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Chapter 41 Configuring Cisco IOS IP SLAs Operations
Understanding Cisco IOS IP SLAs
Figure 41-2
Cisco IOS IP SLAs Responder Time Stamping
An additional benefit of the two time stamps at the target device is the ability to track one-way delay,
jitter, and directional packet loss. Because much network behavior is asynchronous, it is critical to have
these statistics. However, to capture one-way delay measurements, you must configure both the source
router and target router with Network Time Protocol (NTP) so that the source and target are
synchronized to the same clock source. One-way jitter measurements do not require clock
synchronization.
IP SLAs Operation Scheduling
When you configure
an IP SLAs operation, you must schedule the operation to begin capturing statistics
and collecting error information. You can schedule an operation to start immediately or to start at a
certain month, day, and hour. You can use the
pending
option to set the operation to start at a later time.
The pending option is an internal state of the operation that is visible through SNMP. The pending state
is also used when an operation is a reaction (threshold) operation waiting to be triggered. You can
schedule a single IP SLAs operation or a group of operations at one time.
You can schedule several IP SLAs operations by using a single command through the Cisco IOS CLI or
the CISCO RTTMON-MIB. Scheduling the operations to run at evenly distributed times allows you to
control the amount of IP SLAs monitoring traffic. This distribution of IP SLAs operations helps
minimize the CPU utilization and thus improves network scalability.
For more details about the IP SLAs multioperations scheduling functionality, see the “IP
SLAs—Multiple Operation Scheduling” chapter of the Cisco IOS IP SLAs Configuration Guide at this
URL:
http://www.cisco.com/en/US/products/ps6441/products_configuration_guide_book09186a0080707055
.html
IP SLAs Operation Threshold Monitoring
To support successful service level agreement monitoring, you must have mechanisms that notify you
immediately of any possible violation. IP SLAs can send SNMP traps that are triggered by events such
as these:
•
Connection loss
•
Timeout
•
Round-trip time threshold
•
Average jitter threshold
•
One-way packet loss
•
One-way jitter
121380
T1
Source router
RTT (Round-trip time) = T4 (Time stamp 4) - T1 (Time stamp 1) -
Target router
Responder
=T3-T2
T4
T2
T3
