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Configuring Cisco IOS IP SLAs Operations
Information About Configuring Cisco IOS IP SLAs Operations
Average jitter threshold
One-way packet loss
One-way jitter
One-way mean opinion score (MOS)
One-way latency
An IP SLAs threshold violation can also trigger another IP SLAs operation for further analysis. For example, the frequency
could be increased or an ICMP path echo or ICMP path jitter operation could be initiated for troubleshooting.
Determining the type of threshold and the level to set can be complex, and depends on the type of IP service being used
in the network.
IP Service Levels by Using the UDP Jitter Operation
Jitter means interpacket delay variance. When multiple packets are sent consecutively 10 ms apart from source to
destination, if the network is behaving correctly, the destination should receive them 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
more than or less than 10 ms with a positive jitter value meaning that the packets arrived more than 10 ms apart. If the
packets arrive 12 ms apart, positive jitter is 2 ms; if the packets arrive 8 ms apart, negative jitter is 2 ms. For
delay-sensitive networks, positive jitter values are undesirable, and a jitter value of 0 is ideal.
In addition to monitoring jitter, the IP SLAs UDP jitter operation can be used as a multipurpose data gathering operation.
The packets IP SLAs generates carry packet sending and receiving sequence information and sending and receiving time
stamps from the source and the operational target. Based on these, UDP jitter operations measure this data:
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)
Because the paths for the sending and receiving of data can be different (asymmetric), you can use the per-direction
data to more readily identify where congestion or other problems are occurring in the network.
The UDP jitter operation generates synthetic (simulated) UDP traffic and sends a number of UDP packets, each of a
specified size, sent a specified number of milliseconds apart, from a source router to a target router, at a given frequency.
By default, ten packet-frames, each with a payload size of 10 bytes are generated every 10 ms, and the operation is
repeated every 60 seconds. You can configure each of these parameters to best simulate the IP service you want to
provide.
To provide accurate one-way delay (latency) measurements, time synchronization, such as that provided by NTP, is
required between the source and the target device. 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 is returned, but values of 0 are returned for the one-way delay measurements provided by the UDP jitter
operation
Note: Before you configure a UDP jitter operation on the source device, you must enable the IP SLAs responder on the
target device (the operational target).
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