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Deployment of VoIP in Deployment of VoIP in Data NetworksData Networks
Dr. Khaled SalahDr. Khaled Salah
[email protected]@kfupm.edu.sa
2
A step-by-step MethodologyA step-by-step Methodology
To deploy VoIP in Data NetworksTo deploy VoIP in Data Networks
K. Salah 3
OutlineOutline
Introduction and challenging Introduction and challenging questionsquestions
Existing toolsExisting toolsDrawbacks of existing toolsDrawbacks of existing toolsEight-step MethodologyEight-step MethodologyCase StudyCase StudyAnalytical toolAnalytical tool
K. Salah 4
IntroductionIntroduction
Importance of VoIPImportance of VoIP Unification of data and voice networks It is easier to run, manage, and maintain. Future – NGN and Triple Play
Existing IP networks are best effort and VoIP requires QoSExisting IP networks are best effort and VoIP requires QoS
Challenging questionsChallenging questions What are the QoS requirements for VoIP? How will the new VoIP load impact the QoS of currently running
network services and applications? Will my existing network support VoIP and satisfy the standardized
QoS requirements? If so, how many VoIP calls can the network support before upgrading
prematurely any part of the existing network hardware?
K. Salah 5
Existing ToolsExisting Tools
Ample of commercial toolsAmple of commercial tools NetIQ Brix Networks Agilent Cisco Avaya Siemens
Uses two common approaches for assessing the Uses two common approaches for assessing the deployment of VoIPdeployment of VoIP Take network measurements and then predict the
readiness based on the health of network Inject real VoIP traffic and measure QoS
K. Salah 6
Drawbacks of Existing ToolsDrawbacks of Existing Tools
CostCost
Injection approach can be intrusive to operation of Injection approach can be intrusive to operation of existing networkexisting network
None offers a comprehensive approach or methodology None offers a comprehensive approach or methodology for successful VoIP deployment. for successful VoIP deployment. No answers to all challenging questions, e.g.
Number of calls Call distribution Call flow Future growth Impact on existing network apps
K. Salah 7
Case StudyCase Study
Floor 1
Internet
7
Switch 1 Switch 2
. . .
User PCs
Workgroupserver
Floor 3
. . .
User PCs
Floor 2
. . .
User PCs
Databaseserver E-Mail
server
Fileserver HTTP
server
Web &cacheproxy
Firewall
Router
Printerserver
Workgroupserver
Printerserver
Workgroupserver
Printerserver
K. Salah 8
MethodologyMethodology
Determine VoIP characteristics and requirementsDetermine VoIP characteristics and requirements Determine VoIP traffic flow and call distributionDetermine VoIP traffic flow and call distribution Define performance thresholds and growth capacityDefine performance thresholds and growth capacity Perform network measurementsPerform network measurements Early modifications to existing network Early modifications to existing network Theoretical AnalysisTheoretical Analysis OPNET SimulationOPNET Simulation Comparison of Simulation and AnalysisComparison of Simulation and Analysis Final modifications to existing networkFinal modifications to existing network
K. Salah 9
Perform networkmeasurements
Determine VoIP Characteristics,requirements and assumptions
Define performance thresholdsand future growth capacity
Upfront network assessmentor modifications
Analysis Simulation
PilotDeployment
Start
End
(3)(1)
(5)
(6) (7)
(8)
Determine VoIP traffic flowand call distribution
(2) (4)
K. Salah 10
Perform network measurements
Determine VoIP Characteristics, requirements and assumptions
Define performance thresholds and future growth capacity
Upfront network assessment or modifications
Analysis Simulation
Pilot Deployment
Start
End
)3()1(
)5(
)6( )7(
)8(
Determine VoIP traffic flow and call distribution
)2( )4(
K. Salah 11
VoIP Traffic Characteristics, VoIP Traffic Characteristics, Requirements, and AssumptionsRequirements, and Assumptions
A point-to-point conversation for all VoIP calls with no A point-to-point conversation for all VoIP calls with no call conferencing call conferencing
HardwareHardware Gatekeeper or CallManager
handles signaling for establishing, terminating, and authorizing connections of all VoIP calls.
H.323 or SIP Gateway
responsible for converting VoIP calls to/from the Public Switched Telephone Network (PSTN).
VoIP Terminal IP phones Desktop with IP SoftPhones
As an engineering and design issue, the placement of these nodes in the network becomes crucial.
K. Salah 12
VoIP end-to-end ComponentsVoIP end-to-end Components
EncoderEncoder PacketizerPacketizer Playback BufferPlayback Buffer DecoderDecoder
Encoder Packetizer
Sender Receiver
NetworkPlayback
Buffer
Depacketizer Decoder
K. Salah 13
Common ITU-T codecs and their defaults Common ITU-T codecs and their defaults
G.711u gives a MOS of 4.4G.711u gives a MOS of 4.4 Other codes use (to decrease rate):Other codes use (to decrease rate):
compression silence suppression packet loss concealment encapsulating voice packets in one Ethernet frame
K. Salah 14
End-to-End Delay for a Single Voice PacketEnd-to-End Delay for a Single Voice Packet
The end-to-end delay is sometimes referred to by The end-to-end delay is sometimes referred to by M2EM2E or Mouth-to-Ear or Mouth-to-Ear delay delay
G.714 imposes a maximum total one-way packet delay of G.714 imposes a maximum total one-way packet delay of 150ms 150ms end-end-to-end for VoIP applications to-end for VoIP applications
200ms was found to be acceptable by experimentation200ms was found to be acceptable by experimentation Sources of delay:Sources of delay:
(i) encoding, compression, and packetization delay at the sender(ii) propagation, transmission and queuing delay in the network(iii) buffering, decompression, depacketization, decoding, and
playback delay at the receiver.
Encoder Packetizer
Sender Receiver
NetworkPlayback
Buffer
Depacketizer Decoder
K. Salah 15
VoIP Traffic Characteristics and RequirementsVoIP Traffic Characteristics and Requirements
M2E delay for a single callM2E delay for a single call 150ms according to G.714 Sender: 25 ms Receiver: 45 ms
Higher than the sender. It includes jitter buffer delay which is at most 2 packets or 40 ms
Network: 80 ms
Encoder Packetizer
Sender Receiver
NetworkPlayback
Buffer
Depacketizer Decoder
K. Salah 16
Bandwidth for a Single Call Bandwidth for a Single Call
The required bandwidth for a single call, one direction, is 64 kbps. The required bandwidth for a single call, one direction, is 64 kbps. G.711 codec samples 20ms of voice per packet. Therefore, 50 G.711 codec samples 20ms of voice per packet. Therefore, 50
such packets need to be transmitted per second. such packets need to be transmitted per second. Each packet contains 160 voice samples in order to give 8000 Each packet contains 160 voice samples in order to give 8000
samples per second. PCM sampling & quantization is done every samples per second. PCM sampling & quantization is done every 125us.125us.
Each packet is sent in one Ethernet frame. With every packet of Each packet is sent in one Ethernet frame. With every packet of size 160 bytes, headers of additional protocol layers are added. size 160 bytes, headers of additional protocol layers are added. These headers include RTP + UDP + IP + Ethernet with preamble These headers include RTP + UDP + IP + Ethernet with preamble of sizes 12 + 8 + 20 + 26, respectively. of sizes 12 + 8 + 20 + 26, respectively.
Therefore, a total of 226 bytes, or 1808 bits, needs to be Therefore, a total of 226 bytes, or 1808 bits, needs to be transmitted 50 times per second, or 90.4 kbps, transmitted 50 times per second, or 90.4 kbps, in one direction.in one direction.
For both directions,For both directions, the required bandwidth for a single call is 100 the required bandwidth for a single call is 100 pps or 180.8 kbps assuming a symmetric flow. pps or 180.8 kbps assuming a symmetric flow.
K. Salah 17
Other AssumptionsOther Assumptions
Voice calls are symmetric and no voice conferencing Voice calls are symmetric and no voice conferencing We also ignore the signaling traffic generated by the We also ignore the signaling traffic generated by the gatekeepergatekeeper. .
Worst-case scenario is considered signaling traffic involving the gatekeeper is mostly generated prior to
the establishment of the voice call and when the call is finished. This traffic is relatively small compared to the actual voice call traffic.
gatekeeper generates no or very limited signaling traffic throughout the duration of the VoIP call for an already established on-going call
No QoS mechanisms that can enhance the quality of No QoS mechanisms that can enhance the quality of packet delivery in IP networks, such aspacket delivery in IP networks, such as
IEEE 802.1p/Q IETF’s RSVP DiffServ MPLS
K. Salah 18
Perform network measurements
Determine VoIP Characteristics, requirements and assumptions
Define performance thresholds and future growth capacity
Upfront network assessment or modifications
Analysis Simulation
Pilot Deployment
Start
End
)3()1(
)5(
)6( )7(
)8(
Determine VoIP traffic flow and call distribution
)2( )4(
K. Salah 19
VoIP Traffic Flow and Call DistributionVoIP Traffic Flow and Call Distribution Knowing the current telephone call usage or volume of the enterprise is an Knowing the current telephone call usage or volume of the enterprise is an
important step for a successful VoIP deployment. important step for a successful VoIP deployment. Collecting statistics about of the present call volume and profiles is Collecting statistics about of the present call volume and profiles is
essential. essential. Sources
PBX database Telephone records Billing
Key characteristics of existing calls can include the number of calls, number Key characteristics of existing calls can include the number of calls, number of concurrent calls, time, duration, etc of concurrent calls, time, duration, etc
We want to investigate if these characteristics can be still met when migrating to VoIP
Locations of the call endpoints, i.e., the sources and destinations, as well as Locations of the call endpoints, i.e., the sources and destinations, as well as their corresponding path or flow their corresponding path or flow
Call distribution must include percentage of calls within and outside of a Call distribution must include percentage of calls within and outside of a floor, building, department, or organization. floor, building, department, or organization.
As a good capacity planning measure, it is recommended to base the VoIP As a good capacity planning measure, it is recommended to base the VoIP call distribution on the busy hour traffic of phone calls for the busiest day of call distribution on the busy hour traffic of phone calls for the busiest day of a week or a month. a week or a month.
The projected extra calls need to be also combined with current statisticsThe projected extra calls need to be also combined with current statistics
K. Salah 20
Call DistributionCall Distribution
External
Total calls
1/3 2/3
F1 F2 F3
1/31/31/3
F1 F2 F3
1/31/31/3
F1 F2 F1 F3 F2 F3
Intra-floor Inter-floor
1/32/3
Internal
1/31/31/3
K. Salah 21
Perform network measurements
Determine VoIP Characteristics, requirements and assumptions
Define performance thresholds and future growth capacity
Upfront network assessment or modifications
Analysis Simulation
Pilot Deployment
Start
End
)3()1(
)5(
)6( )7(
)8(
Determine VoIP traffic flow and call distribution
)2( )4(
K. Salah 22
Define Performance Thresholds and Define Performance Thresholds and Growth CapacityGrowth Capacity
The maximum tolerable end-to-end delayThe maximum tolerable end-to-end delay determined by the most sensitive application to run on the
network 150ms for VoIP
It is imperative to note that if the network has certain delay-sensitive applications, the delay for these applications should be monitored, when introducing VoIP traffic, such that they do not exceed their required maximum values.
The utilization bounds or thresholds of network resourcesThe utilization bounds or thresholds of network resources Factors to consider: current utilization, future plans, and foreseen
growth of the network. It is extremely important not to utilize fully the network resources.
Packet lossPacket loss Depends on network service or application For VoIP, 0.1% to 5% packet loss is acceptable
K. Salah 23
Future GrowthFuture Growth
What is the projected growth in users, What is the projected growth in users, network services, business, etc.?network services, business, etc.?
In our study we will ascertain that 25% of In our study we will ascertain that 25% of the available network capacity is reserved the available network capacity is reserved for future growth and expansion. for future growth and expansion. we will apply this evenly to all network
resources of the router, switches, and switched-Ethernet links.
K. Salah 24
Perform network measurements
Determine VoIP Characteristics, requirements and assumptions
Define performance thresholds and future growth capacity
Upfront network assessment or modifications
Analysis Simulation
Pilot Deployment
Start
End
)3()1(
)5(
)6( )7(
)8(
Determine VoIP traffic flow and call distribution
)2( )4(
K. Salah 25
Perform Network measurementsPerform Network measurements
Need to characterize the existing network Need to characterize the existing network traffic load, utilization, and flow traffic load, utilization, and flow
Background traffic profilingBackground traffic profilingAvailable tools:Available tools:
Open-source MRTG, STG, SNMPUtil, and GetIF
Commercial HP OpenView, Cisco Netflow, Lucent VitalSuite,
Patrol DashBoard, Omegon NetAlly, Avaya ExamiNet, NetIQ Vivinet Assessor, etc.
K. Salah 26
Perform Network measurementsPerform Network measurements
Network measurements must be performed for network Network measurements must be performed for network elements such as routers, switches, and links. elements such as routers, switches, and links.
Numerous types of measurements and statistics can be Numerous types of measurements and statistics can be obtained using measurement tools. obtained using measurement tools. As a minimum, traffic rates in bps (bits per second) and pps
(packets per second) must be measured for links directly connected to routers and switches.
To get adequate assessment, network measurements To get adequate assessment, network measurements have to be taken over a long period of time, at least 24-have to be taken over a long period of time, at least 24-hour period. hour period. Sometimes it is desirable to take measurements over several
days or a week.
K. Salah 27
K. Salah 28
Worst-case network measurementsWorst-case network measurements
K. Salah 29
Perform network measurements
Determine VoIP Characteristics, requirements and assumptions
Define performance thresholds and future growth capacity
Upfront network assessment or modifications
Analysis Simulation
Pilot Deployment
Start
End
)3()1(
)5(
)6( )7(
)8(
Determine VoIP traffic flow and call distribution
)2( )4(
K. Salah 30
Upfront Network Assessment and Upfront Network Assessment and ModificationsModifications
Examine if any immediate modifications are Examine if any immediate modifications are necessarynecessary may include adding and placing new servers or devices,
upgrading PCs, and re-dimensioning heavily utilized links.
As a good upgrade rule, topology changes need As a good upgrade rule, topology changes need to be kept to minimum and should not be made to be kept to minimum and should not be made unless it is necessary and justifiable. Over-unless it is necessary and justifiable. Over-engineering the network and premature engineering the network and premature upgrades are costly and considered as poor upgrades are costly and considered as poor design practicesdesign practices
K. Salah 31
Changes to topologyChanges to topology
Links are underutilized, no need for 1G linksLinks are underutilized, no need for 1G links Shared links must be replaced with full-duplex switchedShared links must be replaced with full-duplex switched
shared Ethernet offers zero QoS and are not recommended for real-time and delay-sensitive applications as it introduces excessive and variable latency under heavy loads and when subjected to intense bursty traffic
Add Add gatekeepergatekeeper and and gatewaygateway connecting the gatekeeper to Switch 1 is practical in order to
keep the traffic local. Connecting the gateway to Switch 2 balances the projected load
on both switches. It is more reliable and fault-tolerant not to connect both nodes to
the same switch in order to eliminate problems that stem from a single point of failure.
K. Salah 32
Original TopologyOriginal Topology
Floor 1
Internet
7
Switch 1 Switch 2
. . .
User PCs
Workgroupserver
Floor 3
. . .
User PCs
Floor 2
. . .
User PCs
Databaseserver E-Mail
server
Fileserver HTTP
server
Web &cacheproxy
Firewall
Router
Printerserver
Workgroupserver
Printerserver
Workgroupserver
Printerserver
K. Salah 33
New Topology with VoIP ComponentsNew Topology with VoIP Components
Floor 1
Internet
7
Switch 1 Switch 2
Floor 3Database
server E-Mailserver
Fileserver HTTP
server
Web &cacheproxy
Firewall
Router
Gatekeeper
PSTN
VoIPGateway
. . .
Workgroupserver
Printerserver
MultimediaPCs
Floor 2
. . .
Workgroupserver
MultimediaPCs
Printerserver
. . .
Workgroupserver
MultimediaPCs
Printerserver
K. Salah 34
Perform network measurements
Determine VoIP Characteristics, requirements and assumptions
Define performance thresholds and future growth capacity
Upfront network assessment or modifications
Analysis Simulation
Pilot Deployment
Start
End
)3()1(
)5(
)6( )7(
)8(
Determine VoIP traffic flow and call distribution
)2( )4(
K. Salah 35
The analytical approachThe analytical approach
Bandwidth bottleneck analysisBandwidth bottleneck analysis
Delay analysisDelay analysis
The actual number of VoIP calls that the network can sustain and The actual number of VoIP calls that the network can sustain and support is bounded by those two metrics. support is bounded by those two metrics.
Depending on the network under study, either the available Depending on the network under study, either the available bandwidth or delay can be the key dominant factor in determining bandwidth or delay can be the key dominant factor in determining the number of calls that can be supported.the number of calls that can be supported.
K. Salah 36
BW bottleneck analysisBW bottleneck analysis
K. Salah 37
Network Delay AnalysisNetwork Delay Analysis
Poisson VoIP TrafficPoisson VoIP Traffic Using Jackson TheoremUsing Jackson Theorem Links: M/D/1Links: M/D/1 Router and Switches: M/M/1Router and Switches: M/M/1
K. Salah 38
K. Salah 39
Network Capacity AlgorithmNetwork Capacity Algorithm
i.i. Add background trafficAdd background traffic
ii.ii. Add one call based on distribution and flowAdd one call based on distribution and flow
iii.iii. For each node calculate the new arrival rate – For each node calculate the new arrival rate – not all nodes are affected.not all nodes are affected.
iv.iv. Compute packet network delay for all flows by Compute packet network delay for all flows by summing up individual delays per nodesumming up individual delays per node
v.v. If network delay < 80 ms, go to If network delay < 80 ms, go to iiii, otherwise , otherwise STOP. STOP.
K. Salah 40
K. Salah 41
Worst incurred delay vs. number of VoIP callsWorst incurred delay vs. number of VoIP calls
K. Salah 42
Analytical ToolAnalytical Tool
Generic Generic
GUIGUI With drag-and-drop features
Analytical engineAnalytical engine BW bottleneck analysis Compute iteratively the network delay
K. Salah 43
Perform network measurements
Determine VoIP Characteristics, requirements and assumptions
Define performance thresholds and future growth capacity
Upfront network assessment or modifications
Analysis Simulation
Pilot Deployment
Start
End
)3()1(
)5(
)6( )7(
)8(
Determine VoIP traffic flow and call distribution
)2( )4(
K. Salah 44
SimulationSimulation
Using Using OPNETOPNET
Will be discussed in great detail in next presentation
K. Salah 45
ComparisonComparison
A way to validate results of both simulation A way to validate results of both simulation and analysis (or expert intuition).and analysis (or expert intuition).
K. Salah 46
Perform network measurements
Determine VoIP Characteristics, requirements and assumptions
Define performance thresholds and future growth capacity
Upfront network assessment or modifications
Analysis Simulation
Pilot Deployment
Start
End
)3()1(
)5(
)6( )7(
)8(
Determine VoIP traffic flow and call distribution
)2( )4(
K. Salah 47
Pilot DeploymentPilot Deployment
Before embarking on changing any of the network equipment, it is Before embarking on changing any of the network equipment, it is always recommended to build a pilot deployment of VoIP in a test always recommended to build a pilot deployment of VoIP in a test lab to ensure smooth upgrade and transition with minimum lab to ensure smooth upgrade and transition with minimum disruption of network services. disruption of network services.
A pilot deployment is the place for the network engineers, support A pilot deployment is the place for the network engineers, support and maintenance team to get firsthand experience with VoIP and maintenance team to get firsthand experience with VoIP systems and their behavior. systems and their behavior.
New VoIP devices and equipment are evaluated, configured, tuned, New VoIP devices and equipment are evaluated, configured, tuned, tested, managed, monitored, etc.tested, managed, monitored, etc.
Get comfortable with how VoIP works, how it mixes with other traffic, Get comfortable with how VoIP works, how it mixes with other traffic, how to diagnose and troubleshoot potential problems. how to diagnose and troubleshoot potential problems.
Simple VoIP calls can be set up and some benchmark testing can Simple VoIP calls can be set up and some benchmark testing can be performed. be performed.
K. Salah 48
To SummarizeTo Summarize
A step-by-step methodology on how VoIP can be A step-by-step methodology on how VoIP can be deployed successfullydeployed successfully
The methodology can help network researchers and The methodology can help network researchers and designers to determine quickly and easily how well VoIP designers to determine quickly and easily how well VoIP will perform on a network prior to deployment. will perform on a network prior to deployment.
Prior to the purchase and deployment of VoIP Prior to the purchase and deployment of VoIP equipment, it is possible to predict the number of VoIP equipment, it is possible to predict the number of VoIP calls that can be sustained by the network while calls that can be sustained by the network while satisfying QoS requirements of all existing and new satisfying QoS requirements of all existing and new network services and leaving enough capacity for future network services and leaving enough capacity for future growth. growth.
K. Salah 49
Perform networkmeasurements
Determine VoIP Characteristics,requirements and assumptions
Define performance thresholdsand future growth capacity
Upfront network assessmentor modifications
Analysis Simulation
PilotDeployment
Start
End
(3)(1)
(5)
(6) (7)
(8)
Determine VoIP traffic flowand call distribution
(2) (4)