CURRENT_MEETING_REPORT_
Reported by James Davin/MIT
SNMP NM Directorate Minutes
Special Session
These Minutes record statements made during an open session convened at
the IETF meeting in Atlanta. These minutes are an accurate report of
what was said as a concrete reference for future discussion; however, no
statement reported here should be construed either as a consensus of
those present or even as necessarily factually correct (in explicit
content or in implicit assumptions).
Chuck Davin (MIT) called the meeting to order and reviewed the purpose
of the session as it had been announced in mailing list postings:
From: "James R. (Chuck) Davin" <jrd@ptt.lcs.mit.edu>
To: snmp-wg@nisc.nyser.net
Subject: SNMP Directorate Mtg at Atlanta
Date: Wed, 17 Jul 91 20:06:56 -0400
Sender: jrd
Agenda
The SNMP Network Management Directorate session scheduled for the
Atlanta IETF meeting will have as its goal the identification of
concerns about functional deficiencies in the SNMP network management
framework. The scope of the discussion will be lapses in the scope of
extant management instrumentation and functional problems or
deficiencies in the Internet SMI (RFC 1155; also RFC 1212) and the SNMP
protocol (RFC 1157).
o Instrumentation Scope
o Structure of Management Information (RFC 1155; also RFC 1212)
o Simple Network Management Protocol (RFC 1157)
To keep the session productively focused, discussion will not extend to
any identification or description of potential solutions.
Participants are asked to have read relevant documents in advance of the
session.
Davin took pains to emphasize that the purpose of this meeting was to
identify perceptions of functional deficiencies in the internet-
standard network management framework and that discussion of potential
solutions was not in order.
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Davin also stated that this meeting was a tentative, exploratory step in
a process whose future course remains unclear. Regardless of the future
course of any efforts to evolve the internet- standard network
management framework, it would be useful even at the outset to begin to
identify what problems might need addressing in any such future work.
Davin reminded those present of the exceptional character of the meeting
and that no one should draw any conclusions from this meeting about the
content, process, venue, or schedule of any future work on the internet-
standard network management framework.
After this introduction, the floor was opened, and a succession of
speakers addressed the meeting to articulate one or more perceived
problems with the internet-standard NM framework.
David Waitzman (BBN) identified the performance of SNMP in the retrieval
of large amounts of tabular management information as being less than
desirable. He cited as an example the task of retrieving the columns of
a routing table for purposes of comparing its contents to an
administratively determined configuration.
Waitzman also stated that interoperability among SNMP systems may suffer
owing to varying practice with respect to the creation and deletion of
of MIB object instances.
Waitzman also stated that MIB objects with mandatory status that were
not universally implementable posed problems of interoperability, fault
diagnosis, and ill-defined conformance posture.
Waitzman also stated that it is difficult to map between the information
models for OSI and SNMP network management. He characterized this
problem as one of increased difficulty for MIB implementors and
attributed it to a lack of coordination among standards bodies.
Waitzman also stated that the level of granularity in SNMP authorization
mechanisms was inadequate to realize certain policies.
Lynn Monsanto (Sun Microsystems Incorporated) stated that his customers
want to have confidence that significant network events will be reliably
reported to a management station. He emphasized this point by noting a
lack of defined MIBs for management stations. He also cited an example
environment in a brokerage house that requires a very low mean time to
detect errors.
Monsanto stated that the framework was weak in its support for
distributed atomic operations, e.g., to add a user account to multiple
hosts but to back out of the operation under certain circumstances.
Monsanto also stated that the SNMP SMI makes units of measurement for
various instrumented quantities ambiguous. He pointed out that this
makes mechanical interpretation of MIB objects by management stations
difficult. In this context, he also cited the difficulty in displaying
a new, unknown MIB object at a management station.
Karl Auerbach (Sun Microsystems Incorporated) stated that the SNMP SMI
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does not afford support for representing large numbers. He cited the
example of the number of bytes transmitted on an Ethernet interface in
this connection. He also stated that the SNMP SMI was weak in its
distinction between signed and unsigned quantities, offering as an
example the difference between measurements of disk space and a bank
account balance.
Auerbach also stated that it is difficult for a management station to
know how to display a retrieved physical address quantity. He said that
this difficulty limits the range of network types that can be managed by
SNMP.
Auerbach also stated that the SNMP error status values confuse network
operators. He cited the example of the readOnly status.
Auerbach also stated that the use of ASN.1 encodings in the SNMP imposed
an excessive computational burden on agent systems and that this burden
is compounded by the emerging SNMP security proposals.
Auerbach also stated that the atomic failure character of the SNMP Get
operation complicates the implementation of management stations.
Auerbach also stated that ``holes in the MIB'' owing to unimplemented
MIB objects or access control policies cause both a performance problem
and an efficiency problem for the internet-standard network management
framework.
Auerbach also stated that the retrieval of large amounts of tabular
information via the SNMP was inefficient both in terms of bandwidth
consumed and in packet processing overhead. He cited as examples the
need to retrieve log files, large routing tables, and core image dumps
using the SNMP.
Auerbach also stated that the existence of MIB objects with optional
status poses an interoperability problem. He stated that such objects
also pose the problem that important management information may not be
present when it is needed. He further cited in this connection the
inefficiency of repolling when operations may fail owing to the absence
of desired information. Auerbach stated that he personally likes
optional status MIB objects but that, in reality, vendors do not observe
the MIB group as the unit of conformance. In this context, he observed
that a conceptual table in the MIB that currently comprised no
conceptual rows was difficult to distinguish from a failure to implement
the relevant MIB objects.
John Cook (Chipcom Corporation) stated that the framework may lack a
consistent way within the SNMP framework by which agents may document
what MIB objects they support.
Cook also identified a problem with the Ethernet MIB currently under
discussion that it attempts to instrument both IEEE 802.3 and
traditional Ethernet functionality.
Karl Auerbach stated that the feedback afforded by a SNMP Set operation
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is weak and the attendant ambiguity requires that SNMP Sets be done in
the blind. Thus, the results of a Set must be confirmed by a poll, and
this requirement interferes with the need to perform management
operations atomically.
Auerbach also stated that the implementation of management stations is
complicated by the lack of uniform practice with respect to creation and
deletion of MIB object instances. In particular, the implementation of
managers is complicated by lack of knowledge about what is required in
the varbind list for SNMP Sets.
Auerbach also stated that semantic relationships that affect ranges of
acceptable values for MIB objects are not well-represented in the
internet- standard network management framework with the result that
implementation of management stations is more complicated. He cited the
example that if an instance of the ifType MIB object has the value 5,
then the value for the corresponding instance of the ifSpeed object can
not be 10 Mb/s. He also said that constraints of this sort can
transcend the scope of individual conceptual tables.
Auerbach also stated that the lack of a MIB representation for maximum
acceptable SNMP PDU sizes reduces the efficiency of management.
Fred Baker (ACC) stated that the failure to implement mandatory MIB
objects hurts implementors of proxy agents that have made good faith
efforts to conform to MIB standards. Because existing standards are not
clear on the conformance requirements for proxy agents, such agents may
themselves be inappropriately judged as nonconformant when they proxy
for a deficient agent.
John Cook stated that management stations need more information than is
currently represented in the internet-standard network management
framework in order to do a good job of managing the network. He cited
the lack of a common representation for individual objects and
structures of those objects that is oriented to the needs of management
stations.
Cook also stated that the framework may be lacking a way to distribute
``human information'' to management stations -- for example, useful
human-readable text, or textual tags for enumerated values.
Karl Auerbach stated that the internet-standard framework can complicate
the configuration of a management station: constructing ``smart''
management applications may be difficult because the framework lacks a
dynamic, mechanical way of finding out what is in a managed device.
Auerbach also stated that textual ambiguities in the standard
specifications degrades interoperability. He cited as an example of
this problem the phrase ``as if simultaneously.''
John Saperia (Digital Equipment Corporation) stated that in the existing
framework it was difficult to associate information collected over time
with MIB structures that may change over time. He cited the example
that, although statistics may be collected over time about several
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network interfaces, the representation of such interfaces in the MIB may
itself change over time as the result of management operations.
David Waitzman stated that implementation of a management station is
complicated by the possibility of receiving a reference to an
unrecognized MIB object in the varbind list of a SNMP trap PDU. In this
context, Waitzman noted a lack of any mechanism in the framework to
obtain information on how to display an unknown MIB object.
Waitzman also stated that the representation of the IP routing table in
MIB-2 does not support multiple routes to a single destination.
Karl Auerbach stated that the scope of ASN.1 syntax that is legal in
Concise MIB expressions is not made clear in the relevant standards.
Bob Stewart (Xyplex, Incorporated) stated that the cost of agent
implementation for MIB objects is a problem with the current framework.
Stewart stated that limitations on what agents need to do is important
and that too much is expected of managed agents. He also stated that
providing minimal management information in agents is a big job.
Karl Auerbach stated that interoperability suffers in the current
framework owing to a lack of a common communication mechanism between
``head agents'' and ``subordinate agents.''
Anil Rijsinghani (Digital Equipment Corporation) stated that, because
the IEEE allows individual objects to be optional, the translation of
network management definitions from IEEE into the SNMP idiom is
complicated.
Rijsinghani also stated that the framework lacks rules of thumb for
translating IEEE conformance posture into the SNMP idiom. (Marshall
Rose of Dover Beach Consulting interjected a reference to Appendix A of
RFC 1212 at this point in the proceedings.)
Rijsinghani also stated that the IETF process for developing SNMP
standards produced a level of volatility that is incompatible with
gaining essential implementation experience.
Karl Auerbach stated that the semantic context of a SNMP Set operation
(particularly the relation of one MIB object to another) may be
ambiguous in the current framework. He cited the example of a MIB
object whose semantics are ``open bomb bay doors'' and a MIB object
whose semantics are ``drop bombs.'' He pointed out the importance of
temporal sequencing in operations on these two objects.
Bob Stewart stated that the process by which MIBs are developed may be
inconsistent in its discouraging of vendors against shipping
experimental MIBs while at the same time enjoining vendors to experiment
to benefit the community. He stated that companies don't want to do
experiments that don't ship in products but that companies will ship
experiments and assume the risk that entails. Stewart cited as a
problem in the framework that the intended use of the experimental
branch of the MIB namespace is not clearly articulated.
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Karl Auerbach stated that a problem with the current framework is its
excessive use of polling. He stated that a deficiency of the framework
is the lack of a way to generate traps at the discretion of a manager,
in order that knowledge about a serial scenario and its causal structure
may be profitably applied.
David Perkins (Synoptics, Incorporated) stated that a weakness of the
internet- standard network management framework was the difficulty in
understanding it adequately to do an implementation. He stated that the
specifications could be clearer, particularly in the areas of proxy
operations and the function of SNMP communities.
Perkins also stated that a problem with the current framework is that
the heritage of RFC 1155 as a dual SMI for both CMOT and SNMP confuses
some readers owing to now-extraneous provisions.
Perkins also stated that a problem with the framework is its lack of a
MIB for instrumenting the function of the BOOTP protocol and the process
of booting in general. He cited in this context the special problems of
devices that incorporate flash EPROM technologies.
Perkins also stated that the current framework suffered from a model of
network interfaces (as captured in the ifTable of MIB 2) that is
confusing and difficult to understand.
Perkins also stated that the current notation for defining MIBs makes it
hard for people to learn how to write MIBs. In this context, he stated
that the Concise MIB notation should be even more concise. He also said
that the framework lacked notational support for capturing of defined
object identifiers by management stations.
Lynn Monsanto stated that interoperability suffers because the framework
lacks support for management stations to interact easily with new or
unfamiliar devices. He cited the example of the new class of devices
that implement the RMON MIB. He stated that the framework comprises no
algorithms or mechanical notations for communicating the complex
semantics of such MIBs to the management station.
Monsanto also stated that the framework may engender confusion among its
users because the notation for building instance identifiers may be
confusing, particularly for ``messy'' tabular constructs.
Karen Robertson (Concord Communications) stated that interoperability
suffers owing to the lack of a consistent mechanism for configuring and
using SNMP proxy.
Robertson also stated that the effectiveness of the framework in certain
contexts may be compromised by the lack of a common mechanism to recover
from timeouts. She cited a problem raised in the Internet Accounting
Working Group that concerned the loss of valuable information when the
specified polling interval may be too short.
Robertson also stated that the framework makes the definition of new MIB
specifications difficult owing to the lack of provision for defining
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ASN.1 subtypes from existing SMI types. She cited the example of
subrange types defined from the existing Guage type.
Cheryl Krupzak (herself) stated that interoperability and efficiency
suffer for want of a common mechanism for supporting multiple SNMP
agents on the same platform.
Krupzak also stated that interoperability and efficiency suffer from
variations in practice regarding constraints on the minimal set of
varbinds required in a SNMP Set PDU that is to instantiate a conceptual
row in the MIB.
Krupzak also stated that interoperability and efficiency suffer for want
of a common strategy for marking the deletion of conceptual rows from
the MIB.
David Waitzman stated that the framework may be confusing to
implementors in the conventions surrounding the SNMP Trap PDU. Waitzman
cited the names of the fields in the Trap PDU, the semantics of trap
types, and the operation of trap mechanisms in general as possible
points of confusion among implementors.
Keith McCloghrie (Hughes LAN Systems) stated that a weakness of the
current framework was that it did not facilitate development of
management applications because current MIB conformance postures admit
too much optionality and assure too little commonality in what MIB
objects are actually available for applications to use.
McCloghrie stated that the current framework does not foster
interoperability or facilitate management station implementation because
it lacks a common notation for documenting degrees of conformance by an
implementation. He cited the example of an agent that implements a
subset of MIB 2 and observed that there is no common way of documenting
that subset.
McCloghrie also stated that the framework was limited in the range of
MIBs it could generate owing to the lack of a way to define structures
of traditional MIB objects that need not be manipulated individually.
Karl Auerbach stated that interoperability and global management suffer
owing to the lack of a tough requirement on the out-of-the-box state of
every device. He cited the need to characterize new or unfamiliar
devices and stated the desirability of requiring that the system group
of MIB 2 be required to be available for query on every device.
Frank Kastenholz (Clearpoint Research) that the use of SNMP management
in non-IP networks may suffer owing to the inclusion of a NetworkAddress
value in the Trap PDU.
Bob Stewart stated that a concern for agent implementations was that the
framework did not explicitly provide for transient MIB objects
exclusively to support effective use of varbind lists in Trap messages.
He observed that although the contents of a Trap varbind list is
properly derived from MIB objects, the cost entailed by making such
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objects constantly available may not be justified in some cases.
Frank Kastenholz stated that the implementation of mangement stations is
complicated by the lack of a common mechanism for automatic discovery of
network devices.
Jeff Case (University of Tennessee, Knoxville, on behalf of Unni
Warrier, not present) stated that effective management suffered for want
of more intensive transport mechanisms that provide reliable
communication.
Bob Stewart stated that the range of widely deployed SNMP configurations
may be limited by the lack of explicit statement in the standards that a
single-system may realize both agent and manager roles.
Mark Kepke (Hewlett-Packard) stated that a weakness of the current
framework is the difficulty experienced by vendors in developing private
MIB specifications.
Kepke also stated that interoperability may suffer from the want of a
common mechanism for configuring the destinations of Trap PDUs.
Kepke also stated that interoperability may suffer owing to confusion
about the use of DEFVAL clauses and their role in object instantiation.
Kepke also stated that implementation of management stations was
complicated by the lack of a common notation or mechanism for
correlating semantically related constructs in the MIB. He cited the
example of exploiting the analogous structure and content of the ifTable
and the various tables of the Ethernet MIB.
Frank Kastenholz stated that the development of standard MIB
specifications may be impeded by confusion about IAB policy and
procedures for MIB acceptance.
Jeff Case (on behalf of Unni Warrier, not present) stated that the
efficiency of the internet- standard network management framework
suffers from the use of ASN.1 encoding and that, accordingly, a new
transfer syntax is desirable.
John Cook stated that implementation of the SNMP is complicated by its
use of special security mechanisms and that implementation would be
facilitated by the use of a common authentication technology (CAT) in
SNMP.
David Waitzman stated that the effectiveness of the framework may suffer
for want of a LSSR or SSSR mechanism for use in the transmission of Trap
PDUs.
Jeff Case (on behalf of Unni Warrier, not present) stated that a
weakness of the framework is its disregard for international standards
and that compatibility with CMIP should be an important goal for the
future.
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At this point, Chuck Davin adjourned the session, as the time allotted
for the meeting had elapsed.
Attendees
Karl Auerbach karl@eng.sun.com
James Barnes barnes@xylogics.com
Steve Bostock steveb@novell.com
John Burruss jburruss@wellfleet.com
Jeffrey Case case@cs.utk.edu
John Cook cook@chipcom.com
Kurt Dobbins dobbins@ctron.com
Shari Galitzer shari@gateway.mitre.org
Shawn Gallagher gallagher@quiver.enet.dec.com
Phillip Hasse phasse@honchuca-emh8.army.mil
Mark Hoerth mark_hoerth@hp0400.desk.hp.com
Ron Jacoby rj@sgi.com
Ken Jones konkord!ksj@uunet.uu.net
Frank Kastenholz kasten@europa.clearpoint.com
Manu Kaycee kaycee@ctron.com
Mark Kepke mak@cnd.hp.com
Kenneth Key key@cs.utk.edu
Christopher Kolb kolb@psi.com
Bobby Krupczak rdk@cc.gatech.edu
Cheryl Krupczak cheryl@cc.gatech.edu
heryl Krupczak cheryl@cc.gatech.edu
Tim Lee-Thorp ngc!tim@uunet.uu.net
Keith McCloghrie kzm@hls.com
Robert Meierhofer robert@cnt.mn.org
Lynn Monsanto monsanto@sun.com
David Perkins dperkins@synoptics.com
Anil Rijsinghani anil@levers.enet.dec.com
Michael Ritter mwritter@applelink.apple.com
Kary Robertson kr@concord.com
Marshall Rose mrose@dbc.mtview.ca.us
Jonathan Saperia saperia@tcpjon.enet.dec.com
Mark Schaefer schaefer@davidsys.com
John Seligson johns@ultra.com
Timon Sloane peernet!timon@uunet.uu.net
Lance Sprung sprung@sys.smc.com
Bob Stewart rlstewart@eng.xyplex.com
Bruce Taber taber@interlan.com
Dean Throop throop@dg-rtp.dg.com
Maurice Turcotte dnmrt@rm1.uucp
David Waitzman djw@bbn.com
Steven Waldbusser waldbusser@andrew.cmu.edu
Drew Wansley dwansley@ccgate.ColumbiaSC.NCR.COM
Preston Wilson preston@i88.isc.com
Wengyik Yeong yeongw@psi.com
Joseph Zur fibrontics!zur@uunet.uu.net
Peter de Vries peter@wco.ftp.com
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