Re: [IPFIX] new monitoring interval information elements

Gerhard,

> Ok, I see the difference to discontinuity time.
>
> Some further thoughts:
>
> The common understanding is that the "time since re-initialization" 
> means sysUpTime. For example, have a look at the description of 
> flowEndSysUpTime:
> "The relative timestamp of the last packet of this Flow. It indicates 
> the number of milliseconds since the last (re-)initialization of the 
> IPFIX Device (sysUpTime)."

Yes, sysUpTime (so specifically, flowStartSysUpTime and 
flowEndSysUpTime), are times "since the last (re-)initialization of the 
IPFIX Device".

These are not necessarily related to the metering process.

Taking some other examples: octetTotalCount, packetTotalCount, 
droppedOctetTotalCount, droppedPacketTotalCount, observedFlowTotalCount, 
ignoredPacketTotalCount, ignoredOctetTotalCount, 
postMCastOctetTotalCount, ... are all of the form:

     "The total number of X since the Metering Process 
(re-)initialization for this Observation Point."

We could suppose that the Metering Process initialised at system uptime. 
However, that may not be the case: it could have started any amount of 
time later. eg, a user could configure a Metering Process at any time. 
Or, an automated system could start and stop Metering Processes 
according to different times of day or different network conditions. 
Without timestamps to tell us, we simply do not know.



> Your proposed IEs do not mention neither (re-)initialization nor 
> sysUpTime. They rather seem to specify a time interval which is 
> located somewhere within the sysuptime interval. Hence, the interval 
> does not work to define the time frame of exportedMessageTotalCount, 
> for example. You would need to define a new IE 
> exportedMessageInMonitoringInterval.

Indeed, because the IEs which I'm specifying here are particular to the 
Monitoring Process, whereas exportedMessageTotalCount seems to require a 
time reference for the Exporting Process. It's a related, though 
different, issue.

(ie, the Exporting Process may start from system init, or at any time 
since then. It may have been started before, or after, the Metering 
Process. Without a suitable timestamp IE, we simply do not know.)


> The different IE descriptions suggest that the time of 
> re-initialization (i.e. sysuptime) can be different for Metering 
> Process, Exporting Process etc.

Indeed this is so. There is no necessity for these to be the same.


> It seems that we need IE to export sysUpTime for each process.

We agree.

So in principal, you understand what I'm trying to do. However, you 
would like clearer definitions of the Information Elements?

Thanks,
P.
_______________________________________________
IPFIX mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/ipfix