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Minutes of snmpconf WG sessions at IETF50 - Final version



Attached is the final version of the minutes from the snmpconf Working Group sessions at IETF50.
 
Thanks to all who contributed input and advice.
 
Glen Morehead

 

 
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Minutes from the snmpconf Working Group sessions
IETF50, Minneapolis, Minnesota USA
21 and 23 March 2001
Reported by Glen Morehead


Session 1 - 1530 to 1730, 21 March
Minutes prepared by Glen Morehead
Note takers were David Harrington (dbh@enterasys.com) backed up by
Glen Morehead (glen.morehead@powerupnetworks.com)

NOTE:  The slides referenced in these minutes are available at
       ftp.snmp.com/pub/snmpconf/ietf50/ and will be submitted
       with the minutes.

---

The agenda was presented by Jon Saperia for bashing; no changes were
requested. (slides in working-group-agenda.ppt)

---

Presentation:  Dave Partain - Status Update.
(continuing with Jon's slides)

Good progress has been made in the last month.  There has been lots of
activity on the mail list.  We are getting close to completion.  The
primary focus now is to discuss any new items for each document.
Nearly all of the items from the January 12 ToDo list are completed.
Work will continue on the list until forward progress stops.

We're hoping to resolve all issues and set a deadline within the next
week or two.  The deadline will be announced on the mailing list.  If
changes are requested, the person that wants the change has the burden
of proof.  We will work to complete any issues raised on the mailing
list, and then will issue the WG last call.

---

Presentation:  Wayne Tackabury - Status of the BCP Document.
(slides in bcp.ppt)

Wayne recapped the focus of the BCP Document, and summarized the
changes made since San Diego.
  *  The topic reorganization has been finalized.
  *  There has been an extensive rework of the existing text, including
     significant clarification and invocation of many new examples.
  *  The previous example MIB was replaced with a new sample MIB
     designed for this document (BLDG-HVAC-MIB).
  *  The glossary section was rewritten.

The changes are detailed in the slides.

There was some additional discussion of whether this is best current
practice, reflecting discussion from the mailing list.

---

Presentation:  Harrie Hazewinkel - Status of the Diffserv Policy MIB.
(no slides were used)

This MIB is small because diffserv modified their MIB to adopt our
design.  The example of how to use the MIB has been extended, but it
has been kept simple.

---

Presentation:  Steve Waldbusser - Status of the Policy MIB.

A printout of the changes made was 4.5 pages long, but we are closer to
the end than to the beginning. The ToDo list is getting shorter rather
than longer.  Now is a good time to read the document because it is
getting stable.

Loosely-typed variables were added.  A concern was raised that the
management station can get confused if a string is used as an OID.
This discussion was taken offline.

The reference language is now C++ not C.  This change allows pass-by
reference and loosely-typed variables.

QuickStart guides were added.

A new "unity" element was defined.

Counter32Delta() was reviewed.

CounterRate() was described and discussed.  CounterRate() stores N
values.  For example, if the sampling rate is set to every 5 minutes,
store 12 values to get 1-hour smoothing.  A question was raised about
how to synchronize between two different counters, and the answer was
to start both counters on the same pass.  The calling script must be
responsible for discontinuity management.  Questions were asked whether
it is possible to change minInterval algorithmically, and what happens
if there are errors doing reads of some samples.  Steve and Jeff Case
decided to take the discussion offline.

SignalError() can send an error for a scripts that doesn't die when it
hits an exception.

PmPolicyAdminStatus - Should a 0 enum be used?

There was extensive discussion on createAndGo().  Questions and
comments raised:
  *  Does setRowStatus do random indexing or incremental indexing?
     With createAndGo(), you need to keep an index to the row just
     created.
  *  There is an error in the example - status varbind must be set
     to createAndGo.
  *  Should createAndGo be classified as a convenience function or a
     general function?
  *  Dave Partain doesn't like the createAndGo() function, but some
     agents don't support createAndWait().
  *  Maybe this should be abstracted to create() to hide the
     differences between createAndGo and createAndWait.
  *  Do we need both semantics in the row creation?
  *  Should we continue work on createAndGo(), or just assume
     createAndWait()?
  *  A higher-level abstraction does more work, and simplifies the
     scripts.
  *  Different tables may have different support levels.

The ElementType Filter Rationale was discussed.  A question was raised
concerning how to run a policy on multiple types.  The answer given was
to use an "any".  This is an implicit "foreach element in XXX".

There was lots of discussion on TypeRegOIDPrefix.  It was decided to
continue the discussion on the mailing list.

The PmSchedTable was discussed.  It was suggested that maybe we're not
using the right model here, and maybe PCIM got it right.  It was
suggested that it would be good to include a simple example of the
types of schedules needed, specifically some of the RFC2445 types.

---

David Partain finished the presentations with some comments.
(included under Additional To Do Items in his slides,
 working-group-agenda.ppt):
  *  Examples are needed to help clarity, for example with all of the
     accessor functions.
  *  We need to document how to create vendor-specific extensions such
     as setCli.
  *  The IMPLIED question was addressed.  It was agreed - IMPLIED is
     evil, and is now gone.
  *  Table indexing on pmRoleTable needs to be fixed.

---

Jon Saperia wrapped up the day with a preview of Friday's agenda.

----------------------------------

Session 2 - 0900 to 1130, 23 March
Minutes prepared by Glen Morehead.
Note takers were Steve Moulton (moulton@snmp.com) backed up by
Glen Morehead (glen.morehead@powerupnetworks.com)

NOTE:  The slides referenced in these minutes are available at
       ftp.snmp.com/pub/snmpconf/ietf50/ and will be submitted
       with the minutes.

---

Agenda bashing was completed at the first working group meeting.

---

The first presentation was a continuation of Steve Waldbusser's
presentation from Wednesday, March 21, 2001.

Presentation: Steve Waldbusser - Policy MIB Issues.
(slides in friday-policy-mib.ppt)

Cleaning up after failed action script is difficult.  In particular,
a script may make changes to the agent state that are difficult to
back out on a script failure.  One possible solution is to have
a regCleanup() call that takes the row status variable for each
row created, which is called on script failure.

Similarly, cleaning up scratchpad variables is difficult.  A proposed
change is to change the functionality of setScratchpad to remove
a variable if no value is supplied.  This can be called on script
failure.  Scratchpad variables need a storageType, to disambiguate
which are stored across an agent reboot, and which are not.

In the case of a policy action script failing, there needs to be a
mechanism to allow the lower precedence script to execute.  One
approach is to have the failing script call a function called defer()
to allow another script to run.  Concerns were expressed from the
floor about the additional complexity this adds to the execution 
environment.   Steve remarked that the original very synchronous model
will not work effectively for this reason.

Wes Hardaker remarked that other policy working groups specify a
fallback action, rather than a lower precedence action.  Falling back
to a lower precedence works in QoS but in a security policy realm is a
bad thing to do.  Steve agreed with this principle with regard to
security and remarked that in this case you just not use defer.
Unfortunately, this means that things might remain unconfigured.

Jon Saperia made the point that distinction between fallback and
failure is important.  

Wes continued with the fallback issue saying that the way this was
handled in the in the IPSEC policy MIB is that there are multiple
fallback actions specifiable.  You also have runtime failures.
He wants configuration to be external to the script in this case.
We need a recommendation on the interaction between run time error
and defer().

Steve Waldbusser clarified by saying that if you die with an execution
failure in the filter, you fall back.  If you die in the action you do
not fall back.  There is currently no semantic for falling back along
the filter chain in the document.

Joel Halpern made the point that you need to clarify in the text what
you expect to happen if policy one executes, it fails and defers().
You hit policy 2 and hit a defer().   What do you intend to remember?
You need to tell the reader.

The next discussion point was on entity naming.  Should the manager be
called the PDP (Policy Decision Point) and the agent the
PEP (Policy Enforcement Point)?  Are these terms still in use?
Joel Halpern said that the terms are still in use in COPS, but
elsewhere, the document has expired and has not been replaced.

Jon Saperia mentioned that Bert has sent out note saying that we need
to review latest Policy Terminology draft to align our terms.

Bob Moore said the use of these terms in core policy is not precise.
We should not get too hung up as to the placement of the decision in
PDP.  There is no suggestion in PCIM that the PDP is the one and only
point that makes the decision.  Within the broad meaning, these terms
do no violence do PCIM or core policy.

Jeff Case mentioned that is that somewhere around page 2 or 3 you might
want to make a reference to RFC2571 snmp architecture spec that talks
about command generator and command responder, and say we are going to
use manager and agent.  These are loosely similar (but do not create a
normative reference) to terms in such a such a document.

Wes Hardaker expressed concern that this language is going to undergo
a lot of changes after deployment.  There is no way to version the
language.  He would like an object he can query to determine the
version of the language.  David Partain would like such a facility to
determine versions of vendor extension libraries.  The issue arose of
how to deal with incompatible forward revisions; a version object
would be adequate.  All scripts will need a capMatch(version)
invocation once there are multiple versions of the language.

Randy Presuhn mentioned that there are cases where library bugs get
fixed but you have code that has become dependent on erroneous
behavior.  This can also happen when there are semantic ambiguities
in the language.

David Partain stated that he didn't think we are going to fix this
today.  What are the chances that you will change out a script engine
without looking at your scripts?  I think we need to take this to the
list.

Several issues came up on notifications, and were not resolved:

  *  Should there be a configuration notification on script failure
     facility?
  *  Should there be a way to throttle failure notifications?  Should
     they be throttled by state change?
  *  Should the notification section be placed in a difference
     compliance statement, to make it optionally implementable?
  *  Should there be a time-based throttle on notifications?

The final discussion in this presentation covered code reuse.  The
original design did not allow for functions.  There was tepid support
for the ability to invoke a script from within another script, and
stronger support for user-definable functions.  One possibility would
be to put function support into a capability set not required by the
baseline.

---

Presentation: Jon Saperia - Capability Table Changes
(slides in capabilities-objects.ppt).

Several objects are removed from the pmCapabilitiesTable to simplify
the table, in keeping with the starting small approach.  In general,
instance-specific objects were removed.   capMatch() now works on a
system-wide, not per-element, basis.  A pmCapabilitiesOverrideTable
was added to allow overriding the information in the
pmCapabilitiesTable when the capabilities discovered were either
erroneous or undesired.  A fuller explication of this change will
be sent to the mailing list.

There was some discussion about how security should be handled.
The text says that policies are executed in the context of the last
writer to the policy script.  Is this text adequate?  Do we need an 
OwnerString?

Brian Carpenter brought up the separate point that many router vendors
have difficulties with storageType and don't like it.  The problem is
that entire configurations need to be written back to flash as opposed
to the data associated with a single configuration, and that the
flash environment on many router implementations does not handle this
well.  Several possibilities were discussed, including delayed write to
NVRAM and having a "write all configuration" object.  This has been an
issue with the Diffserv MIB.  Jeff Case reminded the meeting that
rowStatus is a textual convention, and it is not the only reasonable
paradigm.  Bert Wijnen mentioned that issue on diffserv is that there
was no persistence discussion in the document at all.  That MIB is
close to WG last call; we may need to help them with that.

Randy Presuhn refocused us back to the security discussion.  Access
rights are just one part of the problem.  In a large system you may
have different owners for different policies.  The current indexing
structure in the -05 draft is going to make multiple manager access
control difficult.  To make it tractable there has to be some sort of
automatic correlation between the indexing and the VACM table.

David Partain brought up the point of the likelihood of someone being
responsible for diffserv policy and someone else being responsible for
user policy.  You can do it with what you have now, but it would be
more difficult than it could be.

Jeff Case reminded us that once you are on your favorite router
vendor's console, you have no constraints on what you can change.  Once
you are in, you are in.  We have more functionality that that today.
To put in more w/out implementation experience is not correct.  We may
already have too much.  A brain cramp to consider:  If you want to keep
policy writers separate, you may want to run separate agents instances
in different contexts.

---

Presentation:  Configuring DiffServ DataPaths using PolicyScript,
               PolicyMIB and diffServ Templates - Thippanna Hongal

(slides in diffservmib2.ppt)

Hongal has done some work on showing pictorially what happens in
diffserv MIB.

Jon Saperia summarized this presentation as the best exposition seen so
far of how the Policy MIB and Diffserv Policy Modules work together.

Brian Carpenter make the comment that the Gold example is a bit naive.
It turns out that the usual case is less complicated, which is not
exactly what was expected.

---

Harrie Hazewinkel reviewed the discussions taking place with respect
to the diffserv MIB.  There is still much learning going on.  In
particular, templates can be reused across interfaces.

---

BCP Document Discussion - Mike MacFaden

(slides in bcp-2.ppt)

Mike reviewed the goals from IETF48, and what steps have taken place
since then.

---

The final part of meeting consisted of a review of the action items.

Wes is to address the issue of language versioning and code reuse.

Steve Waldbusser is to make a proposal on ToDo item #33 (helper objects
for management system fallover).

wstrlen() was removed as an action item.  Randy Presuhn will look at
international issues in general.

Steve Waldbusser will work on explaining why the notification
registration table will not work, and will work on a discussion of
duplication with respect to the notification MIB.

The IMPLIED keyword on the pmRoleTAddress will be removed unless there
are objections from the mailing list.

There are three very different open questions in security:
  *  rights delegation
  *  ownership and management of the security
  *  notification scheme for configuration changes.

NOW IS THE TIME TO READ THE DOCUMENT.

It is proposed that we take two weeks maximum to propose changes to the
documents and air any other concerns.  On April 6 we close any
additional items, assuming the diffserv documents are finished.  The
next draft can be done in two weeks.  There will be two or three more
versions before all is done.


The meeting adjourned somewhat ahead of time.