Transcript IP SLA - net324d

Voice Performance Measurement
and related technologies
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PART1: IP SLA
outline
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 IP SLA principles
 IP SLA components
 Highlighted features of IP SLA
 IP SLA performance metrics
 IP SLA operations
What is IP SLA
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 Cisco IP SLA is an embedded feature set in Cisco IOS
Software that allows you to analyze service levels for
IP applications and services
The basic principle of IP SLA
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 An active measurement that uses injected test
packets (synthetic traffic) marked with a time stamp
to calculate performance metrics.
IP SLA measurements benefits
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 The results allow indirect assessment of the network,
such as Service-Level Agreements (SLA) and QoS
class definitions.
IP SLA components
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IP SLA consists of two components, both
implemented in Cisco devices:
• Mandatory source device, which generates, receives,
and analyzes the traffic.
• The IP SLA Responder, which is optionally used to
increase accuracy and measurement details.
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Using time stamps
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By adding time stamps to the measurement packets at
the destination device, the IP SLA Responder allows
the elimination of the measurement packet
processing time on the destination device. The IP
SLA Responder listens on any standard or userdefined port for UDP, TCP, and Frame Relay packets
generated by the IP SLA source.
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RTT= T4-T1
Latency (one way)=T2-T1
Where :
 T4 is the time stamp at the source after receiving
the traffic
 T1 is the time stamp at the source when
generating traffic
 T2 is the time stamp at the target when receiving
traffic
IP SLA scope
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 IP SLA is an example of a device instrumentation
technique that does not overlap between accounting
and performance, because it is dedicated to
performance measurement
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 IP SLA is applicable to both service providers and
enterprises for performance management.
Highlighted features of IP SLA
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 Network performance monitoring
 SLA monitoring
 IP service network health assessment
 Edge-to-edge network availability monitoring
 Voice over IP (VoIP) performance monitoring
 Application-aware monitoring
 Accuracy
 Flexible operations
 Pervasiveness
 Troubleshooting of network operation
Network performance monitoring
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 Network performance monitoring— Measures delay,
jitter, packet loss, packet ordering, and packet
corruption in the network.
SLA monitoring
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 SLA monitoring— Provides service-level monitoring
and verification
IP service network health assessment
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 IP service network health assessment— Verifies that
the existing QoS settings are sufficient for new IP
services.
Edge-to-edge network availability monitoring
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 Edge-to-edge network availability monitoring—
Provides proactive verification and connectivity
testing of network resources (for example, indicates
the network availability of a web server).
Voice over IP (VoIP) performance monitoring
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 Voice over IP (VoIP) performance monitoring—
Analyzes critical parameters for a VoIP deployment,
which are not only jitter and packet loss, but also the
Mean Opinion Score (MOS) and
Impairment/Calculated Planning Impairment Factor
(ICPIF) values. The ICPIF value represents
predefined combinations of loss and delay.
Application-aware monitoring
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 Application-aware monitoring— IP SLA can emulate
traffic up to the application level—for example, DNS,
DHCP, and web server requests—and can measure
the related performance statistics.
Accuracy
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 Accuracy— Microsecond granularity for jitter delay
measurements offers the required precision for
business-critical applications.
Flexible operations
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 Flexible operations— Offer various kinds of
scheduling, alerting, and triggered measurements
Pervasiveness
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 Pervasiveness— IP SLA is implemented in Cisco
networking devices ranging from low-end to highend
routers and switches. This avoids the deployment
and management of dedicated measurement boxes.
Troubleshooting of network operation
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 Troubleshooting of network operation— Provides
consistent, reliable measurement that proactively
identifies performance and connectivity problems.
IP SLA collects the following performance
metrics:
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• Delay (both round-trip and one-way)
• Jitter (one-way)
• Packet loss (one-way)
• Packet sequencing (packet ordering)
• Packet corruption detection
• Path (per hop)
• Connectivity (one-way)
• FTP server or HTTP website download time
• Voice quality scores (MOS, ICPIF)
The various IP SLA operations can be classified
as follows:
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• ICMP-based operations for Echo, Path Echo, and
Path Jitter.
• UDP-based operations, such as echo, jitter, DNS, and
DHCP.
• TCP-based operations, such as TCP Connect, FTP,
HTTP.
• Layer 2 operations, such as Frame Relay, ATM, and
MPLS.
• VoIP-related operations, such as VoIP Jitter
Abbreviations
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Meaning
IOS
Internetwork Operating System
ICPIF
Impairment/Calculated Planning Impairment Factor
ICMP
Internet Control Message Protocol
MPLS
Multiprotocol Label Switching
ATM
Asynchronous Transfer Mode