Re: [IPFIX] new monitoring interval information elements

Gerhard,

It's not entirely clear what a "discontinuity" is since it's not clearly 
defined. However, inferring from section 5.8 of RFC 5815, 
ipfixMeteringProcessCacheDiscontinuityTime and cacheDiscontinuityTime 
are intended to indicate when the Metering Process was running but 
wasn't able to meter correctly.

The new Information Elements which I'm proposing below aren't related to 
discontinuities. They address a different set of problems. In this case 
the Metering Process is functioning correctly, so there are no 
discontinuities. If there were, they can be expressed with 
ipfixMeteringProcessCacheDiscontinuityTime and cacheDiscontinuityTime. 
However, they are not relevant to the discussion here.

Looking in IANA's IPFIX Information Element registry, we can see many 
Information Elements (about 15) defined as "The number of X since the 
Metering Process (re-)initialization" - so we need to know when that was 
in order to be able to use these Information Elements properly.

These definitions suggest an expectation that the Metering Process will 
start and may subsequently restart. That could be for many reasons; 
there's no suggestion that it's an error.

The new Information Elements proposed below serve to indicate when the 
Metering Process (re)started, and when it ended. As far as I know, there 
are currently no Information Elements for this.

Reviewing RFC 5101, I noticed that the "Metering Process Statistics 
Option Template" contains several fields defined as, "The total number X 
since the Exporting Process re-initialization", so it seems that an 
additional Information Element is required for that too, in the case of 
connectionless export transports.

Thanks,
P.


On 17/06/12 18:17, Gerhard Muenz wrote:
>
> Paul,
>
> Please check if the proposed IEs are compatible with 
> ipfixMeteringProcessCacheDiscontinuityTime in IPFIX-MIB and 
> cacheDiscontinuityTime in IPFIX-CONFIG.
>
> Parameters which exist in IPFIX-MIB, IPFIX-CONFIG and as IE should 
> follow the same naming scheme and semantic, if possible.
>
> Thanks,
> Gerhard
>
>
> On 16.06.2012 16:56, Paul Aitken wrote:
>> Dear IPFIX experts,
>>
>> FYI, I'm requesting two new IPFIX Information Elements from IANA to
>> record the start and end of a monitoring interval, which is a period of
>> time during which the Metering Process is running.
>>
>> The existing IPFIX Information Elements provide flow based timestamps,
>> system init, and observation times. There's no indication of the
>> Metering Process, whichmay be running for a period of time during which
>> no flows of interest or relevanceare observed.
>>
>> In fact, many existing elements are described as "The total number of X
>> since the Metering Process (re-)initialization". However, there's
>> currently no indication of when that (re-)initialization was. These new
>> Information Elements enable an IPFIX device to indicate when the
>> Metering Process started and ended.
>>
>> These new elements are particularly useful when the Metering Process is
>> windowed - ie, it runs for a fixed interval, exporting all its
>> observations only at the end of that interval, before optionally
>> starting over. With these new Information Elements, an IPFIX device can
>> readily indicate the start (and end) of each interval.
>>
>> Our present need is only for milliseconds resolution. At this time we
>> don't need the equivalent seconds, microseconds, or nanoseconds
>> elements, although these could be created in future if needs be.
>>
>> Also note the subtle distinction between "monitoring" and "metering": a
>> device could be monitoring traffic for some time, without detecting
>> anything of interest or relevance to be metered. The metering interval
>> could almost be expressed by minFlowStart* to maxFlowEnd*. We've chosen
>> to name these elements "monitoring interval" rather than "metering
>> interval" to clearly express this difference.
>>
>>
>> Name:         monitoringIntervalStartMilliSeconds
>> Data Type:    dateTimeMilliseconds
>> Sematics:     -
>> Description: The absolute timestamp at which the monitoring interval
>> started.
>>                 A Monitoring interval is the period of time during which
>> the Metering Process is running.
>> Units:        milliseconds
>>
>>
>> Name:         monitoringIntervalEndMilliSeconds
>> Data Type:    dateTimeMilliseconds
>> Sematics:     -
>> Description: The absolute timestamp at which the monitoring interval 
>> ended.
>>                 A Monitoring interval is the period of time during which
>> the Metering Process is running.
>> Units:        milliseconds
>>
>>
>> Thanks,
>> P.
>>
>> _______________________________________________
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