H Chu, > I found ipfix plugin declares that passive time must be greater than > active timer. At Cisco router, we configure cache active timeout or inactive > timeout for ipfix or netflow. I think that active timer in vpp compares to > active timeout in Cisco router and passive timer in vpp compares to inactive > timeout in Cisco router. Howerver, At Cisco router, we always configure > inactive timeout smaller than active timeout. > Why vpp is different from Cisco router at ipfix? Please help me! > Thanks.
These two timers determine flow expiration. The active timer denotes the frequency of how often the metering process expire a flow record for an active flow. It does not delete the flow record from the cache. E.g. an active timer of 5 seconds, will for an active flow export a flow record roughly every seconds. The passive timer states the time that an inactive flow record should be kept in the cache. If the packet arrival rate of a flow is one packet every 10 seconds. The active timer is 30 seconds and the passive timer is 5 seconds, then the passive timer would win, and expire the flow record before the active timer fired. I.e. you'd get a single packet per flow. You are right though, these two timers are independent so we can probably remove that check. Feel like adding a JIRA ticket? For full disclosure the active timer isn't really a timer, it's a time stamp that we check on packet arrival. Which means that you might be left with the last packet in a flow being dealt with by the passive timer. Best regards, Ole
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