340
edits
Path measurement: Difference between revisions
Jump to navigation
Jump to search
→Lost packets
| Line 141: | Line 141: | ||
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: | 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: | ||
A capture button for lost packets is available for capturing packets seen on main device but considered as lost on the remote device. The capture is available for live mode only, i.e. if a time interval is selected in the Allegro Network Multimeter it will be ignored. When starting the capture, the path measurement engine will store all packets on the main device with the configured length and write them after the packet delay timeout into the PCAP. Only packets of the main device are considered (packets lost on main device but seen on remote device will '''not''' be captured). | |||
#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 Allegro Network 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 Allegro Network 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 ==== | ==== Monitored packet rate ==== | ||