RE: discontinuity timers for Counters

["Wijnen, Bert (Bert)" <bwijnen@lucent.com>]

Inline

> -----Original Message-----
> From: Randy Presuhn [mailto:randy_presuhn@mindspring.com]
> Sent: dinsdag 27 juli 2004 23:11
> To: Mreview (E-mail)
> Subject: Re: discontinuity timers for Counters
> 
> 
> Hi -
> 
> > From: "Wijnen, Bert (Bert)" <bwijnen@lucent.com>
> > To: <j.schoenwaelder@iu-bremen.de>
> > Cc: "Mreview (E-mail)" <mreview@ops.ietf.org>
> > Sent: Tuesday, July 27, 2004 2:01 AM
> > Subject: RE: discontinuity timers for Counters
> ...
> > > Looking at the MIB, the question that I have is the interaction of
> > > discontinuities with these ZeroBasedCounter32 objects. Does a
> > > discontinuity couse these counters to be reset to zero?
> >
> > I believe that we (MIB doctors) agree that they cannot state that a
> > ZeroBasedCounter32 MUST be re-initialized to zero at some point
> > in time (they are only required to be zero at creation time).
> > So I had them remove that sort of text from an earlier revision.
> > So current text is silent about it, meaning that an implementation
> > could do anything, right? There is a discontinuity, so we need to
> > start with new values and then check at least 2 queries.
> ...
> 
> This seems contrary to the whole motivation for using a zero-based
> counter.  I'd think that if they *really* need a zero-based counter,
> that the appropriate semantic is for its value to represent the number
> of events since the beginning of the epoch defined by its discontinuity
> indicator.  If that is so, then the appropriate discontinuity 
> behaviour would indeed be a reset to zero.

Sect 4.6.1.2 iof mib review guidelines towards the end:

   There also exist closely-related textual conventions
   ZeroBasedCounter32 and ZeroBasedCounter64 defined in RMON2-MIB
   [RFC2021] and HCNUM-TC [RFC2856], respectively.

   The only difference between ZeroBasedCounter32/64 TCs and
   Counter32/64 is their starting value;  at time=X, where X is their
   minimum-wrap-time after they were created, the behaviour of
   ZeroBasedCounter32/64 becomes exactly the same as Counter32/64.
   Thus, the preceding paragraphs/rules apply not only to Counter32/64,
   but also to ZeroBasedCounter32/64 TCs.

I conclude from that that we will not allow that a ZeroBasedCounter XX
can REQUIRE a reset to zero at any time other than at creation time?

Do I not interpret that correctly?

> However, I remain sceptical that zero-based is actually needed here.
> 
I have asked that question on the IPCDN list now

> What bothers me more is that it specifies TWO discontinuity indicators.

That is (more or less in my view) the same as what you see in IF-MIB, no?

> I'd read that as an implicit requirement for management applications
> to retrieve BOTH with every query, in order to determine whether either
> gives evidence of a discontinuity.
> 
Yep. Not great, but ?

Bert
> Randy
> 
> 
>