draft-ietf-snmpv3-next-gen-arch-03.txt   draft-ietf-snmpv3-next-gen-arch-04.txt 
stracts.txt'' listing contained in the Internet- Drafts Shadow
An Architecture for Describing
SNMP Management Frameworks
1 August 1997
D. Harrington
Cabletron Systems, Inc.
dbh@cabletron.com
B. Wijnen
IBM T.J. Watson Research
wijnen@vnet.ibm.com
<draft-ietf-snmpv3-next-gen-arch-04.txt>
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference material
or to cite them other than as ``work in progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe), Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe),
ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim).
Abstract Abstract
This document describes an architecture for describing Internet This document describes an architecture for describing SNMP Management
Management Frameworks. The architecture is designed to be modular Frameworks. The architecture is designed to be modular to allow the
to allow the evolution of the protocol over time. The major portions evolution of the SNMP protocol standards over time. The major portions
of the architecture are an SNMP engine containing a Message Processing of the architecture are an SNMP engine containing a Message Processing
subsystem, a Security Subsystem and an Access Control Subsystem, and Subsystem, a Security Subsystem and an Access Control Subsystem, and
possibly multiple SNMP applications which provide specific functional possibly multiple SNMP applications which provide specific functional
processing of network management data. These SNMP applications are processing of network management data.
of various types, including Command Generator and Command Responder
applications, Notification Originator and Notification Receiver
applications, and Proxy Forwarding applications.
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0. Issues 0. Issues
0.1. Issues to be resolved 0.1. Resolved Issues
. contextEngineID in reportPDU = snmpEngineID of report generator
. returnResponsePDU - are all parameters needed? overrides allowed?
all parameters kept for future flexibility
overrides not supported by SNMPv3
. use of IN/OUT indicators in primitives accepted
. NT/Unix-like access control - can be defined as future model
. user-friendly names? yes, but with limits
. SnmpAdminString as index? yes, but restrict sizes
. need both MMS and maxSizeResponseScopedPDU? yes.
. synchronous vs. asynchronous primitives? synchronous preferred
. should we change MIB naming? no, it is acceptable
. is it ok that USM is bound to SNMPv3? while undesirable, it is
acceptable. A cleaner model may be defined in the future.
. should securityModel "any" be supported? for ACM use, not SNMPv3
. what defines SNMPv3? a document will be published after Munich
. Is an application-level handle needed for request/response matching?
yes. create sendPduhandle
. Is wildcard contextEngineID/pduType registration needed? No. This is
an internal interface, and wildcarding can be supported by an
implementation, but is not required in the standard.
. Should indices be integers or SnmpAdminStrings? SnmpAdminStrings
is the consensus.
. Should protocols be identified as OIDs or Integers? OIDs
. terminology:
securityLevel rather than LoS
msgXXXX to identify message fields in SNMPv3
. OID or Integer for auth/priv protocol identifiers . OID or Integer for auth/priv protocol identifiers
second interim meeting reached consensus on OIDs Consensus: use OID
some mailing list members still say Integers preferred
. forward references need to be handled
. Is Glossary needed to describe primitive parameters, or is the . Is Glossary needed to describe primitive parameters, or is the
expanded template adequate for this purpose? expanded template adequate for this purpose?
. state_reference releases - are these consistently defined? Consensus: Terms are basically all defined in section 3.
check documents. . state_reference releases
. discuss utf8. - probably open WG discussion in Munich per NMAD Consensus: documents checked; we think it is OK now
discuss tomorrow; remains open issue.
. need mechanism to discover securityModels supported
. new SnmpEngineID format rules to be discussed yet. . new SnmpEngineID format rules to be discussed yet.
Consensus: Limit size to be 1..32
. needs changes to meet STDGUIDE guidelines . needs changes to meet STDGUIDE guidelines
. add a "Decision History" section (as an appendix?) We think we're meeting them now
. we punted snmpEngineMaxMessageSize at 2nd interim because that . we punted snmpEngineMaxMessageSize at 2nd interim because that
info travels in each SNMPv3 message. However, we may want to info travels in each SNMPv3 message. However, we may want to
re-introduce it so that SNMPv1/v2c managers can learn the value!! re-introduce it so that SNMPv1/v2c managers can learn the value!!
Consensus: Nobody picked up on this, so it seems not needed.
. Do we need a mechanism to discover securityModels supported
Can be decided after Munich
. add a "Decision History" section (as an appendix?)
Can be decided after Munich
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0.1.1. Issues discussed at second Interim Meeting: 0.1.1. Issues discussed at second Interim Meeting:
. A "readable" introduction supplement may be done after Munich. . A "readable" introduction supplement may be done after Munich.
. Applications are responsible for retries, but implementations may . Applications are responsible for retries, but implementations may
differ. differ.
. TCs should not be defined just to describe primitive parameters. . TCs should not be defined just to describe primitive parameters.
If they cannot be described adequately in text, they can be defined If they cannot be described adequately in text, they can be defined
in a Glossary. Avoid describing implementation details. in a Glossary. Avoid describing implementation details.
. Is SnmpAdminString appropriate for all strings, such as . Is SnmpAdminString appropriate for all strings, such as
skipping to change at page 10, line ? skipping to change at page 10, line ?
. mappings may exist between different (model, Name) and the same . mappings may exist between different (model, Name) and the same
securityName by varying the model or the Name. securityName by varying the model or the Name.
. the securityName and a MDID may be identical. This can be defined . the securityName and a MDID may be identical. This can be defined
by the Security Model. by the Security Model.
(user,"public") may map to securityName "public" (user,"public") may map to securityName "public"
. [securityName, securityModel] yields zero or one MDName, with . [securityName, securityModel] yields zero or one MDName, with
exceptions for backwards compatibility. The exception is defined exceptions for backwards compatibility. The exception is defined
by the model, and the problems are the province of the model to by the model, and the problems are the province of the model to
resolve. resolve.
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0.2. Change Log 0.2. Change Log
[version 4.14]
. formatting
. pagination
[version 4.13]
. new acknowledgements
. updated references
. updated issues list
. ordered security, editors, acknowledgements, references sections
. checked line lengths
[version 4.12]
. cleanup
. added expectResponse to processIncomingMsg to address Levi-raised
concern
. acknowledgements
. MIB checked by SMICng
. post to snmpv3 mailing list
[version 4.11]
. Change Primitives between MP and SEC to try and address the issue
of architectural binding to message format.
. Added securityName and securityLevel to the returnResponsePdu
primitive so that architecturally it could be different for a
request and a response.
. Rename processMsg primitive to processIncomingMsg
[version 4.10]
. spell check
[version 4.9]
. editorial changes
. fix SnmpEngineID TC
. add a note to SnmpAdminString
. rename title of section 1.1
. expand description of Dispatcher a bit
[version 4.8]
. Added parameter pduVersion on primitives:
sendPdu
processPdu
returnResponsePdu
processResponsePdu
prepareDataElements
prepareOutgoingMessage
prepareResponseMessage
. Added parameter messageProcessingModel on the primitive:
processPdu
processResponsePdu
returnResponsePdu
. Removed messageProcessingModel parameter from primitives:
registerContextEngineID
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unregisterContextEngineID
. Renamed SNMP Version Multiplexer to Dispatcher
. Renamed Version Multiplexer to Message Multiplexer
. Renamed Application Multiplexer to PDU Dispatcher
. Rearranged some parameters in various Primitives so the sequence
of parameters is now more consistent.
[version 4.7]
. editorial cleanup
. changed asterisk text
. modified snmpv3 framework description to eliminate dependencies
. reorder 4.2.x to reflect transaction order
. changed SnmpEngineID size to 1..32
[version 4.6]
. Changes to use synchronous primitives where possible
. Changes to describe SNMP Version Multiplexer
. Remove (empty) glossary
. Redraw documentation figure
. Redraw Operational Overview Figure
. Remove old section 4 (Architectural Elements of Procedure)
These moved to the MP document into the SNMP Version Multiplexer
section.
. Move Overview of all primitives from Appendix to Section 4.
. Simplify Appendix A to just described Model Designer Guidelines
and refer back to section 4 for specific primitives
. Remove Appendix B (An Evolutionary Architecture - Design Goals)
. added design decision regarding security
. Included latest Snmp SecurityModel TC (as it was actually posted
to the SNMPv3 mailing list).
[version 4.5]
. start with <draft-ietf-snmpv3-next-gen-arch-03.txt>
. change vendor to implementor
. change LoS to securityLevel
. remove mention of enterprise
. change Internet Management Framework to SNMP Management Framework
. modify usage of "frameworks" to improve internal consistency.
. change Message Processing Abstract Service Interface to
Application Multiplexor
. change description of SNMP engine
. moved "one-to-one association" for entity and engine to discussion
of engine.
. changed distributing to dispatching
. added asterisks to indicate v3* items are also not required.
. changed "community access control" to "other access control"
. added TC for SnmpMessageProcessingModel
. modified Security Considerations
. modified acknowledgements
[version 4.4] [version 4.4]
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. Fixed one error in the MIB (found with SMICng) . Fixed one error in the MIB (found with SMICng)
. Reformatted text for SnmpAdminString, no change in text. . Reformatted text for SnmpAdminString, no change in text.
. Changed text for SnmpEngineID.. this is still under discussion. . Changed text for SnmpEngineID.. this is still under discussion.
But this new text seems to be getting close to what we want. But this new text seems to be getting close to what we want.
. Added an issue w.r.t. snmpEngineMaxMessageSize . Added an issue w.r.t. snmpEngineMaxMessageSize
. adapt Primitive names and parameters to very latest (july 11) names . adapt Primitive names and parameters to very latest (july 11) names
. removed blank lines before the .p page controls. . removed blank lines before the .p page controls.
. publish as <draft-ietf-snmpv3-next-gen-arch-03.txt>
[version 4.3] [version 4.3]
. some minor editing adjustments . some minor editing adjustments
[version 4.2] [version 4.2]
. modify abstract so there is no requirement for one entity . modify abstract so there is no requirement for one entity
to contain both a command generator and a notification receiver. to contain both a command generator and a notification receiver.
. modify Introduction list of entities which are meant to be . modify Introduction list of entities which are meant to be
supported supported
. reorganized sections 1 through 4 for more consistency in contents. . reorganized sections 1 through 4 for more consistency in contents.
. described section contents in Introduction:Target Audience . described section contents in Introduction:Target Audience
. move documentation descriptions to section 2 . move documentation descriptions to section 2
. rewrite section 4 to be more like a real elements of procedure. . rewrite section 4 to be more like a real elements of procedure.
. modified SnmpSecurityModel and SnmpEngineID definitions . modified SnmpSecurityModel and SnmpEngineID definitions
skipping to change at page 10, line ? skipping to change at page 10, line ?
traditional manager. This is in section 2. traditional manager. This is in section 2.
. Changed overview figure in section 3. to address the comments . Changed overview figure in section 3. to address the comments
by Dave Levi. It now lists the type of applications by Dave Levi. It now lists the type of applications
. At various places ensure that text (easily) fits within 72 . At various places ensure that text (easily) fits within 72
columns as required by RFC-editors Guidelines document. columns as required by RFC-editors Guidelines document.
. Section 2.3 (new section) has the documents set overview. . Section 2.3 (new section) has the documents set overview.
I verified the claims about standards. Not sure I worded the I verified the claims about standards. Not sure I worded the
SNMPv2 std correctly,. We'll hear it if we did it wrong. SNMPv2 std correctly,. We'll hear it if we did it wrong.
. Section 2.4 (new section) gives overview of SNMP entities based . Section 2.4 (new section) gives overview of SNMP entities based
on modified Dave Levi figure. I (Bert) wonder however if it would on modified Dave Levi figure. I (Bert) wonder however if it would
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not be better to move it to after section 3.1.13 not be better to move it to after section 3.1.13
. Section 3. Added more figures... please let us know if you find . Section 3. Added more figures... please let us know if you find
then useful and/or helpful. We could also move these back to then useful and/or helpful. We could also move these back to
section 2 if such makes more sense. section 2 if such makes more sense.
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. Added a picture in section 3.2. . Added a picture in section 3.2.
It also shows some of access control, so not sure it really fits It also shows some of access control, so not sure it really fits
here, although it does map principal to model dependent security here, although it does map principal to model dependent security
ID to securityName ID to securityName
. Replace "<" with "is lower than" in section 3.4.3 which seems . Replace "<" with "is lower than" in section 3.4.3 which seems
better in a text document. better in a text document.
. Renamed section 4.1 to "SNMP engine processing" instead of . Renamed section 4.1 to "SNMP engine processing" instead of
"The Message Processing Subsystem" because the transport "The Message Processing Subsystem" because the transport
mappings, mpc multiplexor and such is done in ARCH document so mappings, mpc multiplexor and such is done in ARCH document so
it is done "in general in the engine" and it passes a specific it is done "in general in the engine" and it passes a specific
skipping to change at page 10, line ? skipping to change at page 10, line ?
removed from ARCH and that it would all be done in SEC document. removed from ARCH and that it would all be done in SEC document.
. Modified Security Considerations. Was still talking about LPM. . Modified Security Considerations. Was still talking about LPM.
. Appendix. I am still wondering if we need to use capitals for . Appendix. I am still wondering if we need to use capitals for
things like "Security Model" "Subsystem" and such. This is only things like "Security Model" "Subsystem" and such. This is only
an appendix... but we better be consistent, no? Anyway an appendix... but we better be consistent, no? Anyway
I changed it so it is consistent (at least I tried). I changed it so it is consistent (at least I tried).
. Appendix, renamed imf to snmpFramework . Appendix, renamed imf to snmpFramework
. Appendix, changed state_reference and state_release to . Appendix, changed state_reference and state_release to
stateReference and stateRelease to be consistent with other names stateReference and stateRelease to be consistent with other names
for abstract data and primitives. for abstract data and primitives.
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. A.2 changed MessageEngine to SNMP engine . A.2 changed MessageEngine to SNMP engine
. Fixed ASI primitives to be in sync with SEC document. . Fixed ASI primitives to be in sync with SEC document.
I also thought that our ARCH document-outline wanted to at least I also thought that our ARCH document-outline wanted to at least
have the primitives listed within the main body of the text, no? have the primitives listed within the main body of the text, no?
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. Adapted send_pdu to sendPdu primitive as reconciled by Randy . Adapted send_pdu to sendPdu primitive as reconciled by Randy
In fact I made sure all primitives are in-line with current In fact I made sure all primitives are in-line with current
agreement on names and parameters. agreement on names and parameters.
. Rename title of A.2.4 and A.2.5 so it fits on 1 line in contents . Rename title of A.2.4 and A.2.5 so it fits on 1 line in contents
. I did not look at appendix B. That is your (DBH) specialty is it . I did not look at appendix B. That is your (DBH) specialty is it
not ? ;-). not ? ;-).
. Quick simple spell check done with "spell" on AIX . Quick simple spell check done with "spell" on AIX
[version 4.0] [version 4.0]
. move section 7 - Model Requirements to an appendix . move section 7 - Model Requirements to an appendix
. move Section 3 - Design Goals to an appendix . move Section 3 - Design Goals to an appendix
. modified Section 5 - Naming . modified Section 5 - Naming
. remove "possibly multiple" . remove "possibly multiple"
. moved Section 5 to Section 3 . moved Section 5 to Section 3
. change orangelets to applications . change orangelets to applications
. modify description of applications . modify description of applications
. change scopedPDU-MMS and PDU-MMS to maxSizeResponseScopedPDU . change scopedPDU-MMS and PDU-MMS to maxSizeResponseScopedPDU
. change Scoped-PDU and ScopedPDU to scopedPDU (no dash, lower case S) . change Scoped-PDU and ScopedPDU to scopedPDU (no dash, lower case S)
skipping to change at page 10, line ? skipping to change at page 10, line ?
data, the access control data, and the orangelet data. data, the access control data, and the orangelet data.
. identify issues . identify issues
. publish as <draft-ietf-snmpv3-next-gen-arch-02.txt> . publish as <draft-ietf-snmpv3-next-gen-arch-02.txt>
[version 3.0] [version 3.0]
. add section on threats for message security . add section on threats for message security
. add section on threats for access control . add section on threats for access control
. change application to orangelet . change application to orangelet
. remove references to F-Ts . remove references to F-Ts
. change securityIdentity to security-identity . change securityIdentity to security-identity
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. change securityCookie to securityIdentity . change securityCookie to securityIdentity
. the format of securityIdentity is defined by the model . the format of securityIdentity is defined by the model
. add securityModel to passed parameters as needed . add securityModel to passed parameters as needed
. eliminate group from passed parameters . eliminate group from passed parameters
. remove unused IMPORTS . remove unused IMPORTS
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. add glossary section with initial set of words to define . add glossary section with initial set of words to define
. differentiate the messageEngine from the contextEngine . differentiate the messageEngine from the contextEngine
. eliminate the term SNMPng . eliminate the term SNMPng
. rewrote 1.1. A Note on Terminology . rewrote 1.1. A Note on Terminology
. eliminated assumptions about SNMP processing always being . eliminated assumptions about SNMP processing always being
message related message related
. rewrote 4.x to reflect new thinking . rewrote 4.x to reflect new thinking
. rewrote 5.x to reflect new thinking . rewrote 5.x to reflect new thinking
. rewrote 6.x (the MIB) to reflect new thinking . rewrote 6.x (the MIB) to reflect new thinking
. added MIB objects at this level (previously only TCs) . added MIB objects at this level (previously only TCs)
. rewrote 7.x . rewrote 7.x
. sent to v3edit list . sent to v3edit list
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1. Introduction 1. Introduction
1.1. Target Audience 1.1. Overview
This document will have as its audience persons with varying levels This document assumes an audience with varying levels of technical
of technical understanding of SNMP. understanding of SNMP.
This document does not provide a general introduction to SNMP. Other This document does not provide a general introduction to SNMP. Other
documents and books can provide a much better introduction to SNMP. documents and books can provide a much better introduction to SNMP.
Nor does this document provide a history of SNMP. That also can be Nor does this document provide a history of SNMP. That also can be
found in books and other documents. found in books and other documents.
This document does define a vocabulary for describing Internet This document defines a vocabulary for describing SNMP Management
Management Frameworks, and an architecture for describing the Frameworks, and an architecture for describing the major portions of
major portions of Internet Management Frameworks. SNMP Management Frameworks.
Section 1 describes the purpose, goals, and design decisions of Section 1 describes the purpose, goals, and design decisions of
the architecture. this architecture.
Section 2 describes various types of documents which define Internet Section 2 describes various types of documents which define SNMP
Frameworks, and how they fit into this architecture. It also provides Frameworks, and how they fit into this architecture. It also provides
a minimal roadmap to the documents which have defined previous a minimal roadmap to the documents which have previously defined
SNMP frameworks. SNMP frameworks.
Section 3 details the vocabulary of this architecture and its pieces. Section 3 details the vocabulary of this architecture and its pieces.
This section is important for understanding the remaining sections, This section is important for understanding the remaining sections,
and for understanding documents which are written to fit within this and for understanding documents which are written to fit within this
architecture. architecture.
Section 4 describes the elements of procedure followed by an SNMP Section 4 describes the primitives used for the abstract service
engine in coordinating the processing of messages by the subsystems interfaces between the various subsystems, models and applications
of the engine and by applications. within this architecture.
Section 5 defines a collection of managed objects used to instrument Section 5 defines a collection of managed objects used to instrument
SNMP engines within this architecture. SNMP entities within this architecture.
Sections 6, 7, 8, and 9 are administrative in nature. Sections 6, 7, 8, and 9 are administrative in nature.
Appendix A contains guidelines for developers of Models which are Appendix A contains guidelines for designers of Models which are
expected to fit within this architecture. expected to fit within this architecture.
Appendix B contains a discussion of software design principles which 1.2. SNMP Management Systems
guided the development of this architecture. Many books provide a
more in-depth discussion of these topics.
1.2. Management Systems
A management system contains: An SNMP management system contains:
- several (potentially many) nodes, each with an SNMP entity - several (potentially many) nodes, each with an SNMP entity
containing command responder and notification originator containing command responder and notification originator
applications, which have access to management instrumentation; applications, which have access to management instrumentation;
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- at least one SNMP entity containing command generator and/or - at least one SNMP entity containing command generator and/or
notification receiver applications; and, notification receiver applications; and,
- a management protocol, used to convey management information - a management protocol, used to convey management information
between the SNMP entities. between the SNMP entities.
SNMP entities executing command generator and notification receiver SNMP entities executing command generator and notification receiver
applications monitor and control managed elements. Managed elements applications monitor and control managed elements. Managed elements
are devices such as hosts, routers, terminal servers, etc., which are devices such as hosts, routers, terminal servers, etc., which
are monitored and controlled via access to their management are monitored and controlled via access to their management
information. information.
Operations of the protocol are carried out under an administrative
framework which defines minimum requirements for standard services,
such as sending and receiving messages, countering security threats
to messages, controlling access to managed objects, and processing
various types of requests.
It is the purpose of this document to define an architecture which It is the purpose of this document to define an architecture which
can evolve to realize effective network management in a variety can evolve to realize effective network management in a variety
of configurations and environments. The architecture has been of configurations and environments. The architecture has been
designed to meet the needs of implementations of: designed to meet the needs of implementations of:
- minimal SNMP entities with command responder and/or notification - minimal SNMP entities with command responder and/or notification
originator applications (traditionally called SNMP agents), originator applications (traditionally called SNMP agents),
- SNMP entities with proxy forwarder applications (traditionally - SNMP entities with proxy forwarder applications (traditionally
called SNMP proxy agent), called SNMP proxy agent),
- command line driven SNMP entities with command generator and/or - command line driven SNMP entities with command generator and/or
notification receiver applications (traditionally called SNMP notification receiver applications (traditionally called SNMP
command line managers), command line managers),
- SNMP entities with command generator and/or notification - SNMP entities with command generator and/or notification
receiver, plus command responder and/or notification originator receiver, plus command responder and/or notification originator
applications (traditionally called SNMP mid-level managers or applications (traditionally called SNMP mid-level managers or
dual-role entities), dual-role entities),
- SNMP entities with command generator and/or notification - SNMP entities with command generator and/or notification
receiver and possibly other types of applications for managing receiver and possibly other types of applications for managing
a potentially very large number of managed nodes (traditionally a potentially very large number of managed nodes (traditionally
called network enterprise management stations). called network management stations).
1.3. Goals of this Architecture 1.3. Goals of this Architecture
This architecture was driven by the following goals: This architecture was driven by the following goals:
- Use existing materials as much as possible. - Use existing materials as much as possible. It is heavily based
It is heavily based on previous work, informally on previous work, informally known as SNMPv2u and SNMPv2*.
known as SNMPv2u and SNMPv2*.
- Address the need for secure SET support, which is considered - Address the need for secure SET support, which is considered
the most important deficiency in SNMPv1 and SNMPv2c. the most important deficiency in SNMPv1 and SNMPv2c.
- Make it possible to move portions of the architecture forward - Make it possible to move portions of the architecture forward
in the standards track, even if consensus has not been reached in the standards track, even if consensus has not been reached
on all pieces. on all pieces.
- Define an architecture that allows for longevity of the SNMP - Define an architecture that allows for longevity of the SNMP
Frameworks that have been and will be defined. Frameworks that have been and will be defined.
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- Keep SNMP as simple as possible. - Keep SNMP as simple as possible.
- Make it relatively inexpensive to deploy a minimal conformant - Make it relatively inexpensive to deploy a minimal conformant
implementation implementation
- Make it possible to upgrade portions of a framework as new - Make it possible to upgrade portions of SNMP as new approaches
approaches become available, without disrupting the entire become available, without disrupting an entire SNMP framework.
framework.
- Make it possible to support features required in large networks, - Make it possible to support features required in large networks,
but make the expense of supporting a feature directly related but make the expense of supporting a feature directly related
to the support of the feature. to the support of the feature.
1.4. Security Requirements of this Architecture 1.4. Security Requirements of this Architecture
Several of the classical threats to network protocols are applicable Several of the classical threats to network protocols are applicable
to the network management problem and therefore would be applicable to the network management problem and therefore would be applicable
to any Security Model used in an Internet Management Framework. Other to any Security Model used in an SNMP Management Framework. Other
threats are not applicable to the network management problem. This threats are not applicable to the network management problem. This
section discusses principal threats, secondary threats, and threats section discusses principal threats, secondary threats, and threats
which are of lesser importance. which are of lesser importance.
The principal threats against which any Security Model used within The principal threats against which any Security Model used within
this architecture SHOULD provide protection are: this architecture SHOULD provide protection are:
Modification of Information Modification of Information
The modification threat is the danger that some unauthorized SNMP The modification threat is the danger that some unauthorized SNMP
entity may alter in-transit SNMP messages generated on behalf of entity may alter in-transit SNMP messages generated on behalf of
skipping to change at page 10, line ? skipping to change at page 12, line 45
may be maliciously re-ordered, delayed or replayed to an extent may be maliciously re-ordered, delayed or replayed to an extent
which is greater than can occur through the natural operation of which is greater than can occur through the natural operation of
a subnetwork service, in order to effect unauthorized management a subnetwork service, in order to effect unauthorized management
operations. operations.
Disclosure Disclosure
The disclosure threat is the danger of eavesdropping on the The disclosure threat is the danger of eavesdropping on the
exchanges between SNMP engines. Protecting against this threat exchanges between SNMP engines. Protecting against this threat
may be required as a matter of local policy. may be required as a matter of local policy.
Harrington/Wijnen Expires December 1997 [Page 9] There are at least two threats against which a Security Model within
\ this architecture need not protect.
There are at least two threats against which a Security Model used by
a framework within this architecture need not protect.
Denial of Service Denial of Service
A Security Model need not attempt to address the broad range of A Security Model need not attempt to address the broad range of
attacks by which service on behalf of authorized users is denied. attacks by which service on behalf of authorized users is denied.
Indeed, such denial-of-service attacks are in many cases Indeed, such denial-of-service attacks are in many cases
indistinguishable from the type of network failures with which any indistinguishable from the type of network failures with which any
viable network management protocol must cope as a matter of course. viable network management protocol must cope as a matter of course.
Traffic Analysis Traffic Analysis
A Security Model need not attempt to address traffic analysis A Security Model need not attempt to address traffic analysis
attacks. Many traffic patterns are predictable - entities may attacks. Many traffic patterns are predictable - entities may
be managed on a regular basis by a relatively small number of be managed on a regular basis by a relatively small number of
management stations - and therefore there is no significant management stations - and therefore there is no significant
advantage afforded by protecting against traffic analysis. advantage afforded by protecting against traffic analysis.
1.5. Design Decisions 1.5. Design Decisions
Various designs decision were made in support of these goals: Various designs decision were made in support of the goals of the
architecture and the security requirements:
- Architecture - Architecture
An architecture should be defined which identifies the An architecture should be defined which identifies the conceptual
conceptual boundaries between the documents of a framework. boundaries between the documents. Subsystems should be defined
Subsystems should be defined which describe the abstract which describe the abstract services provided by specific
services provided by specific portions of the framework. portions of an SNMP framework. Abstract service interfaces, as
Abstract service interfaces, as described by service primitives, described by service primitives, define the abstract boundaries
define the abstract boundaries between documents, and the between documents, and the abstract services that are provided
abstract services that are provided by the conceptual by the conceptual subsystems of an SNMP framework.
subsystems of a framework.
- Self-contained Documents - Self-contained Documents
Elements of procedure plus the MIB objects which are needed for Elements of procedure plus the MIB objects which are needed for
processing for a specific portion of a framework should be processing for a specific portion of an SNMP framework should be
defined in the same document, and as much as possible, should defined in the same document, and as much as possible, should
not be referenced in other documents. This allows various not be referenced in other documents. This allows pieces to be
pieces of SNMP Frameworks to be designed and documented as designed and documented as independent and self-contained parts,
independent and self-contained parts, which is consistent with which is consistent with the general SNMP MIB module approach.
the general SNMP MIB module approach. As portions of SNMP change As portions of SNMP change over time, the documents describing
over time, the documents describing other portions of the other portions of SNMP are not directly impacted. This modularity
framework are not directly impacted. This modularity allows, allows, for example, Security Models, authentication and privacy
for example, Security Models, authentication and privacy
mechanisms, and message formats to be upgraded and supplemented mechanisms, and message formats to be upgraded and supplemented
as the need arises. The self-contained documents can move as the need arises. The self-contained documents can move along
along the standards track on different time-lines. the standards track on different time-lines.
- The Security Models in the Security Subsystem SHOULD protect
against the principal threats: modification of information,
masquerade, message stream modification and disclosure.
They do not need to protect against denial of service and
traffic analysis.
- Remote Configuration - Remote Configuration
The Security and Access Control Subsystems add a whole new set The Security and Access Control Subsystems add a whole new set
of SNMP configuration parameters. The Security Subsystem also of SNMP configuration parameters. The Security Subsystem also
requires frequent changes of secrets at the various SNMP requires frequent changes of secrets at the various SNMP
entities. To make this deployable in a large operational entities. To make this deployable in a large operational
\
environment, these SNMP parameters must be able to be remotely environment, these SNMP parameters must be able to be remotely
configured. configured.
- Controlled Complexity - Controlled Complexity
It is recognized that simple managed devices want to keep the It is recognized that simple managed devices want to keep the
resources used by SNMP to a minimum. At the same time, there resources used by SNMP to a minimum. At the same time, there
is a need for more complex configurations which can spend more is a need for more complex configurations which can spend more
resources for SNMP and thus provide more functionality. resources for SNMP and thus provide more functionality.
The design tries to keep the competing requirements of these The design tries to keep the competing requirements of these
two environments in balance and allows the more complex two environments in balance and allows the more complex
environments to logically extend the simple environment. environments to logically extend the simple environment.
\
2. Documentation Overview 2. Documentation Overview
The following figure shows the set of documents that fit within the The following figure shows the set of documents that fit within the
SNMP Architecture. SNMP Architecture.
Document Set
+--------------------------------------------------------------------+ +-------------------------- Document Set ----------------------------+
| | | |
| +------------+ +-----------------+ +----------------+ | | +------------+ +-----------------+ +----------------+ |
| | * | | * | | * | | | | Document * | | Applicability * | | Coexistence * | |
| | Document | | Applicability | | Coexistence | |
| | Roadmap | | Statement | | & Transition | | | | Roadmap | | Statement | | & Transition | |
| +------------+ +-----------------+ +----------------+ | | +------------+ +-----------------+ +----------------+ |
| | | |
| +-------------------+ +-----------------------------------------+ | | +----------------------------------------------------------------+ |
| | Operational Model | | Security and Administration | | | | Message Handling | |
| | | | | | | | +-----------------+ +-----------------+ +-----------------+ | |
| | +-------------+ | | +------------+ +----------+ +---------+ | | | | | Transport | | Message | | Security | | |
| | | | | | | | | | | | | | | | | Mappings | | Processing and | | | | |
| | | Protocol | | | | Message | | Security | | Access | | | | | | | | Dispatching | | | | |
| | | Operations | | | | Processing | | | | Control | | | | | +-----------------+ +-----------------+ +-----------------+ | |
| | +-------------+ | | +------------+ +----------+ +---------+ | | | +----------------------------------------------------------------+ |
| | +-------------+ | | | | | |
| | | | | | +--------------+ +----------+ | | | +----------------------------------------------------------------+ |
| | | Transport | | | | | | | | | | | PDU Handling | |
| | | Mappings | | | | Applications | ......... | | | | | | +-----------------+ +-----------------+ +-----------------+ | |
| | +-------------+ | | +--------------+ +----------+ | | | | | Protocol | | Applications | | Access | | |
| | | | | | | | | Operations | | | | Control | | |
| +-------------------+ +-----------------------------------------+ | | | +-----------------+ +-----------------+ +-----------------+ | |
| +----------------------------------------------------------------+ |
| | | |
| +----------------------------------------------------------------+ | | +----------------------------------------------------------------+ |
| | Information Model | | | | Information Model | |
| | | |
| | +--------------+ +--------------+ +---------------+ | | | | +--------------+ +--------------+ +---------------+ | |
| | | Structure of | | Textual | | Conformance | | | | | | Structure of | | Textual | | Conformance | | |
| | | Management | | Conventions | | Statements | | | | | | Management | | Conventions | | Statements | | |
| | | Information | | | | | | | | | | Information | | | | | | |
| | +--------------+ +--------------+ +---------------+ | | | | +--------------+ +--------------+ +---------------+ | |
| +----------------------------------------------------------------+ | | +----------------------------------------------------------------+ |
| | | |
| +----------------------------------------------------------------+ | | +----------------------------------------------------------------+ |
| | MIBs | | | | MIBs | |
| | | |
| | +-------------+ +-------------+ +----------+ +----------+ | | | | +-------------+ +-------------+ +----------+ +----------+ | |
| | | Standard v1 | | Standard v1 | | Historic | | Draft v2 | | | | | | Standard v1 | | Standard v1 | | Historic | | Draft v2 | | |
| | | RFC1157 | | RFC1212 | | RFC14xx | | RFC19xx | | | | | | RFC1157 | | RFC1212 | | RFC14xx | | RFC19xx | | |
| | | format | | format | | format | | format | | | | | | format | | format | | format | | format | | |
| | +-------------+ +-------------+ +----------+ +----------+ | | | | +-------------+ +-------------+ +----------+ +----------+ | |
| +----------------------------------------------------------------+ | | +----------------------------------------------------------------+ |
| | | |
+--------------------------------------------------------------------+ +--------------------------------------------------------------------+
\
Those marked with an asterisk (*) are expected to be written in the Those marked with an asterisk (*) are expected to be written in the
future. Each of these documents may be replaced or supplemented. future. Each of these documents may be replaced or supplemented.
This Architecture document specifically describes how new documents This Architecture document specifically describes how new documents
fit into the set of documents in the Security and Administration area. fit into the set of documents in the area of Message and PDU handling.
2.1. Document Roadmap 2.1. Document Roadmap
One or more documents may be written that will describe how sets One or more documents may be written to describe how sets of documents
of documents taken together form a specific SNMP framework. taken together form specific Frameworks. The configuration of document
The configuration of document sets might change over time, so the sets might change over time, so the "roadmap" should be maintained in
"roadmap" should be maintained in a document separate from the a document separate from the standards documents themselves.
standards documents themselves.
2.2. Applicability Statement 2.2. Applicability Statement
SNMP is used in networks that vary widely in size and complexity, SNMP is used in networks that vary widely in size and complexity,
by organizations that vary widely in their requirements of network by organizations that vary widely in their requirements of network
management. Some models will be designed to address specific management. Some models will be designed to address specific problems
problems of network management, such as message security. of network management, such as message security.
One or more documents may be written which describe the environments One or more documents may be written to describe the environments
to which certain versions of SNMP or models within SNMP would be to which certain versions of SNMP or models within SNMP would be
appropriately applied, and those to which a given model might be appropriately applied, and those to which a given model might be
inappropriately applied. inappropriately applied.
2.3. Coexistence and Transition 2.3. Coexistence and Transition
The purpose of an evolutionary architecture is to permit new models The purpose of an evolutionary architecture is to permit new models
to replace or supplement existing models. The interactions between to replace or supplement existing models. The interactions between
models could result in incompatibilities, security "holes", and models could result in incompatibilities, security "holes", and
other undesirable effects. other undesirable effects.
skipping to change at page 14, line 5 skipping to change at page 17, line 5
Coexistence documents are therefore expected to be prepared separately Coexistence documents are therefore expected to be prepared separately
from model definition documents, to describe and resolve interaction from model definition documents, to describe and resolve interaction
anomalies between a model definition and one or more other model anomalies between a model definition and one or more other model
definitions. definitions.
Additionally, recommendations for transitions between models may Additionally, recommendations for transitions between models may
also be described, either in a coexistence document or in a separate also be described, either in a coexistence document or in a separate
document. document.
\
2.4. Transport Mappings 2.4. Transport Mappings
SNMP messages are sent over various transports. It is the purpose of SNMP messages are sent over various transports. It is the purpose of
Transport Mapping documents to define how the mapping between SNMP Transport Mapping documents to define how the mapping between SNMP
and the transport is done. A specific implementation of an SNMP engine and the transport is done.
defines which transports it supports.
2.5. Message Processing 2.5. Message Processing
A Message Processing Model document defines a message format, which is A Message Processing Model document defines a message format, which is
typically identified by a version field in an SNMP message header. typically identified by a version field in an SNMP message header.
The document may also define a MIB module for use in message The document may also define a MIB module for use in message
processing and for instrumentation of version-specific interactions. processing and for instrumentation of version-specific interactions.
An engine will include one or more Message Processing Models, and thus An SNMP engine includes one or more Message Processing Models, and thus
may support sending and receiving multiple SNMP versions of may support sending and receiving multiple versions of SNMP messages.
messages.
2.6. Security 2.6. Security
Some environments require secure protocol interactions. Security is Some environments require secure protocol interactions. Security is
normally applied at two different stages: normally applied at two different stages:
- in the transmission/receipt of messages, and - in the transmission/receipt of messages, and
- in the processing of the contents of messages. - in the processing of the contents of messages.
For purposes of this document, "security" refers to message-level For purposes of this document, "security" refers to message-level
security; "access control" refers to the security applied to protocol security; "access control" refers to the security applied to protocol
operations. operations.
Authentication, encryption, and timeliness checking are common Authentication, encryption, and timeliness checking are common
functions of message level security. functions of message level security.
A security document will describe a Security Model, the threats A security document describes a Security Model, the threats against
against which the model protects, the goals of the Security Model, which the model protects, the goals of the Security Model, the
the protocols which it uses to meet those goals, and it may define protocols which it uses to meet those goals, and it may define a MIB
a MIB module to describe the data used during processing, and to allow module to describe the data used during processing, and to allow the
the remote configuration of message-level security parameters, remote configuration of message-level security parameters, such as
such as passwords. passwords.
An SNMP engine may support multiple Security Models concurrently. An SNMP engine may support multiple Security Models concurrently.
2.7. Access Control 2.7. Access Control
During processing, it may be required to control access to certain During processing, it may be required to control access to certain
instrumentation for certain operations. An Access Control Model instrumentation for certain operations. An Access Control Model
determines whether access to an object should be allowed. The determines whether access to an object should be allowed. The
mechanism by which access control is checked is defined by the mechanism by which access control is checked is defined by the
Access Control Model. Access Control Model.
An Access Control Model document defines the mechanisms used to An Access Control Model document defines the mechanisms used to
\
determine whether access to a managed object should be allowed, determine whether access to a managed object should be allowed,
and may define a MIB module used during processing, and to allow and may define a MIB module used during processing, and to allow
the remote configuration of access control policies. the remote configuration of access control policies.
2.8. Applications 2.8. Protocol Operations
SNMP messages encapsulate an SNMP Protocol Data Unit (PDU). It is the
purpose of a Protocol Operations document to define the operations
of the protocol with respect to the processing of the PDUs.
An application document defines which Protocol Operations documents
are supported by the application.
2.9. Applications
An SNMP entity normally includes a number of applications. An SNMP entity normally includes a number of applications.
Applications use the services of an SNMP engine to accomplish Applications use the services of an SNMP engine to accomplish
specific tasks. They coordinate the processing of management specific tasks. They coordinate the processing of management
information operations, and may use SNMP messages to communicate information operations, and may use SNMP messages to communicate
with other SNMP entities. with other SNMP entities.
Applications documents describe the purpose of an application, the Applications documents describe the purpose of an application, the
services required of the associated SNMP engine, and the protocol services required of the associated SNMP engine, and the protocol
operations and informational model that the application uses to operations and informational model that the application uses to
perform network management operations. perform network management operations.
An application document defines which set of documents are used to An application document defines which set of documents are used to
specifically define the structure of management information, textual specifically define the structure of management information, textual
conventions, conformance requirements, and operations supported by conventions, conformance requirements, and operations supported by
the application. the application.
2.9. Structure of Management Information 2.10. Structure of Management Information
Management information is viewed as a collection of managed objects, Management information is viewed as a collection of managed objects,
residing in a virtual information store, termed the Management residing in a virtual information store, termed the Management
Information Base (MIB). Collections of related objects are defined Information Base (MIB). Collections of related objects are defined
in MIB modules. in MIB modules.
It is the purpose of a Structure of Management Information document It is the purpose of a Structure of Management Information document
to establish the syntax for defining objects, modules, and other to establish the syntax for defining objects, modules, and other
elements of managed information. elements of managed information.
2.10. Textual Conventions 2.11. Textual Conventions
When designing a MIB module, it is often useful to define new types When designing a MIB module, it is often useful to define new types
similar to those defined in the SMI, but with more precise semantics, similar to those defined in the SMI, but with more precise semantics,
or which have special semantics associated with them. These newly or which have special semantics associated with them. These newly
defined types are termed textual conventions, and may defined in defined types are termed textual conventions, and may defined in
separate documents, or within a MIB module. separate documents, or within a MIB module.
2.11. Conformance Statements 2.12. Conformance Statements
It may be useful to define the acceptable lower-bounds of It may be useful to define the acceptable lower-bounds of
implementation, along with the actual level of implementation implementation, along with the actual level of implementation
achieved. It is the purpose of Conformance Statements to define achieved. It is the purpose of Conformance Statements to define
the notation used for these purposes. the notation used for these purposes.
\
2.12. Protocol Operations
SNMP messages encapsulate an SNMP Protocol Data Unit (PDU). It is the
purpose of a Protocol Operations document to define the operations
of the protocol with respect to the processing of the PDUs.
An application document defines which Protocol Operations documents
are supported by the application.
2.13. Management Information Base Modules 2.13. Management Information Base Modules
MIB documents describe collections of managed objects which MIB documents describe collections of managed objects which instrument
instrument some aspect of a managed node. some aspect of a managed node.
2.13.1. SNMP Instrumentation MIBs 2.13.1. SNMP Instrumentation MIBs
An SNMP MIB document may define a collection of managed objects which An SNMP MIB document may define a collection of managed objects which
instrument the SNMP protocol itself. In addition, MIB modules may be instrument the SNMP protocol itself. In addition, MIB modules may be
defined within the documents which describe portions of the SNMP defined within the documents which describe portions of the SNMP
architecture, such as the documents for Message processing Models, architecture, such as the documents for Message processing Models,
Security Models, etc. for the purpose of instrumenting those Security Models, etc. for the purpose of instrumenting those Models,
Models, and for the purpose of allowing remote configuration of and for the purpose of allowing remote configuration of the Model.
the Model.
2.14. SNMP Framework Documents 2.14. SNMP Framework Documents
This architecture is designed to allow an orderly evolution of This architecture is designed to allow an orderly evolution of
portions of SNMP Frameworks. portions of SNMP Frameworks.
Throughout the rest of this document, the term "subsystem" refers Throughout the rest of this document, the term "subsystem" refers
to an abstract and incomplete specification of a portion of to an abstract and incomplete specification of a portion of
a Framework, that is further refined by a model specification. a Framework, that is further refined by a model specification.
skipping to change at page 16, line 51 skipping to change at page 19, line 44
additional constraints and rules for conformance to the model. additional constraints and rules for conformance to the model.
A model is sufficiently detailed to make it possible to implement A model is sufficiently detailed to make it possible to implement
the specification. the specification.
An "implementation" is an instantiation of a subsystem, conforming An "implementation" is an instantiation of a subsystem, conforming
to one or more specific models. to one or more specific models.
SNMP version 1 (SNMPv1), is the original Internet-standard Network SNMP version 1 (SNMPv1), is the original Internet-standard Network
Management Framework, as described in RFCs 1155, 1157, and 1212. Management Framework, as described in RFCs 1155, 1157, and 1212.
SNMP version 2 (SNMPv2) is an updated design of portions of SNMPv1, SNMP version 2 (SNMPv2), is the SNMPv2 Framework as derived from the
as described in RFCs 1902-1908. SNMPv2 has an incomplete message SNMPv1 Framework. It is described in RFCs 1902-1907. SNMPv2 has no
definition. message definition.
Community-based SNMP version 2 (SNMPv2c) is an experimental Framework Community-based SNMP version 2 (SNMPv2c), is an experimental SNMP
which supplements the incomplete message format of SNMPv2 with Framework which supplements the SNMPv2 Framework, as described in
portions of the message format of SNMPv1, as described in RFC1901.
\ message format.
SNMP version 3 (SNMPv3) Framework is a particular configuration of SNMP version 3 (SNMPv3), is an extensible SNMP Framework which
implemented subsystems, consistent with the architecture described supplements the SNMPv2 Framework, by supporting the following:
in this document. - a new SNMP message format,
- Security for Messages, and
- Access Control.
Other SNMP Frameworks, i.e. other configurations of implemented Other SNMP Frameworks, i.e. other configurations of implemented
subsystems, are expected to also be consistent with this architecture. subsystems, are expected to also be consistent with this architecture.
This document does not describe any framework, but describes an 2.15. Operational Overview
architecture into which multiple frameworks may be fitted.
\ The following pictures show two communicating SNMP entities using
the conceptual modularity described by this SNMP Architecture.
The pictures represent SNMP entities that have traditionally been
called SNMP manager and SNMP agent respectively.
* One or more models may be present.
3. Naming (traditional SNMP manager)
+--------------------------------------------------------------------+
| +--------------+ +--------------+ +--------------+ SNMP entity |
| | NOTIFICATION | | NOTIFICATION | | COMMAND | |
| | ORIGINATOR | | RECEIVER | | GENERATOR | |
| | applications | | applications | | applications | |
| +--------------+ +--------------+ +--------------+ |
| ^ ^ ^ |
| | | | |
| v v v |
| +-------+--------+-----------------+ |
| ^ |
| | +---------------------+ +-----------------+ |
| | | Message Processing | | Security | |
| Dispatcher v | Subsystem | | Subsystem | |
| +-------------------+ | +------------+ | | | |
| | PDU Dispatcher | | +->| v1MP * |<--->| +-------------+ | |
| | | | | +------------+ | | | Other | | |
| | | | | +------------+ | | | Security | | |
| | | | +->| v2cMP * |<--->| | Model | | |
| | Message | | | +------------+ | | +-------------+ | |
| | Dispatcher <--------->+ | | | |
| | | | | +------------+ | | +-------------+ | |
| | | | +->| v3MP * |<--->| | User-based | | |
| | Transport | | | +------------+ | | | Security | | |
| | Mapping | | | +------------+ | | | Model | | |
| | (e.g RFC1906) | | +->| otherMP * |<--->| +-------------+ | |
| +-------------------+ | +------------+ | | | |
| ^ +---------------------+ +-----------------+ |
| | |
| v |
+--------------------------------------------------------------------+
+-----+ +-----+ +-------+
| UDP | | IPX | . . . | other |
+-----+ +-----+ +-------+
^ ^ ^
| | |
v v v
+------------------------------+
| Network |
+------------------------------+
+------------------------------+
| Network |
+------------------------------+
^ ^ ^
| | |
v v v
+-----+ +-----+ +-------+
| UDP | | IPX | . . . | other |
+-----+ +-----+ +-------+ (traditional SNMP agent)
+--------------------------------------------------------------------+
| ^ |
| | +---------------------+ +-----------------+ |
| | | Message Processing | | Security | |
| Dispatcher v | Subsystem | | Subsystem | |
| +-------------------+ | +------------+ | | | |
| | Transport | | +->| v1MP * |<--->| +-------------+ | |
| | Mapping | | | +------------+ | | | Other | | |
| | (e.g. RFC1906) | | | +------------+ | | | Security | | |
| | | | +->| v2cMP * |<--->| | Model | | |
| | Message | | | +------------+ | | +-------------+ | |
| | Dispatcher <--------->+ | | | |
| | | | | +------------+ | | +-------------+ | |
| | | | +->| v3MP * |<--->| | User-based | | |
| | | | | +------------+ | | | Security | | |
| | | | | +------------+ | | | Model | | |
| | PDU Dispatcher | | +->| otherMP * |<--->| +-------------+ | |
| +-------------------+ | +------------+ | | | |
| ^ +---------------------+ +-----------------+ |
| | |
| v |
| +-------+-------------------------+----------------+ |
| ^ ^ ^ |
| | | | |
| v v v |
| +-------------+ +---------+ +--------------+ +-------------+ |
| | COMMAND | | ACCESS | | NOTIFICATION | | PROXY * | |
| | RESPONDER |<->| CONTROL |<->| ORIGINATOR | | FORWARDER | |
| | application | | | | applications | | application | |
| +-------------+ +---------+ +--------------+ +-------------+ |
| ^ ^ |
| | | |
| v v |
| +----------------------------------------------+ |
| | MIB instrumentation | SNMP entity |
+--------------------------------------------------------------------+
This architecture deals with three kinds of naming: 3. Elements of the Architecture
This section describes the various elements of the architecture and
how they are named. There are three kinds of naming:
1) the naming of entities, 1) the naming of entities,
2) the naming of identities, and 2) the naming of identities, and
3) the naming of management information. 3) the naming of management information.
This architecture also defines some names for other constructs that This architecture also defines some names for other constructs that
are used in the documentation. are used in the documentation.
3.1. The Naming of Entities 3.1. The Naming of Entities
The following picture shows detail about an SNMP entity and how The following picture shows detail about an SNMP entity and how
components within it are named. components within it are named.
+--------------------------------------------------------------------+ +--------------------------------------------------------------------+
| |
| SNMP entity | | SNMP entity |
| | | |
| +--------------------------------------------------------------+ | | +--------------------------------------------------------------+ |
| | | |
| | SNMP engine (identified by snmpEngineID) | | | | SNMP engine (identified by snmpEngineID) | |
| | | | | | | |
| | +---------------+ +--------------+ +---------------+ | | | | +-------------+ +------------+ +-----------+ +-----------+ | |
| | | | | | | | | | | | | | | | | | | | | |
| | | Message | | Security | | Access | | | | | | Dispatcher | | Message | | Security | | Access | | |
| | | Processing | | Subsystem | | Control | | | | | | | | Processing | | Subsystem | | Control | | |
| | | Subsystem | | | | Subsystem | | | | | | | | Subsystem | | | | Subsystem | | |
| | | | | | | | | | | | | | | | | | | | | |
| | +---------------+ +--------------+ +---------------+ | | | | +-------------+ +------------+ +-----------+ +-----------+ | |
| | | | | | | |
| +--------------------------------------------------------------+ | | +--------------------------------------------------------------+ |
| | | |
| +--------------------------------------------------------------+ | | +--------------------------------------------------------------+ |
| | | |
| | Application(s) | | | | Application(s) | |
| | | | | | | |
| | +-------------+ +--------------+ +--------------+ | | | | +-------------+ +--------------+ +--------------+ | |
| | | Command | | Notification | | Proxy | | | | | | Command | | Notification | | Proxy | | |
| | | Generator | | Receiver | | Forwarder | | | | | | Generator | | Receiver | | Forwarder | | |
| | +-------------+ +--------------+ +--------------+ | | | | +-------------+ +--------------+ +--------------+ | |
| | | | | | | |
| | +-------------+ +--------------+ +--------------+ | | | | +-------------+ +--------------+ +--------------+ | |
| | | Command | | Notification | | Other | | | | | | Command | | Notification | | Other | | |
| | | Responder | | Originator | | | | | | | | Responder | | Originator | | | | |
| | +-------------+ +--------------+ +--------------+ | | | | +-------------+ +--------------+ +--------------+ | |
| | | | | | | |
| +--------------------------------------------------------------+ | | +--------------------------------------------------------------+ |
| | | |
+--------------------------------------------------------------------+ +--------------------------------------------------------------------+
\
3.1.1. SNMP entity 3.1.1. SNMP entity
An SNMP entity is an implementation of this architecture. Each such An SNMP entity is an implementation of this architecture. Each such
SNMP entity consists of an SNMP engine and one or more associated SNMP entity consists of an SNMP engine and one or more associated
applications. applications.
3.1.2. SNMP engine 3.1.2. SNMP engine
An SNMP engine has three subsystems: An SNMP engine provides services for sending and receiving messages,
authenticating and encrypting messages, and controlling access to
managed objects. There is a one-to-one association between an SNMP
engine and the SNMP entity which contains it.
1) a Message Processing Subsystem, The engine contains:
2) a Security Subsystem, and
3) an Access Control Subsystem. 1) a Dispatcher,
2) a Message Processing Subsystem,
3) a Security Subsystem, and
4) an Access Control Subsystem.
3.1.3. snmpEngineID 3.1.3. snmpEngineID
Within an administrative domain, an snmpEngineID is the unique Within an administrative domain, an snmpEngineID is the unique
and unambiguous identifier of an SNMP engine. Since there is a and unambiguous identifier of an SNMP engine. Since there is a
one-to-one association between SNMP engines and SNMP entities, one-to-one association between SNMP engines and SNMP entities,
it also uniquely and unambiguously identifies the SNMP entity. it also uniquely and unambiguously identifies the SNMP entity.
3.1.4. Message Processing Subsystem 3.1.4. Dispatcher
The Message Processing Subsystem is responsible for preparing and There is only one Dispatcher in an SNMP engine. It allows for
sending messages, and receiving and distributing messages. concurrent support of multiple versions of SNMP messages in the
SNMP engine. It does so by:
- sending and receiving SNMP messages to/from the network,
- determining the version of an SNMP message and interact
with the corresponding Message Processing Model,
- providing an abstract interface to SNMP applications for
dispatching a PDU to an application.
- providing an abstract interface for SNMP applications that
allows them to send a PDU to a remote SNMP entity.
3.1.5. Message Processing Subsystem
The Message Processing Subsystem is responsible for preparing
messages for sending, and extracting data from received messages.
The Message Processing Subsystem potentially contains multiple The Message Processing Subsystem potentially contains multiple
Message Processing Models as shown in the next picture. Those Message Processing Models as shown in the next picture.
marked with an asterisk (*) may be absent. * One or more Message Processing Models may be present.
+------------------------------------------------------------------+ +------------------------------------------------------------------+
| | | |
| Message Processing Subsystem | | Message Processing Subsystem |
| | | |
| +------------+ +------------+ +------------+ +------------+ | | +------------+ +------------+ +------------+ +------------+ |
| | | | * | | * | | * | | | | * | | * | | * | | * | |
| | SNMPv3 | | SNMPv1 | | SNMPv2c | | Other | | | | SNMPv3 | | SNMPv1 | | SNMPv2c | | Other | |
| | Message | | Message | | Message | | Message | | | | Message | | Message | | Message | | Message | |
| | Processing | | Processing | | Processing | | Processing | | | | Processing | | Processing | | Processing | | Processing | |
| | Model | | Model | | Model | | Model | | | | Model | | Model | | Model | | Model | |
| | | | | | | | | | | | | | | | | | | |
| +------------+ +------------+ +------------+ +------------+ | | +------------+ +------------+ +------------+ +------------+ |
| | | |
+------------------------------------------------------------------+ +------------------------------------------------------------------+
3.1.5. Message Processing Model 3.1.6. Message Processing Model
Each Message Processing Model defines the format of a particular Each Message Processing Model defines the format of a particular
version of an SNMP message and coordinates the processing of each version of an SNMP message and coordinates the preparation and
version-specific message. extraction of each such version-specific messages.
\
3.1.6. Security Subsystem 3.1.7. Security Subsystem
The Security Subsystem provides security services such as the The Security Subsystem provides security services such as the
authentication and privacy of messages and potentially contains authentication and privacy of messages and potentially contains
multiple Security Models as shown in the next picture. Those multiple Security Models as shown in the next picture.
marked with an asterisk (*) may be absent. * One or more Security Models may be present.
+------------------------------------------------------------------+ +------------------------------------------------------------------+
| | | |
| Security Subsystem | | Security Subsystem |
| | | |
| +------------+ +-------------------+ +---------------------+ | | +----------------+ +-----------------+ +-------------------+ |
| | | | * | | * | | | | * | | * | | * | |
| | User-Based | | Community-based | | Other | | | | User-Based | | Other | | Other | |
| | Security | | Security | | Security | | | | Security | | Security | | Security | |
| | Model | | Model | | Model | | | | Model | | Model | | Model | |
| | | | | | | | | | | | | | | |
| +------------+ +-------------------+ +---------------------+ | | +----------------+ +-----------------+ +-------------------+ |
| | | |
+------------------------------------------------------------------+ +------------------------------------------------------------------+
3.1.7. Security Model 3.1.8. Security Model
A Security Model defines the threats against which it protects, A Security Model defines the threats against which it protects,
the goals of its services, and the security protocols used to provide the goals of its services, and the security protocols used to provide
security services such as authentication and privacy. security services such as authentication and privacy.
3.1.8. Security Protocol 3.1.9. Security Protocol
A Security Protocol defines the mechanisms, procedures, and MIB A Security Protocol defines the mechanisms, procedures, and MIB
data used to provide a security service such as authentication data used to provide a security service such as authentication
or privacy. or privacy.
\ 3.1.10. Access Control Subsystem
3.1.9. Access Control Subsystem
The Access Control Subsystem provides authorization services by The Access Control Subsystem provides authorization services by
means of one or more Access Control Models. means of one or more Access Control Models.
+------------------------------------------------------------------+ +------------------------------------------------------------------+
| | | |
| Access Control Subsystem | | Access Control Subsystem |
| | | |
| +------------+ +-------------------+ +---------------------+ | | +---------------+ +-----------------+ +------------------+ |
| | | | * | | * | | | | * | | * | | * | |
| | View-Based | | Community | | Other | | | | View-Based | | Other | | Other | |
| | Access | | Access | | Access | | | | Access | | Access | | Access | |
| | Control | | Control | | Control | | | | Control | | Control | | Control | |
| | Model | | Model | | Model | | | | Model | | Model | | Model | |
| | | | | | | | | | | | | | | |
| +------------+ +-------------------+ +---------------------+ | | +---------------+ +-----------------+ +------------------+ |
| | | |
+------------------------------------------------------------------+ +------------------------------------------------------------------+
3.1.10. Access Control Model 3.1.11. Access Control Model
An Access Control Model defines a particular access decision function An Access Control Model defines a particular access decision function
in order to support decisions regarding authorization. in order to support decisions regarding access rights.
3.1.11. Applications 3.1.12. Applications
There are several types of applications, which include: There are several types of applications, including:
- command generator, - command generators, which monitor and manipulate management data,
- command responder, - command responders, which provide access to management data,
- notification originator, - notification originators, which initiate asynchronous messages,
- notification receiver, and - notification receivers, which process asynchronous messages, and
- proxy forwarder. - proxy forwarders, which forward messages between entities.
These applications make use of the services provided by the Security These applications make use of the services provided by the SNMP
and Administration Framework. engine.
3.1.12. SNMP Agent 3.1.13. SNMP Agent
An SNMP entity containing one or more command responder and/or An SNMP entity containing one or more command responder and/or
notification originator applications (along with their associated notification originator applications (along with their associated
SNMP engine) has traditionally been called an SNMP agent. SNMP engine) has traditionally been called an SNMP agent.
3.1.13. SNMP Manager 3.1.14. SNMP Manager
An SNMP entity containing one or more command generator and/or An SNMP entity containing one or more command generator and/or
notification receiver applications (along with their associated notification receiver applications (along with their associated
SNMP engine) has traditionally been called an SNMP manager. SNMP engine) has traditionally been called an SNMP manager.
\
3.2. The Naming of Identities 3.2. The Naming of Identities
principal <---------------------------------+ principal <---------------------------------+
| |
+-------------------------------------|-----+ +-------------------------------------|-----+
| SNMP engine | | | SNMP engine | |
| | | | | |
| +-----------------------+ | | | +-----------------------+ | |
| | Security Model | | | | | Security Model | | |
| | +-------------+ | | | | | +-------------+ | | |
skipping to change at page 23, line 5 skipping to change at page 30, line 5
A model dependent security ID is the model specific representation A model dependent security ID is the model specific representation
of a securityName within a particular Security Model. of a securityName within a particular Security Model.
Model dependent security IDs may or may not be human readable, and Model dependent security IDs may or may not be human readable, and
have a model dependent syntax. Examples include community names, have a model dependent syntax. Examples include community names,
user names, and parties. user names, and parties.
The transformation of model dependent security IDs into securityNames The transformation of model dependent security IDs into securityNames
and vice versa is the responsibility of the relevant Security Model. and vice versa is the responsibility of the relevant Security Model.
\
3.3. The Naming of Management Information 3.3. The Naming of Management Information
Management information resides at an SNMP entity where a Command Management information resides at an SNMP entity where a Command
Responder Application has local access to potentially multiple Responder Application has local access to potentially multiple
contexts. Such a Command Responder application uses a contextEngineID contexts. Such a Command Responder application uses a contextEngineID
equal to the snmpEngineID of its associated SNMP engine. equal to the snmpEngineID of its associated SNMP engine.
+--------------------------------------------------------------+ +-----------------------------------------------------------------+
| SNMP entity (identified by snmpEngineID, example: abcd) | | SNMP entity (identified by snmpEngineID, example: abcd) |
| | | |
| +----------------------------------------------------------+ | | +------------------------------------------------------------+ |
| | SNMP engine (identified by snmpEngineID) | | | | SNMP engine (identified by snmpEngineID) | |
| | | | | | | |
| | +---------------+ +--------------+ +---------------+ | | | | +-------------+ +------------+ +-----------+ +-----------+ | |
| | | | | | | | | | | | | | | | | | | | | |
| | | Message | | Security | | Access | | | | | | Dispatcher | | Message | | Security | | Access | | |
| | | Processing | | Subsystem | | Control | | | | | | | | Processing | | Subsystem | | Control | | |
| | | Subsystem | | | | Subsystem | | | | | | | | Subsystem | | | | Subsystem | | |
| | | | | | | | | | | | | | | | | | | | | |
| | +---------------+ +--------------+ +---------------+ | | | | +-------------+ +------------+ +-----------+ +-----------+ | |
| | | | | | | |
| +----------------------------------------------------------+ | | +------------------------------------------------------------+ |
| | | |
| +----------------------------------------------------------+ | | +------------------------------------------------------------+ |
| | Command Responder Application | | | | Command Responder Application | |
| | (contextEngineID, example: abcd) | | | | (contextEngineID, example: abcd) | |
| | | | | | | |
| | example contextNames: | | | | example contextNames: | |
| | | | | | | |
| | "repeater1" "repeater2" "" (default) | | | | "bridge1" "bridge2" "" (default) | |
| | ----------- ----------- ------------ | | | | --------- --------- ------------ | |
| | | | | | | | | | | | | |
| +-----|-------------------|--------------------|-----------+ | | +------|------------------|-------------------|--------------+ |
| | | | | | | | | |
| +-----|-------------------|--------------------|-----------+ | | +------|------------------|-------------------|--------------+ |
| | MIB | instrumentation | | | | | | MIB | instrumentation | | | |
| |-----v------------+ +----v-------------+ +----v-----------| | | | +---v------------+ +---v------------+ +----v-----------+ | |
| | context | | context | | context | | | | | context | | context | | context | | |
| | | | | | | | | | | | | | | | | |
| | +--------------+ | | +--------------+ | | +------------+ | | | | | +------------+ | | +------------+ | | +------------+ | | |
| | | repeater MIB | | | | repeater MIB | | | | other MIB | | | | | | | bridge MIB | | | | bridge MIB | | | | other MIB | | | |
| | +--------------+ | | +--------------+ | | +------------+ | | | | | +------------+ | | +------------+ | | +------------+ | | |
| | | | | | | | | | | | | | | | | |
| | | | | | +------------+ | | | | | | | | | +------------+ | | |
| | | | | | | some MIB | | | | | | | | | | | some MIB | | | |
| | | | | | +------------+ | | | | | | | | | +------------+ | | |
| | | | | | | | | | | | | | | | | |
+--------------------------------------------------------------+ +-----------------------------------------------------------------+
\
3.3.1. An SNMP Context 3.3.1. An SNMP Context
An SNMP context, or just "context" for short, is a collection of An SNMP context, or just "context" for short, is a collection of
management information accessible by an SNMP entity. An item of management information accessible by an SNMP entity. An item of
management information may exist in more than one context. An SNMP management information may exist in more than one context. An SNMP
engine potentially has access to many contexts. engine potentially has access to many contexts.
Typically, there are many instances of each managed object type within Typically, there are many instances of each managed object type within
a management domain. For simplicity, the method for identifying a management domain. For simplicity, the method for identifying
skipping to change at page 24, line 33 skipping to change at page 31, line 31
multiple devices, but a context is always defined as a subset of a multiple devices, but a context is always defined as a subset of a
single SNMP entity. Thus, in order to identify an individual item of single SNMP entity. Thus, in order to identify an individual item of
management information within the management domain, its contextName management information within the management domain, its contextName
and contextEngineID must be identified in addition to its object type and contextEngineID must be identified in addition to its object type
and its instance. and its instance.
For example, the managed object type ifDescr [RFC1573], is defined as For example, the managed object type ifDescr [RFC1573], is defined as
the description of a network interface. To identify the description the description of a network interface. To identify the description
of device-X's first network interface, four pieces of information are of device-X's first network interface, four pieces of information are
needed: the snmpEngineID of the SNMP entity which provides access to needed: the snmpEngineID of the SNMP entity which provides access to
device-X, the contextName (device-X), the managed object type the management information at device-X, the contextName (device-X),
(ifDescr), and the instance ("1"). the managed object type (ifDescr), and the instance ("1").
Each context has (at least) one unique identification within the Each context has (at least) one unique identification within the
management domain. The same item of management information can exist management domain. The same item of management information can exist
in multiple contexts. So, an item of management information can have in multiple contexts. So, an item of management information can have
multiple unique identifications, either because it exists in multiple multiple unique identifications, either because it exists in multiple
contexts, and/or because each such context has multiple unique contexts, and/or because each such context has multiple unique
identifications. identifications.
The combination of a contextEngineID and a contextName unambiguously The combination of a contextEngineID and a contextName unambiguously
identifies a context within an administrative domain. identifies a context within an administrative domain.
skipping to change at page 25, line 5 skipping to change at page 32, line 7
identifies an SNMP entity that may realize an instance of a identifies an SNMP entity that may realize an instance of a
context with a particular contextName. context with a particular contextName.
3.3.3. contextName 3.3.3. contextName
A contextName is used to name a context. Each contextName A contextName is used to name a context. Each contextName
MUST be unique within an SNMP entity. MUST be unique within an SNMP entity.
3.3.4. scopedPDU 3.3.4. scopedPDU
\
A scopedPDU is a block of data containing a contextEngineID, A scopedPDU is a block of data containing a contextEngineID,
a contextName, and a PDU. a contextName, and a PDU.
The PDU is an SNMP Protocol Data Unit containing information The PDU is an SNMP Protocol Data Unit containing information
named in the context which is unambiguously identified within named in the context which is unambiguously identified within
an administrative domain by the combination of the contextEngineID an administrative domain by the combination of the contextEngineID
and the contextName. See, for example, RFC1905 for more information and the contextName. See, for example, RFC1905 for more information
about SNMP PDUs. about SNMP PDUs.
3.4. Other Constructs 3.4. Other Constructs
skipping to change at page 25, line 35 skipping to change at page 32, line 35
The subsystems, models, and applications within an SNMP entity may The subsystems, models, and applications within an SNMP entity may
need to retain their own sets of configuration information. need to retain their own sets of configuration information.
Portions of the configuration information may be accessible as Portions of the configuration information may be accessible as
managed objects. managed objects.
The collection of these sets of information is referred to The collection of these sets of information is referred to
as an entity's Local Configuration Datastore (LCD). as an entity's Local Configuration Datastore (LCD).
3.4.3. LoS 3.4.3. securityLevel
This architecture recognizes three levels of security (LoS): This architecture recognizes three levels of security:
- without authentication and without privacy (noAuthNoPriv) - without authentication and without privacy (noAuthNoPriv)
- with authentication but without privacy (authNoPriv) - with authentication but without privacy (authNoPriv)
- with authentication and with privacy (authPriv) - with authentication and with privacy (authPriv)
These three values are ordered such that noAuthNoPriv is lower than These three values are ordered such that noAuthNoPriv is less than
authNoPriv and authNoPriv is lower than authPriv. authNoPriv and authNoPriv is less than authPriv.
Every message has an associated LoS. All Subsystems (Message Every message has an associated securityLevel. All Subsystems (Message
Processing, Security, Access Control) and applications are required Processing, Security, Access Control) and applications are required
to either supply a value of LoS or to abide by the supplied value of to either supply a value of securityLevel or to abide by the supplied
LoS while processing the message and its contents. value of securityLevel while processing the message and its contents.
\
4. Architectural Elements of Procedure 4. Abstract Service Interfaces.
The architecture described here contains three subsystems, each Abstract service interfaces have been defined to describe the
capable of being defined as one or more different models which may conceptual interfaces between the various subsystems within an SNMP
be replaced or supplemented as the growing needs of network management entity.
require. The architecture also includes applications which utilize the
services provided by the subsystems.
An SNMP engine deals with SNMP messages, and is responsible for These abstract service interfaces are defined by a set of primitives
sending and receiving messages, including having authentication that define the services provided and the abstract data elements that
and encryption services applied to the messages, and determining are to be passed when the services are invoked. This section lists
to which application the message contents should be delivered. the primitives that have been defined for the various subsystems.
Applications deal with processing network management operations. 4.1. Common Primitives
Depending on the network management service needed, an application
may use the Access Control Subsystem, and may use SNMP messages to
communicate with remote nodes. The network management service may
be requested via the payload of an SNMP message, or may be requested
via a local process.
\ These primitive(s) are provided by multiple Subsystems.
4.1. Operational Overview 4.1.1. Release State Reference Information
The following pictures show two communicating SNMP entities using All Subsystems which pass stateReference information also provide a
the conceptual modularity described by the SNMP Architecture. primitive to release the memory that holds the referenced state
The pictures represent SNMP entities that have traditionally been information:
called SNMP manager and SNMP agent respectively. The boxes marked
with an asterisk (*) may be absent.
(traditional SNMP manager) stateRelease(
+--------------------------------------------------------------------+ IN stateReference -- handle of reference to be released
| SNMP entity | )
| |
| +--------------+ +--------------+ +--------------+ |
| | NOTIFICATION | | NOTIFICATION | | COMMAND | |
| | ORIGINATOR | | RECEIVER | | GENERATOR | |
| | applications | | applications | | applications | |
| +--------------+ +--------------+ +--------------+ |
| ^ ^ ^ |
| | | | |
| v v v |
| +----------------------------------------------------------------+ |
| | Message Processing Application Multiplexor | |
| +----------------------------------------------------------------+ |
| ^ ^ ^ ^ |
| +-----------+ | | | | |
| | | v v v v |
| | Security | +------+ +---------+ +--------+ +-----------+ |
| | Subsystem |<-->| v3MP | | v2cMP * | | v1MP * |...| otherMP * | |
| | | +------+ +---------+ +--------+ +-----------+ |
| +-----------+ ^ ^ ^ ^ |
| | | | | |
| v v v v |
| +----------------------------------------------------------------+ |
| | Message Processing Model selection (incoming only) | |
| +----------------------------------------------------------------+ |
| ^ |
| | |
| v |
| +----------------------------------------------------------------+ |
| | TRANSPORT MAPPING (for example RFC1906) | |
| +----------------------------------------------------------------+ |
+--------------------------------------------------------------------+
+-----+ +-----+ +-------+
| UDP | | IPX | . . . | other |
+-----+ +-----+ +-------+
^ ^ ^
| | |
v v v
+------------------------------+
| Network |
+------------------------------+
\ 4.2. Dispatcher Primitives
+------------------------------+
| Network |
+------------------------------+
^ ^ ^
| | |
v v v
+-----+ +-----+ +-------+
| UDP | | IPX | . . . | other |
+-----+ +-----+ +-------+ (traditional SNMP agent)
+--------------------------------------------------------------------+
| +----------------------------------------------------------------+ |
| | TRANSPORT MAPPING (for example RFC1906) | |
| +----------------------------------------------------------------+ |
| ^ |
| | |
| v |
| +----------------------------------------------------------------+ |
| | Message Processing Model selection (incoming only) | |
| +----------------------------------------------------------------+ |
| ^ ^ ^ ^ |
| +-----------+ | | | | |
| | | v v v v |
| | Security | +------+ +---------+ +--------+ +-----------+ |
| | Subsystem |<-->| v3MP | | v2cMP * | | v1MP * |...| otherMP * | |
| | | +------+ +---------+ +--------+ +-----------+ |
| +-----------+ ^ ^ ^ ^ |
| | | | | |
| v v v v |
| +----------------------------------------------------------------+ |
| | Message Processing Abstract Service Interface | |
| +----------------------------------------------------------------+ |
| ^ ^ ^ |
| | | | |
| v v v |
| +-------------+ +---------+ +--------------+ +-------------+ |
| | COMMAND | | ACCESS | | NOTIFICATION | | PROXY * | |
| | RESPONDER |<->| CONTROL |<->| ORIGINATOR | | FORWARDER | |
| | application | | | | applications | | application | |
| +-------------+ +---------+ +--------------+ +-------------+ |
| ^ ^ |
| | | |
| v v |
| +----------------------------------------------+ |
| | MIB instrumentation | SNMP entity |
+--------------------------------------------------------------------+
\ The Dispatcher typically provides services to the SNMP applications via
its PDU Dispatcher. This section describes the primitives provided by
the PDU Dispatcher.
4.2. Sending and Receiving SNMP Messages 4.2.1. Generate Outgoing Request or Notification
4.2.1. Send a Message to the Network The PDU Dispatcher provides the following primitive for an application
to send an SNMP Request or Notification to another SNMP entity:
Applications may request that messages be generated and sent. The statusInformation = -- sendPduHandle if success
application has the responsibility of providing the information -- errorIndication if failure
necessary to generate the message, as detailed below, and of sendPdu(
providing the transport address to which the message should be sent. IN transportDomain -- transport domain to be used
IN transportAddress -- transport address to be used
IN messageProcessingModel -- typically, SNMP version
IN securityModel -- Security Model to use
IN securityName -- on behalf of this principal
IN securityLevel -- Level of Security requested
IN contextEngineID -- data from/at this entity
IN contextName -- data from/in this context
IN pduVersion -- the version of the PDU
IN PDU -- SNMP Protocol Data Unit
IN expectResponse -- TRUE or FALSE
)
The engine passes a request for a message to be generated to the 4.2.2. Process Incoming Request or Notification PDU
specified Message Processing Model which, utilizing the services of
the selected Security Model, generates the message and prepares it
for sending.
The SNMP engine sends the message to the specified transport address. The PDU Dispatcher provides the following primitive to pass an incoming
It then advises the sending Message Processing Model about the success SNMP PDU to an application:
or failure of the sending of the message.
4.2.2. Receive a Message from the Network processPdu( -- process Request/Notification PDU
IN messageProcessingModel -- typically, SNMP version
IN securityModel -- Security Model in use
IN securityName -- on behalf of this principal
IN securityLevel -- Level of Security
IN contextEngineID -- data from/at this SNMP entity
IN contextName -- data from/in this context
IN pduVersion -- the version of the PDU
IN PDU -- SNMP Protocol Data Unit
IN maxSizeResponseScopedPDU -- maximum size of the Response PDU
IN stateReference -- reference to state information
) -- needed when sending a response
It is the responsibility of the SNMP engine to listen for incoming 4.2.3. Generate Outgoing Response
messages at the appropriate local addresses. Some local addresses
for listening are recommended by SNMP Transport Mapping documents,
such as [RFC1906].
Upon receipt of an SNMP message, the SNMP engine increments the The PDU Dispatcher provides the following primitive for an application
snmpInPkts counter [RFC1907]. to return an SNMP Response PDU to the PDU Dispatcher:
SNMP messages received from the network use a format defined by a returnResponsePdu(
version-specific Message Processing Model, typically identified IN messageProcessingModel -- typically, SNMP version
by a version field in the message header. IN securityModel -- Security Model in use
IN securityName -- on behalf of this principal
IN securityLevel -- same as on incoming request
IN contextEngineID -- data from/at this SNMP entity
IN contextName -- data from/in this context
IN pduVersion -- the version of the PDU
IN PDU -- SNMP Protocol Data Unit
IN maxSizeResponseScopedPDU -- maximum size of the Response PDU
IN stateReference -- reference to state information
-- as presented with the request
IN statusInformation -- success or errorIndication
) -- error counter OID/value if error
The engine determines the SNMP version of an incoming message by 4.2.4. Process Incoming Response PDU
inspecting the serialized values for a recognizable pattern.
The mechanism by which it makes the determination of version is
implementation-specific, and dependent on the Message Processing
Models supported by the engine.
If the engine has no Message Processing Model for the determined The PDU Dispatcher provides the following primitive to pass an incoming
version, then the snmpInBadVersions counter [RFC1907] is incremented, SNMP Response PDU to an application:
and the message is discarded without further processing.
The SNMP engine caches the msgID, which is subsequently used for processResponsePdu( -- process Response PDU
coordinating all processing regarding this received message, and IN messageProcessingModel -- typically, SNMP version
caches the origin network address so a possible response can be IN securityModel -- Security Model in use
sent to the origin address. IN securityName -- on behalf of this principal
IN securityLevel -- Level of Security
IN contextEngineID -- data from/at this SNMP entity
IN contextName -- data from/in this context
IN pduVersion -- the version of the PDU
IN PDU -- SNMP Protocol Data Unit
IN statusInformation -- success or errorIndication
IN sendPduHandle -- handle from sendPDU
)
Based on the SNMP version of the message, the engine passes the 4.2.5. Registering Responsibility for Handling SNMP PDUs.
message to the appropriate version-specific Message Processing Model.
The Message Processing Model extracts the information in the message,
utilizing services of the appropriate Security Model to authenticate
\ Applications can register/unregister responsibility for a specific
contextEngineID, for specific pduTypes, with the PDU Dispatcher
according to these primitives:
and decrypt the message as needed. statusInformation = -- success or errorIndication
registerContextEngineID(
IN contextEngineID -- take responsibility for this one
IN pduType -- the pduType(s) to be registered
)
4.3. Send a Request or Notification Message for an Application unregisterContextEngineID(
IN contextEngineID -- give up responsibility for this one
IN pduType -- the pduType(s) to be unregistered
)
The Application Multiplexor receives a request for the generation 4.3. Message Processing Subsystem Primitives
of an SNMP message from an application via the sendPdu primitive:
sendPdu( The Dispatcher interacts with a Message Processing Model to process a
transportDomain -- transport domain to be used specific version of an SNMP Message. This section describes the
transportAddress -- destination network address primitives provided by the Message Processing Subsystem.
messageProcessingModel -- typically, SNMP version
securityModel -- Security Model to use
securityName -- on behalf of this principal
LoS -- Level of Security requested
contextEngineID -- data from/at this entity
contextName -- data from/in this context
PDU -- SNMP Protocol Data Unit
expectResponse) -- TRUE or FALSE
The SNMP engine checks the "expectResponse" parameter to determine if 4.3.1. Prepare an Outgoing SNMP Request or Notification Message
it is a message which is expected to receive a response, and if so,
caches the msgID of the generated message and which application
made the request.
The engine sends the message according to the procedure detailed The Message Processing Subsystem provides this service primitive for
in section 4.2.1. Send a Message to the Network. preparing an outgoing SNMP Request or Notification Message:
4.4. Receive a Request or Notification Message from the Network statusInformation = -- success or errorIndication
prepareOutgoingMessage(
IN transportDomain -- transport domain to be used
IN transportAddress -- transport address to be used
IN messageProcessingModel -- typically, SNMP version
IN securityModel -- Security Model to use
IN securityName -- on behalf of this principal
IN securityLevel -- Level of Security requested
IN contextEngineID -- data from/at this entity
IN contextName -- data from/in this context
IN pduVersion -- the version of the PDU
IN PDU -- SNMP Protocol Data Unit
IN expectResponse -- TRUE or FALSE
IN sendPduHandle -- the handle for matching
-- incoming responses
OUT destTransportDomain -- destination transport domain
OUT destTransportAddress -- destination transport address
OUT outgoingMessage -- the message to send
OUT outgoingMessageLength -- its length
)
The engine receives the message according to the procedure detailed 4.3.2. Prepare an Outgoing SNMP Response Message
in section 4.2.2. Receive a Message from the Network.
The Application Demultiplexor looks into the scopedPDU to determine The Message Processing Subsystem provides this service primitive for
the contextEngineID and the PDU type, then determines which preparing an outgoing SNMP Response Message:
application has registered (see section 4.7) to support that PDU type
for that contextEngineID.
The Application Demultiplexor passes the request or notification result = -- SUCCESS or FAILURE
to the registered application using the processPdu primitive: prepareResponseMessage(
IN messageProcessingModel -- typically, SNMP version
IN securityModel -- same as on incoming request
IN securityName -- same as on incoming request
IN securityLevel -- same as on incoming request
IN contextEngineID -- data from/at this SNMP entity
IN contextName -- data from/in this context
IN pduVersion -- the version of the PDU
IN PDU -- SNMP Protocol Data Unit
IN maxSizeResponseScopedPDU -- maximum size of the Response PDU
IN stateReference -- reference to state information
-- as presented with the request
IN statusInformation -- success or errorIndication
-- error counter OID/value if error
OUT destTransportDomain -- destination transport domain
OUT destTransportAddress -- destination transport address
OUT outgoingMessage -- the message to send
OUT outgoingMessageLength -- its length
)
processPdu( 4.3.3. Prepare Data Elements from an Incoming SNMP Message
contextEngineID -- data from/at this SNMP engine
contextName -- data from/in this context
PDU -- SNMP Protocol Data Unit
maxSizeResponseScopedPDU -- maximum size of the Response PDU
securityModel -- Security Model in use
securityName -- on behalf of this principal
LoS -- Level of Security
stateReference) -- reference to state information
-- needed when sending a response
\ The Message Processing Subsystem provides this service primitive for
preparing the abstract data elements from an incoming SNMP message:
4.5. Generate a Response Message for an Application result = -- SUCCESS or errorIndication
prepareDataElements(
IN transportDomain -- origin transport domain
IN transportAddress -- origin transport address
IN wholeMsg -- as received from the network
IN wholeMsglength -- as received from the network
OUT messageProcessingModel -- typically, SNMP version
OUT securityModel -- Security Model to use
OUT securityName -- on behalf of this principal
OUT securityLevel -- Level of Security requested
OUT contextEngineID -- data from/at this entity
OUT contextName -- data from/in this context
OUT pduVersion -- the version of the PDU
OUT PDU -- SNMP Protocol Data Unit
OUT pduType -- SNMP PDU type
OUT sendPduHandle -- handle for matched request
OUT maxSizeResponseScopedPDU -- maximum size of the Response PDU
OUT statusInformation -- success or errorIndication
-- error counter OID/value if error
OUT stateReference -- reference to state information
-- to be used for a possible Response
)
The Application Multiplexor receives a request for the generation 4.4. Access Control Subsystem Primitives
of an SNMP response message from an application via the
returnResponsePdu primitive:
returnResponsePdu( Applications are the typical clients of the service(s) of the Access
contextEngineID -- data from/at this SNMP engine Control Subsystem.
contextName -- data from/in this context
securityModel -- Security Model in use
securityName -- on behalf of this principal
LoS -- Level of Security
stateReference -- reference to state information
-- as presented with the request
PDU -- SNMP Protocol Data Unit
maxSizeResponseScopedPDU -- maximum size of the Response PDU
statusInformation -- success or errorIndication
) -- error counter OID/value if error
The engine sends the message according to the procedure detailed The following primitive is provided by the Access Control Subsystem
in section 4.2.1. Send a Message to the Network. to check if access is allowed:
4.6. Receive a Response Message statusInformation = -- success or errorIndication
isAccessAllowed(
IN securityModel -- Security Model in use
IN securityName -- principal who wants to access
IN securityLevel -- Level of Security
IN viewType -- read, write, or notify view
IN contextName -- context containing variableName
IN variableName -- OID for the managed object
)
The engine receives the message according to the procedure detailed 4.5. Security Subsystem Primitives
in section 4.2.2. Receive a Message from the Network.
The Application Demultiplexor looks into the scopedPDU to determine The Message Processing Subsystem is the typical client of the services
the contextEngineID and the PDU type. of the Security Subsystem.
If the PDU type is a Response PDU, the Demultiplexor matches the 4.5.1. Generate a Request or Notification Message
msgID of the incoming response to the cached msgIDs of messages
sent by this SNMP engine.
If a matching cached msgID is found, the cached msgID and the cached The Security Subsystem provides the following primitive to generate
origin network address are released, and the response is passed to the a Request or Notification message:
associated application using the processResponsePdu primitive:
processResponsePdu( statusInformation =
contextEngineID -- data from/at this SNMP engine generateRequestMsg(
contextName -- data from/in this context IN messageProcessingModel -- typically, SNMP version
PDU -- SNMP Protocol Data Unit IN globalData -- message header, admin data
LoS -- Level of Security IN maxMessageSize -- of the sending SNMP entity
statusInformation -- success or errorIndication IN securityModel -- for the outgoing message
IN securityEngineID -- authoritative SNMP entity
IN securityName -- on behalf of this principal
IN securityLevel -- Level of Security requested
IN scopedPDU -- message (plaintext) payload
OUT securityParameters -- filled in by Security Module
OUT wholeMsg -- complete generated message
OUT wholeMsgLength -- length of the generated message
) )
4.7. Registering to Receive Asynchronous Messages 4.5.2. Process Incoming Message
When an SNMP engine receives a message that is not the response to a The Security Subsystem provides the following primitive to process
request from this SNMP engine, it must determine to which application an incoming message:
\ statusInformation = -- errorIndication or success
-- error counter OID/value if error
processIncomingMsg(
IN messageProcessingModel -- typically, SNMP version
IN maxMessageSize -- of the sending SNMP entity
IN securityParameters -- for the received message
IN securityModel -- for the received message
IN securityLevel -- Level of Security
IN wholeMsg -- as received on the wire
IN wholeMsgLength -- length as received on the wire
OUT securityEngineID -- identification of the principal
OUT securityName -- identification of the principal
OUT scopedPDU, -- message (plaintext) payload
OUT maxSizeResponseScopedPDU -- maximum size of the Response PDU
OUT securityStateReference -- reference to security state
) -- information, needed for response
the message should be given. 4.5.3. Generate a Response Message
An Application that wishes to receive asynchronous messages registers The Security Subsystem provides the following primitive to generate
itself with the engine using the registration primitive. The a Response message:
application registers to handle all incoming messages containing
a particular PDU type regarding a specific contextEngineID.
statusInformation = -- success or errorIndication statusInformation =
registerContextEngineID( generateResponseMsg(
contextEngineID -- take responsibility for this one IN messageProcessingModel -- typically, SNMP version
pduType -- the pduType(s) to be registered IN globalData -- message header, admin data
IN maxMessageSize -- of the sending SNMP entity
IN securityModel -- for the outgoing message
IN securityEngineID -- authoritative SNMP entity
IN securityName -- on behalf of this principal
IN securityLevel -- for the outgoing message
IN scopedPDU -- message (plaintext) payload
IN securityStateReference -- reference to security state
-- information from original request
OUT securityParameters -- filled in by Security Module
OUT wholeMsg -- complete generated message
OUT wholeMsgLength -- length of the generated message
) )
Only one registration per PDU type per contextEngineID is permitted 4.6. User Based Security Model Internal Primitives
at the same time. Duplicate registrations are ignored. An
errorIndication will be returned to the application if it attempts
to duplicate an existing registration.
An Application that wishes to stop receiving asynchronous messages 4.6.1. User-based Security Model Primitives for Authentication
should unregister itself with the SNMP engine.
unregisterContextEngineID( The User-based Security Model provides the following internal
contextEngineID -- give up responsibility for this one primitives to pass data back and forth between the Security Model
pduType -- the pduType(s) to be unregistered itself and the authentication service:
statusInformation =
authenticateOutgoingMsg(
IN authKey -- secret key for authentication
IN wholeMsg -- unauthenticated complete message
OUT authenticatedWholeMsg -- complete authenticated message
) )
SNMP does not provide a mechanism for identifying an application, statusInformation =
so the mechanism used to identify which application is registering authenticateIncomingMsg(
is implementation-specific. IN authKey -- secret key for authentication
IN authParameters -- as received on the wire
IN wholeMsg -- as received on the wire
OUT authenticatedWholeMsg -- complete authenticated message
)
\ 4.6.2. User-based Security Model Primitives for Privacy
5. Definition of Managed Objects for Internet Management Frameworks The User-based Security Model provides the following internal
primitives to pass data back and forth between the Security Model
itself and the privacy service:
statusInformation =
encryptData(
IN encryptKey -- secret key for encryption
IN dataToEncrypt -- data to encrypt (scopedPDU)
OUT encryptedData -- encrypted data (encryptedPDU)
OUT privParameters -- filled in by service provider
)
statusInformation =
decryptData(
IN decryptKey -- secret key for decrypting
IN privParameters -- as received on the wire
IN encryptedData -- encrypted data (encryptedPDU)
OUT decryptedData -- decrypted data (scopedPDU)
)
4.7. Scenario Diagrams
4.7.1. Command Generator or Notification Originator Application
This diagram shows how a Command Generator or Notification Originator
application requests that a PDU be sent, and how the response is
returned (asynchronously) to that application.
Command Dispatcher Message Security
Generator | Processing Model
| | Model |
| | | |
| sendPdu | | |
|------------------->| | |
| | prepareOutgoingMessage | |
: |------------------------->| |
: | | generateRequestMsg |
: | |-------------------->|
: | | |
: | |<--------------------|
: | | |
: |<-------------------------| |
: | | |
: |------------------+ | |
: | Send SNMP | | |
: | Request Message | | |
: | to Network | | |
: | v | |
: : : : :
: : : : :
: : : : :
: | | | |
: | | | |
: | Receive SNMP | | |
: | Response Message | | |
: | from Network | | |
: |<-----------------+ | |
: | | |
: | prepareDataElements | |
: |------------------------->| |
: | | processIncomingMsg |
: | |-------------------->|
: | | |
: | |<--------------------|
: | | |
: |<-------------------------| |
| processResponsePdu | | |
|<-------------------| | |
| | | |
4.7.2. Scenario Diagram for a Command Responder Application
This diagram shows how a Command Responder or Notification Receiver
application registers for handling a pduType, how a PDU is dispatched
to the application after a SNMP message is received, and how the
Response is (asynchronously) send back to the network.
Command Dispatcher Message Security
Responder | Processing Model
| | Model |
| | | |
| registerContextEngineID | | |
|------------------------>| | |
|<------------------------| | | |
| | Receive SNMP | | |
: | Message | | |
: | from Network | | |
: |<-------------+ | |
: | | |
: | prepareDataElements | |
: |-------------------->| |
: | | processIncomingMsg |
: | |-------------------->|
: | | |
: | |<--------------------|
: | | |
: |<--------------------| |
| processPdu | | |
|<------------------------| | |
| | | |
: : : :
: : : :
| returnResponsePdu | | |
|------------------------>| | |
: | prepareResponseMsg | |
: |-------------------->| |
: | | generateResponseMsg |
: | |-------------------->|
: | | |
: | |<--------------------|
: | | |
: |<--------------------| |
: | | |
: |--------------+ | |
: | Send SNMP | | |
: | Message | | |
: | to Network | | |
: | v | |
5. Definition of Managed Objects for SNMP Management Frameworks
SNMP-FRAMEWORK-MIB DEFINITIONS ::= BEGIN SNMP-FRAMEWORK-MIB DEFINITIONS ::= BEGIN
IMPORTS IMPORTS
MODULE-IDENTITY, OBJECT-TYPE, MODULE-IDENTITY, OBJECT-TYPE,
OBJECT-IDENTITY, OBJECT-IDENTITY,
snmpModules, Unsigned32, Integer32 FROM SNMPv2-SMI snmpModules, Unsigned32, Integer32 FROM SNMPv2-SMI
TEXTUAL-CONVENTION FROM SNMPv2-TC TEXTUAL-CONVENTION FROM SNMPv2-TC
MODULE-COMPLIANCE, OBJECT-GROUP FROM SNMPv2-CONF; MODULE-COMPLIANCE, OBJECT-GROUP FROM SNMPv2-CONF;
snmpFrameworkMIB MODULE-IDENTITY snmpFrameworkMIB MODULE-IDENTITY
LAST-UPDATED "9707110000Z" -- 11 July 1997, midnight LAST-UPDATED "9707260000Z" -- 26 July 1997, midnight
ORGANIZATION "SNMPv3 Working Group" ORGANIZATION "SNMPv3 Working Group"
CONTACT-INFO "WG-email: snmpv3@tis.com CONTACT-INFO "WG-email: snmpv3@tis.com
Subscribe: majordomo@tis.com Subscribe: majordomo@tis.com
In message body: subscribe snmpv3 In message body: subscribe snmpv3
Chair: Russ Mundy Chair: Russ Mundy
Trusted Information Systems Trusted Information Systems
postal: 3060 Washington Rd postal: 3060 Washington Rd
Glenwood MD 21738 Glenwood MD 21738
USA USA
skipping to change at page 33, line 51 skipping to change at page 42, line 49
phone: +1-603-337-7357 phone: +1-603-337-7357
Co-editor: Bert Wijnen Co-editor: Bert Wijnen
IBM T.J. Watson Research IBM T.J. Watson Research
postal: Schagen 33 postal: Schagen 33
3461 GL Linschoten 3461 GL Linschoten
Netherlands Netherlands
email: wijnen@vnet.ibm.com email: wijnen@vnet.ibm.com
phone: +31-348-432-794 phone: +31-348-432-794
" "
DESCRIPTION "The Internet Management Architecture MIB" DESCRIPTION "The SNMP Management Architecture MIB"
::= { snmpModules 7 } -- DBH: check if this number is indeed OK ::= { snmpModules 7 } -- DBH: check if this number is indeed OK
-- Textual Conventions used in the SNMP Management Architecture ***
SnmpEngineID ::= TEXTUAL-CONVENTION SnmpEngineID ::= TEXTUAL-CONVENTION
STATUS current STATUS current
\
DESCRIPTION "An SNMP engine's administratively-unique identifier. DESCRIPTION "An SNMP engine's administratively-unique identifier.
The value for this object may not be all zeros or The value for this object may not be all zeros or
all 'ff'H. It may also not be the empty string. all 'ff'H or the empty (zero length) string.
The initial value for this object may be configured The initial value for this object may be configured
via an operator console entry or via an algorithmic via an operator console entry or via an algorithmic
function. In the latter case, the following function. In the latter case, the following
example algorithm for a twelve-octet identifier example algorithm is recommended.
is recommended:
1) The first four octets are set to the binary 1) The very first bit is used to indicate how the
equivalent of the entity's SNMP network management rest of the data is composed.
0 - as defined by enterprise using former methods
that existed before SNMPv3. See item 2 below.
1 - as defined by this architecture, see item 3
below.
Note that this allows existing uses of the
engineID (also known as AgentID [RFC1910]) to
co-exist with any new uses.
2) The snmpEngineID has a length of 12 octets.
The first four octets are set to the binary
equivalent of the agent's SNMP network management
private enterprise number as assigned by the private enterprise number as assigned by the
Internet Assigned Numbers Authority (IANA). Internet Assigned Numbers Authority (IANA).
For example, if Acme Networks has been assigned For example, if Acme Networks has been assigned
{ enterprises 696 }, the first four octets would { enterprises 696 }, the first four octets would
be assigned '000002b8'H. be assigned '000002b8'H.
2) The remaining eight octets are determined via The remaining eight octets are determined via
one or more enterprise specific methods. Such one or more enterprise specific methods. Such
methods must be designed so as to maximize the methods must be designed so as to maximize the
possibility that the value of this object will possibility that the value of this object will
be unique in the entity's administrative domain. be unique in the agent's administrative domain.
For example, it may be the IP address of the SNMP For example, it may be the IP address of the SNMP
entity, or the MAC address of one of the entity, or the MAC address of one of the
interfaces, with each address suitably padded interfaces, with each address suitably padded
with random octets. If multiple methods are with random octets. If multiple methods are
defined, then it is recommended that the first defined, then it is recommended that the first
octet that indicates the method being used and octet indicate the method being used and the
the remaining octets are a function of the method. remaining octets be a function of the method.
3) The length of the octet strings varies.
The first four octets are set to the binary
equivalent of the agent's SNMP network management
private enterprise number as assigned by the
Internet Assigned Numbers Authority (IANA).
For example, if Acme Networks has been assigned
{ enterprises 696 }, the first four octets would
be assigned '000002b8'H.
The very first bit is set to 1. For example, the
above value for Acme Networks now changes to be
'800002b8'H.
The fifth octet indicates how the rest (6th and
following octets) are formatted. The values for
the fifth octet are:
0 - reserved, unused.
1 - IPv4 address (4 octets)
lowest non-special IP address
2 - IPv6 address (16 octets)
lowest non-special IP address
3 - MAC address (6 octets)
lowest IEEE MAC address, canonical order
4 - Text, administratively assigned
Maximum remaining length 27
5 - Octets, administratively assigned
Maximum remaining length 27
6-127 - reserved, unused
127-255 - as defined by the enterprise
Maximum remaining length 27
" "
SYNTAX OCTET STRING SYNTAX OCTET STRING (SIZE(1..32))
SnmpSecurityModel ::= TEXTUAL-CONVENTION SnmpSecurityModel ::= TEXTUAL-CONVENTION
STATUS current STATUS current
DESCRIPTION "An identifier that uniquely identifies a securityModel DESCRIPTION "An identifier that uniquely identifies a securityModel
of the Security Subsystem within the Internet of the Security Subsystem within the SNMP
Management Architecture. Management Architecture.
The values for securityModel are allocated as follows: The values for securityModel are allocated as follows:
- Negative and zero values are reserved. - The zero value is reserved.
- Values between 1 and 255, inclusive, are reserved - Values between 1 and 255, inclusive, are reserved
for standards-track Security Models and are managed for standards-track Security Models and are managed
by the Internet Assigned Numbers Authority (IANA). by the Internet Assigned Numbers Authority (IANA).
- Values greater than 255 are allocated to enterprise - Values greater than 255 are allocated to enterprise
specific Security Models. An enterprise specific specific Security Models. An enterprise specific
securityModel value is defined to be: securityModel value is defined to be:
enterpriseID * 256 + security model within enterprise enterpriseID * 256 + security model within enterprise
\
For example, the fourth Security Model defined by For example, the fourth Security Model defined by
the enterprise whose enterpriseID is 1 would be 260. the enterprise whose enterpriseID is 1 would be 260.
The eight bits allow a maximum of 255 (256-1 reserved) The eight bits allow a maximum of 255 (256-1 reserved)
standards based Security Models. Similarly, they standards based Security Models. Similarly, they
allow a maximum of 255 Security Models per enterprise. allow a maximum of 255 Security Models per enterprise.
It is believed that the assignment of new It is believed that the assignment of new
securityModel values will be rare in practice securityModel values will be rare in practice
because the larger the number of simultaneously because the larger the number of simultaneously
skipping to change at page 35, line 50 skipping to change at page 45, line 52
follows: follows:
0 reserved for 'none' 0 reserved for 'none'
1 reserved for SNMPv1 1 reserved for SNMPv1
2 reserved for SNMPv2c 2 reserved for SNMPv2c
3 User-Base Security Model (USM) 3 User-Base Security Model (USM)
255 reserved for 'any' 255 reserved for 'any'
" "
SYNTAX INTEGER(0..2147483647) SYNTAX INTEGER(0..2147483647)
SnmpLoS ::= TEXTUAL-CONVENTION SnmpMessageProcessingModel ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION "An identifier that uniquely identifies a Message
Processing Model of the Message Processing Subsystem
within a SNMP Management Architecture.
The values for messageProcessingModel are allocated
as follows:
- Values between 0 and 255, inclusive, are reserved
for standards-track Message Processing Models and
are managed by the Internet Assigned Numbers
Authority (IANA).
- Values greater than 255 are allocated to enterprise
specific Message Processing Models. An enterprise
messageProcessingModel value is defined to be:
enterpriseID * 256 +
messageProcessingModel within enterprise
For example, the fourth Message Processing Model
defined by the enterprise whose enterpriseID is 1
would be 260.
The eight bits allow a maximum of 256 standards based
Message Processing Models. Similarly, they allow a
maximum 256 Message Processing Models per enterprise.
It is believed that the assignment of new
messageProcessingModel values will be rare in practice
because the larger the number of simultaneously
utilized Message Processing Models, the larger the
chance that interoperability will suffer. It is
believed that such a range will be sufficient.
In the unlikely event that the standards committee
finds this number to be insufficient over time, an
enterprise number can be allocated to obtain an
additional 256 possible values.
Note that the most significant bit must be zero;
hence, there are 23 bits allocated for various
organizations to design and define non-standard
messageProcessingModels. This limits the ability
to define new proprietary implementations of Message
Processing Models to the first 8,388,608 enterprises.
It is worthwhile to note that, in its encoded form,
the securityModel value will normally require only a
single byte since, in practice, the leftmost bits will
be zero for most messages and sign extension is
suppressed by the encoding rules.
As of this writing, there are several values of
messageProcessingModel defined for use with SNMP.
They are as follows:
0 reserved for SNMPv1
1 reserved for SNMPv2c
2 reserved for SNMPv2u
3 reserved for SNMPv3
"
SYNTAX INTEGER(0..2147483647)
SnmpSecurityLevel ::= TEXTUAL-CONVENTION
STATUS current STATUS current
DESCRIPTION "A Level of Security at which SNMP messages can be DESCRIPTION "A Level of Security at which SNMP messages can be
sent or with which operations are being processed; sent or with which operations are being processed;
in particular, one of: in particular, one of:
\
noAuthNoPriv - without authentication and noAuthNoPriv - without authentication and
without privacy, without privacy,
authNoPriv - with authentication but authNoPriv - with authentication but
without privacy, without privacy,
authPriv - with authentication and authPriv - with authentication and
with privacy. with privacy.
These three values are ordered such that noAuthNoPriv These three values are ordered such that noAuthNoPriv
is lower than authNoPriv and authNoPriv is lower than is less than authNoPriv and authNoPriv is less than
authPriv. authPriv.
" "
SYNTAX INTEGER { noAuthNoPriv(1), SYNTAX INTEGER { noAuthNoPriv(1),
authNoPriv(2), authNoPriv(2),
authPriv(3) authPriv(3)
} }
SnmpAdminString ::= TEXTUAL-CONVENTION SnmpAdminString ::= TEXTUAL-CONVENTION
DISPLAY-HINT "255a" DISPLAY-HINT "255a"
STATUS current STATUS current
skipping to change at page 36, line 47 skipping to change at page 48, line 9
The use of control codes should be avoided. The use of control codes should be avoided.
For code points not directly supported by user For code points not directly supported by user
interface hardware or software, an alternative means interface hardware or software, an alternative means
of entry and display, such as hexadecimal, may be of entry and display, such as hexadecimal, may be
provided. provided.
For information encoded in 7-bit US-ASCII, the UTF-8 For information encoded in 7-bit US-ASCII, the UTF-8
representation is identical to the US-ASCII encoding. representation is identical to the US-ASCII encoding.
Note that when this TC is used for an object that
is used or envisioned to be used as an index, then a
SIZE restriction must be specified so that the number
sub-identifiers for any object instance do not exceed
the limit of 128, as defined by [RFC1905].
" "
SYNTAX OCTET STRING (SIZE (0..255)) SYNTAX OCTET STRING (SIZE (0..255))
-- Administrative assignments **************************************** -- Administrative assignments ****************************************
snmpFrameworkAdmin OBJECT IDENTIFIER ::= { snmpFrameworkMIB 1 } snmpFrameworkAdmin OBJECT IDENTIFIER ::= { snmpFrameworkMIB 1 }
snmpFrameworkMIBObjects OBJECT IDENTIFIER ::= { snmpFrameworkMIB 2 } snmpFrameworkMIBObjects OBJECT IDENTIFIER ::= { snmpFrameworkMIB 2 }
snmpFrameworkMIBConformance OBJECT IDENTIFIER ::= { snmpFrameworkMIB 3 } snmpFrameworkMIBConformance OBJECT IDENTIFIER ::= { snmpFrameworkMIB 3 }
\
-- the snmpEngine Group ********************************************** -- the snmpEngine Group **********************************************
snmpEngine OBJECT IDENTIFIER ::= { snmpFrameworkMIBObjects 1 } snmpEngine OBJECT IDENTIFIER ::= { snmpFrameworkMIBObjects 1 }
snmpEngineID OBJECT-TYPE snmpEngineID OBJECT-TYPE
SYNTAX SnmpEngineID SYNTAX SnmpEngineID
MAX-ACCESS read-only MAX-ACCESS read-only
STATUS current STATUS current
DESCRIPTION "An SNMP engine's administratively-unique identifier. DESCRIPTION "An SNMP engine's administratively-unique identifier.
" "
skipping to change at page 37, line 38 skipping to change at page 49, line 5
snmpEngineTime OBJECT-TYPE snmpEngineTime OBJECT-TYPE
SYNTAX Integer32 (0..2147483647) SYNTAX Integer32 (0..2147483647)
MAX-ACCESS read-only MAX-ACCESS read-only
STATUS current STATUS current
DESCRIPTION "The number of seconds since the SNMP engine last DESCRIPTION "The number of seconds since the SNMP engine last
incremented the snmpEngineBoots object. incremented the snmpEngineBoots object.
" "
::= { snmpEngine 3 } ::= { snmpEngine 3 }
-- Registration Points for Authentication and Privacy Protocols **
snmpAuthProtocols OBJECT-IDENTITY snmpAuthProtocols OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION "Registration point for standards-track authentication DESCRIPTION "Registration point for standards-track authentication
protocols used in the Internet Management Framework. protocols used in SNMP Management Frameworks.
" "
::= { snmpFrameworkAdmin 1 } ::= { snmpFrameworkAdmin 1 }
snmpPrivProtocols OBJECT-IDENTITY snmpPrivProtocols OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION "Registration point for standards-track privacy DESCRIPTION "Registration point for standards-track privacy
protocols used in the Internet Management Framework. protocols used in SNMP Management Frameworks.
" "
::= { snmpFrameworkAdmin 2 } ::= { snmpFrameworkAdmin 2 }
-- Conformance information ******************************************* -- Conformance information *******************************************
snmpFrameworkMIBCompliances snmpFrameworkMIBCompliances
\
OBJECT IDENTIFIER ::= { snmpFrameworkMIBConformance 1 } OBJECT IDENTIFIER ::= { snmpFrameworkMIBConformance 1 }
snmpFrameworkMIBGroups snmpFrameworkMIBGroups
OBJECT IDENTIFIER ::= { snmpFrameworkMIBConformance 2 } OBJECT IDENTIFIER ::= { snmpFrameworkMIBConformance 2 }
-- compliance statements -- compliance statements
snmpFrameworkMIBCompliance MODULE-COMPLIANCE snmpFrameworkMIBCompliance MODULE-COMPLIANCE
STATUS current STATUS current
DESCRIPTION "The compliance statement for SNMP engines which DESCRIPTION "The compliance statement for SNMP engines which
implement the Internet Management Framework MIB. implement the SNMP Management Framework MIB.
" "
MODULE -- this module MODULE -- this module
MANDATORY-GROUPS { snmpEngineGroup } MANDATORY-GROUPS { snmpEngineGroup }
::= { snmpFrameworkMIBCompliances 1 } ::= { snmpFrameworkMIBCompliances 1 }
-- units of conformance -- units of conformance
snmpEngineGroup OBJECT-GROUP snmpEngineGroup OBJECT-GROUP
OBJECTS { OBJECTS {
skipping to change at page 39, line 5 skipping to change at page 51, line 5
} }
STATUS current STATUS current
DESCRIPTION "A collection of objects for identifying and DESCRIPTION "A collection of objects for identifying and
determining the configuration and current timeliness determining the configuration and current timeliness
values of an SNMP engine. values of an SNMP engine.
" "
::= { snmpFrameworkMIBGroups 1 } ::= { snmpFrameworkMIBGroups 1 }
END END
\
6. Security Considerations 6. Security Considerations
This document describes how a framework can use a Security Model and This document describes how an implementation can include a Security
an Access Control Model to achieve a level of security for network Model to protect network management messages and an Access Control
management messages and controlled access to management information. Model to control access to management information.
The level of security provided is determined by the specific Security The level of security provided is determined by the specific Security
Model implementation(s) and the specific Access Control Model Model implementation(s) and the specific Access Control Model
implementation(s) incorporated into this framework. implementation(s) used.
Applications have access to data which is not secured. Applications Applications have access to data which is not secured. Applications
should take reasonable steps to protect the data from disclosure. should take reasonable steps to protect the data from disclosure.
It is the responsibility of the purchaser of a management framework It is the responsibility of the purchaser of an implementation to
implementation to ensure that: ensure that:
1) an implementation of this framework complies with the rules 1) an implementation complies with the rules defined by this
defined by this architecture, architecture,
2) the Security and Access Control Models utilized satisfy the 2) the Security and Access Control Models utilized satisfy the
security and access control needs of the organization, security and access control needs of the organization,
3) the implementations of the Models and Applications comply with 3) the implementations of the Models and Applications comply with
the model and application specifications, the model and application specifications,
4) and the implementation protects configuration secrets from 4) and the implementation protects configuration secrets from
inadvertent disclosure. inadvertent disclosure.
\ 7. Editor's Addresses
7. Glossary Co-editor: Bert Wijnen
8. References IBM T.J. Watson Research
postal: Schagen 33
3461 GL Linschoten
Netherlands
email: wijnen@vnet.ibm.com
phone: +31-348-432-794
Co-editor Dave Harrington
Cabletron Systems, Inc
postal: Post Office Box 5005
MailStop: Durham
35 Industrial Way
Rochester NH 03867-5005
USA
email: dbh@cabletron.com
phone: +1-603-337-7357
8. Acknowledgements
This document is the result of the efforts of the SNMPv3 Working Group.
Some special thanks are in order to the following SNMPv3 WG members:
Dave Battle (SNMP Research, Inc.)
Uri Blumenthal (IBM T.J. Watson Research Center)
Jeff Case (SNMP Research, Inc.)
John Curran (BBN)
T. Max Devlin (Hi-TECH Connections)
John Flick (Hewlett Packard)
David Harrington (Cabletron Systems Inc.)
N.C. Hien (IBM T.J. Watson Research Center)
Dave Levi (SNMP Research, Inc.)
Louis A Mamakos (UUNET Technologies Inc.)
Paul Meyer (Secure Computing Corporation)
Keith McCloghrie (Cisco Systems)
Russ Mundy (Trusted Information Systems, Inc.)
Bob Natale (ACE*COMM Corporation)
Mike O'Dell (UUNET Technologies Inc.)
Dave Perkins (DeskTalk)
Peter Polkinghorne (Brunel University)
Randy Presuhn (BMC Software, Inc.)
David Reid (SNMP Research, Inc.)
Shawn Routhier (Epilogue)
Juergen Schoenwaelder (TU Braunschweig)
Bob Stewart (Cisco Systems)
Bert Wijnen (IBM T.J. Watson Research Center)
The document is based on recommendations of the IETF Security and
Administrative Framework Evolution for SNMP Advisory Team.
Members of that Advisory Team were:
David Harrington (Cabletron Systems Inc.)
Jeff Johnson (Cisco Systems)
David Levi (SNMP Research Inc.)
John Linn (Openvision)
Russ Mundy (Trusted Information Systems) chair
Shawn Routhier (Epilogue)
Glenn Waters (Nortel)
Bert Wijnen (IBM T. J. Watson Research Center)
As recommended by the Advisory Team and the SNMPv3 Working Group
Charter, the design incorporates as much as practical from previous
RFCs and drafts. As a result, special thanks are due to the authors
of previous designs known as SNMPv2u and SNMPv2*:
Jeff Case (SNMP Research, Inc.)
David Harrington (Cabletron Systems Inc.)
David Levi (SNMP Research, Inc.)
Keith McCloghrie (Cisco Systems)
Brian O'Keefe (Hewlett Packard)
Marshall T. Rose (Dover Beach Consulting)
Jon Saperia (BGS Systems Inc.)
Steve Waldbusser (International Network Services)
Glenn W. Waters (Bell-Northern Research Ltd.)
9. References
[RFC1155] Rose, M., and K. McCloghrie, "Structure and Identification [RFC1155] Rose, M., and K. McCloghrie, "Structure and Identification
of Management Information for TCP/IP-based internets", STD 16, of Management Information for TCP/IP-based internets", STD 16,
RFC 1155, May 1990. RFC 1155, May 1990.
[RFC1157] Case, J., M. Fedor, M. Schoffstall, and J. Davin, [RFC1157] Case, J., M. Fedor, M. Schoffstall, and J. Davin,
"The Simple Network Management Protocol", STD 15, RFC 1157, "The Simple Network Management Protocol", STD 15, RFC 1157,
University of Tennessee at Knoxville, Performance Systems s University of Tennessee at Knoxville, Performance Systems s
International, Performance International, and the MIT Laboratory International, Performance International, and the MIT Laboratory
for Computer Science, May 1990. for Computer Science, May 1990.
[RFC1212] Rose, M., and K. McCloghrie, "Concise MIB Definitions", [RFC1212] Rose, M., and K. McCloghrie, "Concise MIB Definitions",
STD 16, RFC 1212, March 1991. STD 16, RFC 1212, March 1991.
[RFC1901] The SNMPv2 Working Group, Case, J., McCloghrie, K., [RFC1901] The SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M.,
Rose, M., and S., Waldbusser, "Introduction to and S., Waldbusser, "Introduction to Community-based SNMPv2",
Community-based SNMPv2", RFC 1901, January 1996. RFC 1901, January 1996.
[RFC1902] The SNMPv2 Working Group, Case, J., McCloghrie, K., [RFC1902] The SNMPv2 Working Group, Case, J., McCloghrie, K.,
Rose, M., and S., Waldbusser, "Structure of Management Rose, M., and S., Waldbusser, "Structure of Management
Information for Version 2 of the Simple Network Management Information for Version 2 of the Simple Network Management
Protocol (SNMPv2)", RFC 1905, January 1996. Protocol (SNMPv2)", RFC 1902, January 1996.
[RFC1903] The SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., [RFC1903] The SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M.,
and S. Waldbusser, "Textual Conventions for Version 2 of the Simple and S. Waldbusser, "Textual Conventions for Version 2 of the Simple
Network Management Protocol (SNMPv2)", RFC 1903, January 1996. Network Management Protocol (SNMPv2)", RFC 1903, January 1996.
[RFC1904] The SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., [RFC1904] The SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M.,
and S., Waldbusser, "Conformance Statements for Version 2 of the and S., Waldbusser, "Conformance Statements for Version 2 of the
Simple Network Management Protocol (SNMPv2)", RFC 1904, Simple Network Management Protocol (SNMPv2)", RFC 1904,
January 1996. January 1996.
skipping to change at page 40, line 58 skipping to change at page 55, line 55
Version 2 of the Simple Network Management Protocol (SNMPv2)", Version 2 of the Simple Network Management Protocol (SNMPv2)",
RFC 1906, January 1996. RFC 1906, January 1996.
[RFC1907] The SNMPv2 Working Group, Case, J., McCloghrie, K., [RFC1907] The SNMPv2 Working Group, Case, J., McCloghrie, K.,
Rose, M., and S. Waldbusser, "Management Information Base for Rose, M., and S. Waldbusser, "Management Information Base for
Version 2 of the Simple Network Management Protocol (SNMPv2)", Version 2 of the Simple Network Management Protocol (SNMPv2)",
RFC 1907 January 1996. RFC 1907 January 1996.
[RFC1908] The SNMPv2 Working Group, Case, J., McCloghrie, K., [RFC1908] The SNMPv2 Working Group, Case, J., McCloghrie, K.,
Rose, M., and S. Waldbusser, "Coexistence between Version 1 Rose, M., and S. Waldbusser, "Coexistence between Version 1
and Version 2 of the Internet-standard Network Management and Version 2 of the SNMP-standard Network Management
\
Framework", RFC 1908, January 1996. Framework", RFC 1908, January 1996.
[RFC1909] McCloghrie, K., Editor, "An Administrative Infrastructure [RFC1909] McCloghrie, K., Editor, "An Administrative Infrastructure
for SNMPv2", RFC1909, February 1996 for SNMPv2", RFC1909, February 1996
[RFC1910] Waters, G., Editor, "User-based Security Model for SNMPv2", [RFC1910] Waters, G., Editor, "User-based Security Model for SNMPv2",
RFC1910, February 1996 RFC1910, February 1996
\ [SNMP-MPD] The SNMPv3 Working Group, Case, J., Harrington, D.,
Wijnen, B., "Message Processing and Dispatching for the Simple
9. Editor's Addresses Network Management Protocol (SNMP)",
draft-ietf-snmpv3-mpc-03.txt, August 1997
Co-editor: Bert Wijnen
IBM T.J. Watson Research
postal: Schagen 33
3461 GL Linschoten
Netherlands
email: wijnen@vnet.ibm.com
phone: +31-348-432-794
Co-editor Dave Harrington
Cabletron Systems, Inc
postal: Post Office Box 5005
MailStop: Durham
35 Industrial Way
Rochester NH 03867-5005
USA
email: dbh@cabletron.com
phone: +1-603-337-7357
\
10. Acknowledgements
This document builds on the work of the SNMP Security and [SNMP-USM] The SNMPv3 Working Group, Blumenthal, U., Wijnen, B.,
Administrative Framework Evolution team, composed of "The User-Based Security Model for Version 3 of the Simple
Network Management Protocol (SNMPv3)",
draft-ietf-snmpv3-usm-01.txt, August 1997.
David Harrington (Cabletron Systems Inc.) [SNMP-ACM] The SNMPv3 Working Group, Wijnen, B., Presuhn, R.,
Jeff Johnson (Cisco) McCloghrie, K., "View-based Access Control Model for the Simple
David Levi (SNMP Research Inc.) Network Management Protocol (SNMP)",
John Linn (Openvision) draft-ietf-snmpv3-acm-02.txt, August 1997.
Russ Mundy (Trusted Information Systems) chair
Shawn Routhier (Epilogue)
Glenn Waters (Nortel)
Bert Wijnen (IBM T.J. Watson Research)
\ [SNMP-APPL] The SNMPv3 Working Group, Levi, D. B., Meyer, P.,
Stewart, B., "SNMPv3 Applications",
<draft-ietf-snmpv3-appl-01.txt>, August 1997
APPENDIX A APPENDIX A
A. Guidelines for Model Designers A. Guidelines for Model Designers
This appendix describes guidelines for designers of models which This appendix describes guidelines for designers of models which are
are expected to fit into the architecture defined in this document. expected to fit into the architecture defined in this document.
The basic design elements come from SNMPv2u and SNMPv2*, as
described in RFCs 1909-1910, and from a set of internet drafts.
these are the two most popular de facto "administrative framework"
standards that include security and access control for SNMPv2.
SNMPv1 and SNMPv2c [RFC1901] are two administrative frameworks based SNMPv1 and SNMPv2c are two SNMP frameworks which use communities to
on communities to provide trivial authentication and access control. provide trivial authentication and access control. SNMPv1 and SNMPv2c
SNMPv1 and SNMPv2c Frameworks can coexist with Frameworks designed Frameworks can coexist with Frameworks designed according to this
to fit into this architecture, and modified versions of SNMPv1 and architecture, and modified versions of SNMPv1 and SNMPv2c Frameworks
SNMPv2c Frameworks could be fit into this architecture, but this could be designed to meet the requirements of this architecture, but
document does not provide guidelines for that coexistence. this document does not provide guidelines for that
coexistence.
Within any subsystem model, there should be no reference to any Within any subsystem model, there should be no reference to any
specific model of another subsystem, or to data defined by a specific specific model of another subsystem, or to data defined by a specific
model of another subsystem. model of another subsystem.
Transfer of data between the subsystems is deliberately described Transfer of data between the subsystems is deliberately described as
a fixed set of abstract data elements and primitive functions which
as a fixed set of abstract data elements and primitive functions can be overloaded to satisfy the needs of multiple model definitions.
which can be overloaded to satisfy the needs of multiple model
definitions.
Documents which define models to be used within this architecture Documents which define models to be used within this architecture
SHOULD use the standard primitives between subsystems, possibly SHOULD use the standard primitives between subsystems, possibly
defining specific mechanisms for converting the abstract data elements defining specific mechanisms for converting the abstract data elements
into model-usable formats. This constraint exists to allow subsystem into model-usable formats. This constraint exists to allow subsystem
and model documents to be written recognizing common borders of the and model documents to be written recognizing common borders of the
subsystem and model. Vendors are not constrained to recognize these subsystem and model. Vendors are not constrained to recognize these
borders in their implementations. borders in their implementations.
The architecture defines certain standard services to be provided The architecture defines certain standard services to be provided
between subsystems, and the architecture defines abstract service between subsystems, and the architecture defines abstract service
interfaces to request the services. interfaces to request these services.
Each model definition for a subsystem SHOULD support the standard Each model definition for a subsystem SHOULD support the standard
service interfaces, but whether, or how, or how well, it performs service interfaces, but whether, or how, or how well, it performs
the service is defined by the model definition. the service is dependent on the model definition.
A.1. Security Model Design Requirements A.1. Security Model Design Requirements
A.1.1. Threats A.1.1. Threats
A document describing a Security Model MUST describe how the model A document describing a Security Model MUST describe how the model
protects against the threats described under "Security Requirements protects against the threats described under "Security Requirements
of this Architecture", section 1.4. of this Architecture", section 1.4.
\
A.1.2. Security Processing A.1.2. Security Processing
Received messages MUST be validated by a Model of the Security Received messages MUST be validated by a Model of the Security
Subsystem. Validation includes authentication and privacy processing Subsystem. Validation includes authentication and privacy processing
if needed, but it is explicitly allowed to send messages which do
not require authentication or privacy.
A received message contains a specified Level of Security to be if needed, but it is explicitly allowed to send messages which do not
used during processing. All messages requiring privacy MUST also require authentication or privacy.
require authentication.
A received message contains a specified Level of Security to be used
during processing. All messages requiring privacy MUST also require
authentication.
A Security Model specifies rules by which authentication and privacy A Security Model specifies rules by which authentication and privacy
are to be done. A model may define mechanisms to provide additional are to be done. A model may define mechanisms to provide additional
security features, but the model definition is constrained to using security features, but the model definition is constrained to using
(possibly a subset of) the abstract data elements defined in this (possibly a subset of) the abstract data elements defined in this
document for transferring data between subsystems. document for transferring data between subsystems.
Each Security Model may allow multiple security mechanisms to be used Each Security Model may allow multiple security protocols to be used
concurrently within an implementation of the model. Each Security Model concurrently within an implementation of the model. Each Security
defines how to determine which protocol to use, given the LoS and the Model defines how to determine which protocol to use, given the
security parameters relevant to the message. Each Security Model, with securityLevel and the security parameters relevant to the message.
its associated protocol(s) defines how the sending/receiving entities Each Security Model, with its associated protocol(s) defines how the
are identified, and how secrets are configured. sending/receiving entities are identified, and how secrets are
configured.
Authentication and Privacy protocols supported by Security Models are Authentication and Privacy protocols supported by Security Models are
uniquely identified using Object Identifiers. IETF standard protocol uniquely identified using Object Identifiers. IETF standard protocols
for authentication or privacy should have an identifier defined within for authentication or privacy should have an identifier defined within
the snmpAuthProtocols or the snmpPrivProtocols subtrees. Enterprise the snmpAuthProtocols or the snmpPrivProtocols subtrees. Enterprise
specific protocol identifiers should be defined within the enterprise specific protocol identifiers should be defined within the enterprise
subtree. subtree.
For privacy, the Security Model defines what portion of the message For privacy, the Security Model defines what portion of the message
is encrypted. is encrypted.
The persistent data used for security should be SNMP-manageable, but The persistent data used for security should be SNMP-manageable, but
the Security Model defines whether an instantiation of the MIB is a the Security Model defines whether an instantiation of the MIB is a
conformance requirement. conformance requirement.
Security Models are replaceable within the Security Subsystem. Security Models are replaceable within the Security Subsystem.
Multiple Security Model implementations may exist concurrently within Multiple Security Model implementations may exist concurrently within
an SNMP engine. The number of Security Models defined by the SNMP an SNMP engine. The number of Security Models defined by the SNMP
community should remain small to promote interoperability. community should remain small to promote interoperability.
A.1.3. validate the security-stamp in a received message A.1.3. Validate the security-stamp in a received message
The Message Processing Model requests that the Security Model verify
that the message has not been altered, and authenticate the
identification of the principal for whom the message was generated.
If encrypted, decrypt the message.
\ A Message Processing Model requests that a Security Model:
- verifies that the message has not been altered,
- authenticates the identification of the principal for whom the
message was generated.
- decrypts the message if it was encrypted.
Additional requirements may be defined by the model, and additional Additional requirements may be defined by the model, and additional
services provided by the model, but the model is constrained to use services may be provided by the model, but the model is constrained
the following primitives for transferring data between subsystems. to use the following primitives for transferring data between
Implementations are not so constrained.
The Message Processing Model uses the following primitive:
processMsg(
messageProcessingModel -- typically, SNMP version
msgID -- of the received message
mms -- of the sending SNMP entity
msgFlags -- for the received message
securityParameters -- for the received message
securityModel -- for the received message
LoS -- Level of Security
wholeMsg -- as received on the wire
wholeMsgLength -- length as received on the wire
)
The Security Model uses the following primitive to respond: subsystems. Implementations are not so constrained.
returnProcessedMsg( A Message Processing Model uses the processMsg primitive as
securityName -- identification of the principal described in section 4.5.
scopedPDU, -- message (plaintext) payload
maxSizeResponseScopedPDU -- maximum size of the Response PDU
securityStateReference -- reference to security state
-- information, needed for response
statusInformation -- errorIndication or success
) -- error counter OID/value if error
A.1.5. Security MIBs A.1.4. Security MIBs
Each Security Model defines the MIB modules required for security Each Security Model defines the MIB module(s) required for security
processing, including any MIB modules required for the security processing, including any MIB module(s) required for the security
mechanism(s) supported. The MIB modules SHOULD be defined concurrently protocol(s) supported. The MIB module(s) SHOULD be defined
with the procedures which use the MIB module. The MIB modules are concurrently with the procedures which use the MIB module(s). The
subject to normal security and access control rules. MIB module(s) are subject to normal access control rules.
The mapping between the model-dependent identifier and the securityName The mapping between the model dependent security ID and the
MUST be able to be determined using SNMP, if the model-dependent securityName MUST be able to be determined using SNMP, if the model
MIB is instantiated and access control policy allows access. dependent MIB is instantiated and if access control policy allows
access.
A.1.6. Security State Cache A.1.5. Cached Security Data
For each message received, the Security Subsystem caches the state For each message received, the Security Model caches the state
information such that a Response message can be generated using the information such that a Response message can be generated using the
same security state information, even if the Local Configuration same security information, even if the Local Configuration Datastore
Datastore is altered between the time of the incoming request and is altered between the time of the incoming request and the outgoing
the outgoing response. response.
\
Applications have the responsibility for explicitly releasing the
cached data. To enable this, an abstract stateReference data element
is passed from the Security Subsystem to the Message Processing
Subsystem, which passes it to the application.
The cached security data may be implicitly released via the
generation of a response, or explicitly released by using the
stateRelease primitive:
stateRelease( A Message Processing Model has the responsibility for explicitly
stateReference -- handle of reference to be released releasing the cached data if such data is no longer needed. To enable
) this, an abstract securityStateReference data element is passed from
the Security Model to the Message Processing Model.
\ The cached security data may be implicitly released via the generation
of a response, or explicitly released by using the stateRelease
primitive, as described in section 4.1.
A.2. SNMP engine and Message Processing Model Requirements A.2. Message Processing Model Design Requirements
An SNMP engine contains a Message Processing Subsystem which may An SNMP engine contains a Message Processing Subsystem which may
contain multiple version-specific Message Processing Models. contain multiple Message Processing Models.
Within any version-specific Message Processing Model, there may be
an explicit binding to a particular Security Model but there should
be no reference to any data defined by a specific Security Model.
There should be no reference to any specific application, or to any
data defined by a specific application; there should be no reference
to any specific Access Control Model, or to any data defined by a
specific Access Control Model.
The Message Processing Model MUST always (conceptually) pass the The Message Processing Model MUST always (conceptually) pass the
complete PDU, i.e. it never forwards less than the complete list of complete PDU, i.e. it never forwards less than the complete list of
varBinds. varBinds.
A.2.1. Receiving an SNMP Message from the Network A.2.1. Receiving an SNMP Message from the Network
Upon receipt of a message from the network, the SNMP engine notes the Upon receipt of a message from the network, the Dispatcher in the
msgID, which is subsequently used for coordinating all processing SNMP engine determines the version of the SNMP message and interacts
regarding this received message. with the corresponding Message Processing Model to determine the
abstract data elements.
A Message Processing Model specifies how to determine the values of
the global data (mms, the securityModel, the LoS), and the security
parameters block. The Message Processing Model calls the Security
Model to provide security processing for the message using the
primitive:
processMsg(
messageProcessingModel -- typically, SNMP version
msgID -- of the received message
mms -- of the sending SNMP entity
msgFlags -- for the received message
securityParameters -- for the received message
securityModel -- for the received message
LoS -- Level of Security
wholeMsg -- as received on the wire
wholeMsgLength -- length as received on the wire
)
The Security Model uses the following primitive to respond:
returnProcessedMsg(
securityName -- identification of the principal
scopedPDU, -- message (plaintext) payload
maxSizeResponseScopedPDU -- maximum size of the Response PDU
securityStateReference -- reference to security state
-- information, needed for response
statusInformation -- errorIndication or success
) -- error counter OID/value if error
\
A.2.2. Send SNMP messages to the network
The Message Processing Model passes a PDU, the
securityName, and all global data to be included in the message to
the Security model using the following primitives:
For requests and notifications:
generateRequestMsg(
messageProcessingModel -- typically, SNMP version
msgID -- for the outgoing message
mms -- of the sending SNMP entity
msgFlags -- for the outgoing message
securityParameters -- filled in by Security Module
securityModel -- for the outgoing message
securityName -- on behalf of this principal
LoS -- Level of Security requested
snmpEngineID -- authoritative SNMP engine
scopedPDU -- message (plaintext) payload
)
For response messages:
generateResponseMsg(
messageProcessingModel -- typically, SNMP version
msgID -- for the outgoing message
mms -- of the sending SNMP entity
msgFlags -- for the outgoing message
securityParameters -- filled in by Security Module
securityModel -- for the outgoing message
scopedPDU -- message (plaintext) payload
securityStateReference -- reference to security state
-- information, as received in
) -- processPdu primitive
The Security model constructs the message, and returns the completed
message to the Message Processing Model using the returnGeneratedMsg
primitive:
returnGeneratedMsg(
wholeMsg -- complete generated message
wholeMsgLength -- length of the generated message
statusInformation -- errorIndication or success
)
The SNMP engine sends the message to the desired address using the
appropriate transport.
A.2.3. Generate Request or Notification Message for an Application
\
The SNMP engine receives a request for the generation of an SNMP
message from an application via the sendPdu primitive:
sendPdu(
transportDomain -- transport domain to be used
transportAddress -- destination network address
messageProcessingModel -- typically, SNMP version
securityModel -- Security Model to use
securityName -- on behalf of this principal
LoS -- Level of Security requested
contextEngineID -- data from/at this entity
contextName -- data from/in this context
PDU -- SNMP Protocol Data Unit
expectResponse -- TRUE or FALSE
)
The SNMP engine checks the "expectResponse" parameter to determine if
it is a message which is expected to receive a response, and if so,
caches the msgID of the generated message and the associated
application.
The Message Processing Model generates the message according to the
process described in A.2.2.
A.2.4. Pass Received Response Message to an Application
The Message Processing Model receives the SNMP message according to
the process described in A.2.1.
The Message Processing Model determines which application is awaiting
this response, using the msgID and the cached information from
step A.2.3
The Message Processing Model matches the msgID of an incoming response
to the cached msgIDs of messages sent by this SNMP engine, and
forwards the response to the associated application using the
processResponsePdu primitive:
processResponsePdu( -- process Response PDU
contextEngineID -- data from/at this SNMP entity
contextName -- data from/in this context
PDU -- SNMP Protocol Data Unit
LoS -- Level of Security
statusInformation -- success or errorIndication
)
A.2.5. Pass Received Request or Notification Message to Application A Message Processing Model specifies the SNMP Message format it
supports and describes how to determine the values of the abstract
data elements (like msgID, msgMaxSize, msgFlags, msgSecurityParameters,
securityModel, securityLevel etc). A Message Processing Model interacts
with a Security Model to provide security processing for the message
using the processMsg primitive, as described in section 4.5.
The Message Processing Model receives the SNMP message according to A.2.2. Sending an SNMP Message to the Network
the process described in A.2.1.
\ The Dispatcher in the SNMP engine interacts with a Message Processing
Model to prepare an outgoing message. For that it uses the following
primitives:
The SNMP engine looks into the scopedPDU to determine the - for requests and notifications:
contextEngineID, then determine which application has registered to prepareOutgoingMessage, as described in section 4.4
support that contextEngineID, and forwards the request or notification
to the registered application using the processPdu primitive:
processPdu( -- process Request/Notification PDU - for response messages:
contextEngineID -- data from/at this SNMP engine prepareResponseMessage, as described in section 4.4
contextName -- data from/in this context
PDU -- SNMP Protocol Data Unit
maxSizeResponseScopedPDU -- maximum size of the Response PDU
securityModel -- Security Model in use
securityName -- on behalf of this principal
LoS -- Level of Security
stateReference -- reference to state information
) -- needed when sending a response
A.2.6. Generate a Response Message for an Application A Message Processing Model, when preparing an Outgoing SNMP Message,
interacts with a Security Model to secure the message. For that it uses
the following primitives:
The SNMP engine receives a request for the generation of an SNMP - for requests and notifications:
response message from an application via the returnResponsePdu generateRequestMsg, as described in section 4.5.
primitive:
returnResponsePdu( - for response messages:
contextEngineID -- data from/at this SNMP engine generateResponseMsg as described in section 4.5.
contextName -- data from/in this context
PDU -- SNMP Protocol Data Unit
maxSizeResponseScopedPDU -- maximum size of the Response PDU
securityModel -- Security Model in use
securityName -- on behalf of this principal
LoS -- Level of Security
stateReference -- reference to state information
-- as presented with the request
statusInformation -- success or errorIndication
) -- error counter OID/value if error
The SNMP engine generates the message according to the process Once the SNMP message is prepared by a Message Processing Model, the
described in A.2.2. Dispatcher sends the message to the desired address using the appropriate
transport.
A.3. Application Design Requirements A.3. Application Design Requirements
Within an application, there may be an explicit binding to a specific Within an application, there may be an explicit binding to a specific
SNMP message version, i.e. a specific Message Processing Model, and to SNMP message version, i.e. a specific Message Processing Model, and to
a specific Access Control Model, but there should be no reference to a specific Access Control Model, but there should be no reference to
any data defined by a specific Message Processing Model or Access any data defined by a specific Message Processing Model or Access
Control Model. Control Model.
Within an application, there should be no reference to any specific Within an application, there should be no reference to any specific
Security Model, or any data defined by a specific Security Model. Security Model, or any data defined by a specific Security Model.
\
An application determines whether explicit or implicit access control An application determines whether explicit or implicit access control
should be applied to the operation, and, if access control is needed, should be applied to the operation, and, if access control is needed,
which Access Control Model should be used. which Access Control Model should be used.
An application has the responsibility to define any MIB modules used An application has the responsibility to define any MIB module(s) used
to provide application-specific services. to provide application-specific services.
Applications interact with the SNMP engine to initiate messages, Applications interact with the SNMP engine to initiate messages,
receive responses, receive asynchronous messages, and send responses. receive responses, receive asynchronous messages, and send responses.
A.3.1. Applications that Initiate Messages A.3.1. Applications that Initiate Messages
Applications may request that the SNMP engine send messages containing Applications may request that the SNMP engine send messages containing
SNMP commands or notifications using the sendPdu primitive: SNMP commands or notifications using the sendPdu primitive as described
in section 4.2.
sendPdu(
transportDomain -- transport domain to be used
transportAddress -- destination network address
messageProcessingModel -- typically, SNMP version
securityModel -- Security Model to use
securityName -- on behalf of this principal
LoS -- Level of Security requested
contextEngineID -- data from/at this entity
contextName -- data from/in this context
PDU -- SNMP Protocol Data Unit
expectResponse -- TRUE or FALSE
)
If it is desired that a message be sent to multiple targets, it is the If it is desired that a message be sent to multiple targets, it is the
responsibility of the application to provide the iteration. responsibility of the application to provide the iteration.
The SNMP engine assumes necessary access control has been applied The SNMP engine assumes necessary access control has been applied to
to the PDU, and provides no access control services. the PDU, and provides no access control services.
The SNMP engine looks at the "expectResponse" parameter, and for
operations which elicit a response, the msgID and the associated
application are cached.
A.3.2. Applications that Receive Responses
The SNMP engine matches the msgID of an incoming response to the
cached msgIDs of messages sent by this SNMP engine, and forwards the
response to the associated application using the processResponsePdu
primitive:
processResponsePdu( -- process Response PDU The SNMP engine looks at the "expectResponse" parameter, and if a
contextEngineID -- data from/at this SNMP entity response is expected, then the appropriate information is cached such
contextName -- data from/in this context that a later response can be associated to this message, and can then
PDU -- SNMP Protocol Data Unit be returned to the application. A sendPduHandle is returned to the
LoS -- Level of Security application so it can later correspond the response with this message
statusInformation -- success or errorIndication as well.
\ A.3.2. Applications that Receive Responses
)
The SNMP engine then releases its own state information about this The SNMP engine matches the incoming response messages to outstanding
message. messages sent by this SNMP engine, and forwards the response to the
associated application using the processResponsePdu primitive, as
described in section 4.2.
A.3.3. Applications that Receive Asynchronous Messages A.3.3. Applications that Receive Asynchronous Messages
When an SNMP engine receives a message that is not the response to a When an SNMP engine receives a message that is not the response to a
request from this SNMP engine, it must determine to which application request from this SNMP engine, it must determine to which application
the message should be given. the message should be given.
An Application that wishes to receive asynchronous messages registers An Application that wishes to receive asynchronous messages registers
itself with the engine using the registration primitive. itself with the engine using the primitive registerContextEngineID
An Application that wishes to stop receiving asynchronous messages as described in section 4.2.
should unregister itself with the SNMP engine.
statusInformation = -- success or errorIndication
registerContextEngineID(
contextEngineID -- take responsibility for this one
pduType -- the pduType(s) to be registered
)
unregisterContextEngineID( An Application that wishes to stop receiving asynchronous messages
contextEngineID -- give up responsibility for this one should unregister itself with the SNMP engine using the primitive
pduType -- the pduType(s) to be unregistered unregisterContextEngineID as described in section 4.2.
)
Only one registration per PDU type per contextEngineID is permitted Only one registration per combination of PDU type and contextEngineID
at the same time. Duplicate registrations are ignored. An is permitted at the same time. Duplicate registrations are ignored.
errorIndication will be returned to the application that attempts An errorIndication will be returned to the application that attempts
to duplicate a registration. to duplicate a registration.
All asynchronously received messages containing a registered All asynchronously received messages containing a registered
PDU type and contextEngineID are sent to the application which combination of PDU type and contextEngineID are sent to the
registered to support that combination. application which registered to support that combination.
The engine forwards the PDU to the registered application, using the The engine forwards the PDU to the registered application, using the
processPdu primitive: processPdu primitive, as described in section 4.2.
processPdu( -- process Request/Notification PDU
contextEngineID -- data from/at this SNMP engine
contextName -- data from/in this context
PDU -- SNMP Protocol Data Unit
maxSizeResponseScopedPDU -- maximum size of the Response PDU
securityModel -- Security Model in use
securityName -- on behalf of this principal
LoS -- Level of Security
stateReference -- reference to state information
) -- needed when sending a response
A.3.4. Applications that Send Responses A.3.4. Applications that Send Responses
\ Request operations require responses. An application sends
a response via the returnResponsePdu primitive, as described in
Request operations require responses. These operations include Get section 4.2.
requests, Set requests, and Inform requests. An application sends a
response via the returnResponsePdu primitive:
returnResponsePdu(
contextEngineID -- data from/at this SNMP engine
contextName -- data from/in this context
PDU -- SNMP Protocol Data Unit
maxSizeResponseScopedPDU -- maximum size of the Response PDU
securityModel -- on behalf of this principal
securityName -- on behalf of this principal
LoS -- Level of Security
stateReference -- reference to state information
-- as presented with the request
statusInformation -- success or errorIndication
) -- error counter OID/value if error
The contextEngineID, contextName, securityModel, securityName, LoS, and The contextEngineID, contextName, securityModel, securityName,
stateReference parameters are from the initial processPdu primitive. securityLevel, and stateReference parameters are from the initial
The PDU and statusInformation are the results of processing. processPdu primitive. The PDU and statusInformation are the results
of processing.
A.4. Access Control Model Design Requirements A.4. Access Control Model Design Requirements
An Access Control Model determines whether the specified An Access Control Model determines whether the specified securityName
securityName is allowed to perform the requested operation on is allowed to perform the requested operation on a specified managed
a specified managed object. The Access Control Model specifies the object. The Access Control Model specifies the rules by which access
rules by which access control is determined. control is determined.
The persistent data used for access control should be manageable
using SNMP, but the Access Control model defines whether an
instantiation of the MIB is a conformance requirement.
The following primitive is used to invoke the access control service:
statusInformation = -- success or errorIndication
isAccessAllowed(
securityModel -- Security Model in use
securityName -- principal who wants to access
LoS -- Level of Security
viewType -- read, write, or notify view
contextName -- context containing variableName
variableName -- OID for the managed object
)
\
APPENDIX B
B. An Evolutionary Architecture - Design Goals
The goals of the architectural design are to use encapsulation,
cohesion, hierarchical rules, and loose coupling to reduce complexity
of design and make the evolution of portions of the architecture
possible.
B.1. Encapsulation
Encapsulation describes the practice of hiding the details that are
used internal to a process. Some data is required for a given
procedure, but isn't needed by any other part of the process.
In networking, the concept of a layered stack reflects this approach.
The transport layer contains data specific to its processing; the data
is not visible to the other layers. In programming this is reflected
in language elements such as "file static" variables in C, and
"private" in C++, etc.
In this architecture, all data used for processing only within
a functional portion of the architecture should have its visibility
restricted to that portion if possible. The data should be accessed
only by that functionality defined with the data. No reference to the
data should be made from outside the functional portion of the
architecture, except through predefined public interfaces.
B.2. Cohesion
Similar functions can be grouped together and their differences
ignored, so they can be dealt with as a single entity. It is important
that the functions which are grouped together are actually similar.
Similarity of the data used to perform functions can be a good
indicator of the similarity of the functions.
For example, authentication and encryption are both security functions
which are applied to a message. Access control, while similar in some
ways, is dissimilar in that it is not applied to a message, it is
applied to a (proposed) request for a management operation.
The data required to perform authentication and encryption are
different than the data needed to perform access control, and the
two sets of services can be described independently.
Similar functions, especially those that use the same data elements,
should be defined together. The security functions which operate at
the message level should be defined in a document together with the
definitions for those data elements that are used only by those
security functions. For example, a MIB with authentication keys is
used only by authentication functions; they should be defined together.
\
B.3. Hierarchical Rules
Functionality can be grouped into hierarchies where each element in the
hierarchy receives general characteristics from its direct superior,
and passes on those characteristics to each of its direct subordinates.
This architecture uses the hierarchical approach by defining
subsystems, which specify the general rules of a portion of the system,
models which define the specific rules to be followed by an
implementation of the portion of the system, and implementations which
encode those rules into reality for a portion of the system.
Within portions of the system, hierarchical relationships are used to
compartmentalize, or modularize, the implementation of specific
functionality. For example, within the security portion of the system,
authentication and privacy may be contained in separate modules, and
multiple authentication and privacy mechanisms may be supported by
allowing supplemental modules that provide protocol-specific
authentication and privacy services.
B.4. Coupling
Coupling describes the amount of interdependence between parts of
a system. Loose coupling indicates that two sub-systems are relatively
independent of each other; tight coupling indicates a high degree of
mutual dependence.
To make it possible to evolve the architecture by replacing only part
of the system, or by supplementing existing portions with alternate
mechanisms for similar functionality, without obsoleting the complete
system, it is necessary to limit the coupling of the parts.
Encapsulation and cohesion help to reduce coupling by limiting the
visibility of those parts that are only needed within portions of a
system. Another mechanism is to constrain the nature of interactions
between various parts of the system.
This can be done by defining fixed, generic, flexible interfaces
for transferring data between the parts of the system. The concept of
plug-and-play hardware components is based on that type of interface
between the hardware component and system into which it is "plugged."
This approach has been chosen so individual portions of the system
can be upgraded over time, while keeping the overall system intact.
To avoid specifying fixed interfaces, which would constrain a vendor's
choice of implementation strategies, a set of abstract data elements
is used for (conceptually) transferring data between subsystems in
documents which describe subsystem or model interactions. Documents
describing the interaction of subsystems or models should use only
the abstract data elements provided for transferring data but vendors
\
are not constrained to using the described data elements for
transferring data between portions of their implementation.
Loose coupling works well with the IETF standards process. If we The persistent data used for access control should be manageable using
separate message-handling from security and from local processing, SNMP, but the Access Control Model defines whether an instantiation of
then the separate portions of the system can move through the standards the MIB is a conformance requirement.
process with less dependence on the status of the other portions of the
standard. Security models may be able to be re-opened for discussion
due to patents, new research, export laws, etc., as is clearly expected
by the WG, without needing to reopen the documents which detail the
message format or the local processing of PDUs. Thus, the standards
track status of related, but independent, documents is not affected.
\ The Access Control Model must provide the primitive isAccessAllowed
Table of Contents Table of Contents
0. Issues 2 0. Issues 2
0.1. Issues to be resolved 2 0.1. Resolved Issues 2
0.1.1. Issues discussed at second Interim Meeting: 2 0.1.1. Issues discussed at second Interim Meeting: 3
0.2. Change Log 3 0.2. Change Log 4
1. Introduction 7 1. Introduction 10
1.1. Target Audience 7 1.1. Overview 10
1.2. Management Systems 7 1.2. SNMP Management Systems 10
1.3. Goals of this Architecture 8 1.3. Goals of this Architecture 11
1.4. Security Requirements of this Architecture 9 1.4. Security Requirements of this Architecture 12
1.5. Design Decisions 10 1.5. Design Decisions 13
2. Documentation Overview 12 2. Documentation Overview 15
2.1. Document Roadmap 13 2.1. Document Roadmap 16
2.2. Applicability Statement 13 2.2. Applicability Statement 16
2.3. Coexistence and Transition 13 2.3. Coexistence and Transition 16
2.4. Transport Mappings 14 2.4. Transport Mappings 17
2.5. Message Processing 14 2.5. Message Processing 17
2.6. Security 14 2.6. Security 17
2.7. Access Control 14 2.7. Access Control 17
2.8. Applications 15 2.8. Protocol Operations 18
2.9. Structure of Management Information 15 2.9. Applications 18
2.10. Textual Conventions 15 2.10. Structure of Management Information 18
2.11. Conformance Statements 15 2.11. Textual Conventions 18
2.12. Protocol Operations 16 2.12. Conformance Statements 18
2.13. Management Information Base Modules 16 2.13. Management Information Base Modules 19
2.13.1. SNMP Instrumentation MIBs 16 2.13.1. SNMP Instrumentation MIBs 19
2.14. SNMP Framework Documents 16 2.14. SNMP Framework Documents 19
3. Naming 18 2.15. Operational Overview 21
3.1. The Naming of Entities 18 3. Elements of the Architecture 23
3.1.1. SNMP entity 19 3.1. The Naming of Entities 23
3.1.2. SNMP engine 19 3.1.1. SNMP entity 24
3.1.3. snmpEngineID 19 3.1.2. SNMP engine 24
3.1.4. Message Processing Subsystem 19 3.1.3. snmpEngineID 24
3.1.5. Message Processing Model 19 3.1.4. Dispatcher 24
3.1.6. Security Subsystem 20 3.1.5. Message Processing Subsystem 25
3.1.7. Security Model 20 3.1.6. Message Processing Model 25
3.1.8. Security Protocol 20 3.1.7. Security Subsystem 26
3.1.9. Access Control Subsystem 21 3.1.8. Security Model 26
3.1.10. Access Control Model 21 3.1.9. Security Protocol 26
3.1.11. Applications 21 3.1.10. Access Control Subsystem 27
3.1.12. SNMP Agent 21 3.1.11. Access Control Model 27
3.1.13. SNMP Manager 21 3.1.12. Applications 28
3.2. The Naming of Identities 22 3.1.13. SNMP Agent 28
3.2.1. Principal 22 3.1.14. SNMP Manager 28
3.2.2. securityName 22 3.2. The Naming of Identities 29
3.2.3. Model dependent security ID 22 3.2.1. Principal 29
3.3. The Naming of Management Information 23 3.2.2. securityName 29
3.3.1. An SNMP Context 24 3.2.3. Model dependent security ID 29
3.3.2. contextEngineID 24 3.3. The Naming of Management Information 30
3.3.3. contextName 24 3.3.1. An SNMP Context 31
3.3.4. scopedPDU 24 3.3.2. contextEngineID 31
3.4. Other Constructs 25 3.3.3. contextName 31
\^L
3.4.1. maxSizeResponseScopedPDU 25 3.3.4. scopedPDU 32
3.4.2. Local Configuration Datastore 25 3.4. Other Constructs 32
3.4.3. LoS 25 3.4.1. maxSizeResponseScopedPDU 32
4. Architectural Elements of Procedure 26 3.4.2. Local Configuration Datastore 32
4.1. Operational Overview 27 3.4.3. securityLevel 32
4.2. Sending and Receiving SNMP Messages 29 4. Abstract Service Interfaces. 33
4.2.1. Send a Message to the Network 29 4.1. Common Primitives 33
4.2.2. Receive a Message from the Network 29 4.1.1. Release State Reference Information 33
4.3. Send a Request or Notification Message for an Application 30 4.2. Dispatcher Primitives 33
4.4. Receive a Request or Notification Message from the Network 30 4.2.1. Generate Outgoing Request or Notification 33
4.5. Generate a Response Message for an Application 31 4.2.2. Process Incoming Request or Notification PDU 34
4.6. Receive a Response Message 31 4.2.3. Generate Outgoing Response 34
4.7. Registering to Receive Asynchronous Messages 31 4.2.4. Process Incoming Response PDU 34
5. Definition of Managed Objects for Internet Management Frameworks 33 4.2.5. Registering Responsibility for Handling SNMP PDUs. 35
6. Security Considerations 39 4.3. Message Processing Subsystem Primitives 35
7. Glossary 40 4.3.1. Prepare an Outgoing SNMP Request or Notification Message 35
8. References 40 4.3.2. Prepare an Outgoing SNMP Response Message 36
9. Editor's Addresses 42 4.3.3. Prepare Data Elements from an Incoming SNMP Message 36
10. Acknowledgements 43 4.4. Access Control Subsystem Primitives 37
A. Guidelines for Model Designers 44 4.5. Security Subsystem Primitives 37
A.1. Security Model Design Requirements 44 4.5.1. Generate a Request or Notification Message 37
A.1.1. Threats 44 4.5.2. Process Incoming Message 37
A.1.2. Security Processing 45 4.5.3. Generate a Response Message 38
A.1.3. validate the security-stamp in a received message 45 4.6. User Based Security Model Internal Primitives 38
A.1.5. Security MIBs 46 4.6.1. User-based Security Model Primitives for Authentication 38
A.1.6. Security State Cache 46 4.6.2. User-based Security Model Primitives for Privacy 39
A.2. SNMP engine and Message Processing Model Requirements 48 4.7. Scenario Diagrams 40
A.2.1. Receiving an SNMP Message from the Network 48 4.7.1. Command Generator or Notification Originator Application 40
A.2.2. Send SNMP messages to the network 49 4.7.2. Scenario Diagram for a Command Responder Application 41
A.2.3. Generate Request or Notification Message for an Application 49 5. Definition of Managed Objects for SNMP Management Frameworks 42
A.2.4. Pass Received Response Message to an Application 50 6. Security Considerations 51
A.2.5. Pass Received Request or Notification Message to Application 50 7. Editor's Addresses 52
A.2.6. Generate a Response Message for an Application 51 8. Acknowledgements 53
A.3. Application Design Requirements 51 9. References 55
A.3.1. Applications that Initiate Messages 52 A. Guidelines for Model Designers 57
A.3.2. Applications that Receive Responses 52 A.1. Security Model Design Requirements 57
A.3.3. Applications that Receive Asynchronous Messages 53 A.1.1. Threats 57
A.3.4. Applications that Send Responses 53 A.1.2. Security Processing 57
A.4. Access Control Model Design Requirements 54 A.1.3. Validate the security-stamp in a received message 58
A.1.4. Security MIBs 59
A.1.5. Cached Security Data 59
A.2. Message Processing Model Design Requirements 60
A.2.1. Receiving an SNMP Message from the Network 60
A.2.2. Sending an SNMP Message to the Network 60
A.3. Application Design Requirements 60
A.3.1. Applications that Initiate Messages 61
A.3.2. Applications that Receive Responses 61
A.3.3. Applications that Receive Asynchronous Messages 61
A.3.4. Applications that Send Responses 62
A.4. Access Control Model Design Requirements 62
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