Juniper Networks J-Series manual RPM Tests, Probe and Test Intervals, Configuring RPM Probes

Chapter 14: Configuring RPM Probes

UDP and TCP probe types require that the remote server be configured as an RPM receiver so that it generates responses to the probes.

RPM Tests

Each probed target is monitored over the course of a test. A test represents a collection of probes, sent out at regular intervals, as defined in the configuration. Statistics are then returned for each test. Because a test is a collection of probes that have been monitored over some amount of time, test statistics such as standard deviation and jitter can be calculated and included with the average probe statistics.

Probe and Test Intervals

Within a test, RPM probes are sent at regular intervals, configured in seconds. When the total number of probes has been sent and the corresponding responses received, the test is complete. You can manually set the probe interval for each test to control how the RPM test is conducted.

After all the probes for a particular test have been sent, the test begins again. The time between tests is the test interval. You can manually set the test interval to tune RPM performance.

Jitter Measurement with Hardware Timestamping

Jitter is the difference in relative transit time between two consecutive probes.

You can timestamp the following RPM probes to improve the measurement of latency or jitter:

■ICMP ping

■ICMP ping timestamp

■UDP ping

■UDP ping timestamp

NOTE: The Services Router supports hardware timestamping of UDP ping and UDP ping timestamp RPM probes only if the destination port is UDP-ECHO (port 7).

Timestamping takes place during the forwarding process of the Services Router originating the probe (the RPM client), but not on the remote router that is the target of the probe (the RPM server).

The supported encapsulations on a Services Router for timestamping are Ethernet including VLAN, synchronous PPP, and Frame Relay. The only logical interface supported is an lt services interface.

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