Table Of Contents
IP SLAs—Analyzing IP Service Levels Using the ICMP Path Jitter Operation
Information About the IP SLAs ICMP Path Jitter Operation
How to Configure the IP SLAs ICMP Path Jitter Operation
Configuring and Scheduling a ICMP Path Jitter Operation
Configuring and Scheduling a Basic ICMP Path Jitter Operation
Configuring and Scheduling an ICMP Path Jitter Operation with Additional Parameters
Configuration Examples for the IP SLAs ICMP Path Jitter Operation
Configuring a Path Jitter Operation: Example
Feature Information for the IP SLAs ICMP Path Jitter Operation
IP SLAs—Analyzing IP Service Levels Using the ICMP Path Jitter Operation
First Published: August 14, 2006Last Updated: February 9, 2009This document describes how to use the Cisco IOS IP Service Level Agreements (SLAs) ICMP Path Jitter operation to monitor hop-by-hop jitter (inter-packet delay variance).
Cisco IOS IP SLAs is an embedded feature set in Cisco IOS software that allows you to analyze IP service levels for IP applications and services, to increase productivity, to lower operational costs, and to reduce occurrences of network congestion or outages. IP SLAs uses active traffic monitoring—the generation of traffic in a continuous, reliable, and predictable manner—for measuring network performance. The accuracy of measured data is enhanced by enabling the IP SLAs responder, available in Cisco routers, on the destination device. This document also demonstrates how the data gathered using the Path Jitter operations can be displayed and analyzed using the Cisco IOS CLI.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for the IP SLAs ICMP Path Jitter Operation" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
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Information About the IP SLAs ICMP Path Jitter Operation
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Prerequisites
Before configuring the IP SLAs ICMP Path Jitter operation you should be familiar with the "Cisco IOS IP SLAs Overview" chapter of the Cisco IOS IP SLAs Configuration Guide.
Information About the IP SLAs ICMP Path Jitter Operation
To perform the tasks required to monitor ICMP Path Jitter performance using IP SLA, you should understand the following concept:
ICMP Path Jitter Operation
The IP SLAs ICMP Path Jitter operation provides hop-by-hop jitter, packet loss, and delay measurement statistics in an IP network. The Path Jitter operation functions differently than the standard UDP Jitter operation, which provides total one-way data and total round-trip data.
The ICMP Path Jitter operation can be used a supplement to the standard UDP Jitter operation. For example, results from the UDP Jitter operation may indicate unexpected delays or high jitter values; the ICMP Path Jitter operation could then be used to troubleshoot the network path and determine if traffic is bottlenecking in a particular segment along the transmission path.
The operation first discovers the hop-by-hop IP route from the source to the destination using a traceroute utility, and then uses ICMP echoes to determine the response times, packet loss and approximate jitter values for each hop along the path. The jitter values obtained using the ICMP Path Jitter operation are approximates because ICMP only provides round trip times.
The ICMP Path Jitter operation is not supported in the RTTMON MIB; configuration and performance data can only be obtained using the CLI.
How to Configure the IP SLAs ICMP Path Jitter Operation
This section contains the following procedure:
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Configuring and Scheduling a ICMP Path Jitter Operation
The ICMP Path Jitter operation functions by tracing the IP path from a source device to a specified destination device, then sending N number of Echo probes to each hop along the traced path, with a time interval of T milliseconds between each Echo probe. The operation as a whole is repeated at a frequency of once every F seconds. The attributes are user-configurable, as shown here:
Perform one of the following procedures in this section, depending on whether you want to configure and schedule a basic ICMP Path Jitter operation or configure and schedule an ICMP Jitter Operation with additional parameters.
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Restrictions
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Note
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Configuring and Scheduling a Basic ICMP Path Jitter Operation
Perform the following steps to configure and schedule an ICMP Path Jitter operation using the general default characteristics for the operation. Start in privileged EXEC mode.
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DETAILED STEPS
Examples
In the following example, the targetOnly keyword is used to bypass the hop-by-hop measurements. With this version of the command, echo probes will be sent to the destination only.
Router(config)# ip sla 1Router(config-ip-sla)# path-jitter 172.17.246.20 num-packets 50 interval 30 targetOnlyWhat to Do Next
To view and interpret the results of an IP SLAs operation use the show ip sla statistics command. Checking the output for fields that correspond to criteria in your service level agreement will help you determine whether the service metrics are acceptable.
Configuring and Scheduling an ICMP Path Jitter Operation with Additional Parameters
Perform the following steps to configure and schedule an ICMP Path Jitter operation with additional parameters, using any of the optional commands needed. Start in Privileged Exec mode.
Restrictions
The IP SLAs Path Jitter operation does not support the IP SLAs History feature (statistics history buckets) because of the large data volume involved with Jitter operations. This means that the following IP SLAs commands are not supported for Jitter operations: history buckets-kept, history filter, history lives-kept, samples-of-history-kept, and show ip sla history.
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DETAILED STEPS
The following commands, available in Path Jitter configuration mode, do not apply to Path Jitter operations:
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Examples
In the following example, a Path Jitter operation is configured to run over a VPN using the VRF "red" to the CE at 10.3.30.130:
Router# configure terminalEnter configuration commands, one per line. End with the end command.Router(config)# ip sla 7Router(config-ip-sla)# path-jitter 10.3.30.130Router(config-ip-sla-pathJitter)# vrf redRouter(config-ip-sla-pathJitter)# exitRouter(config)# ip sla schedule 7 start-time now life foreverIn the following example, the targetOnly keyword is used to bypass the hop-by-hop measurements. With this version of the command, echo probes will be sent to the destination only.
Router(config)# ip sla 1router(config-ip-sla)# path-jitter 172.17.246.20 num-packets 50 interval 30 targetOnlyTroubleshooting Tips
Use the debug ip sla trace and debug ip sla error commands to help troubleshoot issues with an IP SLAs operation.
What to Do Next
To view and interpret the results of an IP SLAs operation use the show ip sla statistics command. Checking the output for fields that correspond to criteria in your service level agreement will help you determine whether the service metrics are acceptable.
Configuration Examples for the IP SLAs ICMP Path Jitter Operation
This section provides the following configuration example:
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Configuring a Path Jitter Operation: Example
The following example shows the output when the ICMP Path Jitter operation is configured:
Router# configure terminalRouter(config)# ip sla 15011Router(config-sla-monitor)# path-jitter 10.222.1.100 source-ip 10.222.3.100 num-packets 20Router(config-sla-monitor-pathJitter)# frequency 30Router(config-sla-monitor-pathJitter)# exitRouter(config)# ip sla schedule 15011 life forever start-time nowRouter(config)# exitRouter# show ip sla statistics 15011Round Trip Time (RTT) for Index 15011Latest RTT: 1 millisecondsLatest operation start time: 15:37:35.443 EDT Mon Jun 16 2008Latest operation return code: OK---- Path Jitter Statistics ----Hop IP 10.222.3.252:Round Trip Time milliseconds:Latest RTT: 1 msNumber of RTT: 20RTT Min/Avg/Max: 1/1/3 msJitter time milliseconds:Number of jitter: 2Jitter Min/Avg/Max: 2/2/2 msPacket Values:Packet Loss (Timeouts): 0Out of Sequence: 0Discarded Samples: 0Operation time to live: Forever
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Where to Go Next
For information about other types of IP SLAs operations and IP SLAs features, see the Cisco IOS IP SLAs Features Roadmap.
Additional References
The following sections provide references related to monitoring UDP echo operations using IP SLA.
Related Documents
Cisco IOS IP SLAs command-line interface enhancements
Cisco IOS IP Service Level Agreements Command Line Interface, Cisco white paper
Cisco IOS IP SLAs commands
Standards
No new or modified standards are supported by this feature, and support for existing standards has not been modified by features in this document.
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MIBs
RFCs
RFC 18891
RTP: A Transport Protocol for Real-Time Applications; see the section "Estimating the Interarrival Jitter"
1 Support for the listed RFC is not claimed; listed as a reference only.
Technical Assistance
Feature Information for the IP SLAs ICMP Path Jitter Operation
Table 1 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
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