IP Addressing Configuration Guide, Cisco IOS XE 17.x
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This document describes how to schedule multiple operations at once using the IP Service Level Agreements (SLAs) Multioperations
Scheduler feature.
Restrictions for
an IP SLAs Multioperation Scheduler
Do not use the
no ip sla group
schedule and
ip sla group
schedule commands consecutively in a configuration file and copy
it into the running configuration. This causes some of the Service Level
Agreement (SLA) probes to go down.
Prerequisites for an IP SLAs Multioperation Scheduler
Configure the IP SLAs operations to be included in a group before scheduling the group.
Determine the IP SLAs operations you want to schedule as a single group.
Identify the network traffic type and the location of your network management station.
Identify the topology and the types of devices in your network.
Decide on the frequency of testing for each operation.
Information About an IP SLAs Multioperation Scheduler
IP SLAs Multioperations Scheduler
Normal scheduling of IP SLAs operations allows you to schedule one operation at a time. If you have large networks with thousands
of IP SLAs operations to monitor network performance, normal scheduling (scheduling each operation individually) will be inefficient
and time-consuming.
Multiple operations scheduling allows you to schedule multiple IP SLAs operations using a single command through the command
line interface (CLI) or the CISCO-RTTMON-MIB. This feature allows you to control the amount of IP SLAs monitoring traffic
by scheduling the operations to run at evenly distributed times. You must specify the operation ID numbers to be scheduled
and the time range over which all the IP SLAs operations should start. This feature automatically distributes the IP SLAs
operations at equal intervals over a specified time frame. The spacing between the operations (start interval) is calculated
and the operations are started. This distribution of IP SLAs operations helps minimize the CPU utilization and thereby enhances
the scalability of the network.
The IP SLAs multiple operations scheduling functionality allows you to schedule multiple IP SLAs operations as a group, using
the following configuration parameters:
Group operation number--Group configuration or group schedule number of the IP SLAs operation to be scheduled.
Operation ID numbers--A list of IP SLAs operation ID numbers in the scheduled operation group.
Schedule period--Amount of time for which the IP SLAs operation group is scheduled.
Ageout--Amount of time to keep the operation in memory when it is not actively collecting information. By default, the operation
remains in memory indefinitely.
Frequency--Amount of time after which each IP SLAs operation is restarted. When the frequency option is specified, it overwrites
the operation frequency of all operations belonging to the group. Note that when the frequency option is not specified, the
frequency for each operation is set to the value of the schedule period.
Life--Amount of time the operation actively collects information. The operation can be configured to run indefinitely. By
default, the lifetime of an operation is one hour.
Start time--Time when the operation starts collecting information. You can specify an operation to start immediately or at
an absolute start time using hours, minutes, seconds, day, and month.
The IP SLAs multiple operations scheduling functionality schedules the maximum number of operations possible without terminating.
However, this functionality skips those IP SLAs operations that are already running or those that are not configured and hence
do not exist. The total number of operations will be calculated based on the number of operations specified in the command,
irrespective of the number of operations that are missing or already running. The IP SLAs multiple operations scheduling functionality
displays a message showing the number of active and missing operations. However, these messages are displayed only if you
schedule operations that are not configured or are already running.
A main benefit for scheduling multiple IP SLAs operations is that the load on the network is reduced by distributing the operations
equally over a scheduled period. This distribution helps you to achieve more consistent monitoring coverage. To illustrate
this scenario, consider configuring 60 operations to start during the same 1-second interval over a 60-second schedule period.
If a network failure occurs 30 seconds after all 60 operations have started and the network is restored before the operations
are due to start again (in another 30 seconds), then this failure would never be detected by any of the 60 operations. However,
if the 60 operations are distributed equally at 1-second intervals over a 60-second schedule period, then some of the operations
would detect the network failure. Conversely, if a network failure occurs when all 60 operations are active, then all 60 operations
would fail, indicating that the failure is possibly more severe than it really is.
Operations of the same type and same frequency should be used for IP SLAs multiple operations scheduling. If you do not specify
a frequency, the default frequency will be the same as that of the schedule period. The schedule period is the period of time
in which all the specified operations should run.
The following sections focus on the interaction of the schedule period and frequency values, additional values, such as start
time and lifetime values, are not included in the illustrations.
Default Behavior of IP SLAs Multiple Operations Scheduling
The IP SLAs Multiple Operations Scheduling feature allows you to schedule multiple IP SLAs operations as a group.
The figure below illustrates the scheduling of operation group 1 that includes operation 1 to operation 10. Operation group
1 has a schedule period of 20 seconds, which means that all operations in the group will be started at equal intervals within
a 20-second period. By default, the frequency is set to the same value as the configured schedule period. As shown in the
figure below, configuring the frequencyis optional because 20 is the default.
Figure 1. Schedule Period Equals Frequency--Default Behavior
In this example, the first operation (operation 1) in operation group 1 will start at 0 seconds. All 10 operations in operation
group 1 (operation 1 to operation 10) must be started in the schedule period of 20 seconds. The start time of each IP SLAs
operation is evenly distributed over the schedule period by dividing the schedule period by the number of operations (20 seconds
divided by 10 operations). Therefore, each operation will start 2 seconds after the previous operation.
The frequency is the period of time that passes before the operation group is started again (repeated). If the frequency
is not specified, the frequency is set to the value of the schedule period. In the example shown above, operation group 1
will start again every 20 seconds. This configuration provides optimal division (spacing) of operations over the specified
schedule period.
IP SLAs Multiple Operations Scheduling with Scheduling Period Less Than Frequency
The frequency value is the amount of time that passes before the schedule group is restarted, if the schedule period is less
than the frequency, there will be a period of time in which no operations are started.
The figure below illustrates the scheduling of operation 1 to operation 10 within operation group 2. Operation group 2 has
a schedule period of 20 seconds and a frequency of 30 seconds.
Figure 2. Schedule Period Is Less Than Frequency
In this example, the first operation (operation 1) in operation group 2 will start at 0 seconds. All 10 operations in operation
group 2 (operation 1 to operation 10) must be started in the schedule period of 20 seconds. The start time of each IP SLAs
operation is evenly distributed over the schedule period by dividing the schedule period by the number of operations (20 seconds
divided by 10 operations). Therefore, each operation will start 2 seconds after the previous operation.
In the first iteration of operation group 2, operation 1 starts at 0 seconds, and the last operation (operation 10) starts
at 18 seconds. However, because the group frequency has been configured to 30 seconds each operation in the operation group
is restarted every 30 seconds. So, after 18 seconds, there is a gap of 10 seconds as no operations are started in the time
from 19 seconds to 29 seconds. Hence, at 30 seconds, the second iteration of operation group 2 starts. As all ten operations
in the operation group 2 must start at an evenly distributed interval in the configured schedule period of 20 seconds, the
last operation (operation 10) in the operation group 2 will always start 18 seconds after the first operation (operation 1).
As illustrated in the figure above, the following events occur:
At 0 seconds, the first operation (operation 1) in operation group 2 is started.
At 18 seconds, the last operation (operation 10) in operation group 2 is started. This means that the first iteration (schedule
period) of operation group 1 ends here.
From 19 to 29 seconds, no operations are started.
At 30 seconds, the first operation (operation 1) in operation group 2 is started again. The second iteration of operation
group 2 starts here.
At 48 seconds (18 seconds after the second iteration started) the last operation (operation 10) in operation group 2 is started,
and the second iteration of operation group 2 ends.
At 60 seconds, the third iteration of operation group 2 starts.
This process continues until the lifetime of operation group 2 ends. The lifetime value is configurable. The default lifetime
for an operation group is forever.
Multiple Operations Scheduling When the Number of IP SLAs Operations Are Greater Than the Schedule Period
The minimum time interval between the start of IP SLAs operations in a group operation is 1 second. Therefore, if the number
of operations to be multiple scheduled is greater than the schedule period, the IP SLAs multiple operations scheduling functionality
will schedule more than one operation to start within the same 1-second interval. If the number of operations getting scheduled
does not equally divide into 1-second intervals, then the operations are equally divided at the start of the schedule period
with the remaining operations to start at the last 1-second interval.
The figure below illustrates the scheduling of operation 1 to operation 10 within operation group 3. Operation group 3 has
a schedule period of 5 seconds and a frequency of 10 seconds.
Figure 3. Number of IP SLAs Operations Is Greater Than the Schedule Period--Even Distribution
In this example, when dividing the schedule period by the number of operations (5 seconds divided by 10 operations, which
equals one operation every 0.5 seconds) the start time of each IP SLAs operation is less than 1 second. Since the minimum
time interval between the start of IP SLAs operations in a group operation is 1 second, the IP SLAs multiple operations scheduling
functionality instead calculates how many operations it should start in each 1-second interval by dividing the number of operations
by the schedule period (10 operations divided by 5 seconds). Therefore, as shown in the figure above, two operations will
be started every 1 second.
As the frequency is set to 10 in this example, each iteration of operation group 3 will start 10 seconds after the start
of the previous iteration. However, this distribution is not optimal as there is a gap of 5 seconds (frequency minus schedule
period) between the cycles.
If the number of operations getting scheduled does not equally divide into 1-second intervals, then the operations are equally
divided at the start of the schedule period with the remaining operations to start at the last 1-second interval.
The figure below illustrates the scheduling of operation 1 to operation 10 within operation group 4. Operation group 4 has
a schedule period of 4 seconds and a frequency of 5 seconds.
Figure 4. Number of IP SLAs Operations Is Greater Than the Schedule Period--Uneven Distribution
In this example, the IP SLAs multiple operations scheduling functionality calculates how many operations it should start
in each 1-second interval by dividing the number of operations by the schedule period (10 operations divided by 4 seconds,
which equals 2.5 operations every 1 second). Since the number of operations does not equally divide into 1-second intervals,
this number will be rounded off to the next whole number (see the figure above) with the remaining operations to start at
the last 1-second interval.
IP SLAs Multiple Operations Scheduling with Scheduling Period Greater Than Frequency
The value of frequency is the amount of time that passes before the schedule group is restarted. If the schedule period is
greater than the frequency, there will be a period of time in which the operations in one iteration of an operation group
overlap with the operations of the following iteration.
The figure below illustrates the scheduling of operation 1 to operation 10 within operation group 5. Operation group 5 has
a schedule period of 20 seconds and a frequency of 10 seconds.
Figure 5. IP SLAs Group Scheduling with Schedule Period Greater Than Frequency
In this example, the first operation (operation 1) in operation group 5 will start at 0 seconds. All 10 operations in operation
group 5 (operation 1 to operation 10) must be started in the schedule period of 20 seconds. The start time of each IP SLAs
operation is evenly distributed over the schedule period by dividing the schedule period by the number of operations (20 seconds
divided by 10 operations). Therefore, each operation will start 2 seconds after the previous operation.
In the first iteration of operation group 5, operation 1 starts at 0 seconds, and operation 10, the last operation in the
operation group, starts at 18 seconds. Because the operation group is configured to restart every 10 seconds (frequency10), the second iteration of operation group 5 starts again at 10 seconds, before the first iteration is completed. Therefore,
an overlap of operations 6 to 10 of the first iteration occurs with operations 1 to 5 of the second iteration during the time
period of 10 to 18 seconds (see the figure above). Similarly, there is an overlap of operations 6 to 10 of the second iteration
with operations 1 to 5 of the third iteration during the time period of 20 to 28 seconds.
In this example, the start time of operation 1 and operation 6 need not be at exactly the same time, but will be within the
same 2-second interval.
The configuration described in this section is not recommended as you can configure multiple operations to start within the
same 1-second interval by configuring the number of operations greater than the schedule period. For information, see the
"Multiple Operations Scheduling When the Number of IP SLAs Operations Are Greater Than the Schedule Period" section.
IP SLAs Random Scheduler
The IP SLAs Random Scheduler feature is an enhancement to the existing IP SLAs Multioperation Scheduling feature. The IP SLAs
Multioperation Scheduling feature provides the capability to easily schedule multiple IP SLAs operations to begin at intervals
equally distributed over a specified duration of time and to restart at a specified frequency. With the IP SLAs Random Scheduler
feature, you can now schedule multiple IP SLAs operations to begin at random intervals uniformly distributed over a specified
duration of time and to restart at uniformly distributed random frequencies within a specified frequency range. Random scheduling
improves the statistical metrics for assessing network performance.
Note
The IP SLAs Random Scheduler feature is not in compliance with RFC2330 because it does not account for inter-packet randomness.
The IP SLAs random scheduler option is disabled by default. To enable the random scheduler option, you must set a frequency
range when configuring a group schedule in global configuration mode. The group of operations restarts at uniformly distributed
random frequencies within the specified frequency range. The following guidelines apply for setting the frequency range:
The starting value of the frequency range should be greater than the timeout values of all the operations in the group operation.
The starting value of the frequency range should be greater than the schedule period (amount of time for which the group operation
is scheduled). This guideline ensures that the same operation does not get scheduled more than once within the schedule period.
The following guidelines apply if the random scheduler option is enabled:
The individual operations in a group operation will be uniformly distributed to begin at random intervals over the schedule
period.
The group of operations restarts at uniformly distributed random frequencies within the specified frequency range.
The minimum time interval between the start of each operation in a group operation is 100 milliseconds (0.1 seconds). If the
random scheduler option is disabled, the minimum time interval is 1 second.
Only one operation can be scheduled to begin at any given time. If the random scheduler option is disabled, multiple operations
can begin at the same time.
The first operation will always begin at 0 milliseconds of the schedule period.
The order in which each operation in a group operation begins is random.
How to Configure an IP SLAs Multioperation Scheduler
Scheduling Multiple 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 should be the same.
List of one or more operation ID numbers to be added to a multioperation group is limited to a maximum of 125 characters,
including commas (,).
Device(config)# ip sla group schedule 2 1-3 schedule-period 50 frequency range 80-100
Specifies the scheduling parameters of a group of IP SLAs operations.
To enable the IP SLAs random scheduler option, you must configure the
frequencyrangerandom-frequency-range keywords and argument.
Step 4
exit
Example:
Device(config)# exit
Exits global configuration mode and returns to privileged EXEC mode.
Verifying IP SLAs Multiple Operations Scheduling
SUMMARY STEPS
showipslastatistics
showipslagroupschedule
showipslaconfiguration
DETAILED STEPS
Command or Action
Purpose
Step 1
showipslastatistics
Example:
Device# show ip sla statistics
(Optional) Displays the IP SLAs operation details.
Step 2
showipslagroupschedule
Example:
Device# show ip sla group schedule
(Optional) Displays the IP SLAs group schedule details.
Step 3
showipslaconfiguration
Example:
Device# show ip sla configuration
(Optional) Displays the IP SLAs configuration details.
Examples
After you have scheduled the multiple IP SLAs operations, you can verify the latest operation details using the appropriate
show commands.
The following example schedules IP SLAs operations 1 through 20 in the operation group 1 with a schedule period of 60 seconds
and a life value of 1200 seconds. By default, the frequency is equivalent to the schedule period. In this example, the start
interval is 3 seconds (schedule period divided by number of operations).
Device# ip sla group schedule 1 1-20 schedule-period 60 life 1200
The following example shows the details of the scheduled multiple IP SLAs operation using the
showipslagroupschedule command.
Device# show ip sla group schedule
Group Entry Number: 1
Probes to be scheduled: 1-20
Total number of probes: 20
Schedule period: 60
Group operation frequency: Equals schedule period
Status of entry (SNMP RowStatus): Active
Next Scheduled Start Time: Start Time already passed
Life (seconds): 1200
Entry Ageout (seconds): never
The following example shows the details of the scheduled multiple IP SLAs operation using the
showipslaconfiguration command. The last line in the example indicates that the IP SLAs operations are multiple scheduled (TRUE).
Device# show ip sla configuration 1
Entry number: 1
Owner:
Tag:
Type of operation to perform: udpEcho
Target address: 10.2.31.121
Source address: 0.0.0.0
Target port: 9001
Source port: 0
Request size (ARR data portion): 16
Operation timeout (milliseconds): 5000
Type Of Service parameters: 0x0
Verify data: No
Data pattern:
Vrf Name:
Control Packets: enabled
Operation frequency (seconds): 60
Next Scheduled Start Time: Start Time already passed
Life (seconds): 1200
Entry Ageout (seconds): never
Recurring (Starting Everyday): FALSE
Status of entry (SNMP RowStatus): Active
Threshold (milliseconds): 5000
Number of statistic hours kept: 2
Number of statistic distribution buckets kept: 1
Statistic distribution interval (milliseconds): 20
Enhanced History:
Number of history Lives kept: 0
Number of history Buckets kept: 15
History Filter Type: None
Group Scheduled : TRUE
The following example shows the latest operation start time of the scheduled multiple IP SLAs operation, when the operations
are scheduled at equal intervals, using the
showipslastatistics command:
Device# show ip sla statistics | include Latest operation start time
Latest operation start time: *03:06:21.760 UTC Tue Oct 21 2003
Latest operation start time: *03:06:24.754 UTC Tue Oct 21 2003
Latest operation start time: *03:06:27.751 UTC Tue Oct 21 2003
Latest operation start time: *03:06:30.752 UTC Tue Oct 21 2003
Latest operation start time: *03:06:33.754 UTC Tue Oct 21 2003
Latest operation start time: *03:06:36.755 UTC Tue Oct 21 2003
Latest operation start time: *03:06:39.752 UTC Tue Oct 21 2003
Latest operation start time: *03:06:42.753 UTC Tue Oct 21 2003
Latest operation start time: *03:06:45.755 UTC Tue Oct 21 2003
Latest operation start time: *03:06:48.752 UTC Tue Oct 21 2003
Latest operation start time: *03:06:51.753 UTC Tue Oct 21 2003
Latest operation start time: *03:06:54.755 UTC Tue Oct 21 2003
Latest operation start time: *03:06:57.752 UTC Tue Oct 21 2003
Latest operation start time: *03:07:00.753 UTC Tue Oct 21 2003
Latest operation start time: *03:07:03.754 UTC Tue Oct 21 2003
Latest operation start time: *03:07:06.752 UTC Tue Oct 21 2003
Latest operation start time: *03:07:09.752 UTC Tue Oct 21 2003
Latest operation start time: *03:07:12.753 UTC Tue Oct 21 2003
Latest operation start time: *03:07:15.755 UTC Tue Oct 21 2003
Latest operation start time: *03:07:18.752 UTC Tue Oct 21 2003
Configuration Examples for an IP SLAs Multioperation Scheduler
Example Scheduling Multiple IP SLAs Operations
The following example shows how to scheduls IP SLAs operations 1 to 10 in the operation group 1 with a schedule period of
20 seconds. By default, the frequency is equivalent to the schedule period.
Device# ip sla group schedule 1 1-10 schedule-period 20
The following example shows the details of the scheduled multiple IP SLAs operation using the
showipslagroupschedule command. The last line in the example indicates that the IP SLAs operations are multiple scheduled (TRUE).
Device# show ip sla group schedule
Multi-Scheduling Configuration:
Group Entry Number: 1
Probes to be scheduled: 1-10
Schedule period :20
Group operation frequency: 20
Multi-scheduled: TRUE
Example Enabling the IP SLAs Random Scheduler
The following example shows how to schedule IP SLAs operations 1 to 3 as a group (identified as group 2). In this example,
the operations are scheduled to begin at uniformly distributed random intervals over a schedule period of 50 seconds. The
first operation is scheduled to start immediately. The interval is chosen from the specified range upon every invocation of
the probe. The random scheduler option is enabled and the uniformly distributed random frequencies at which the group of operations
will restart is chosen within the range of 80-100 seconds.
ip sla group schedule 2 1-3 schedule-period 50 frequency range 80-100 start-time now
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Feature Information for a IP
SLAs Multioperation Scheduler
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 1. Feature Information for IP
SLAs Multioperation Scheduling
Feature
Name
Releases
Feature
Information
IP SLAs
Multioperation Scheduler
The IP SLAs
Multioperation Scheduler feature provides a highly scalable infrastructure for
IP SLAs by allowing you to schedule multiple IP SLAs operations using a single
command.
IP SLAs
Random Scheduler
The IP SLAs
Random Scheduler feature provides the capability to schedule multiple IP SLAs
operations to begin at random intervals uniformly distributed over a specified
duration of time and to restart at uniformly distributed random frequencies
within a specified frequency range.