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Cache Flow Export
Using UDP as the transport method, the ERX router can export the content of the
flow cache as the system removes the entries. You can specify one export destination
for each VR.
Each export packet contains a header and flow records. The version 5 header contains
the following fields:
NOTE: The J-Flow setting for Engine type is always RP=0.
If, for any reason, the virtual router is unable to export records to the collector, the
unsent records are discarded. However, the virtual router continues to increase the
sequence number by one as if it sent the records. Discrepancies between the sequence
number and sent records can assist in recognizing discontinuities at the collector
end.
Aging Flows
After the virtual router creates a flow in the cache, the flow is removed at the
expiration of either the active or the inactive timer.
In sampled environments, methods for detecting the end of a flow can be unreliable.
The active timer places a hard limit on how long a flow may last before the virtual
router closes it and gathers the necessary statistics. If the flow is still active when
the active timer expires, the virtual router creates a new flow entry to replace the
closed flow.
The inactive timer removes flows if they do not contain any data traffic for a specified
period of time.
Destination port number (DP)
Layer 3 protocol type
Type of service (ToS byte) or Differentiated Services code point (DSCP)
Input interface
Version-Format version
Count-Number of records in this packet
SysUpTime-System up time value when this packet was built
Unix Timestamp-Number of seconds and nanoseconds since 0000 UTC 1970
(Coordinated Universal Time)
Sequence Number-Number of total records sent on this export stream
Engine type-Type of switching engine (line module or route processor)
Engine ID-SRP slot number
Chapter 3: Configuring J-Flow Statistics
Overview
97
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