Subject: Re: <draft-ietf-disman-schedule-mib-v2-04.txt>

From: Alan Luchuk <[email-masked]>
Date: Thu, 21 Jun 2001 12:47:35 -0400 (EDT)

Hello all,

>I have updated the schedule MIB revision. Despite some minor editorial
>changes, I have added new compliance and conformance definitions that
>were needed because of the introduction of schedTriggers.
>
>I also rewrote the section on time transitions as was discussed in
>Minneapolis and on the disman list in March. Below is the unified
>context diff (which is actually showing lots of editorial changes).

I've recently been back on the DISMAN-SCHEDULE-MIB, so I have been care-
fully reviewing the differences between the latest round of drafts and
RFC 2591.  Overall, I believe the changes to the latest round of drafts
are positive clarifications, I support them, and am almost complete in
implementing and testing <draft-ietf-disman-schedule-mib-v2-03.txt>.

My first comment about the latest round of drafts is a very simple edit-
orial change:  Dave Levi's telephone area code has changed from 423 to 865.

Second, I have several observations about the clarifications about what
happens during time transitions (Section 3.4).

Having looked over the DISMAN WG mailing list archives from March 2001,
the argument in favor of the behavior described in  <draft-ietf-disman-
schedule-mib-v2-04.txt> appears to be:

1.  One could argue that either the time transition behavior described
    in RFC 2591 is more useful or the time transition behavior described
    in <draft-ietf-disman-schedule-mib-v2-04.txt> is more useful; there
    are situations in which either behavior might be more useful or more
    problematic.

2.  The time transition behavior described in
    <draft-ietf-disman-schedule-mib-v2-04.txt>:

    A.  Is simpler to implement; and
    B.  Provides analogous behavior for events scheduled for non-existent
        times, similar to what happens for events scheduled on non-existent
        days.

Several people (Tammy Ferris, Randy Presuhn, Mike Ayers) expressed support
for the time transition behavior described in <draft-ietf-disman-schedule-
mib-v2-04.txt>, and nobody expressed support for the time transition behavior
described in RFC 2591.  Hence, this is seen as the preferable behavior.

Observations:

1.  First, if the DISMAN-SCHEDULE-MIB agent is running on a heavily-loaded
    system, and doesn't get serviced for several minutes, how can the agent
    differentiate this from a situation where the system time is administ-
    ratively changed by several minutes?  What is the agent supposed to do
    with events calendar-scheduled for the minutes during which the agent
    was suspended by the system?  Skipping these events because the system 
    was heavily loaded seems like a undesirable behavior.

2.  Although (as far as I can see), all of the other changes/clarifications
    in <draft-ietf-disman-schedule-mib-v2-04.txt> are upwardly-compatible
    with RFC 2591, changing the time-transition behavior breaks this.  That
    is, users that expect RFC 2591 time-transition behavior may be surprised
    by the time transition behavior described in <draft-ietf-disman-schedule-
    mib-v2-04.txt>.  Hence, this behavioral change must be documented in
    release notes for the user.

I cannot argue for or against either time transition behavior as being the
"correct" behavior, so I have no preference based upon "correctness".  How-
ever, I prefer the time transition behavior described in RFC 2591 because
we have a released product with an installed customer base that expects the
time transition behavior documented in RFC 2591.

Regards,
--Alan

 -----------------------------------------------------------------------------
 Alan Luchuk        SNMP Research, Inc.                Voice:  +1 865 573 1434
 Software Engineer  3001 Kimberlin Heights Road        FAX:    +1 865 573 9197
 [email-masked]    Knoxville, TN  37920-9716  U.S.A.  http://www.snmp.com/
 -----------------------------------------------------------------------------