Cisco Nexus 7000 Series NX-OS IP SLAs Configuration Guide, Release 6.x
Configuring IP SLAs UDP Jitter Operations
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Configuring IP SLAs UDP Jitter Operations

Configuring IP SLAs UDP Jitter Operations

This chapter 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 networks. This chapter also demonstrates how the data gathered using the UDP jitter operation can be displayed and analyzed using the Cisco software commands.

This chapter includes the following sections:

Information About the IP SLAs UDP Jitter Operation

The IP SLAs UDP jitter operation can 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 (such as 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 such as 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 that IP SLAs generate carry packet sending sequence, receiving sequence information, and sending and receiving time stamps from the source and the operational target. UDP jitter operations can measure 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 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 switch to a target switch, 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 as shown in the following table.

Table 1 UDP Jitter Operation Parameters

UDP Jitter Operation Parameter

Default

Command

Number of packets (N)

10 packets

udp-jitter command, numpackets 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

Prerequisites for Configuring IP SLAs UDP Jitter Operations

The prerequisites for configuring IP SLAs UDP jitter operations are as follows:

  • 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. Time synchronization is not required for the one-way jitter and packet loss measurements. If the time is not synchronized between the source and target devices, one-way jitter and packet loss data are returned, but values of “0” are 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.

Guidelines and Limitations for UDP Jitter Operations

Configuring CoPP for IP SLA Packets

When using IP SLA operations on a large scale, a specific CoPP configuration to allow the IP SLA packets to pass through might be needed. Since IP SLA uses user defined UDP ports, there is no way to allow all IP SLA packets to the control plane. However, you can specify each destination/source port that IP SLA can use.

For more information about the verified scalability of the number of IP SLA probes, see the Cisco Nexus 7000 Series NX-OS Verified Scalability Guide.

The following shows an example of a CoPP configuration that allows IP SLA packets to pass through. It assumes destination ports and source ports in the range of 6500-7000.

ip access-list copp-system-sla-allow
  10 remark ### ALLOW SLA control packets from 1.1.1.0/24
  20 permit udp 1.1.1.0/24 any eq 1967
  30 remark ### ALLOW SLA data packets from 1.1.1.0/24 using ports 6500-7000
  40 permit udp 1.1.1.0/24 any range 6500 7000
  statistics per-entry
ip access-list copp-system-sla-deny
  10 remark ### this is a catch-all to match any other traffic
  20 permit ip any any
  statistics  per-entry
class-map type control-plane match-any copp-system-class-management-allow
  match access-group name copp-system-sla-allow
class-map type control-plane match-any copp-system-class-management-deny
  match access-group name copp-system-sla-deny
policy-map type control-plane copp-system-policy
    class copp-system-class-management-allow
    set cos 7
    police cir 4500 kbps bc 250 ms conform transmit violate drop
    class copp-system-class-management-deny
    police cir 4500 kbps bc 250 ms conform drop violate drop
control-plane
  service-policy input copp-system-policy

Configuring and Scheduling a UDP Jitter Operation on the Source Device

This section describes how to configure and schedule a UDP jitter operation.

Configuring the IP SLAs Responder on the Destination Device

This section describes how to configure the responder on the destination device.


Note


A 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 are zero.


Procedure
 Command or ActionPurpose
Step 1enable


Example:
switch> enable
 

Enables privileged EXEC mode.

Enter your password if prompted.

 
Step 2configure terminal


Example:
switch# configure terminal
 

Enters global configuration mode.

 
Step 3Do one of the following:
  • ip sla responder
    Example: switch(config)# ip sla responder
  • ip sla responder udp-echo ipaddress ip-address port port
    Example: switch(config)# ip sla responder udp-echo
    ipaddress 172.29.139.132 port 5000
 

-

  • (Optional) Temporarily enables the responder functionality on a Cisco device in response to control messages from a source.

  • (Optional) Required only if protocol control is disabled on a source. Permanently enables the responder functionality on the specified IP addresses and port.

    Control is enabled by default.

 
Step 4exit


Example:
switch(config)# exit
 

(Optional) Exits global configuration mode and returns to privileged EXEC mode.

 

Configuring and Scheduling a Basic UDP Jitter Operation on the Source Device

This section describes how to configure and schedule a basic UDP jitter operation on the source device.


Tip


  • If the IP SLAs operation is not running and 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 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 debug ip sla sender trace and debug ip sla sender error commands to help troubleshoot issues with an IP SLAs operation.


Procedure
 Command or ActionPurpose
Step 1enable


Example:
switch# enable
 

Enables privileged EXEC mode.

Enter your password if prompted.

 
Step 2configure terminal


Example:
switch# configure terminal
 

Enters global configuration mode.

 
Step 3ip sla operation-number


Example:
switch(config)# ip sla 10
 

Begins configuration for an IP SLAs operation and enters IP SLA configuration mode.

 
Step 4udp-jitter {destination-ip-address | destination-hostname} destination-port [source-ip {ip-address | hostname}] [sourceport port-number] [control { enable| disable}] [num-packets number-of-packets] [interval interpacket-interval]


Example:
switch(config-ip-sla)# udp-jitter 172.29.139.134 5000
 

Configures the IP SLAs operation as a UDP jitter operation and enters UDP jitter configuration submode.

Use the control disable keyword combination only if you disable the IP SLAs control protocol on both the source and target switches.

 
Step 5frequency seconds


Example:
switch(config-ip-sla-jitter)# frequency 30
 

(Optional) Sets the rate at which a specified IP SLAs operation repeats.

 
Step 6exit


Example:
switch(config-ip-sla-jitter)# exit
 

Exits UDP jitter configuration submode and returns to global configuration mode.

 
Step 7ip sla schedule operation-number [life {forever| seconds}] [start-time {hh:mm[:ss] [month day | day month] | pending | now | after hh:mm:ss}] [ageout seconds] [recurring]


Example:
switch(config)# ip sla schedule 5 start-time now life forever 
 

Configures the scheduling parameters for an individual IP SLAs operation.

 
Step 8exit


Example:
switch(config)# exit
 

(Optional) Exits global configuration mode and returns to privileged EXEC mode.

 
Step 9show ip sla configuration [operation-number]


Example:
switch# show ip sla configuration 10
 

(Optional) Displays configuration values including all defaults for all IP SLAs operations or a specified operation.

 
What to Do Next

To add proactive threshold conditions and reactive triggering for generating traps or for starting another operation, see the "Configuring Proactive Threshold Monitoring" section.

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 helps you to determine whether the service metrics are acceptable.

Configuring and Scheduling a UDP Jitter Operation with Additional Characteristics

This section describes how to configure and schedule a UDP jitter operation with additional characteristics.

  • 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, which means that the following commands are not supported for UDP jitter operations: history buckets-kept, history filter, historylives-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-statisticshours global configuration change does 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.

Tip


  • If the IP SLAs operation is not running and 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 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 debug ip sla sender trace and debug ip sla sender error commands to help troubleshoot issues with an IP SLAs operation.

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 NX-OS software based devices. To enable the responder, perform the task in the “Configuring the IP SLAs Responder on the Destination Device” section.

Procedure
 Command or ActionPurpose
Step 1 enable


Example:
Switch> enable
 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2 configure terminal


Example:
Switch# configure terminal
 

Enters global configuration mode.

 
Step 3 ip sla operation-number


Example:
Switch(config)# ip sla 10 
 

Begins configuration for an IP SLAs operation and enters IP SLA configuration mode.

 
Step 4 udp-jitter {destination-ip-address | destination-hostname} destination-port [source-ip {ip-address | hostname}] [source-port port-number] [control {enable | disable}] [num-packetsnumber-of-packets] [interval interpacket-interval]


Example:
Switch(config-ip-sla)# udp-jitter 172.29.139.134 5000
 

Configures the IP SLAs operation as a UDP jitter operation and enters UDP jitter configuration submode.

  • Use the control disable keyword combination only if you disable the IP SLAs control protocol on both the source and target switches.
 
Step 5 history distributions-of-statistics-kept size


Example:
Switch(config-ip-sla-jitter)# history distributions-of-statistics-kept 5
 

(Optional) Sets the number of statistics distributions kept per hop during an IP SLAs operation.

 
Step 6 history enhanced [interval seconds] [buckets number-of-buckets]


Example:
Switch(config-ip-sla-jitter)# history enhanced interval 900 buckets 100
 

(Optional) Enables enhanced history gathering for an IP SLAs operation.

 
Step 7 frequency seconds


Example:
Switch(config-ip-sla-jitter)# frequency 30
 

(Optional) Sets the rate at which a specified IP SLAs operation repeats.

 
Step 8 history hours-of-statistics-kept hours


Example:
Switch(config-ip-sla-jitter)# history hours-of-statistics-kept 4
 

(Optional) Sets the number of hours for which statistics are maintained for an IP SLAs operation.

 
Step 9 owner owner-id


Example:
Switch(config-ip-sla-jitter)# owner admin 
 

(Optional) Configures the Simple Network Management Protocol (SNMP) owner of an IP SLAs operation.

 
Step 10 request-data-size bytes


Example:
Switch(config-ip-sla-jitter)# request-data-size 64 
 

(Optional) Sets the protocol data size in the payload of an IP SLAs operation's request packet.

 
Step 11 history statistics-distribution-interval milliseconds


Example:
Switch(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 tag text


Example:
Switch(config-ip-sla-jitter)# tag TelnetPollServer1 
 

(Optional) Creates a user-specified identifier for an IP SLAs operation.

 
Step 13 threshold milliseconds


Example:
Switch(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 timeout milliseconds


Example:
Switch(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 tos number


Example:
Switch(config-ip-sla-jitter)# tos 160 
 

(Optional) In an IPv4 network only, defines the ToS byte in the IPv4 header of an IP SLAs operation.

 
Step 16 verify-data


Example:
Switch(config-ip-sla-jitter)# verify-data
 

(Optional) Causes an IP SLAs operation to check each reply packet for data corruption.

 
Step 17 vrf vrf-name


Example:
Switch(config-ip-sla-jitter)# vrf vpn-A 
 

(Optional) Allows monitoring within Multiprotocol Label Switching (MPLS) Virtual Private Networks (VPNs) using IP SLAs operations.

 
Step 18 exit


Example:
Switch(config-ip-sla-jitter)# exit
 

Exits UDP jitter configuration submode and returns to global configuration mode.

 
Step 19 ip sla schedule operation-number [life {forever| seconds}] [start-time {hh:mm[:ss] [monthday | daymonth] | pending | now | afterhh:mm:ss}] [ageoutseconds] [recurring]


Example:
Switch(config)# ip sla schedule 5 start-time now life forever
 

Configures the scheduling parameters for an individual IP SLAs operation.

 
Step 20 exit


Example:
Switch(config)# exit
 

(Optional) Exits global configuration mode and returns to privileged EXEC mode.

 
Step 21 show ip sla configuration [operation-number]


Example:
Switch# show ip sla configuration 10
 

(Optional) Displays configuration values including all defaults for all IP SLAs operations or a specified operation.

 
What to Do Next

To add proactive threshold conditions and reactive triggering for generating traps or for starting another operation, see the Proactive Configuring Proactive Threshold Monitoring .

To view and interpret the results of IP SLAs operations, 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 Example for a UDP Jitter Operation

This example shows two operations that 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
 

On the target (destination) device:

ip sla responder

Feature History for UDP Jitter

This table includes only the updates for those releases that have resulted in additions or changes to the feature.

Table 2 Feature History for UDP Jitter
Feature Name Release Feature Information

UDP Jitter

6.1(1)

This feature was introduced.