Re: [IPFIX] template lifetime

Benoit,

> Paul,
>> Brian, Gerhard,
>>
>> Thanks for your replies. I know it's an old problem, but someone 
>> asked what the default refresh interval should be.
>>
>> So it seems we should either define a mechanism for Exporters to 
>> inform Collectors what their default refresh interval is (eg, define 
>> a new standard options template), or re-work (or even remove?) the 
>> template timeout sections.
>>
>> Currently this is a gap which allows an Exporting Process and a 
>> Collecting Process to both claim to be IPFIX compliant, while being 
>> quite un-interoperable.
> Can you please clarify the un-interoperable aspect. I don't get it.

An Exporting Process has a template refresh time in order to satisfy RFC 
5101 / 10.3.6 :

10.3.6.  Template Management

    When IPFIX uses UDP as the transport protocol, Template Sets and
    Option Template Sets MUST be re-sent at regular intervals.  The
    frequency of the (Options) Template transmission MUST be
    configurable.  The default value for the frequency of the (Options)
    Template transmission is 10 minutes.



Meanwhile the Collecting Process follows RFC 5101 / 10.3.7 :

10.3.7.  Collecting Process

    The Collecting Process MUST associate a lifetime with each Template
    (or another definition of an identifier considered unique within the
    Transport Session) received via UDP.  Templates (and similar
    definitions) not refreshed by the Exporting Process within the
    lifetime are expired at the Collecting Process.  If the Template (or
    other definition) is not refreshed before that lifetime has expired,
    the Collecting Process MUST discard that definition and any current
    and future associated Data Records.


Since the CP doesn't know what the EP's template refresh time is, 
perhaps it assumes to follow the "10 minutes" advice in 10.3.6
- and for good measure, it allows three times as much - so, it 
associates a 30 minute lifetime with each template.


However, the EP actually refreshes templates hourly. Or every 90 
minutes. Or daily. Whatever you like, > 30 mins (since, "The frequency 
of the (Options) Template transmission MUST be configurable.").


So both are quite RFC5101 compliant, but fail to interoperate properly - 
because for some period, the CP will have discarded the template and 
won't be able to decode further data until the


P.

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