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PART1: IP SLA

Voice Performance Measurement and related

technologies

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outline

IP SLA principlesIP SLA componentsHighlighted features of IP SLAIP SLA performance metricsIP SLA operations

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What is IP SLA

Cisco IP SLA is an embedded feature set in Cisco IOS Software that allows you to analyze service levels for IP applications and services

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The basic principle of IP SLA

An active measurement that uses injected test packets (synthetic traffic) marked with a time stamp to calculate performance metrics.

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IP SLA measurements benefits

The results allow indirect assessment of the network, such as Service-Level Agreements (SLA) and QoS class definitions.

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IP SLA components

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

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 user-defined port for UDP, TCP, and Frame Relay packets generated by the IP SLA source.

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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

RTT= T4-T1Latency (one way)=T2-T1

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IP SLA scope

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.

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Highlighted features of IP SLA

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 PervasivenessTroubleshooting of network operation

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Network performance monitoring

Network performance monitoring— Measures delay, jitter, packet loss, packet ordering, and packet corruption in the network.

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SLA monitoring

SLA monitoring— Provides service-level monitoring and verification

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IP service network health assessment

IP service network health assessment— Verifies that the existing QoS settings are sufficient for new IP services.

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Edge-to-edge network availability monitoring

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).

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Voice over IP (VoIP) performance monitoring

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.

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Application-aware monitoring

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.

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Accuracy

Accuracy— Microsecond granularity for jitter delay measurements offers the required precision for business-critical applications.

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Flexible operations

Flexible operations— Offer various kinds of scheduling, alerting, and triggered measurements

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Pervasiveness

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.

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Troubleshooting of network operation

Troubleshooting of network operation— Provides consistent, reliable measurement that proactively identifies performance and connectivity problems.

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IP SLA collects the following performance metrics:

• 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)

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The various IP SLA operations can be classified as follows:

• 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

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Abbreviations

Meaning

IOS Internetwork Operating System

ICPIF Impairment/Calculated Planning Impairment Factor

ICMP Internet Control Message Protocol

MPLS Multiprotocol Label Switching

ATM Asynchronous Transfer Mode