Table Of Contents
IP SLAs—Analyzing IP Service Levels Using the UDP Jitter Operation
Information About the IP SLAs UDP Jitter Operation
How to Configure the IP SLAs UDP Jitter Operation
Configuring the IP SLAs Responder on the Destination Device
Configuring and Scheduling a UDP Jitter Operation on the Source Device
Configuring and Scheduling a Basic UDP Jitter Operation on the Source Device
Configuring and Scheduling a UDP Jitter Operation with Additional Characteristics
Configuration Examples for the IP SLAs UDP Jitter Operation
Configuring a UDP Jitter Operation: Example
Feature Information for the IP SLAs UDP Jitter Operation
IP SLAs—Analyzing IP Service Levels Using the UDP Jitter Operation
First Published: August 14, 2006Last Updated: March 10, 2009This document describes how to use the Cisco IOS IP Service Level Agreements (SLAs) UDP jitter operation to analyze round-trip delay, one-way delay, one-way jitter, one-way packet loss, and connectivity in networks that carry UDP traffic in IPv4 or IPv6 networks.
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 module also demonstrates how the data gathered using the UDP jitter operation can be displayed and analyzed using the Cisco IOS command-line interface (CLI).
Note
A VoIP-specific implementation of the UDP jitter operation is available to measure performance by simulating specific voice codecs and returned voice quality scores. For more information, see the "IP SLAs—Analyzing VoIP Service Levels Using the UDP Jitter Operation" chapter of the Cisco IOS IP SLAs Configuration Guide.
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 UDP 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.
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Information About the IP SLAs UDP Jitter Operation
To perform the tasks required to verify service levels using the IP SLAs UDP jitter operation, you should understand the following concept:
IP SLAs UDP Jitter Operation
The IP SLAs UDP jitter operation was primarily designed to diagnose network suitability for real-time traffic applications such as voice over IP (VoIP), video over IP, or real-time conferencing.
Jitter means inter-packet delay variance. When multiple packets are sent consecutively from source to destination, for example, 10 ms apart, and if the network is behaving ideally, the destination should be receiving them 10 ms apart. But if there are delays in the network (like queuing, arriving through alternate routes, and so on) the arrival delay between packets might be greater than or less than 10 ms. Using this example, a positive jitter value indicates that the packets arrived greater than 10 ms apart. If the packets arrive 12 ms apart, then positive jitter is 2 ms; if the packets arrive 8 ms apart, then negative jitter is 2 ms. For delay-sensitive networks like VoIP, positive jitter values are undesirable, and a jitter value of 0 is ideal.
However, the IP SLAs UDP jitter operation does more than just monitor jitter. As the UDP jitter operation includes the data returned by the IP SLAs UDP operation, the UDP jitter operation can be used as a multipurpose data gathering operation. The packets IP SLAs generates carry packet sending sequence and receiving sequence information, and sending and receiving time stamps from the source and the operational target. Based on these, UDP jitter operations are capable of measuring the following:
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As the paths for the sending and receiving of data may be different (asymmetric), the per-direction data allow you to more readily identify where congestion or other problems are occurring in the network.
The UDP jitter operation functions by generating synthetic (simulated) UDP traffic. The UDP jitter operation sends N UDP packets, each of size S, sent T milliseconds apart, from a source router to a target router, at a given frequency of F. By default, ten packet-frames (N), each with a payload size of 10 bytes (S) are generated every 10 ms (T), and the operation is repeated every 60 seconds (F). Each of these parameters are user-configurable, so as to best simulate the IP service you are providing, or want to provide.
How to Configure the IP SLAs UDP Jitter Operation
This section contains the following procedures:
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Configuring the IP SLAs Responder on the Destination Device
Before configuring a UDP jitter operation on the source device, the IP SLAs Responder must be enabled on the target device (the operational target). The IP SLAs Responder is available only on Cisco IOS software-based devices.
Perform this task to enable the IP SLAs Responder.
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DETAILED STEPS
Configuring and Scheduling a UDP Jitter Operation on the Source Device
Perform one of the following tasks in this section, depending on whether you want to configure a basic UDP jitter operation or configure a UDP jitter operation with additional characteristics:
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The IP SLAs operations function by generating synthetic (simulated) network traffic. A single IP SLAs operation (for example, IP SLAs operation 10) will repeat at a given frequency for the lifetime of the operation.
A single UDP jitter operation consists of N UDP packets, each of size S, sent T milliseconds apart, from a source router to a target router, at a given frequency of F. By default, ten packets (N), each with an RTP payload size of 32 bytes (S), are generated every 20 ms (T), and the operation is repeated every 60 seconds (F). Each of these parameters are user-configurable, as shown in Table 1.
Prerequisites
Use of the UDP jitter operation requires that the IP SLAs Responder be enabled on the target Cisco device. To enable the Responder, perform the task in the "Configuring the IP SLAs Responder on the Destination Device" section.
Time synchronization, such as that provided by NTP, is required between the source and the target device in order to provide accurate one-way delay (latency) measurements. To configure NTP on the source and target devices, perform the tasks in the "Performing Basic System Management" chapter of the Cisco IOS Network Manageent Configuration Guide. Time synchronization is not required for the one-way jitter and packet loss measurements, however. If the time is not synchronized between the source and target devices, one-way jitter and packet loss data will be returned, but values of "0" will be returned for the one-way delay measurements provided by the UDP jitter operation.
Before configuring any IP SLAs application, you can use the show ip sla application command to verify that the operation type is supported on your software image.
Restrictions
The responder should not configure a permanent port for the same sender. If the responder configures the permanent port for the same sender, even if the packets are successfully sent (no timeout or packet loss issues), the jitter values will be zero.
Configuring and Scheduling a Basic UDP Jitter Operation on the Source Device
Perform this task to configure and schedule a basic UDP jitter operation.
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DETAILED STEPS
Troubleshooting Tips
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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.
If you with configure and schedule a UDP jitter operation with additional characteristics, perform the task in the "Configuring and Scheduling a UDP Jitter Operation with Additional Characteristics" section.
Configuring and Scheduling a UDP Jitter Operation with Additional Characteristics
Perform this task to configure and schedule a UDP jitter operation with additional parameters.
Restrictions
The IP SLAs UDP jitter operation does not support the IP SLAs History feature (statistics history buckets) because of the large data volume involved with UDP jitter operations. This means that the following commands are not supported for UDP jitter operations: history buckets-kept, history filter, history lives-kept, samples-of-history-kept, and show ip sla history.
The MIB used by IP SLAs (CISCO-RTTMON-MIB) limits the hours-of-statistics kept for the UDP jitter operation to two hours. Configuring a larger value using the history hours-of-statistics hours global configuration change will not increase the value beyond two hours.
However, the Data Collection MIB can be used to collect historical data for the operation. See the CISCO-DATA-COLLECTION-MIB (available from http://www.cisco.com/go/mibs).
Note
The flow-label command defines the value in the flow label field in the IPv6 header for a supported IP SLAs operation and is valid only in IPv6 networks.
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DETAILED STEPS
Troubleshooting Tips
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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 UDP Jitter Operation
This section provides the following configuration example:
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Configuring a UDP Jitter Operation: Example
In the following example, two operations are configured as UDP jitter operations, with operation 2 starting five seconds after the first operation. Both operations will run indefinitely.
ip sla 1udp-jitter 20.0.10.3 65051 num-packets 20request-data-size 160tos 128frequency 30ip sla schedule 1 start-time after 00:05:00ip sla 2udp-jitter 20.0.10.3 65052 num-packets 20 interval 10request-data-size 20tos 64frequency 30ip sla schedule 2 start-time after 00:05:05On the target (destination) device:
ip sla responderWhere 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 configuring IP SLAs UDP Jitter operations.
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
CISCO-RTTMON-MIB
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
RFCs
Technical Assistance
Feature Information for the IP SLAs UDP Jitter Operation
Table 2 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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