NetStream flow aging is a prerequisite for exporting flow statistics to the NSC. Once NetStream is enabled on a device, flow statistics are stored in the NetStream cache on the device. When a NetStream flow is aged out, the NDE exports the flow statistics in the cache to the NSC using NetStream packets of the specified version.
NetStream flows are aged out in the following modes:
Active aging
Packets are continuously added to a flow for a specified period from when the first packet is added. When the active aging timer expires, the flow statistics are exported. Active aging enables the NDE to periodically export statistics about flows that last for long periods.
Inactive aging
Inactive aging clears unnecessary entries in the NetStream cache so that the system can fully leverage statistics entries. Inactive aging requires the device to export flow statistics that last for short periods. Once packets are no longer being added to a flow, the device exports the flow statistics to conserve memory.
FIN- or RST-based aging
A FIN or RST flag in a TCP packet indicates that the TCP connection is terminated. The NDE immediately ages the corresponding NetStream flow when it receives a packet with a FIN or RST flag.
Byte-based aging
The NetStream cache records the number of bytes for each flow. Overflow occurs when the number of bytes exceeds the specified upper limit, and the NDE immediately ages the flow to prevent a byte counting error. The hardware byte counter is a 32-bit counter, and the upper limit is 4,294,967,295 bytes (about 3.9 GB).
Forced aging
If a flow fails to age due to abnormal NetStream services or the latest statistics are needed before the flow meets aging conditions, you can run commands to forcibly age all flows in the NetStream cache.