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accuracy of the measurements. An IP SLA operation is a network measurement to a destination in the network
from the source device using a specific protocol, such as User Datagram Protocol (UDP) for the operation.
Figure 4: IP SLA Operations
Operations are divided into two classes, which depend on whether they rely on the IP SLA Responder
component to be running at the target device or not. The former is used only with Cisco devices; whereas,
the latter is used with any device that has IP connectivity. Operations that are based on Internet Control
Message Protocol (ICMP) are examples of the second class; whereas, UDP-based operations are examples
of the first.
In responder-based operations, the IP SLA Responder is enabled in the destination device and provides
information such as the processing delays of IP SLA packets. The responder-based operation has improved
accuracy over the ICMP operation discussed above, and offers the capability of unidirectional measurements.
In replies to the IP SLA source device, the responder includes information about processing delays. The IP
SLA source device removes the delays in its final performance calculation. Use of the responder is optional
for the UDP echo operation, but it is required for the UDP jitter operation. If no IP SLA Responder is used,
the target device should support the UDP echo operation.
In ICMP operations, the source IP SLA device sends several ICMP packets to the destination. The destination
device, which is any IP device, echoes with replies. The source IP SLA device uses the sent and received time
stamps to calculate the response time. The ICMP echo operation resembles the traditional extended ping
utility, and it measures only the response time between the source device and the destination device. ICMP
path-echo and path-jitter operations use the traceroute mechanism to identify the whole path. Subsequent
ICMP packets are sent to each path node, and the measurements are correlated to provide hop-by-hop round-trip
delay and jitter information.
To implement IP SLA network performance measurement, perform these tasks:
1
Enable the IP SLA Responder, if appropriate.
2
Configure the required IP SLA operation type.
3
Configure any options available for the specified IP SLA operation type.
4
Configure reaction conditions, if required.
5
Schedule the operation to run. Then, let the operation run for a period of time to gather statistics.
Cisco ASR 9000 Series Aggregation Services Router System Monitoring Configuration Guide, Release 4.2.x
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Implementing IP Service Level Agreements
Measuring Network Performance with IP Service Level Agreements