IP SLAs Configuration Guide, Cisco IOS XE Release 3S
IP SLAs QFP Time Stamping
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IP SLAs QFP Time Stamping

IP SLAs QFP Time Stamping

This module describes how to configure the IP SLA QFP Time Stamping feature for IP Service Level Agreements (SLAs) UDP jitter operations. This new probe and responder structure enables more accurate network performance measurements.

Finding Feature Information

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 www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Prerequisites for IP SLAs QFP Time Stamping

  • The devices on which the responder and probe are to configured must both be running Cisco software images that support QFP time stamping in order for the IP SLAs QFP Time Stamping feature to work.
  • 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.
  • 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 for IP SLA QFP Time Stamping

  • After rebooting the sender or responder devices, the Forward Processor (FP) and Route Processor (RP) times can be inaccurate until SNTP synchronizes the FP clock to the RP clock. To avoid running an operation before the device FP and RP times are stable, wait several minutes after a reboot before starting the UDP jitter operation.
  • The one way delay value reported by an IP SLAs UDP jitter operation are dependent on the NTP synchronization level. Even if the device is synchronized, if the NTP offset values on the device are large, then one way values can be inaccurate. In cases where offset value becomes too large, the one way value may not be reported. Also, the NTP offset value on the device can fluctuate and these changes will be reflected in one way values reported.
  • If you configure the optimized time stamp location on the source device and the device on which the targeted IP SLAs Responder is configured does not support the optimized time stamp location, the IP SLAs operation will fail.

Information About IP SLAs QFP Time Stamping

IP SLAs UDP Jitter Operation

The IP Service Level Agreements (SLAs) UDP jitter operation diagnoses network suitability for real-time traffic applications such as VoIP, video over IP, or real-time conferencing.

Jitter means inter-packet delay variance. When multiple packets are sent consecutively from a source to a destination, for example, 10 ms apart, and if the network is behaving ideally, the destination should receive the packets 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 packets arrived greater than 10 ms apart. If packets arrive 12 ms apart, then positive jitter is 2 ms; if packets arrive 8 ms apart, 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 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 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 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. Asymmetric probes support custom-defined packet sizes per direction with which different packet sizes can be sent in request packets (from the source device to the destination device) and in response packets (from the destination device to the source device).

The UDP jitter operation sends N number of UDP packets, each of size S, T milliseconds apart, from a source device to a destination device, at a given frequency of F. In response, UDP packets of size P is sent from the destination device to the source device. 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 that you provide, as shown in the table below.

Table 1 UDP Jitter Operation Parameters

UDP Jitter Operation Parameter

Default

Configuration Commands

Number of packets (N)

10 packets

udp-jitter num-packets

Payload size per request packet (S)

10 bytes

request-data-size

Payload size per response packet (P)

The default response data size varies depending on the type of IP SLAs operation configured.

Note    If the response-data-size command is not configured, then the response data size value is the same as the request data size value.

response-data-size

Time between packets, in milliseconds (T)

10 ms

udp-jitter interval

Elapsed time before the operation repeats, in seconds (F)

60 seconds

frequency (IP SLA)

The IP SLAs operations function by generating synthetic (simulated) network traffic. A single IP SLAs operation (for example, IP SLAs operation 10) repeats at a given frequency for the lifetime of the operation.

QFP Time Stamping

IP SLAs UDP jitter is the most widely-used IP SLAs operation for measuring metrics such as round-trip time, one-way delay, jitter, and packet loss. The accuracy of measurements depends on the location where the time stamps are taken while the packet moves from the sender to responder, and back.

Typically, time stamps for IP SLAs operations are taken in the IP SLAs process at the Route Processor (RP). This time-stamp location results in inaccurate and inconsistent measurements because the time stamps are subject to scheduling delays experienced at the RP. QFP time stamping moves the location of the time stamping from the RP to the Cisco Packet Processor (CPP).

However, to measure the one-way delay, the clocks on the source and target devices must be synchronized. Because device CPP clocks cannot be synchronized directly to an external clock source, the RP clocks are synchronized with an external clock source and SNTP is used to synchronize RP and Forwarding Processor (FP) clocks. The accuracy of the RP-FP synchronization is poor. To address this issue, the enhanced UDP jitter probe in the QFP Time Stamping feature stores both the RP and CPP time stamps. RTT and jitter calculations utilize the CPP time stamps, and one-way calculations continue to be based on RP time stamping. Therefore, 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. One-way latency values are computed using RP time stamps are corrected by applying estimated-correction algorithms based on CPP time stamps.

QFP time stamping includes an enhanced UDP probe and enhanced responder. The devices on which the UDP probe and IP SLAs responder are configured must both be running Cisco software images that support QFP time stamping and the optimized time stamp location (for more accurate RTT measurements). If the UDP jitter operation is targeted to an responder on a device that does not support the optimized time stamp location, the IP SLAs probe will fail.

How to Configure IP SLAs QFP Time Stamping

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.    configure terminal

    3.    Do one of the following:

    • ip sla responder
    • ip sla responder udp-echo ipaddress ip-address port port

    4.    exit


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Device> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2 configure terminal


    Example:
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3Do one of the following:
    • ip sla responder
    • ip sla responder udp-echo ipaddress ip-address port port


    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 a Source Device

    Configuring a Basic UDP Jitter Operation with QFP Time Stamping

    Perform this task to configure a UDP jitter probe with QFP time stamping on the source device.

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    ip sla operation-number

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

      5.    frequency seconds

      6.    precision microseconds

      7.    optimize timestamp

      8.    end

      9.    show ip sla configuration [operation-number]


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Device> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.
       
      Step 2 configure terminal


      Example:
      Device# configure terminal
       

      Enters global configuration mode.

       
      Step 3 ip sla operation-number


      Example:
      Device(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-packets number-of-packets] [interval interpacket-interval]


      Example:
      Device(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 destination devices.
       
      Step 5 frequency seconds


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

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

       
      Step 6 precision microseconds


      Example:
      Device(config-ip-sla-jitter)# precision microseconds
       

      Enables QFP time stamping.

       
      Step 7 optimize timestamp


      Example:
      Device(config-ip-sla-jitter)# optimize timestamp
       

      (Optional) For Cisco ASR 1000 Series routers only. Enables CPP ticks which is more accurate than cpp UNIX time.

      Note   

      If the Responder does not support cpp ticks, the IP SLAs operation will fail.

       
      Step 8 end


      Example:
      Device(config-ip-sla-jitter)# end
       

      Returns to privileged EXEC mode.

       
      Step 9 show ip sla configuration [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 UPD Jitter Operation with QFP Time Stamping and 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: 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. For information, see the CISCO-DATA-COLLECTION-MIB at http:/​/​www.cisco.com/​go/​mibs.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    ip sla operation-number

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

        5.    precision microseconds

        6.    optimize timestamp

        7.    history distributions-of-statistics-kept size

        8.    history enhanced [interval seconds] [buckets number-of-buckets]

        9.    frequency seconds

        10.    history hours-of-statistics-kept hours

        11.    owner owner-id

        12.    request-data-size bytes

        13.    history statistics-distribution-interval milliseconds

        14.    tag text

        15.    threshold milliseconds

        16.    timeout milliseconds

        17.    Do one of the following:

        • tos number
        • traffic-class number

        18.    flow-label number

        19.    verify-data

        20.    vrf vrf-name

        21.    end

        22.    show ip sla configuration [operation-number]


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Device> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.
         
        Step 2 configure terminal


        Example:
        Device# configure terminal
         

        Enters global configuration mode.

         
        Step 3 ip sla operation-number


        Example:
        Device(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-packets number-of-packets] [interval interpacket-interval]


        Example:
        Device(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 devices.
         
        Step 5 precision microseconds


        Example:
        Device(config-ip-sla-jitter)# precision microseconds
         

        Enables QFP time stamping.

         
        Step 6 optimize timestamp


        Example:
        Device(config-ip-sla-jitter)# optimize timestamp
         

        (Optional) For Cisco ASR 1000 Series routers only, optimizes the time stamp location for IP SLAs.

        Note   

        If the device on which the targeted IP SLAs Responder is configured does not also support the optimized time stamp location, the IP SLAs operation will fail.

         
        Step 7 history distributions-of-statistics-kept size


        Example:
        Device(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 8 history enhanced [interval seconds] [buckets number-of-buckets]


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

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

         
        Step 9 frequency seconds


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

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

         
        Step 10 history hours-of-statistics-kept hours


        Example:
        Device(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 11 owner owner-id


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

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

         
        Step 12 request-data-size bytes


        Example:
        Device(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 13 history statistics-distribution-interval milliseconds


        Example:
        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 14 tag text


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

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

         
        Step 15 threshold milliseconds


        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 16 timeout milliseconds


        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 17Do one of the following:
        • tos number
        • traffic-class number


        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 18 flow-label number


        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 19 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 20 vrf vrf-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 21 end


        Example:
        Device(config-ip-sla-jitter)# end
         

        Returns to privileged EXEC mode.

         
        Step 22 show ip sla configuration [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

        Before You Begin
        • All IP Service Level Agreements (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 must be limited to a maximum of 125 characters in length, including commas (,).
        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    Enter one of the following commands:

          • ip 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]
          • ip sla group schedule group-operation-number operation-id-numbers {schedule-period schedule-period-range | schedule-together} [ageout seconds] [frequency group-operation-frequency] [life {forever | seconds}] [start-time {hh:mm [:ss] [month day | day month] | pending | now | after hh:mm [:ss]}]

          4.    end

          5.    show ip sla group schedule

          6.    show ip sla configuration


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example:
          Device> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.
           
          Step 2 configure terminal


          Example:
          Device# configure terminal
           

          Enters global configuration mode.

           
          Step 3 Enter one of the following commands:
          • ip 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]
          • ip sla group schedule group-operation-number operation-id-numbers {schedule-period schedule-period-range | schedule-together} [ageout seconds] [frequency group-operation-frequency] [life {forever | seconds}] [start-time {hh:mm [:ss] [month day | day month] | pending | now | after hh:mm [:ss]}]


          Example:
          Device(config)# ip sla schedule 10 life forever start-time now
          Device(config)# ip sla schedule 10 schedule-period frequency
          Device(config)# ip sla group schedule 1 3,4,6-9 life forever start-time now 
          Device(config)# ip sla schedule 1 3,4,6-9 schedule-period 50 frequency range 80-100
           
          • Configures the scheduling parameters for an individual IP SLAs operation.
          • Specifies an IP SLAs operation group number and the range of operation numbers for a multioperation scheduler.
           
          Step 4 end


          Example:
          Device(config)# end
           

          Exits global configuration mode and returns to privileged EXEC mode.

           
          Step 5 show ip sla group schedule


          Example:
          Device# show ip sla group schedule
           

          (Optional) Displays IP SLAs group schedule details.

           
          Step 6 show ip sla configuration


          Example:
          Device# show ip sla configuration
           

          (Optional) Displays IP SLAs configuration details.

           

          Troubleshooting Tips

          • 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 debug ip sla trace and debug ip sla error 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 show ip sla statistics 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 QFP Time Stamping

          Example: Configuring a UDP Operation with QFP Time Stamping

          In the following example, two operations are configured as enhanced UDP jitter operations with QFP time stamping and the optimized time stamp location. Operation 2 starts five seconds after the first operation.


          Note


          The device on which ther esponder is configured must (also) support the optimized time stamp location or the probe will fail.


          On the source (sender) device:

          ip sla 1
           udp-jitter 192.0.2.134 5000 num-packets 20
           request-data-size 160
           tos 128
           frequency 30
           precision microseconds    !enables QFP time stamping
           optimize timestamp        !configures optimized time stamp location
          ip sla schedule 1 start-time after 00:05:00
          ip sla 2
           udp-jitter 192.0.2.134 65052 num-packets 20 interval 10
           request-data-size 20
           tos 64
           frequency 30
           precision microseconds
           optimize timestamp
          ip sla schedule 2 start-time after 00:05:05
           

          On the destination (responder) device:

          ip sla responder

          Additional References

          Related Documents

          Related Topic

          Document Title

          Cisco IOS commands

          Cisco IOS Master Command List, All Releases

          Cisco IOS IP SLAs commands

          Cisco IOS IP SLAs Command Reference

          MIBs

          MIBs

          MIBs Link

          • CISCO-RTTMON-MIB
          • IPV6-FLOW-LABEL-MIB

          To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

          http:/​/​www.cisco.com/​go/​mibs

          Technical Assistance

          Description

          Link

          The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

          http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

          Feature Information for IP SLAs QFP Time Stamping

          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 QFP Time Stamping

          Feature Name

          Releases

          Feature Information

          IP SLAs QFP Time Stamping

          Cisco IOS XE Release 3.7S

          This feature enables IP SLAs Cisco Packet Processor (CPP) time stamping to improve the accuracy of IP SLAs UDP jitter operations.

          For Cisco ASR 1000 Series routers only, this feature also supports optimizing the time stamp location for more accurate RTT measurements.

          The following commands were introduced or modified: optimize timestamp, precision microseconds, show ip sla configuration.