This document describes how to configure an 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. This module also demonstrates how the data gathered using the UDP jitter operation can be displayed and analyzed using Cisco software commands.
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see
Bug Search Tool and 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 table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
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Prerequisites
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
Network Management
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
showipslaapplication command to verify that the operation type is supported on your software image.
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 and receiving sequence information, and sending and receiving time stamps from the source and the operational target. Based on this information, UDP jitter operations are capable of measuring the following:
Per-direction jitter (source to destination and destination to source)
Per-direction packet loss
Per-direction delay (one-way delay)
Round-trip delay (average round-trip time)
As the paths for sending and receiving data may be different (asymmetric), the per-direction data allows 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, T milliseconds apart, from a source device to a target device, 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 is user-configurable, so as to best simulate the IP service you are providing, or want to provide, as shown in the table below.
Table 1
UDP Jitter Operation Parameters
UDP Jitter Operation Parameter
Default
Configured Using:
Number of packets (N)
10 packets
udp-jittercommand,
num-packets option
Payload size per packet (S)
32 bytes
request-data-size command
Time between packets, in milliseconds (T)
20 ms
udp-jitter command,
interval option
Elapsed time before the operation repeats, in seconds (F)
60 seconds
frequency (IP SLA) command
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.
Configuring the IP SLAs Responder on the Destination Device
Note
A responder should not configure a permanent port for the same sender. If the responder configures a 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.
SUMMARY STEPS
1.enable
2.configureterminal
3.Do one of the following:
ipslaresponder
ipslaresponderudp-echoipaddressip-addressportport
4.exit
DETAILED STEPS
Command or Action
Purpose
Step 1
enable
Example:
Device> enable
Enables privileged EXEC mode.
Enter your password if prompted.
Step 2
configureterminal
Example:
Device# configure terminal
Enters global configuration mode.
Step 3
Do one of the following:
ipslaresponder
ipslaresponderudp-echoipaddressip-addressportport
Example:
Device(config)# ip sla responder
Example:
Device(config)# ip sla responder udp-echo ipaddress 172.29.139.132 port 5000
(Optional) Temporarily enables IP SLAs Responder functionality on a Cisco device in response to control messages from the source.
(Optional) Required only if protocol control is disabled on the source. Enables IP SLAs responder functionality on the specified IP address and port.
Protocol control is enabled by default.
Step 4
exit
Example:
Device(config)# exit
(Optional) Exits global configuration mode and returns to privileged EXEC mode.
Configuring and Scheduling a UDP Jitter Operation on the Source Device
Configures the IP SLAs operation as a UDP jitter operation and enters UDP jitter configuration submode.
Use the
controldisable keyword combination only if you disable the IP SLAs control protocol on both the source and destination devices.
Step 5
frequencyseconds
Example:
Device(config-ip-sla-jitter)# frequency 30
(Optional) Sets the rate at which a specified IP SLAs operation repeats.
Step 6
end
Example:
Device(config-ip-sla-jitter)# end
Returns to privileged EXEC mode.
Step 7
showipslaconfiguration [operation-number]
Example:
Device# show ip sla configuration 10
(Optional) Displays configuration values including all defaults for all IP SLAs operations or a specified operation.
Configuring a UDP Jitter Operation with Additional Characteristics
Note
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:
historybuckets-kept,
historyfilter,
historylives-kept,
samples-of-history-kept, and
showipslahistory.
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
historyhours-of-statisticshours 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. For information, see the CISCO-DATA-COLLECTION-MIB at
http://www.cisco.com/go/mibs ).
Before You Begin
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. To enable the Responder, perform the task in the "Configuring the IP SLAs Responder on the Destination Device" section.
Device(config-ip-sla-jitter)# history statistics-distribution-interval 10
(Optional) Sets the time interval for each statistics distribution kept for an IP SLAs operation.
Step 12
tagtext
Example:
Device(config-ip-sla-jitter)# tag TelnetPollServer1
(Optional) Creates a user-specified identifier for an IP SLAs operation.
Step 13
thresholdmilliseconds
Example:
Device(config-ip-sla-jitter)# threshold 10000
(Optional) Sets the upper threshold value for calculating network monitoring statistics created by an IP SLAs operation.
Step 14
timeoutmilliseconds
Example:
Device(config-ip-sla-jitter)# timeout 10000
(Optional) Sets the amount of time an IP SLAs operation waits for a response from its request packet.
Step 15
Do one of the following:
tosnumber
traffic-classnumber
Example:
Device(config-ip-sla-jitter)# tos 160
Example:
Device(config-ip-sla-jitter)# traffic-class 160
(Optional) In an IPv4 network only, defines the ToS byte in the IPv4 header of an IP SLAs operation.
or
(Optional) In an IPv6 network only, defines the traffic class byte in the IPv6 header for a supported IP SLAs operation.
Step 16
flow-labelnumber
Example:
Device(config-ip-sla-jitter)# flow-label 112233
(Optional) In an IPv6 network only, defines the flow label field in the IPv6 header for a supported IP SLAs operation.
Step 17
verify-data
Example:
Device(config-ip-sla-jitter)# verify-data
(Optional) Causes an IP SLAs operation to check each reply packet for data corruption.
Step 18
vrfvrf-name
Example:
Device(config-ip-sla-jitter)# vrf vpn-A
(Optional) Allows monitoring within Multiprotocol Label Switching (MPLS) Virtual Private Networks (VPNs) using IP SLAs operations.
Step 19
end
Example:
Device(config-ip-sla-jitter)# end
Returns to privileged EXEC mode.
Step 20
showipslaconfiguration [operation-number]
Example:
Device# show ip sla configuration 10
(Optional) Displays configuration values including all defaults for all IP SLAs operations or a specified operation.
Scheduling IP SLAs Operations
Note
All IP SLAs operations to be scheduled must be already configured.
The frequency of all operations scheduled in a multioperation group must be the same.
The list of one or more operation ID numbers to be added to a multioperation group is limited to a maximum of 125 characters in length, including commas (,).
If the IP SLAs operation is not running and not generating statistics, add the
verify-data command to the configuration of the operation (while configuring in IP SLA configuration mode) to enable data verification. When data verification is enabled, each operation response is checked for corruption. Use the
verify-data command with caution during normal operations because it generates unnecessary overhead.
Use the
debugipslatrace and
debugipslaerror commands to help troubleshoot issues with an IP SLAs operation.
What to Do Next
To add proactive threshold conditions and reactive triggering for generating traps (or for starting another operation) to an IP SLAs operation, see the "Configuring Proactive Threshold Monitoring" section.
operation)
To display and interpret the results of an IP SLAs operation, use the
showipslastatistics command. Check the output for fields that correspond to criteria in your service level agreement to determine whether the service metrics are acceptable.
Configuration Examples for IP SLAs UDP Jitter Operations
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 1
udp-jitter 20.0.10.3 65051 num-packets 20
request-data-size 160
tos 128
frequency 30
ip sla schedule 1 start-time after 00:05:00
ip sla 2
udp-jitter 20.0.10.3 65052 num-packets 20 interval 10
request-data-size 20
tos 64
frequency 30
ip sla schedule 2 start-time after 00:05:05
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Feature Information for IP SLAs UDP Jitter Operations
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 2
Feature Information for IP SLAs UDP Jitter Operations
Feature Name
Releases
Feature Information
IP SLAs UDP Jitter Operation
12.2(31)SB2
12.2(33)SRB1
12.2(33)SXH
12.3(14)T
15.0(1)S
Cisco IOS XE 3.1.0SG
The Cisco IOS IP SLAs User Datagram Protocol (UDP) jitter operation allows you to measure round-trip delay, one-way delay, one-way jitter, one-way packet loss, and connectivity in networks that carry UDP traffic.
Support was added for operability in IPv6 networks.
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