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Path measurement: Difference between revisions
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=== Lost packets === | === Lost packets === | ||
The second and third graph show the number of lost packets in each direction. Lost packets are only accounted for connections that have been seen on both devices. | The second and third graph show the number of lost packets in each direction. Lost packets are only accounted for connections that have been seen on both devices. | ||
Depending on the installation point and routing setup, connections might be not be routed to the second device on purpose. | |||
These connections are not accounted as loss on the other device. | Depending on the installation point and routing setup, connections might be not be routed to the second device on purpose. These connections are not accounted as loss on the other device. | ||
The second graph accounts all packets that have been seen on the remote device, but are missed on the main device. | |||
That means that those packets got loss on its way to the main device. | The second graph accounts all packets that have been seen on the remote device, but are missed on the main device. That means that those packets got loss on its way to the main device. | ||
Accordingly, the third graph accounts all packets that have been seen on the main device, but are missed on the remote device. | |||
Accordingly, the third graph accounts all packets that have been seen on the main device, but are missed on the remote device. An additional counter "'''Client packet drop due to overload'''" indicates if some packets could not have been captured on the client device so they are missing for comparison at the main device. If this value is not zero, those packets are accounted as packet loss even though it might not be actually losses. For correct measurements, make sure the graph for remote packet drops is never non-zero. These drops may happen due to several reasons: | |||
If this value is not zero, those packets are accounted as packet loss even though it might not be actually losses. | |||
For correct measurements, make sure the graph for remote packet drops is never non-zero. These drops may happen due to several reasons: | |||
#System capture overload: If multiple captures are running in parallel, the CPU might be overloaded. Check the '''All''' tab in the Capture page to see how many captures are running. In best case there is only the one capturing connection to the main device. | #System capture overload: If multiple captures are running in parallel, the CPU might be overloaded. Check the '''All''' tab in the Capture page to see how many captures are running. In best case there is only the one capturing connection to the main device. | ||
#The capturing connection is encrypted with SSL. The small Allegro 200 has a limited encryption capacity so for large traffic this can be a bottleneck. The only solution is to use a more powerful Multimeter. | #The capturing connection is encrypted with SSL. The small Allegro 200 has a limited encryption capacity so for large traffic this can be a bottleneck. The only solution is to use a more powerful Multimeter. | ||
#Capture drops can also occur if the network connection is not capable of transferring the data fast enough. Rule of thumb is that approximately 5% of the total traffic is used for the measurement connection. For example, if the traffic is 500 MBit/s, the measurement requires ~25 MBit/s of bandwidth on the management port. | #Capture drops can also occur if the network connection is not capable of transferring the data fast enough. Rule of thumb is that approximately 5% of the total traffic is used for the measurement connection. For example, if the traffic is 500 MBit/s, the measurement requires ~25 MBit/s of bandwidth on the management port. | ||
=== Monitored packet rate === | |||
The fourth graph shows all packets that are monitored for the path measurement. This will cover all connections that have been seen on both devices. | The fourth graph shows all packets that are monitored for the path measurement. This will cover all connections that have been seen on both devices. | ||