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Path measurement: Difference between revisions
→Limitations
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The path measurement module allows to passively measure the packet loss and latency between two Allegro Network Multimeter installations. | The path measurement module allows to passively measure the packet loss and latency between two Allegro Network Multimeter installations. | ||
For example, | For example, a network connection (line/link) between the main office and a remote office can be analyzed by installing one Multimeter at the main office and another Multimeter at the remote office. | ||
Only | Only network traffic (packets) passing through both Multimeters can be analyzed. The packet loss and two-way-latency thereof is measured and shown in graphs. | ||
The time synchronization setting (e.g. NTP/PTP or OFF) should be the same on both devices for the best results. | |||
== Overview == | == Overview == | ||
The main (or master) device captures packet meta data from the remote (or client) device which takes only a fraction of the total traffic. | The main (or master) device captures packet meta data from the remote (or client) device which takes only a fraction of the total traffic. | ||
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The delay must be large enough to cover the actual latency of the connection and delay of the capture connection. | The delay must be large enough to cover the actual latency of the connection and delay of the capture connection. | ||
Typical values are between 2 and 5 seconds. Larger values requires more memory to buffer packet meta data so very large values might only be selectable on larger Multimeter devices (Allegro 1000 or greater). | Typical values are between 2 and 5 seconds. Larger values requires more memory to buffer packet meta data so very large values might only be selectable on larger Multimeter devices (Allegro 1000 or greater). | ||
== Configuration == | == Configuration == | ||
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There are some limitations about the path measurement: | There are some limitations about the path measurement: | ||
# Due to technical reasons, large clock adjustments cannot be filtered out | # Due to technical reasons, large clock adjustments cannot be filtered out. So in such cases, a very large two-way-latency is measured. Both devices need not be time synchronized however, considerable time differantiation must be avoided. This means that time synchronization (e.g. NTP) should either be enabled or disabled on both devices for best results. Clock differantiation miss-measurements are however one-time events, and will not lead to false values for the following packets. | ||
# The maximum supported packet size for the path measurement is currently 2048 bytes. Larger packets are truncated for the measurement. | # The maximum supported packet size for the path measurement is currently 2048 bytes. Larger packets are truncated for the measurement. | ||
# NAT setups and different VLAN combinations on master and client are not supported at the moment. Such flows will be accounted as unmonitored flows in the debug view. | # NAT setups and different VLAN combinations on master and client are not supported at the moment. Such flows will be accounted as unmonitored flows in the debug view. | ||