3,230,848.49 Performance MonitorEthernet Speed 10,000,000.00 10,000,000.00 10 MbpsUtilization Unet 28.51% 32.31% % Performance MonitorBusy Time Bnet 1,026.53 1,163.11 sec = Ui * TAverage Service Time Snet 0.0000001 0.0000001 sec 10 Mbps Network InterfaceService Completions Cnet 10,265,253,583.4 11,631,054,555.7 bits = Bi / SiThroughput Xnet 2,851,459.3 3,230,848.5 bits/sec = Ui / SiVisits to Network Vnet 37,879,164.5 37,279,021.0 = Ci / CoService Demand Dnet 3.788 3.728 sec = Ui / Xo
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Data AnalysisThread CPU Usage
• Notice that the CPU utilization for the PCM class is low compared to that of the VOIP class.
• The service demands show this trend.
•D(cpu, PCM) = 0.824 sec. D(cpu, VOIP) = 4.652 sec.
• The reason is the additional CPU requirements of the thread called to decode and extract data from VOIP data streams.
Thread Processor Usage
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Data AnalysisPCM Throughput and Resource Utilization vs. Number of Lines
PCM Resource Utilization & System Throughput vs. Number of Lines
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PCMLines
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Data AnalysisPCM Resource Utilization vs. System Throughput
PCM Resouce Utilization vs. System Throughput
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Data AnalysisVOIP Throughput and Resource Utilization vs. Number of Lines
VOIP Resource Utilization & System Throughput vs. Number of Lines
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Data AnalysisVOIP Resource Utilization vs. System Throughput
VOIP Resouce Utilization vs. System Throughput
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Throughput (requests/sec)
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CPU Utilization Disk Utilization Netw ork Utilization
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Data AnalysisPCM Throughput Bounds
Throughput Performance Bound (PCM Inputs Only)
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Heavy Load = 1 / max Di Light Load = N/sum(Di) Actual Throughput Xo
NOTE: Scale of X-axis N is not linear.
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Data AnalysisPCM Throughput Bounds (close-up)
Throughput Performance Bound (PCM Inputs Only)
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Data AnalysisThroughput Bounds
Throughput Performance Bound (VOIP Inputs Only)
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Heavy Load = 1 / max Di Light Load = N/sum(Di) Actual Throughput Xo
NOTE: Scale of X-axis N is not linear.
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Data AnalysisVOIP Throughput Bounds (close-up)
Throughput Performance Bound (VOIP Inputs Only)
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Data Analysis PCM Response Time Bounds
Response Time Bound (PCM Inputs Only)
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Light Load = sum(Di) Heavy Load = N*maxDi Actual Response Time R
NOTE: Scale of X-axis N is not linear.
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Data AnalysisPCM Response Time Bounds (close-up)
Response Time Bound (PCM Inputs Only)
0.0002.0004.0006.0008.000
10.00012.00014.000
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Data Analysis VOIP Response Time Bounds
NOTE: Scale of X-axis N is not linear.
Response Time Bound (VOIP Inputs Only)
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0.031 0.200 0.401 0.642 0.940 1.314 1.804 2.471 3.446 5.028 8.173 18.945N
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Light Load = sum(Di) Heavy Load = N*maxDi Actual Response Time R
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Data AnalysisVOIP Response Time Bounds (close-up)
Response Time Bound (VOIP Inputs Only)
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Light Load = sum(Di) Heavy Load = N*maxDi Response Time R
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Data AnalysisThroughput and Response Time vs. Number of Concurrent PCM Requests
Throughput and Response Time vs. Number of Concurrent PCM Requests
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Number of Concurrent PCM Requests
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Data AnalysisThroughput and Response Time vs. Number of Concurrent VOIP Requests
Throughput and Response Time vs. Number of Concurrent VOIP Requests
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Conclusions• PCM and VOIP classes are similar in their service demands for disk and
network usage. However, VOIP has a much higher CPU service demand that PCM.
• System throughput is limited by the network demands of both classes. Additionally, system throughput is limited by the CPU service demand of the VOIP class.
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Open Queuing Network Solution
PCM Lines
Average Session Length
System Completions
System Throughtput
Service Demand Utilizaton Busy Time Service Time
Resource Throughput
Queue Length Residence Time
Co Xo Di Ui Bi Si Xi Ni Ri'CPU 24 5.31 271.0 0.075 0.824 0.062 223.436 7.918E-10 78,388,678 0.116 1.542Disk 24 5.31 271.0 0.075 0.004 0.000 1.121 0.014 0.022 0.000 0.004Network 24 5.31 271.0 0.075 3.788 0.285 1,026.525 1.000E-07 2,851,459 0.728 9.669
Total Response Time 11.215
VOIP Lines
Average Session Length
System Completions
System Throughtput
Service Demand Utilizaton Busy Time Service Time
Resource Throughput
Queue Length Residence Time
Co Xo Di Ui Bi Si Xi Ni Ri'CPU 24 4.62 312.0 0.087 4.652 0.403 1,451.461 7.918E-10 509,220,842 0.754 8.700Disk 24 4.62 312.0 0.087 0.005 0.000 1.663 0.014 0.032 0.000 0.005Network 24 4.62 312.0 0.087 3.728 0.323 1,163.105 1.000E-07 3,230,848 0.825 9.516
Total Response Time 18.220
Total Lines
Average Session Length
System Completions
System Throughtput
Average Service Demand Utilizaton Busy Time Service Time
Resource Throughput
Queue Length
Average Residence Time
Co Xo Di Ui Bi Si Xi Ni Ri'CPU 48 4.62 583.0 0.162 2.873 0.465 1,674.896 7.918E-10 587,609,520 0.870 5.372Disk 48 4.62 583.0 0.162 0.005 0.001 2.783 0.014 0.054 0.001 0.005Network 48 4.62 583.0 0.162 3.756 0.608 2,189.631 1.000E-07 6,082,308 1.553 9.587
Total Response Time 14.964
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Maximum WorkloadNumber of Lines for PCM and VOIP at 100% Resource Utilization
Number of Lines for PCM and VOIP at 100% Resource Utilization
0
10
20
30
40
50
60
70
0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84
PCM Lines
VOIP
Lin
es
0.00000.10000.20000.30000.40000.50000.60000.70000.80000.90001.00001.1000
Number of Lines CPU Utilization Network Utilization
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Maximum WorkloadNumber of Lines for PCM and VOIP vs. System Throughput
Number of Lines for PCM and VOIP vs. System Throughput at 100% Utilization
0
10
20
30
40
50
60
70
0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84
PCM Lines
VOIP
Lin
es
0.000
0.050
0.100
0.150
0.200
0.250
0.300
Number of Lines System Throughput
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Number of Lines for PCM and VOIP vs. Response Time at 100% Utilization
010
203040
50
6070
0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84
PCM Lines
VOIP
Lin
es
0.000
2,000.000
4,000.000
6,000.000
8,000.000
10,000.000
Number of Lines Response Time Trend Line (Response Time)
Maximum WorkloadNumber of Lines for PCM and VOIP vs. Response Time
CPU Utilization approaching 100%
Network Utilization approaching 100%
Average Response Time at maximum workload is 1,194 seconds
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Recommendations for Improvement
• Both classes will benefit from an upgrade network connection between the Call Center Telecom Interface and the Call Center Monitor/Recorder.
• Suggest 100 Mbps ethernet.
• Both classes will benefit from a faster CPU, but it is most important for the response time and throughput of the VOIP class. Today’s Intel Pentium 4 processors run at speeds over 3 GHz.
• Suggest 3 Ghz.
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Improvement AnalysisImproved Service Demand Calculations
Type Description Symbol PCM VOIP Units Formula CommentTime Total Time T 3,600 3,600 sec Performance MonitorInput Lines 24 24 lines Test SimulatorCompleted Sessions System Arrivals/Completions A (Co) 271 312 sessions System Log
Average Time Per Session 318.82 276.92 secondsAverage Time Per Session 5.31 4.62 minutes
Throughput System Throughput Xo 0.075 0.087 sessions/sec = A / TCPU Utilization Ucpu 2.61% 16.97% % = Bi / 3600
Busy Time Bcpu 94.07 611.07 sec = Si * CiAverage Service Time Scpu 3.33E-10 3.33E-10 sec/transaction 3.00 Ghz processorService Completions Ccpu 282,199,242,017 1,833,195,030,583 transactionsThroughput Xcpu 78,388,678 509,220,842 transactions/sec = Ui / Si Utilization LawVisits to CPU Vcpu 1,041,325,616.3 5,875,625,098.0 = Ci / CoService Demand Dcpu 0.347 1.959 sec = Ui / Xo Service Demand Law
Disk Utilization Udisk 0.0311% 0.0462% % Performance MonitorBusy Time Bdisk 1.12 1.66 sec = Ui * TAverage Service Time Sdisk 0.014300000 0.014300000 sec/byte = Ui / Xi StorageReview.com Seagate Data SheetService Completions Cdisk 78.37 116.28 bytes = Bi / SiThroughput Xdisk 5,108.29 4,585.89 bytes/sec Performance MonitorVisits to Disk Vdisk 0.29 0.37 = Ci / CoService Demand Ddisk 0.004135392 0.005329316 sec = Ui / Xo
Network Interface Bytes Sent/sec 356,432.42 403,856.06 bytes/sec Performance MonitorTotal Bits/sec 2,851,459.33 3,230,848.49 Performance MonitorEthernet Speed 100,000,000.00 100,000,000.00 100 MbpsUtilization Unet 2.85% 3.23% % = Total Bits per sec / Ethernet SpeedBusy Time Bnet 102.65 116.31 sec = Ui * TAverage Service Time Snet 0.00000001 0.00000001 sec 100 Mbps Network InterfaceService Completions Cnet 10,265,253,583.4 11,631,054,555.7 bits = Bi / SiThroughput Xnet 2,851,459.3 3,230,848.5 bits/sec = Ui / SiVisits to Network Vnet 37,879,164.5 37,279,021.0 = Ci / CoService Demand Dnet 0.379 0.373 sec = Ui / Xo
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Improvement AnalysisImproved Open Queuing Network Solution
PCM Lines
Average Session Length
System Completions
System Throughtput
Service Demand Utilizaton Busy Time Service Time
Resource Throughput
Queue Length Residence Time
Co Xo Di Ui Bi Si Xi Ni Ri'CPU 24 5.31 271.0 0.075 0.347 0.026 94.066 3.333E-10 78,388,678 0.032 0.432Disk 24 5.31 271.0 0.075 0.004 0.000 1.121 0.014 0.022 0.000 0.004Network 24 5.31 271.0 0.075 0.379 0.029 102.653 1.000E-08 2,851,459 0.030 0.403
Total Response Time 0.839
VOIP Lines
Average Session Length
System Completions
System Throughtput
Service Demand Utilizaton Busy Time Service Time
Resource Throughput
Queue Length Residence Time
Co Xo Di Ui Bi Si Xi Ni Ri'CPU 24 4.62 312.0 0.087 1.959 0.170 611.065 3.333E-10 509,220,842 0.211 2.436Disk 24 4.62 312.0 0.087 0.005 0.000 1.663 0.014 0.032 0.000 0.005Network 24 4.62 312.0 0.087 0.373 0.032 116.311 1.000E-08 3,230,848 0.034 0.397
Total Response Time 2.838
Total Lines
Average Session Length
System Completions
System Throughtput
Average Service Demand Utilizaton Busy Time Service Time
Resource Throughput
Queue Length
Average Residence Time
Co Xo Di Ui Bi Si Xi Ni Ri'CPU 48 4.96 583.0 0.162 1.209 0.196 705.131 3.333E-10 587,609,520 0.244 1.504Disk 48 4.96 583.0 0.162 0.005 0.001 2.783 0.014 0.054 0.001 0.005Network 48 4.96 583.0 0.162 0.376 0.061 218.963 1.000E-08 6,082,308 0.065 0.400
Total Response Time 1.909
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Improvement AnalysisPCM Throughput and Resource Utilization vs. Number of Lines
PCM Resource Utilization & System Throughput vs. Number of Lines
0.00
0.50
1.00
1.50
2.00
2.50
3.00
PCMLines
90 190 290 390 490 590 690 790 890 990
Thro
ughp
ut
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Util
izat
ion
PCM Throughput CPU Utilization Disk Utilization Netw ork Utilization
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Improvement AnalysisPCM Resource Utilization vs. System Throughput
PCM Resouce Utilization vs. System Throughput
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
0.000 0.500 1.000 1.500 2.000 2.500 3.000 3.500
Throughput (request/sec)
Util
izat
ion
CPU Utilization Disk Utilization Netw ork Utilization
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Improvement AnalysisVOIP Throughput and Resource Utilization vs. Number of Lines
VOIP Resource Utilization & System Throughput vs. Number of Lines
0.00
0.10
0.20
0.30
0.40
0.50
0.60
VOIP Lines 90 190
Thro
ughp
ut
0.0
0.5
1.0
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2.0
2.5
Util
izat
ion
VOIP Throughput CPU Utilization Disk Utilization Netw ork Utilization
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Improvement AnalysisVOIP Resource Utilization vs. System Throughput
VOIP Resouce Utilization vs. System Throughput
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700
Throughput (request/sec)
Util
izat
ion
CPU Utilization Disk Utilization Netw ork Utilization
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Improvement AnalysisImproved Throughput and Response Time vs. Number of Concurrent PCM Requests
Throughput and Response Time vs. Number of Concurrent PCM Requests
0.000
0.500
1.000
1.500
2.000
2.500
3.000
0 10 20 30 40 50 60 70 80
Number of Concurrent PCM Requests
Thro
ughp
ut (r
eque
st/s
ec)
0.000
5.000
10.000
15.000
20.000
25.000
30.000
35.000
Res
pons
e Ti
me
(sec
onds
)
Throughput Response Time
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Improvement AnalysisImproved Throughput and Response Time vs. Number of Concurrent VOIP Requests
Throughput and Response Time vs. Number of Concurrent VOIP Requests
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
0.450
0.500
0 1 2 3 4 5 6 7 8 9 10 11 12
Number of Concurrent VOIP Requests
Thro
ughp
ut (r
eque
st/s
ec)
0.000
5.000
10.000
15.000
20.000
25.000
Res
pons
e Ti
me
(sec
onds
)
Throughput Response Time
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Improvement AnalysisImproved Maximum Workload
Number of Lines for PCM and VOIP at 100% Resource Utilization
0
20
40
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120
140
160
0 40 80 120
160
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680
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760
800
840
PCM Lines
VOIP
Lin
es
0.0000
0.2000
0.4000
0.6000
0.8000
1.0000
1.2000
CPU Utilization Network Utilization Number of Lines
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Improvement AnalysisNumber of Lines for PCM and VOIP vs. System Throughput
Number of Lines for PCM and VOIP vs. System Throughput at 100% Resource Utilization
0
20
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120
140
160
0 40 80 120
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360
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720
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800
840
PCM Lines
VO
IP L
ines
0.000
0.500
1.000
1.500
2.000
2.500
3.000
Thro
ughp
ut
Number of Lines System Throughtput
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Number of Lines for PCM and VOIP vs. Response Time at 100% Resource Utilization
0
20
40
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80
100
120
140
160
0 40 80 120
160
200
240
280
320
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480
520
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640
680
720
760
800
840
PCM Lines
VOIP
Lin
es
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
Resp
onse
Tim
e
Number of Lines Average Response Time
Improvement AnalysisNumber of Lines for PCM and VOIP vs. Response Time
CPU Utilization approaching 100%
Average Response Time at maximum workload is 446 seconds
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Outstanding Issues• The theoretical line capacity depends on adding additional 24 channel
T1 cards to the system. The overhead associated with each T1 card will slightly reduce the actual maximum line capacity.
• A good return on investment may not be possible when configuring the interface units at their maximum capacity. Investment costs need to be returned via software license fees, requiring the sale of a predetermined number of units.
• Response Time when configured at maximum line capacity is beyond acceptable limits. It is recommended to configure units at 50% of maximum capacity. The average response time when configure at 50% CPU utilization is 1.7 seconds.
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Outstanding IssuesNumber of PCM vs. VOIP lines at 50% CPU Utilization
Number of Lines for PCM and VOIP at 50% Resource Utilization
0
10
20
30
40
50
60
0 20 40 60 80 100
120
140
160
180
200
220
240
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300
320
340
360
380
400
420
440
PCM Lines
VOIP
Lin
es
Number of Lines