INTERNET-DRAFT                                           Jeffrey D. Case
                                                     SNMP Research, Inc.
                                                              Russ Mundy
                                       Trusted Information Systems, Inc.
                                                           David Partain
                                                    SNMP Research Europe
                                                             Bob Stewart
                                                           Cisco Systems

                    Introduction to Version 3 of the
             Internet-standard Network Management Framework

                          1998/08/07 13:38:54

                     draft-ietf-snmpv3-intro-01.txt
                       1.3 -- 1998/08/07 13:38:54

Status of this Memo

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                                 Abstract

   The purpose of this document is to provide an overview of the third
   version of the Internet-standard Management Framework, termed the
   SNMP version 3 Framework (SNMPv3).  This Framework is derived from
   and builds upon both the original Internet-standard Management
   Framework (SNMPv1) and the second Internet-standard Management
   Framework (SNMPv2).

   The architecture is designed to be modular to allow the evolution of
   the Framework over time.

1.  Introduction

   This document is an introduction to the third version of the
   Internet-standard Management Framework, termed the SNMP version 3
   Management Framework (SNMPv3).  This document (SNMPv3) and has multiple purposes.

   First, it describes the relationship between the SNMPv3 SNMP version 3
   (SNMPv3) specifications and the specifications of the SNMPv1 SNMP version 1
   (SNMPv1) Management Framework, the SNMPv2 SNMP version 2 (SNMPv2) Management
   Framework, and the Community-based Administrative Framework for
   SNMPv2.

   Second, it provides a roadmap to the multiple documents which contain
   the relevant specifications.

   Third, this document provides a brief easy-to-read summary of the
   contents of each of the relevant specification documents.

   [Finally, this document may someday contain information regarding
   what it means to be a compliant SNMPv3 implementation, i.e., a set of
   applicability statements, but it does not now, and if it never does,
   then this sentence will be deleted.]

   This document is intentionally tutorial in nature and, as such, may
   occasionally be "guilty" of oversimplification.  In the event of a
   conflict or contradiction between this document and the more detailed
   documents for which this document is a roadmap, the specifications in
   the more detailed documents shall prevail.

   Furthermore,

   Further, the detailed documents attempt to maintain separation
   between the various component modules in order to specify well-
   defined interfaces between them.  This roadmap document, however,
   takes a different approach and attempts to provide an integrated view
   of the various component modules in the interest of readability.

2.  The Internet Standard Management Framework

   The third version of the Internet Standard Management Framework (the
   SNMPv3 Framework) is derived from and builds upon both the original
   Internet-standard Management Framework (SNMPv1) and the second
   Internet-standard Management Framework (SNMPv2).

   All versions (SNMPv1, SNMPv2, and SNMPv3) of the Internet Standard
   Management Framework share the same basic structure and components.
   Furthermore, all versions of the specifications of the Internet
   Standard Management Framework follow the same architecture.

2.1  Basic Structure and Components

   An enterprise deploying the Internet Standard Management Framework
   contains four basic components:

     * several (typically many) managed nodes, each with an SNMP entity
       which provides remote access to management instrumentation
       (traditionally called an agent);

     * at least one SNMP entity with management applications (typically
       called a manager),

     * a management protocol used to convey management information
       between the SNMP entities, and

     * management information.

   That is, the

   The management protocol is used to convey management information
   between SNMP entities such as managers and agents.

   This basic structure is common to all versions of the Internet
   Standard Management Framework; i.e., SNMPv1, SNMPv2, and SNMPv3.

2.2  Architecture of the Internet Standard Management Framework

   The specifications of the Internet Standard Management Framework are
   based on a modular architecture.  This framework is more than just a
   protocol for moving data.  It consists of:

     * a data definition language,

     * definitions of management information (the Management
       Information Base, or MIB),

     * a protocol definition, and
     * security and administration.

   Over time, as the Framework has evolved from SNMPv1, through SNMPv2,
   to SNMPv3, the definitions of each of these architectural components
   have become richer and more clearly defined, but the fundamental
   architecture has remained consistent.

   One prime motivator for this modularity was to enable the ongoing
   evolution of the Framework as is documented in RFC 1052 [14].  When
   originally envisioned, this capability was to be used to ease the
   transition from SNMP-based management of internets to management
   based on OSI protocols.  To this end, the framework was architected
   with a protocol-independent data definition language and Management
   Information Base along with a MIB-independent protocol.  This
   separation was designed to allow the SNMP-based protocol to be
   replaced without requiring the management information to be redefined
   or reinstrumented.  History has shown that the selection of this
   architecture was the right decision for the wrong reason -- it turned
   out that this architecture has eased the transition from SNMPv1 to
   SNMPv2 and from SNMPv2 to SNMPv3 rather than easing the transition
   away from management based on the Simple Network Management Protocol.

   The SNMPv3 Framework builds and extends these architectural
   principles by:

     * building on these four basic architectural components, in some
       cases incorporating them from the SNMPv2 Framework by reference,
       and

     * by using these same layering principles in the definition of new
       capabilities in the security and administration portion of the
       architecture.

   Those who are familiar with the architecture of the SNMPv1 Management
   Framework and the SNMPv2 Management Framework will find many familiar
   concepts in the architecture of the SNMPv3 Management Framework.
   However, in some cases, the terminology may be somewhat different.

2.2.1

3.  The SNMPv1 Management Framework

   The original Internet-standard Network Management Framework (SNMPv1)
   consists of three
   is defined in the following documents:

     * STD 16, RFC 1155 [1] which defines the Structure of Management
       Information (SMI), the mechanisms used for describing and naming
       objects for the purpose of management.

     * STD 16, RFC 1212 [2] which defines a more concise description
      mechanism,
       mechanism for describing and naming management information objects,
       but which is wholly consistent with the SMI.

     * STD 15, RFC 1157 [3] which defines the Simple Network Management
       Protocol (SNMP), the protocol used for network access to managed
      objects.
       objects and event notification. Note this document also defines an
       initial set of event notifications.

   Additionally, two documents are generally considered to be companions
   to these three:

     * STD 17, RFC 1213 [13] which contains definitions for the base
       set of management information

     * RFC 1215 [25] defines a concise description mechanism for
       defining event notifications, which are called traps in the SNMPv1
       protocol. It also specifies the generic traps from RFC 1157 in the
       concise notation.

   These documents describe the four parts of the first version of the
   SNMP Framework.

3.1  The SNMPv1 Data Definition Language.

   The first two of these
   documents (STD 16) and the last document describe the SNMPv1 data
   definition language.   Note that due to the initial requirement that
   the SMI be protocol-independent, the first two SMI documents do not
   provide a means for defining event notifications (traps).  Instead,
   the SNMP protocol document defines a few standardized event
   notifications (generic traps) and provides a means for additional
   event notifications to be defined. The last document specifies a
   straight-forward approach towards defining event notifications used
   with the SNMPv1 Definitions protocol. At the time that it was written, use of
   traps in the Internet-standard network management framework was
   controversial.  As such, RFC 1215 was put forward with the status of
   "Informational", which was never updated because it was believed that
   the second version of the SNMP Framework would replace the first
   version.  Note that the SNMPv1 data definition language is sometimes
   refered to as SMIv1.

3.2 Management Information.

   The data definition language described in these the first two documents was
   first used to define the now-historic MIB-I as specified in RFC 1066
   [12], and was subsequently used to define MIB-II as specified in RFC
   1213 [13].

   Later, after the publication of MIB-II, a different approach to
   management information definition was taken from the earlier approach
   of having a single committee staffed by generalists work on a single
   document to define the Internet-standard MIB.  Rather, many mini-MIB
   documents were produced in a parallel and distributed fashion by
   groups chartered to produce a specification for a focused portion of
   the Internet-standard MIB and staffed by personnel with expertise in
   those particular areas ranging from various aspects of network
   management, to system management, and application management.

   SNMPv1

3.3 Protocol Operations.

   The third document, STD 15, describes the SNMPv1 protocol operations
   performed by protocol data units (PDUs) on lists of variable bindings. bindings
   and describes the format of SNMPv1 messages. The operators defined by
   SNMPv1 are:  get, get-next, get-response, set-request, and trap.
   Typical layering of SNMP on a connectionless transport service is
   also defined.

3.4 SNMPv1 Security and Administration.

   STD 15 also describes an approach to security and administration.
   Many of the these concepts found in
   the SNMPv3 security and administration are found in carried forward into the SNMPv1 SNMPv3 Framework.

   The SNMPv1 Framework describes the encapsulation of SNMPv1 PDUs in
   SNMP messages between SNMP entities and distinguishes between
   application entities and protocol entities.  In SNMPv3, these are
   renamed applications and engines, respectively.

   The SNMPv1 Framework also introduces the concept of an authentication
   service supporting one or more authentication schemes.  In SNMPv3,
   the concept of an authentication service is expanded to include other
   services, such as privacy.

   Finally, the SNMPv1 Framework introduces access control based on a
   concept called an SNMP MIB view.  The SNMPv3 Framework specifies a
   fundamentally similar concept called view-based access control.

   However, while the SNMPv1 Framework anticipated the definition of
   multiple authentication schemes, it did not define any such schemes
   other than a trivial authentication scheme based on community
   strings.  This was a known fundamental weakness in the SNMPv1
   Framework but it was thought at that time that the definition of
   commercial grade security might be contentious in its design and
   difficult to get approved because "security" means many different
   things to different people.  To that end, and because some users do
   not require strong authentication, the SNMPv1 architected an
   authentication service as a separate block to be defined "later" and
   the SNMPv3 Framework provides an architecture for use within that
   block as well as a definition for its subsystems.

2.2.2

4. The SNMPv2 Management Framework

   The SNMPv2 Management Framework is fully described in [4-9] and
   coexistence and transition issues relating to SNMPv1 and SNMPv2 are
   discussed in [10].

   SNMPv2 provides several advantages over SNMPv1, including:

     * expanded data types (e.g., 64 bit counter)

     * improved efficiency and performance (get-bulk operator)

     * confirmed event notification (inform operator)

     * richer error handling (errors and exceptions)

     * improved sets, especially row creation and deletion

     * fine tuning of the data definition language

   However, the SNMPv2 Framework, as described in these documents, is
   incomplete in that it does not meet the original design goals of the
   SNMPv2 project.  The unmet goals included provision of security and
   administration delivering so-called "commercial grade" security with

     * authentication:  origin identification, message integrity,
       and some aspects of replay protection;

     * privacy:  confidentiality;

     * authorization and access control; and

     * suitable remote configuration and administration capabilities
       for these features.

   The SNMPv3 Management Framework, as described in this document and
   the companion documents, addresses these significant deficiencies.

2.3

5. The SNMPv3 Working Group

   This document, and its companion documents, were produced by the
   SNMPv3 Working Group of the Internet Engineering Task Force (IETF).
   The SNMPv3 Working Group was chartered to prepare recommendations for
   the next generation of SNMP.  The goal of the Working Group was to
   produce the necessary set of documents that will provide a single standard
   for the next generation of core SNMP functions.  The single, most
   critical need in the next generation is to define a definition of security and
   administration that makes SNMP-based management transactions secure
   in a way which is useful for users who wish to use SNMPv3 to manage
   networks, the systems that make up those networks, and the
   applications which reside on those systems, including manager-to-
   agent, agent-to-manager, and manager-to-manager transactions.

   In the several years prior to the chartering of the Working Group,
   there were a number of activities aimed at incorporating security and
   other improvements to SNMP.  These efforts included:

     * "SNMP Security" circa 1991-1992 [RFC 1351 - RFC 1353],

     * "SMP" circa 1992-1993,

     * "The Party-based SNMPv2" circa 1993-1995 [RFC 1441 - RFC 1452].

   Each of these efforts incorporated commercial grade, industrial
   strength security including authentication, privacy, authorization,
   view-based access control, and administration, including remote
   configuration.

   These efforts fed the development of the SNMPv2 Management Framework
   as described in RFCs 1902 - 1908.  However, the Framework described
   in those RFCs had no standards-based security and administrative
   framework of its own; rather, it was associated with multiple
   security and administrative frameworks, including:

     * "The Community-based SNMPv2" (SNMPv2c) [RFC 1901],

     * "SNMPv2u" [RFCs 1909 - 1910] and

     * "SNMPv2*."

   SNMPv2c had the endorsement of the IETF but no security and
   administration whereas both SNMPv2u and SNMPv2* had security but
   lacked the endorsement of the IETF.

   The SNMPv3 Working Group was chartered to produce a single set of
   specifications for the next generation of SNMP, based upon a
   convergence of the concepts and technical elements of SNMPv2u and
   SNMPv2*, as was suggested by an advisory team which was formed to
   provide a single recommended approach for SNMP evolution.

   In so doing, the Working Group charter defined the following
   objectives:

     * accommodate the wide range of operational environments with
       differing management demands;

     * facilitate the need to transition from previous, multiple
       protocols to SNMPv3;

     * facilitate the ease of setup and maintenance activities.

   In the initial work of the SNMPv3 Working Group, the group focused on
   security and administration, including

     * authentication and privacy,

     * authorization and view-based access control, and

     * standards-based remote configuration of the above.

   The SNMPv3 Working Group did not "reinvent the wheel," but reused the
   SNMPv2 Draft Standard documents, i.e., RFCs 1902 through 1908.

   The SNMPv3 Working Group produced a design based on a modular
   architecture with evolutionary capabilities with emphasis on
   layering.  As a result, SNMPv3 is SNMPv2 plus security and
   administration.

   In doing so, the Working Group achieved the goal of producing a
   single specification which has both the endorsement of the IETF and
   security and administration.

3.

6.  SNMPv3 Framework Module Specifications

   The specification of the SNMPv3 Management Framework is partitioned
   in a modular fashion among several documents.  It is the intention of
   the SNMPv3 Working Group that, with proper care, any or all of the
   individual documents can be revised, upgraded, or replaced as
   requirements change, new understandings are obtained, and new
   technologies become available.

   Whenever feasible, the initial document set which defines the SNMPv3
   Management Framework leverages prior investments defining and
   implementing the SNMPv2 Management Framework by incorporating by
   reference each of the specifications of the SNMPv2 Management
   Framework.

   The SNMPv3 Framework augments those specifications with
   specifications for security and administration for SNMPv3.

   The documents which specify the SNMPv3 Management Framework follow
   the same architecture as those of the prior versions and can be
   organized for expository purposes into four main categories as
   follows:

     * the data definition language,

     * Management Information Base (MIB) modules,

     * protocol operations, and

     * security and administration.

   The first three sets of documents are incorporated from SNMPv2.  The
   fourth set of documents are new to SNMPv3, but, as described
   previously, build on significant prior related works.

3.1

6.1  Data Definition Language

   The specifications of the data definition language includes RFC 1902,
   "The Structure of Management Information for Version 2 of the Simple
   Network Management Protocol (SNMPv2)" [4], and related
   specifications.  The Structure of Management Information (SMI)
   defines fundamental data types, an object model, and the rules for
   writing and revising MIB modules.  Related specifications include RFC
   1903 and RFC 1904.  The updated data definition language is sometimes
   refered to as SMIv2.

   RFC 1903, "Textual Conventions for Version 2 of the Simple Network
   Management Protocol (SNMPv2)" [5], defines an initial set of
   shorthand abbreviations which are available for use within all MIB
   modules for the convenience of human readers and writers.

   RFC 1904, "Conformance Statements for Version 2 of the Simple Network
   Management Protocol (SNMPv2)" [6], defines the format for compliance
   statements which are used for describing requirements for agent
   implementations and capability statements which can be used to
   document the characteristics of particular implementations.

3.2

6.2  MIB Modules

   MIB modules usually contain object definitions, may contain
   definitions of event notifications, and sometimes include compliance
   statements specified in terms of appropriate object and event
   notification groups.  As such, MIB modules define the management
   information maintained by the instrumentation in managed nodes, made
   remotely accessible by management agents, conveyed by the management
   protocol, and manipulated by management applications.

   MIB modules are defined according the rules defined in the documents
   which specify the data definition language, principally the SMI as
   supplemented by the related specifications.

   There is a large and growing number of standards-based MIB modules,
   as defined in the periodically updated list of standard protocols
   [STD 0001, RFC 2000].  As of this writing, there are nearly 100
   standards-based MIB modules with a total number of defined objects
   approaching 10,000. In addition, there is an even larger and growing
   number of enterprise-specific MIB modules defined unilaterally by
   various vendors, research groups, consortia, and the like resulting
   in an unknown and virtually uncountable number of defined objects.

   In general, management information defined in any MIB module,
   regardless of the version of the data definition language used, can
   be used with any version of the protocol.  For example, MIB modules
   defined in terms of the SNMPv1 SMI (SMIv1) are compatible with the
   SNMPv3 Management Framework and can be conveyed by the protocols
   specified therein.  Furthermore, MIB modules defined in terms of the
   SNMPv2 SMI (SMIv2) are compatible with SNMPv1 protocol operations and
   can be conveyed by it.  However, there is one noteworthy exception:
   the Counter64 datatype which can be defined in a MIB module defined
   in SNMPv2 SMIv2 format but which cannot be conveyed by an SNMPv1 protocol
   engine.

3.3

6.3  Protocol Operations and Transport Mappings

   The specifications for the protocol operations and transport mappings
   of the SNMPv3 Framework are incorporated by reference to the two
   SNMPv2 Framework documents.

   The specification for protocol operations is found in RFC 1905,
   "Protocol Operations for Version 2 of the Simple Network Management
   Protocol (SNMPv2)" [7].

   The specification of transport mappings is found in RFC 1906,
   "Transport Mappings for Version 2 of the Simple Network Management
   Protocol (SNMPv2)" [8].

3.4

6.4  SNMPv3 Security and Administration

   The SNMPv3 document series defined by the SNMPv3 Working Group
   consists of six [seven] documents at this time:

      RFC xxxx, "Introduction to the Third Version of the Internet
      Standard Management Framework (SNMPv3)," which is this document.

      RFC 2271, "An Architecture for Describing SNMP Management
      Frameworks" [15], describes the overall architecture with special
      emphasis on the architecture for security and administration.

      RFC 2272, "Message Processing and Dispatching for the Simple
      Network Management Protocol (SNMP)" [16], describes the possibly
      multiple message processing models and the dispatcher portion that
      can be a part of an SNMP protocol engine.

      RFC 2273, "SNMPv3 Applications" [17], describes the five types of
      applications that can be associated with an SNMPv3 engine and
      their elements of procedure.

      RFC 2274, "The User-Based Security Model for Version 3 of the
      Simple Network Management Protocol (SNMPv3)" [18], describes the
      threats, mechanisms, protocols, and supporting data used to
      provide SNMP message-level security.

      RFC 2275, "View-based Access Control Model for the Simple Network
      Management Protocol (SNMP)" [19], describes how view-based access
      control can be applied within command responder and notification
      originator applications.

      RFC yyyy, "SNMPv3 Coexistence and Transition" [20], does not exist
      yet and is still in development.

4.

7.  Document Summaries

   The following sections provide brief summaries of each document with
   slightly more detail than is provided in the overviews, above.

4.1

7.1  Structure of Management Information

   Management information is viewed as a collection of managed objects,
   residing in a virtual information store, termed the Management
   Information Base (MIB).  Collections of related objects are defined
   in MIB modules.  These modules are written using a subset in the SNMP MIB module
   language, which contains elements of OSI's Abstract Syntax Notation
   One (ASN.1) [11].  It is the purpose of [11] language.  RFC 1902, RFC 1903, and RFC 1904 together
   define the Structure MIB module language, specify the base data types for
   objects, specify a core set of Management Information short-hand specifications for SNMPv2 [4], to
   define that subset. data
   types called textual conventions, and specify a few administrative
   assignments of object identifier (OID) values.

   The SMI is divided into three parts:  module definitions, object
   definitions, and, trap definitions.

   (1)  Module definitions are used when describing information modules.
        An ASN.1 macro, MODULE-IDENTITY, is used to convey concisely the
        semantics of an information module.

   (2)  Object definitions are used when describing managed objects.  An
        ASN.1 macro, OBJECT-TYPE, is used to convey concisely convey concisely the syntax
        and semantics of a managed object.

   (3)  Notification definitions are used when describing unsolicited
        transmissions of management information.  An ASN.1 macro,
        NOTIFICATION-TYPE, is used to convey concisely the syntax and
        semantics of a notification.

   7.1.1  Base SMI Specification

   RFC 1902 specifies the base data types for the MIB module language,
   which include: Integer32, enumerated integers, Unsigned32, Gauge32,
   Counter32,  Counter64, TimeTicks, OCTET STRING, OBJECT IDENTIFIER,
   IpAddress, Opaque, and BITS. It also assigns values to several object
   identifiers.  RFC 1902 further defines the following constructs of
   the MIB module language:

     * IMPORTS to allow the specification of items that are used
       in a MIB module, but defined in another MIB module.

     * MODULE-IDENTITY to specify for a MIB module a description
       and administrative information such as contact and revision
       history.

     * OBJECT-IDENTITY and OID value assignments to specify a
       an OID value.

     * OBJECT-TYPE to specify the syntax data type, status, and the semantics
       of a managed object.

   (3)  Notification definitions are used when describing unsolicited
        transmissions of management information.  An ASN.1 macro,
        NOTIFICATION-TYPE, is used objects.

     * SEQUENCE type assignement to convey concisely list the syntax and
        semantics of columnar objects in
       a table.

     * NOTIFICATION-TYPE construct to describe an event notification.

4.2

7.1.2  Textual Conventions

   When designing a MIB module, it is often useful to define new types
   similar to those defined specify in a
   short-hand way the SMI.  In comparison to semantics for a set of objects with similar
   behavior.  This is done by defining a new data type defined using a base data
   type specified in the SMI, each of these SMI.  Each new types type has a different name, and
   specifies a similar
   syntax, but a base type with more precise restrictive semantics.  These newly
   defined types are termed textual conventions, and are used for the
   convenience of humans reading the a MIB module. module and potentially by
   "intelligent" management applications.  It is the purpose of RFC
   1903, Textual Conventions for SNMPv2 [5], to define the construct,
   TEXTUAL-CONVENTION, of the MIB module language used to define such
   new types and to specify an initial set of textual conventions
   available to all MIB modules.

   Objects defined using a textual convention are always encoded by
   means of the rules that define their primitive type.  However,
   textual conventions often have special semantics associated with
   them.  As such, an ASN.1 macro, TEXTUAL-CONVENTION, is used to convey
   concisely the syntax and semantics of a textual convention.

4.3

7.1.3  Conformance Statements

   It may be useful to define the acceptable lower-bounds of
   implementation, along with the actual level of implementation
   achieved.  It is the purpose of RFC 1904, Conformance Statements for
   SNMPv2 [6], to define the notation constructs of the MIB module language used
   for these purposes.  There are two kinds of notations: constructs:

   (1)  Compliance statements are used when describing requirements for
        agents with respect to object and event notification definitions.  An ASN.1 macro,
        MODULE-COMPLIANCE,
        The MODULE-COMPLIANCE construct is used to convey concisely
        such requirements.

   (2)  Capability statements are used when describing capabilities of
        agents with respect to object and event notification definitions.  An ASN.1 macro, AGENT-
        CAPABILITIES,
        The AGENT-CAPABILITIES construct is used to convey concisely such
        capabilities.

   Finally, collections of related objects and collections of related
   event notifications are grouped together to form a unit of
   conformance.  An ASN.1 macro, OBJECT-GROUP,  The OBJECT-GROUP construct is used to convey concisely
   the syntax objects in and the semantics of a an object group. The
   NOTIFICATION-GROUP construct is used to convey concisely the event
   notifications in and the semantics of an event notification group.

4.4

7.2  Protocol Operations

   The management protocol provides for the exchange of messages which
   convey management information between the agents and the management
   stations.  The form of these messages is a message "wrapper" which
   encapsulates a Protocol Data Unit (PDU).

   It is the purpose of RFC 1905, Protocol Operations for SNMPv2 [7], to
   define the operations of the protocol with respect to the sending and
   receiving of the PDUs.

4.5

7.3  Transport Mappings

   The management protocol, version 2 of the Simple Network Management
   Protocol,

   SNMP Messages may be used over a variety of protocol suites.  It is
   the purpose of RFC 1906, Transport Mappings for SNMPv2 [8], to define
   how
   SNMPv2 SNMP messages maps onto an initial set of transport domains.
   Other mappings may be defined in the future.

   Although several mappings are defined, the mapping onto UDP is the
   preferred mapping.  As such, to provide for the greatest level of
   interoperability, systems which choose to deploy other mappings
   should also provide for proxy service to the UDP mapping.

4.6

7.4  Protocol Instrumentation

   It is the purpose of RFC 1907, the Management Information Base for
   SNMPv2 document [9] to define managed objects which describe the
   behavior of an SNMPv2 entity.

4.7

7.5  Architecture / Security and Administration

   It is the purpose of RFC 2271, "SNMPv3 Architecture" [15], to define
   an architecture for defining SNMP Management Frameworks.  While
   addressing general architectural issues, it focuses on aspects
   related to security and administration.  It defines a number of terms
   used throughout the SNMPv3 Management Framework and, in so doing,
   clarifies and extends the naming of

     * engines and applications,

     * entities (service providers such as the engines in agents
       and managers),
     * identities (service users), and

     * management information, including support for multiple
       logical contexts.

   The document contains a small MIB module which is implemented by all
   authoritative SNMPv3 protocol engines.

4.8

7.6  Message Processing and Dispatch (MPD)

   RFC 2272, "Message Processing and Dispatching for the Simple Network
   Management Protocol (SNMP)" [16], describes the Message Processing
   and Dispatching for SNMP messages within the SNMP architecture.  It
   defines the procedures for dispatching potentially multiple versions
   of SNMP messages to the proper SNMP Message Processing Models, and
   for dispatching PDUs to SNMP applications.  This document also
   describes one Message Processing Model - the SNMPv3 Message
   Processing Model.

   It is expected that an SNMPv3 protocol engine MUST support at least
   one Message Processing Model.  An SNMPv3 protocol engine MAY support
   more than one, for example in a multilingual system which provides
   simultaneous support of SNMPv3 and SNMPv1 and/or SNMPv2c.

4.9

7.7  SNMPv3 Applications

   It is the purpose of RFC 2273, "SNMPv3 Applications" to describe the
   five types of applications which can be associated with an SNMP
   engine.  They are:  Command Generators, Command Responders,
   Notification Originators, Notification Receivers, and Proxy
   Forwarders.

   The document also defines MIB modules for specifying targets of
   management operations (including notifications), for notification
   filtering, and for proxy forwarding.

4.10

7.8  User-based Security Model (USM)

   RFC 2274, the "User-based Security Model (USM) for version 3 of the
   Simple Network Management Protocol (SNMPv3)" describes the User-based
   Security Model for SNMPv3.  It defines the Elements of Procedure for
   providing SNMP message-level security.

   The document describes the two primary and two secondary threats
   which are defended against by the User-based Security Model.  They
   are:  modification of information, masquerade, message stream
   modification, and [optionally] disclosure.

   The USM utilizes MD5 [21] and the Secure Hash Algorithm [22] as keyed
   hashing algorithms [22] for digest computation to provide data
   integrity

     * to directly protect against data modification attacks,

     * to indirectly provide data origin authentication, and

     * to defend against masquerade attacks.

   The USM uses loosely synchronized monotonically increasing time
   indicators to defend against certain message stream modification
   attacks.  Automatic clock synchronization mechanisms based on the
   protocol are specified without dependence on third-party time sources
   and concomitant security considerations.

   The USM uses the Data Encryption Standard (DES) [24] in the cipher
   block chaining mode (CBC) [optionally] to protect against disclosure.

   The document also includes a MIB suitable for remotely monitoring and
   managing the configuration parameters for the USM, including key
   distribution and key management.

   A single protocol entity may provide simultaneous support for
   multiple security models as well as multiple authentication and
   privacy protocols.  All of the protocols used by the USM are based on
   symmetric cryptography, i.e., private key mechanisms.  The SNMPv3
   architecture admits the use of public key cryptography, but as of
   this writing, no SNMPv3 security models utilizing public key
   cryptography have been published.

4.11

7.9  View-based Access Control (VACM)

   The purpose of RFC 2275, the "View-based Access Control Model (VACM)
   for the Simple Network Management Protocol (SNMP)" is to describe the
   View-based Access Control Model for use in the SNMP architecture.
   The VACM can simultaneously be associated in a single engine
   implementation with multiple Message Processing Models and multiple
   Security Models.

   It is architecturally possible to have multiple, different, Access
   Control Models active and present simultaneously in a single engine
   implementation, but this is expected to be *_very_* rare in practice
   and *_far_* less common than simultaneous support for multiple
   Message Processing Models and/or multiple Security Models.

4.12

7.10  SNMPv3 Coexistence and Transition
   This document does not exist yet.  It needs to contain:
       background of 2 approaches to coexistence and transition
           multilingual approach
           proxy approach

       mapping functions derived from rfc 2089 but incorporated by value
       rather than by reference in order to get these functions onto the
       standards track and to fix up any lingering problems

       a community-based security model consistent with the architecture
       and containing a suitable MIB module for remote configuration thereof
       for use by multilingual engines supporting snmpv1 and snmpv2c in
       addition to snmpv3

   This could be multiple documents, but it really isn't necessary to have more
   than one and fewer are better than many.

5.

8.  Security Considerations

   As this document is primarily a roadmap document, it introduces no
   new security considerations.  The reader is referred to the relevant
   sections of each of the referenced documents for information about
   security considerations.

6.

9.  Editors' Addresses

      Jeffrey Case
      SNMP Research, Inc.
      3001 Kimberlin Heights Road
      Knoxville, TN 37920-9716
      USA
      Phone:  +1 423 573 1434
      EMail:  case@snmp.com

      Russ Mundy
      Trusted Information Systems
      3060 Washington Rd
      Glenwood, MD 21738
      USA
      Phone:  +1 301 854 6889
      Email:  mundy@tis.com

      David Partain
      SNMP Research Europe
      Teknikringen 1
      S-583 30 Linkoping
      Sweden
      Phone:  +46 13 21 18 81
      Email:  partain@europe.snmp.com

      Bob Stewart
      Cisco Systems, Inc.
      170 West Tasman Drive
      San Jose, CA 95134-1706
      U.S.A.
      Phone:  +1 603 654 6923
      EMail:  bstewart@cisco.com

7.

10.  Full Copyright Statement

      Copyright (C) The Internet Society (1998).  All Rights Reserved.

      This document and translations of it may be copied and furnished to
      others, and derivative works that comment on or otherwise explain it
      or assist in its implmentation may be prepared, copied, published and
      distributed, in whole or in part, without restriction of any kind,
      provided that the above copyright notice and this paragraph are
      included on all such copies and derivative works.  However, this
      document itself may not be modified in any way, such as by removing
      the copyright notice or references to the Internet Society or other
      Internet organizations, except as needed for the purpose of
      developing Internet standards in which case the procedures for
      copyrights defined in the Internet Standards process must be
      followed, or as required to translate it into languages other than
      English.

      The limited permissions granted above are perpetual and will not be
      revoked by the Internet Society or its successors or assigns.

      This document and the information contained herein is provided on an
      "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
      TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
      BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
      HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
      MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."

8.

11.  References

   [1]  Rose, M., and K. McCloghrie, "Structure and Identification of
        Management Information for TCP/IP-based internets", STD 16, RFC
        1155, May 1990.

   [2]  Rose, M., and K. McCloghrie, "Concise MIB Definitions", STD 16,
        RFC 1212, March 1991.

   [3]  Case, J., Fedor, M., Schoffstall, M., Davin, J., "Simple Network
        Management Protocol", STD 15, RFC 1157, SNMP Research, Performance
        Systems International, MIT Laboratory for Computer Science, May
        1990.

   [4]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
        S. Waldbusser, "Structure of Management Information for Version 2
        of the Simple Network Management Protocol (SNMPv2)", RFC 1902,
        January 1996.

   [5]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
        S. Waldbusser, "Textual Conventions for Version 2 of the Simple
        Network Management Protocol (SNMPv2)", RFC 1903, January 1996.

   [6]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
        S. Waldbusser, "Conformance Statements for Version 2 of the Simple
        Network Management Protocol (SNMPv2)", RFC 1904, January 1996.

   [7]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
        S. Waldbusser, "Protocol Operations for Version 2 of the Simple
        Network Management Protocol (SNMPv2)", RFC 1905, January 1996.

   [8]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
        S. Waldbusser, "Transport Mappings for Version 2 of the Simple
        Network Management Protocol (SNMPv2)", RFC 1906, January 1996.

   [9]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
        S. Waldbusser, "Management Information Base for Version 2 of the
        Simple Network Management Protocol (SNMPv2)", RFC 1907,
        January 1996.

   [10] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
        S. Waldbusser, "Coexistence between Version 1 and Version 2 of the
        Internet-standard Network Management Framework", RFC 1908,
        January 1996.

   [11] Information processing systems - Open Systems Interconnection -
        Specification of Abstract Syntax Notation One (ASN.1),
        International Organization for Standardization.  International
        Standard 8824, (December, 1987).

   [12] McCloghrie, K., and M. Rose, "Management Information Base for
        Network Management of TCP/IP-based Internets", RFC 1066, August 1988.

   [13] McCloghrie, K., and M. Rose, "Management Information Base for
        Network Management of TCP/IP-based internets:  MIB-II, RFC 1213,
        March 1991.

   [14] Cerf, V.,  "IAB Recommendations for the Development of Internet
        Network Management Standards", RFC 1052, April 1988.

   [15] Harrington, D, R. Presuhn, and B. Wijnen, "An Architecture for
        Describing SNMP Management Frameworks, RFC 2271, January, 1998.

   [16] Case, J., Harrington, D., Presuhn, R., and B. Wijnen, "Message
        Processing and Dispatching for the Simple Network Management
        Protocol (SNMP)", RFC 2272, January 1998.

   [17] Levi, D., Meyer, P., and B. Stewart, "SNMPv3 Applications", RFC 2273,
        January 1998.

   [18] Blumenthal, U., and B. Wijnen, "The User-Based Security Model for
        Version 3 of the Simple Network Management Protocol (SNMPv3)",
        RFC 2274, January 1998.

   [19] Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based Access Control
        Model for the Simple Network Management Protocol (SNMP)", RFC 2275,
        January 1998.

   [20] TBD, "SNMPv3 Coexistence and Transition", RFC yyyy, Work in progress,
        date TBD.

   [21] Rivest,  R.,  "Message Digest Algorithm MD5", RFC 1321, April 1992.

   [22] Secure Hash Algorithm. NIST FIPS 180-1, (April, 1995)
        http://csrc.nist.gov/fips/fip180-1.txt (ASCII)
        http://csrc.nist.gov/fips/fip180-1.ps  (Postscript)

   [23] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC:
        Keyed-Hashing  for Message Authentication", RFC 2104, February
        1997.

   [24] Data Encryption Standard, National Institute of Standards
        and Technology.  Federal Information Processing Standard (FIPS)
        Publication 46-1.  Supersedes FIPS Publication 46, (January, 1977;
        reaffirmed January, 1988).

   [25] M.T. Rose, "A Convention for Defining Traps for use with the
        SNMP", RFC 1215, March 1991.