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rfc:rfc1445
        Network Working Group                                J. Galvin
        Request for Comments: 1445         Trusted Information Systems
                                                         K. McCloghrie
                                                    Hughes LAN Systems
                                                            April 1993
                             Administrative Model
                             for version 2 of the
                 Simple Network Management Protocol (SNMPv2)
        Status of this Memo
        This RFC specifes an IAB standards track protocol for the
        Internet community, and requests discussion and suggestions
        for improvements.  Please refer to the current edition of the
        "IAB Official Protocol Standards" for the standardization
        state and status of this protocol.  Distribution of this memo
        is unlimited.
        Table of Contents
        1 Introduction ..........................................    2
        1.1 A Note on Terminology ...............................    2
        2 Elements of the Model .................................    3
        2.1 SNMPv2 Party ........................................    3
        2.2 SNMPv2 Entity .......................................    6
        2.3 SNMPv2 Management Station ...........................    7
        2.4 SNMPv2 Agent ........................................    7
        2.5 View Subtree ........................................    7
        2.6 MIB View ............................................    8
        2.7 Proxy Relationship ..................................    8
        2.8 SNMPv2 Context ......................................   10
        2.9 SNMPv2 Management Communication .....................   10
        2.10 SNMPv2 Authenticated Management Communication ......   12
        2.11 SNMPv2 Private Management Communication ............   13
        2.12 SNMPv2 Management Communication Class ..............   14
        2.13 SNMPv2 Access Control Policy .......................   14
        3 Elements of Procedure .................................   17
        3.1 Generating a Request ................................   17
        3.2 Processing a Received Communication .................   18
        3.3 Generating a Response ...............................   21
        Galvin & McCloghrie                                   [Page i]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        4 Application of the Model ..............................   23
        4.1 Non-Secure Minimal Agent Configuration ..............   23
        4.2 Secure Minimal Agent Configuration ..................   26
        4.3 MIB View Configurations .............................   28
        4.4 Proxy Configuration .................................   32
        4.4.1 Foreign Proxy Configuration .......................   33
        4.4.2 Native Proxy Configuration ........................   37
        4.5 Public Key Configuration ............................   41
        5 Security Considerations ...............................   44
        6 Acknowledgements ......................................   45
        7 References ............................................   46
        8 Authors' Addresses ....................................   47
        Galvin & McCloghrie                                   [Page 1]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        1.  Introduction
        A network management system contains: several (potentially
        many) nodes, each with a processing entity, termed an agent,
        which has access to management instrumentation; at least one
        management station; and, a management protocol, used to convey
        management information between the agents and management
        stations.  Operations of the protocol are carried out under an
        administrative framework which defines both authentication and
        authorization policies.
        Network management stations execute management applications
        which monitor and control network elements.  Network elements
        are devices such as hosts, routers, terminal servers, etc.,
        which are monitored and controlled through access to their
        management information.
        It is the purpose of this document, the Administrative Model
        for SNMPv2, to define how the administrative framework is
        applied to realize effective network management in a variety
        of configurations and environments.
        The model described here entails the use of distinct
        identities for peers that exchange SNMPv2 messages.  Thus, it
        represents a departure from the community-based administrative
        model of the original SNMP [1].  By unambiguously identifying
        the source and intended recipient of each SNMPv2 message, this
        new strategy improves upon the historical community scheme
        both by supporting a more convenient access control model and
        allowing for effective use of asymmetric (public key) security
        protocols in the future.
        1.1.  A Note on Terminology
        For the purpose of exposition, the original Internet-standard
        Network Management Framework, as described in RFCs 1155, 1157,
        and 1212, is termed the SNMP version 1 framework (SNMPv1).
        The current framework is termed the SNMP version 2 framework
        (SNMPv2).
        Galvin & McCloghrie                                   [Page 2]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        2.  Elements of the Model
        2.1.  SNMPv2 Party
        A SNMPv2 party  is a conceptual, virtual execution environment
        whose operation is restricted (for security or other purposes)
        to an administratively defined subset of all possible
        operations of a particular SNMPv2 entity (see Section 2.2).
        Whenever a SNMPv2 entity processes a SNMPv2 message, it does
        so by acting as a SNMPv2 party and is thereby restricted to
        the set of operations defined for that party.  The set of
        possible operations specified for a SNMPv2 party may be
        overlapping or disjoint with respect to the sets of other
        SNMPv2 parties; it may also be a proper or improper subset of
        all possible operations of the SNMPv2 entity.
        Architecturally, each SNMPv2 party comprises
        o    a single, unique party identity,
        o    a logical network location at which the party executes,
             characterized by a transport protocol domain and
             transport addressing information,
        o    a single authentication protocol and associated
             parameters by which all protocol messages originated by
             the party are authenticated as to origin and integrity,
             and
        o    a single privacy protocol and associated parameters by
             which all protocol messages received by the party are
             protected from disclosure.
        Galvin & McCloghrie                                   [Page 3]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        Conceptually, each SNMPv2 party may be represented by an ASN.1
        value with the following syntax:
             SnmpParty ::= SEQUENCE {
               partyIdentity
                  OBJECT IDENTIFIER,
               partyTDomain
                  OBJECT IDENTIFIER,
               partyTAddress
                  OCTET STRING,
               partyMaxMessageSize
                  INTEGER,
               partyAuthProtocol
                  OBJECT IDENTIFIER,
               partyAuthClock
                  INTEGER,
               partyAuthPrivate
                  OCTET STRING,
               partyAuthPublic
                  OCTET STRING,
               partyAuthLifetime
                  INTEGER,
               partyPrivProtocol
                  OBJECT IDENTIFIER,
               partyPrivPrivate
                  OCTET STRING,
               partyPrivPublic
                  OCTET STRING
             }
        For each SnmpParty value that represents a SNMPv2 party, the
        following statements are true:
        o    Its partyIdentity component is the party identity.
        o    Its partyTDomain component is called the transport domain
             and indicates the kind of transport service by which the
             party receives network management traffic.  An example of
             a transport domain is snmpUDPDomain (SNMPv2 over UDP,
             using SNMPv2 parties).
        o    Its partyTAddress component is called the transport
             addressing information and represents a transport service
             address by which the party receives network management
             traffic.
        Galvin & McCloghrie                                   [Page 4]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        o    Its partyMaxMessageSize component is called the maximum
             message size and represents the length in octets of the
             largest SNMPv2 message this party is prepared to accept.
        o    Its partyAuthProtocol component is called the
             authentication protocol and identifies a protocol and a
             mechanism by which all messages generated by the party
             are authenticated as to integrity and origin.  In this
             context, the value noAuth signifies that messages
             generated by the party are not authenticated as to
             integrity and origin.
        o    Its partyAuthClock component is called the authentication
             clock and represents a notion of the current time that is
             specific to the party.  The significance of this
             component is specific to the authentication protocol.
        o    Its partyAuthPrivate component is called the private
             authentication key and represents any secret value needed
             to support the authentication protocol.  The significance
             of this component is specific to the authentication
             protocol.
        o    Its partyAuthPublic component is called the public
             authentication key and represents any public value that
             may be needed to support the authentication protocol.
             The significance of this component is specific to the
             authentication protocol.
        o    Its partyAuthLifetime component is called the lifetime
             and represents an administrative upper bound on
             acceptable delivery delay for protocol messages generated
             by the party.  The significance of this component is
             specific to the authentication protocol.
        o    Its partyPrivProtocol component is called the privacy
             protocol and identifies a protocol and a mechanism by
             which all protocol messages received by the party are
             protected from disclosure.  In this context, the value
             noPriv signifies that messages received by the party are
             not protected from disclosure.
        o    Its partyPrivPrivate component is called the private
             privacy key and represents any secret value needed to
             support the privacy protocol.  The significance of this
        Galvin & McCloghrie                                   [Page 5]
        RFC 1445       Administrative Model for SNMPv2      April 1993
             component is specific to the privacy protocol.
        o    Its partyPrivPublic component is called the public
             privacy key and represents any public value that may be
             needed to support the privacy protocol.  The significance
             of this component is specific to the privacy protocol.
        If, for all SNMPv2 parties realized by a SNMPv2 entity, the
        authentication protocol is noAuth and the privacy protocol is
        noPriv, then that entity is called non-secure.
        2.2.  SNMPv2 Entity
        A SNMPv2 entity is an actual process which performs network
        management operations by generating and/or responding to
        SNMPv2 protocol messages in the manner specified in [2].  When
        a SNMPv2 entity is acting as a particular SNMPv2 party (see
        Section 2.1), the operation of that entity must be restricted
        to the subset of all possible operations that is
        administratively defined for that party.
        By definition, the operation of a SNMPv2 entity requires no
        concurrency between processing of any single protocol message
        (by a particular SNMPv2 party) and processing of any other
        protocol message (by a potentially different SNMPv2 party).
        Accordingly, implementation of a SNMPv2 entity to support more
        than one party need not be multi-threaded.  However, there may
        be situations where implementors may choose to use multi-
        threading.
        Architecturally, every SNMPv2 entity maintains a local
        database that represents all SNMPv2 parties known to it -
        those whose operation is realized locally, those whose
        operation is realized by proxy interactions with remote
        parties or devices, and those whose operation is realized by
        remote entities.  In addition, every SNMPv2 entity maintains a
        local database that represents all managed object resources
        (see Section 2.8) which are known to the SNMPv2 entity.
        Finally, every SNMPv2 entity maintains a local database that
        represents an access control policy (see Section 2.11) that
        defines the access privileges accorded to known SNMPv2
        parties.
        Galvin & McCloghrie                                   [Page 6]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        2.3.  SNMPv2 Management Station
        A SNMPv2 management station is the operational role assumed by
        a SNMPv2 party when it initiates SNMPv2 management operations
        by the generation of appropriate SNMPv2 protocol messages or
        when it receives and processes trap notifications.
        Sometimes, the term SNMPv2 management station is applied to
        partial implementations of the SNMPv2 (in graphics
        workstations, for example) that focus upon this operational
        role.  Such partial implementations may provide for
        convenient, local invocation of management services, but they
        may provide little or no support for performing SNMPv2
        management operations on behalf of remote protocol users.
        2.4.  SNMPv2 Agent
        A SNMPv2 agent is the operational role assumed by a SNMPv2
        party when it performs SNMPv2 management operations in
        response to received SNMPv2 protocol messages such as those
        generated by a SNMPv2 management station (see Section 2.3).
        Sometimes, the term SNMPv2 agent is applied to partial
        implementations of the SNMPv2 (in embedded systems, for
        example) that focus upon this operational role.  Such partial
        implementations provide for realization of SNMPv2 management
        operations on behalf of remote users of management services,
        but they may provide little or no support for local invocation
        of such services.
        2.5.  View Subtree
        A view subtree is the set of all MIB object instances which
        have a common ASN.1 OBJECT IDENTIFIER prefix to their names.
        A view subtree is identified by the OBJECT IDENTIFIER value
        which is the longest OBJECT IDENTIFIER prefix common to all
        (potential) MIB object instances in that subtree.
        When the OBJECT IDENTIFIER prefix identifying a view subtree
        is longer than the OBJECT IDENTIFIER of an object type defined
        according to the SMI [3], then the use of such a view subtree
        for access control has granularity at the object instance
        level.  Such granularity is considered beyond the scope of a
        Galvin & McCloghrie                                   [Page 7]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        SNMPv2 entity acting in an agent role.  As such, no
        implementation of a SNMPv2 entity acting in an agent role is
        required to support values of viewSubtree [6] which have more
        sub-identifiers than is necessary to identify a particular
        leaf object type.  However, access control information is also
        used in determining which SNMPv2 entities acting in a manager
        role should receive trap notifications (Section 4.2.6 of [2]).
        As such, agent implementors might wish to provide instance-
        level granularity in order to allow a management station to
        use fine-grain configuration of trap notifications.
        2.6.  MIB View
        A MIB view is a subset of the set of all instances of all
        object types defined according to the SMI [3] (i.e., of the
        universal set of all instances of all MIB objects), subject to
        the following constraints:
        o    Each element of a MIB view is uniquely named by an ASN.1
             OBJECT IDENTIFIER value.  As such, identically named
             instances of a particular object type (e.g., in different
             agents) must be contained within different MIB views.
             That is, a particular object instance name resolves
             within a particular MIB view to at most one object
             instance.
        o    Every MIB view is defined as a collection of view
             subtrees.
        2.7.  Proxy Relationship
        A proxy relationship exists when, in order to process a
        received management request, a SNMPv2 entity must communicate
        with another, logically remote, entity.  A SNMPv2 entity which
        processes management requests using a proxy relationship is
        termed a SNMPv2 proxy agent.
        When communication between a logically remote party and a
        SNMPv2 entity is via the SNMPv2 (over any transport protocol),
        then the proxy party is called a SNMPv2 native proxy
        relationship.  Deployment of SNMPv2 native proxy relationships
        is a means whereby the processing or bandwidth costs of
        management may be amortized or shifted - thereby facilitating
        Galvin & McCloghrie                                   [Page 8]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        the construction of large management systems.
        When communication between a logically remote party and a
        SNMPv2 entity party is not via the SNMPv2, then the proxy
        party is called a SNMPv2 foreign proxy relationship.
        Deployment of foreign proxy relationships is a means whereby
        otherwise unmanageable devices or portions of an internet may
        be managed via the SNMPv2.
        The transparency principle that defines the behavior of a
        SNMPv2 entity in general applies in particular to a SNMPv2
        proxy relationship:
             The manner in which one SNMPv2 entity processes SNMPv2
             protocol messages received from another SNMPv2 entity is
             entirely transparent to the latter.
        The transparency principle derives directly from the
        historical SNMP philosophy of divorcing architecture from
        implementation.  To this dichotomy are attributable many of
        the most valuable benefits in both the information and
        distribution models of the Internet-standard Network
        Management Framework, and it is the architectural cornerstone
        upon which large management systems may be built.  Consistent
        with this philosophy, although the implementation of SNMPv2
        proxy agents in certain environments may resemble that of a
        transport-layer bridge, this particular implementation
        strategy (or any other!) does not merit special recognition
        either in the SNMPv2 management architecture or in standard
        mechanisms for proxy administration.
        Implicit in the transparency principle is the requirement that
        the semantics of SNMPv2 management operations are preserved
        between any two SNMPv2 peers.  In particular, the "as if
        simultaneous" semantics of a Set operation are extremely
        difficult to guarantee if its scope extends to management
        information resident at multiple network locations.  For this
        reason, proxy configurations that admit Set operations that
        apply to information at multiple locations are discouraged,
        although such operations are not explicitly precluded by the
        architecture in those rare cases where they might be supported
        in a conformant way.
        Also implicit in the transparency principle is the requirement
        that, throughout its interaction with a proxy agent, a
        Galvin & McCloghrie                                   [Page 9]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        management station is supplied with no information about the
        nature or progress of the proxy mechanisms by which its
        requests are realized.  That is, it should seem to the
        management station - except for any distinction in underlying
        transport address - as if it were interacting via SNMPv2
        directly with the proxied device.  Thus, a timeout in the
        communication between a proxy agent and its proxied device
        should be represented as a timeout in the communication
        between the management station and the proxy agent.
        Similarly, an error response from a proxied device should - as
        much as possible - be represented by the corresponding error
        response in the interaction between the proxy agent and
        management station.
        2.8.  SNMPv2 Context
        A SNMPv2 context is a collection of managed object resources
        accessible by a SNMPv2 entity.  The object resources
        identified by a context are either local or remote.
        A SNMPv2 context referring to local object resources is
        identified as a MIB view.  In this case, a SNMPv2 entity uses
        local mechanisms to access the management information
        identified by the SNMPv2 context.
        A remote SNMPv2 context referring to remote object resources
        is identified as a proxy relationship.  In this case, a SNMPv2
        entity acts as a proxy agent to access the management
        information identified by the SNMPv2 context.
        2.9.  SNMPv2 Management Communication
        A SNMPv2 management communication is a communication from one
        specified SNMPv2 party to a second specified SNMPv2 party
        about management information that is contained in a SNMPv2
        context accessible by the appropriate SNMPv2 entity.  In
        particular, a SNMPv2 management communication may be
        o    a query by the originating party about information
             accessible to the addressed party (e.g., getRequest,
             getNextRequest, or getBulkRequest),
        Galvin & McCloghrie                                  [Page 10]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        o    an indicative assertion to the addressed party about
             information accessible to the originating party (e.g.,
             Response, InformRequest, or SNMPv2-Trap),
        o    an imperative assertion by the originating party about
             information accessible to the addressed party (e.g.,
             setRequest), or
        o    a confirmation to the addressed party about information
             received by the originating party (e.g., a Response
             confirming an InformRequest).
        A management communication is represented by an ASN.1 value
        with the following syntax:
             SnmpMgmtCom ::= [2] IMPLICIT SEQUENCE {
               dstParty
                  OBJECT IDENTIFIER,
               srcParty
                  OBJECT IDENTIFIER,
               context
                  OBJECT IDENTIFIER,
               pdu
                  PDUs
             }
        For each SnmpMgmtCom value that represents a SNMPv2 management
        communication, the following statements are true:
        o    Its dstParty component is called the destination and
             identifies the SNMPv2 party to which the communication is
             directed.
        o    Its srcParty component is called the source and
             identifies the SNMPv2 party from which the communication
             is originated.
        o    Its context component identifies the SNMPv2 context
             containing the management information referenced by the
             communication.
        o    Its pdu component has the form and significance
             attributed to it in [2].
        Galvin & McCloghrie                                  [Page 11]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        2.10.  SNMPv2 Authenticated Management Communication
        A SNMPv2 authenticated management communication is a SNMPv2
        management communication (see Section 2.9) for which the
        originating SNMPv2 party is (possibly) reliably identified and
        for which the integrity of the transmission of the
        communication is (possibly) protected.  An authenticated
        management communication is represented by an ASN.1 value with
        the following syntax:
             SnmpAuthMsg ::= [1] IMPLICIT SEQUENCE {
               authInfo
                  ANY, -- defined by authentication protocol
               authData
                  SnmpMgmtCom
             }
        For each SnmpAuthMsg value that represents a SNMPv2
        authenticated management communication, the following
        statements are true:
        o    Its authInfo component is called the authentication
             information and represents information required in
             support of the authentication protocol used by the SNMPv2
             party originating the message.  The detailed significance
             of the authentication information is specific to the
             authentication protocol in use; it has no effect on the
             application semantics of the communication other than its
             use by the authentication protocol in determining whether
             the communication is authentic or not.
        o    Its authData component is called the authentication data
             and represents a SNMPv2 management communication.
        Galvin & McCloghrie                                  [Page 12]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        2.11.  SNMPv2 Private Management Communication
        A SNMPv2 private management communication is a SNMPv2
        authenticated management communication (see Section 2.10) that
        is (possibly) protected from disclosure.  A private management
        communication is represented by an ASN.1 value with the
        following syntax:
             SnmpPrivMsg ::= [1] IMPLICIT SEQUENCE {
               privDst
                  OBJECT IDENTIFIER,
               privData
                  [1] IMPLICIT OCTET STRING
             }
        For each SnmpPrivMsg value that represents a SNMPv2 private
        management communication, the following statements are true:
        o    Its privDst component is called the privacy destination
             and identifies the SNMPv2 party to which the
             communication is directed.
        o    Its privData component is called the privacy data and
             represents the (possibly encrypted) serialization
             (according to the conventions of [5]) of a SNMPv2
             authenticated management communication (see Section
             2.10).
        Galvin & McCloghrie                                  [Page 13]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        2.12.  SNMPv2 Management Communication Class
        A SNMPv2 management communication class corresponds to a
        specific SNMPv2 PDU type defined in [2].  A management
        communication class is represented by an ASN.1 INTEGER value
        according to the type of the identifying PDU (see Table 1).
                            Get              1
                            GetNext          2
                            Response         4
                            Set              8
                            -- unused       16
                            GetBulk         32
                            Inform          64
                            SNMPv2-Trap    128
                  Table 1: Management Communication Classes
        The value by which a communication class is represented is
        computed as 2 raised to the value of the ASN.1 context-
        specific tag for the appropriate SNMPv2 PDU.
        A set of management communication classes is represented by
        the ASN.1 INTEGER value that is the sum of the representations
        of the communication classes in that set.  The null set is
        represented by the value zero.
        2.13.  SNMPv2 Access Control Policy
        A SNMPv2 access control policy is a specification of a local
        access policy in terms of a SNMPv2 context and the management
        communication classes which are authorized between a pair of
        SNMPv2 parties.  Architecturally, such a specification
        comprises four parts:
        o    the targets of SNMPv2 access control - the SNMPv2 parties
             that may perform management operations as requested by
             management communications received from other parties,
        o    the subjects of SNMPv2 access control - the SNMPv2
             parties that may request, by sending management
        Galvin & McCloghrie                                  [Page 14]
        RFC 1445       Administrative Model for SNMPv2      April 1993
             communications to other parties, that management
             operations be performed,
        o    the managed object resources of SNMPv2 access control -
             the SNMPv2 contexts which identify the management
             information on which requested management operations are
             to be performed, and
        o    the policy that specifies the classes of SNMPv2
             management communications pertaining to a particular
             SNMPv2 context that a particular target is authorized to
             accept from a particular subject.
        Conceptually, a SNMPv2 access policy is represented by a
        collection of ASN.1 values with the following syntax:
             AclEntry ::= SEQUENCE {
               aclTarget
                  OBJECT IDENTIFIER,
               aclSubject
                  OBJECT IDENTIFIER,
               aclResources
                  OBJECT IDENTIFIER,
               aclPrivileges
                  INTEGER
             }
        For each such value that represents one part of a SNMPv2
        access policy, the following statements are true:
        o    Its aclTarget component is called the target and
             identifies the SNMPv2 party to which the partial policy
             permits access.
        o    Its aclSubject component is called the subject and
             identifies the SNMPv2 party to which the partial policy
             grants privileges.
        o    Its aclResources component is called the managed object
             resources and identifies the SNMPv2 context referenced by
             the partial policy.
        o    Its aclPrivileges component is called the privileges and
             represents a set of SNMPv2 management communication
             classes which, when they reference the specified SNMPv2
        Galvin & McCloghrie                                  [Page 15]
        RFC 1445       Administrative Model for SNMPv2      April 1993
             context, are authorized to be processed by the specified
             target party when received from the specified subject
             party.
        The application of SNMPv2 access control policy only occurs on
        receipt of management communications; it is not applied on
        transmission of management communications.  Note, however,
        that ASN.1 values, having the syntax AclEntry, are also used
        in determining the destinations of a SNMPv2-Trap [2].
        Galvin & McCloghrie                                  [Page 16]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        3.  Elements of Procedure
        This section describes the procedures followed by a SNMPv2
        entity in processing SNMPv2 messages.  These procedures are
        independent of the particular authentication and privacy
        protocols that may be in use.
        3.1.  Generating a Request
        This section describes the procedure followed by a SNMPv2
        entity whenever either a management request or a trap
        notification is to be transmitted by a SNMPv2 party.
        (1)  A SnmpMgmtCom value is constructed for which the srcParty
             component identifies the originating party, for which the
             dstParty component identifies the receiving party, for
             which the context component identifies the desired SNMPv2
             context, and for which the pdu component represents the
             desired management operation.
        (2)  The local database of party information is consulted to
             determine the authentication protocol and other relevant
             information for the originating and receiving SNMPv2
             parties.
        (3)  A SnmpAuthMsg value is constructed with the following
             properties:
                  Its authInfo component is constructed according to
                  the authentication protocol specified for the
                  originating party.
                    In particular, if the authentication protocol for
                    the originating SNMPv2 party is identified as
                    noAuth, then this component corresponds to the
                    OCTET STRING value of zero length.
                 Its authData component is the constructed SnmpMgmtCom
                 value.
        (4)  The local database of party information is consulted to
             determine the privacy protocol and other relevant
             information for the receiving SNMPv2 party.
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        RFC 1445       Administrative Model for SNMPv2      April 1993
        (5)  A SnmpPrivMsg value is constructed with the following
             properties:
                  Its privDst component identifies the receiving
                  SNMPv2 party.
                  Its privData component is the (possibly encrypted)
                  serialization of the SnmpAuthMsg value according to
                  the conventions of [5].
                    In particular, if the privacy protocol for the
                    receiving SNMPv2 party is identified as noPriv,
                    then the privData component is unencrypted.
                    Otherwise, the privData component is processed
                    according to the privacy protocol.
        (6)  The constructed SnmpPrivMsg value is serialized according
             to the conventions of [5].
        (7)  The serialized SnmpPrivMsg value is transmitted using the
             transport address and transport domain for the receiving
             SNMPv2 party.
        Note that the above procedure does not include any application
        of any SNMPv2 access control policy (see section 2.13).
        3.2.  Processing a Received Communication
        This section describes the procedure followed by a SNMPv2
        entity whenever a management communication is received.
        (1)  The snmpStatsPackets counter [7] is incremented.  If the
             received message is not the serialization (according to
             the conventions of [5]) of an SnmpPrivMsg value, then
             that message is discarded without further processing.
             (If the first octet of the packet has the value
             hexadecimal 30, then the snmpStats30Something counter [7]
             is incremented prior to discarding the message; otherwise
             the snmpStatsEncodingErrors counter [7] is incremented.)
        (2)  The local database of party information is consulted for
             information about the receiving SNMPv2 party identified
             by the privDst component of the SnmpPrivMsg value.
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        (3)  If information about the receiving SNMPv2 party is absent
             from the local database of party information, or
             indicates that the receiving party's operation is not
             realized by the local SNMPv2 entity, then the received
             message is discarded without further processing, after
             the snmpStatsUnknownDstParties counter [7] is
             incremented.
        (4)  An ASN.1 OCTET STRING value is constructed (possibly by
             decryption, according to the privacy protocol in use)
             from the privData component of said SnmpPrivMsg value.
             In particular, if the privacy protocol recorded for the
             party is noPriv, then the OCTET STRING value corresponds
             exactly to the privData component of the SnmpPrivMsg
             value.
        (5)  If the OCTET STRING value is not the serialization
             (according to the conventions of [5]) of an SnmpAuthMsg
             value, then the received message is discarded without
             further processing, after the snmpStatsEncodingErrors
             counter [7] is incremented.
        (6)  If the dstParty component of the authData component of
             the obtained SnmpAuthMsg value is not the same as the
             privDst component of the SnmpPrivMsg value, then the
             received message is discarded without further processing,
             after the snmpStatsDstPartyMismatches counter [7] is
             incremented.
        (7)  The local database of party information is consulted for
             information about the originating SNMPv2 party identified
             by the srcParty component of the authData component of
             the SnmpAuthMsg value.
        (8)  If information about the originating SNMPv2 party is
             absent from the local database of party information, then
             the received message is discarded without further
             processing, after the snmpStatsUnknownSrcParties counter
             [7] is incremented.
        (9)  The obtained SnmpAuthMsg value is evaluated according to
             the authentication protocol and other relevant
             information associated with the originating and receiving
             SNMPv2 parties in the local database of party
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             information.
             In particular, if the authentication protocol is
             identified as noAuth, then the SnmpAuthMsg value is
             always evaluated as authentic.
        (10) If the SnmpAuthMsg value is evaluated as unauthentic,
             then the received message is discarded without further
             processing, and if the snmpV2EnableAuthenTraps object [7]
             is enabled, then the SNMPv2 entity sends
             authorizationFailure traps [7] according to its
             configuration (Section 4.2.6 of[2]).
        (11) The SnmpMgmtCom value is extracted from the authData
             component of the SnmpAuthMsg value.
        (12) The local database of context information is consulted
             for information about the SNMPv2 context identified by
             the context component of the SnmpMgmtCom value.
        (13) If information about the SNMPv2 context is absent from
             the local database of context information, then the
             received message is discarded without further processing,
             after the snmpStatsUnknownContexts counter [7] is
             incremented.
        (14) The local database of access policy information is
             consulted for access privileges permitted by the local
             access policy to the originating SNMPv2 party with
             respect to the receiving SNMPv2 party and the indicated
             SNMPv2 context.
        (15) The management communication class is determined from the
             ASN.1 tag value associated with the PDUs component of the
             SnmpMgmtCom value.  If the management information class
             of the received message is either 32, 8, 2, or 1 (i.e.,
             GetBulk, Set, GetNext or Get) and the SNMPv2 context is
             not realized by the local SNMPv2 entity, then the
             received message is discarded without further processing,
             after the snmpStatsUnknownContexts counter [7] is
             incremented.
        (16) If the management communication class of the received
             message is either 128, 64 or 4 (i.e., SNMPv2-Trap,
             Inform, or Response) and this class is not among the
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             access privileges, then the received message is discarded
             without further processing, after the
             snmpStatsBadOperations counter [7] is incremented.
        (17) If the management communication class of the received
             message is not among the access privileges, then the
             received message is discarded without further processing
             after generation and transmission of a response message.
             This response message is directed to the originating
             SNMPv2 party on behalf of the receiving SNMPv2 party.
             Its context, var-bind-list and request-id components are
             identical to those of the received request.  Its error-
             index component is zero and its error-status component is
             authorizationError [2].
        (18) If the SNMPv2 context refers to local object resources,
             then the management operation represented by the
             SnmpMgmtCom value is performed by the receiving SNMPv2
             entity with respect to the MIB view identified by the
             SNMPv2 context according to the procedures set forth in
             [2].
        (19) If the SNMPv2 context refers to remote object resources,
             then the management operation represented by the
             SnmpMgmtCom value is performed through the appropriate
             proxy relationship.
        3.3.  Generating a Response
        The procedure for generating a response to a SNMPv2 management
        request is identical to the procedure for transmitting a
        request (see Section 3.1), with these exceptions:
        (1)  In Step 1, the dstParty component of the responding
             SnmpMgmtCom value is taken from the srcParty component of
             the original SnmpMgmtCom value; the srcParty component of
             the responding SnmpMgmtCom value is taken from the
             dstParty component of the original SnmpMgmtCom value; the
             context component of the responding SnmpMgmtCom value is
             taken from the context component of the original
             SnmpMgmtCom value; and, the pdu component of the
             responding SnmpMgmtCom value is the response which
             results from applying the operation specified in the
             original SnmpMgmtCom value.
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        (2)  In Step 7, the serialized SnmpPrivMsg value is
             transmitted using the transport address and transport
             domain from which its corresponding request originated -
             even if that is different from the transport information
             recorded in the local database of party information.
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        4.  Application of the Model
        This section describes how the administrative model set forth
        above is applied to realize effective network management in a
        variety of configurations and environments.  Several types of
        administrative configurations are identified, and an example
        of each is presented.
        4.1.  Non-Secure Minimal Agent Configuration
        This section presents an example configuration for a minimal,
        non-secure SNMPv2 agent that interacts with one or more SNMPv2
        management stations.  Table 2 presents information about
        SNMPv2 parties that is known both to the minimal agent and to
        the manager, while Table 3 presents similarly common
        information about the local access policy.
        As represented in Table 2, the example agent party operates at
        UDP port 161 at IP address 1.2.3.4 using the party identity
        gracie; the example manager operates at UDP port 2001 at IP
        address 1.2.3.5 using the identity george.  At minimum, a
        non-secure SNMPv2 agent implementation must provide for
        administrative configuration (and non-volatile storage) of the
        identities and transport addresses of two SNMPv2 parties:
        itself and a remote peer.  Strictly speaking, other
        information about these two parties (including access policy
        information) need not be configurable.
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             Identity          gracie                george
                               (agent)               (manager)
             Domain            snmpUDPDomain         snmpUDPDomain
             Address           1.2.3.4, 161          1.2.3.5, 2001
             Auth Prot         noAuth                noAuth
             Auth Priv Key     ""                    ""
             Auth Pub Key      ""                    ""
             Auth Clock        0                     0
             Auth Lifetime     0                     0
             Priv Prot         noPriv                noPriv
             Priv Priv Key     ""                    ""
             Priv Pub Key      ""                    ""
                 Table 2: Party Information for Minimal Agent
        Target    Subject    Context    Privileges
        gracie    george     local       35 (Get, GetNext & GetBulk)
        george    gracie     local      132 (Response & SNMPv2-Trap)
                Table 3: Access Information for Minimal Agent
        Suppose that the managing party george wishes to interrogate
        management information about the SNMPv2 context named "local"
        held by the agent named gracie by issuing a SNMPv2 GetNext
        request message.  The manager consults its local database of
        party information.  Because the authentication protocol for
        the party george is recorded as noAuth, the GetNext request
        message generated by the manager is not authenticated as to
        origin and integrity.  Because, according to the manager's
        local database of party information, the privacy protocol for
        the party gracie is noPriv, the GetNext request message is not
        protected from disclosure.  Rather, it is simply assembled,
        serialized, and transmitted to the transport address (IP
        address 1.2.3.4, UDP port 161) associated in the manager's
        local database of party information with the party gracie.
        When the GetNext request message is received at the agent, the
        identity of the party to which it is directed (gracie) is
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        extracted from the message, and the receiving entity consults
        its local database of party information.  Because the privacy
        protocol for the party gracie is recorded as noPriv, the
        received message is assumed not to be protected from
        disclosure.  Similarly, the identity of the originating party
        (george) is extracted, and the local database of party
        information is consulted.  Because the authentication protocol
        for the party george is recorded as noAuth, the received
        message is immediately accepted as authentic.
        The received message is fully processed only if the agent's
        local database of access policy information authorizes GetNext
        request communications by the party george to the agent party
        gracie with respect to the SNMPv2 context "local".  The
        database of access policy information presented as Table 3
        authorizes such communications (as well as Get and GetBulk
        operations).
        When the received request is processed, a Response message is
        generated which references the SNMPv2 context "local" and
        identifies gracie as the source party and george, the party
        from which the request originated, as the destination party.
        Because the authentication protocol for gracie is recorded in
        the local database of party information as noAuth, the
        generated Response message is not authenticated as to origin
        or integrity.  Because, according to the local database of
        party information, the privacy protocol for the party george
        is noPriv, the response message is not protected from
        disclosure.  The response message is transmitted to the
        transport address from which the corresponding request
        originated - without regard for the transport address
        associated with george in the local database of party
        information.
        When the generated response is received by the manager, the
        identity of the party to which it is directed (george) is
        extracted from the message, and the manager consults its local
        database of party information.  Because the privacy protocol
        for the party george is recorded as noPriv, the received
        response is assumed not to be protected from disclosure.
        Similarly, the identity of the originating party (gracie) is
        extracted, and the local database of party information is
        consulted.  Because the authentication protocol for the party
        gracie is recorded as noAuth, the received response is
        immediately accepted as authentic.
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        The received message is fully processed only if the manager's
        local database of access policy information authorizes
        Response communications from the party gracie to the manager
        party george which reference the SNMPv2 context "local".  The
        database of access policy information presented as Table 3
        authorizes such Response messages (as well as SNMPv2-Trap
        messages).
        4.2.  Secure Minimal Agent Configuration
        This section presents an example configuration for a secure,
        minimal SNMPv2 agent that interacts with a single SNMPv2
        management station.  Table 4 presents information about SNMPv2
        parties that is known both to the minimal agent and to the
        manager, while Table 5 presents similarly common information
        about the local access policy.
        The interaction of manager and agent in this configuration is
        very similar to that sketched above for the non-secure minimal
        agent - except that all protocol messages are authenticated as
        to origin and integrity and protected from disclosure.  This
        example requires encryption in order to support distribution
        of secret keys via the SNMPv2 itself.  A more elaborate
        example comprising an additional pair of SNMPv2 parties could
        support the exchange of non-secret information in
        authenticated messages without incurring the cost of
        encryption.
        An actual secure agent configuration may require SNMPv2
        parties for which the authentication and privacy protocols are
        noAuth and noPriv, respectively, in order to support clock
        synchronization (see [6]).  For clarity, these additional
        parties are not represented in this example.
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             Identity          ollie                stan
                               (agent)              (manager)
             Domain            snmpUDPDomain        snmpUDPDomain
             Address           1.2.3.4, 161         1.2.3.5, 2001
             Auth Prot         v2md5AuthProtocol    v2md5AuthProtocol
             Auth Priv Key     "0123456789ABCDEF"   "GHIJKL0123456789"
             Auth Pub Key      ""                   ""
             Auth Clock        0                    0
             Auth Lifetime     300                  300
             Priv Prot         desPrivProtocol     desPrivProtocol
             Priv Priv Key     "MNOPQR0123456789"   "STUVWX0123456789"
             Priv Pub Key      ""                   ""
             Table 4: Party Information for Secure Minimal Agent
        Target    Subject    Context    Privileges
        ollie     stan       local       35 (Get, GetNext & GetBulk)
        stan      ollie      local      132 (Response & SNMPv2-Trap)
             Table 5: Access Information for Secure Minimal Agent
        As represented in Table 4, the example agent party operates at
        UDP port 161 at IP address 1.2.3.4 using the party identity
        ollie; the example manager operates at UDP port 2001 at IP
        address 1.2.3.5 using the identity stan.  At minimum, a secure
        SNMPv2 agent implementation must provide for administrative
        configuration (and non-volatile storage) of relevant
        information about two SNMPv2 parties: itself and a remote
        peer.  Both ollie and stan authenticate all messages that they
        generate by using the SNMPv2 authentication protocol
        v2md5AuthProtocol and their distinct, private authentication
        keys.  Although these private authentication key values
        ("0123456789ABCDEF" and "GHIJKL0123456789") are presented here
        for expository purposes, knowledge of private authentication
        keys is not normally afforded to human beings and is confined
        to those portions of the protocol implementation that require
        it.
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        When using the v2md5AuthProtocol, the public authentication
        key for each SNMPv2 party is never used in authentication and
        verification of SNMPv2 exchanges.  Also, because the
        v2md5AuthProtocol is symmetric in character, the private
        authentication key for each party must be known to another
        SNMPv2 party with which authenticated communication is
        desired.  In contrast, asymmetric (public key) authentication
        protocols would not depend upon sharing of a private key for
        their operation.
        All protocol messages generated for transmission to the party
        stan are encrypted using the desPrivProtocol privacy protocol
        and the private key "STUVWX0123456789"; they are decrypted
        upon reception according to the same protocol and key.
        Similarly, all messages generated for transmission to the
        party ollie are encrypted using the desPrivProtocol protocol
        and private privacy key "MNOPQR0123456789"; they are
        correspondingly decrypted on reception.  As with
        authentication keys, knowledge of private privacy keys is not
        normally afforded to human beings and is confined to those
        portions of the protocol implementation that require it.
        4.3.  MIB View Configurations
        This section describes a convention for the definition of MIB
        views and, using that convention, presents example
        configurations of MIB views for SNMPv2 contexts that refer to
        local object resources.
        A MIB view is defined by a collection of view subtrees (see
        Section 2.6), and any MIB view may be represented in this way.
        Because MIB view definitions may, in certain cases, comprise a
        very large number of view subtrees, a convention for
        abbreviating MIB view definitions is desirable.
        The convention adopted in [4] supports abbreviation of MIB
        view definitions in terms of families of view subtrees that
        are either included in or excluded from the definition of the
        relevant MIB view.  By this convention, a table locally
        maintained by each SNMPv2 entity defines the MIB view
        associated with each SNMPv2 context that refers to local
        object resources.  Each entry in the table represents a family
        of view subtrees that (according to the type of that entry) is
        either included in or excluded from the MIB view of some
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        SNMPv2 context.  Each table entry represents a subtree family
        as a pairing of an OBJECT IDENTIFIER value (called the family
        name) together with a bitstring value (called the family
        mask).  The family mask indicates which sub-identifiers of the
        associated family name are significant to the definition of
        the represented subtree family.  For each possible MIB object
        instance, that instance belongs to the view subtree family
        represented by a particular table entry if
        o    the OBJECT IDENTIFIER name of that MIB object instance
             comprises at least as many sub-identifiers as does the
             family name for said table entry, and
        o    each sub-identifier in the name of said MIB object
             instance matches the corresponding sub-identifier of the
             relevant family name whenever the corresponding bit of
             the associated family mask is non-zero.
        The appearance of a MIB object instance in the MIB view for a
        particular SNMPv2 context is related to the membership of that
        instance in the subtree families associated with that SNMPv2
        context in local table entries:
        o    If a MIB object instance belongs to none of the relevant
             subtree families, then that instance is not in the MIB
             view for the relevant SNMPv2 context.
        o    If a MIB object instance belongs to the subtree family
             represented by exactly one of the relevant table entries,
             then that instance is included in, or excluded from, the
             relevant MIB view according to the type of that entry.
        o    If a MIB object instance belongs to the subtree families
             represented by more than one of the relevant table
             entries, then that instance is included in, or excluded
             from, the relevant MIB view according to the type of the
             single such table entry for which, first, the associated
             family name comprises the greatest number of sub-
             identifiers, and, second, the associated family name is
             lexicographically greatest.
        The subtree family represented by a table entry for which the
        associated family mask is all ones corresponds to the single
        view subtree identified by the family name for that entry.
        Because the convention of [4] provides for implicit extension
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        of family mask values with ones, the subtree family
        represented by a table entry with a family mask of zero length
        always corresponds to a single view subtree.
          Context    Type        Family Name    Family Mask
          lucy       included    internet       ''H
                  Table 6: View Definition for Minimal Agent
        Using this convention for abbreviating MIB view definitions,
        some of the most common definitions of MIB views may be
        conveniently expressed.  For example, Table 6 illustrates the
        MIB view definitions required for a minimal SNMPv2 entity that
        having a single SNMPv2 context for which the associated MIB
        view embraces all instances of all MIB objects defined within
        the SNMPv2 Network Management Framework.  The represented
        table has a single entry.  The SNMPv2 context (lucy) for which
        that entry defines the MIB view is identified in the first
        column.  The type of that entry (included) signifies that any
        MIB object instance belonging to the subtree family
        represented by that entry may appear in the MIB view for the
        SNMPv2 context lucy.  The family name for that entry is
        internet, and the zero-length family mask value signifies that
        the relevant subtree family corresponds to the single view
        subtree rooted at that node.
        Another example of MIB view definition (see Table 7) is that
        of a SNMPv2 entity having multiple SNMPv2 contexts with
        distinct MIB views.  The MIB view associated with the SNMPv2
        context lucy comprises all instances of all MIB objects
        defined within the SNMPv2 Network Management Framework, except
        those pertaining to the administration of SNMPv2 parties.  In
        contrast, the MIB view attributed to the SNMPv2 context ricky
        contains only MIB object instances defined in the system group
        of the Internet-standard MIB together with those object
        instances by which SNMPv2 parties are administered.
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             Context    Type        Family Name    Family Mask
             lucy       included    internet       ''H
             lucy       excluded    snmpParties    ''H
             ricky      included    system         ''H
             ricky      included    snmpParties    ''H
                Table 7: View Definition for Multiple Contexts
        A more complicated example of MIB view configuration
        illustrates the abbreviation of related collections of view
        subtrees by view subtree families (see Table 8).  In this
        example, the MIB view associated with the SNMPv2 context lucy
        includes all object instances in the system group of the
        Internet-standard MIB together with some information related
        to the second network interface attached to the managed
        device.  However, this interface-related information does not
        include the speed of the interface.  The family mask value
        'FFA0'H in the second table entry signifies that a MIB object
        instance belongs to the relevant subtree family if the initial
        prefix of its name places it within the ifEntry portion of the
        registration hierarchy and if the eleventh sub-identifier of
        its name is 2.  The MIB object instance representing the speed
        of the second network interface belongs to the subtree
        families represented by both the second and third entries of
        the table, but that particular instance is excluded from the
        MIB view for the SNMPv2 context lucy because the
        lexicographically greater of the relevant family names appears
        in the table entry with type excluded.
        The MIB view for the SNMPv2 context ricky is also defined in
        this example.  The MIB view attributed to the SNMPv2 context
        ricky includes all object instances in the icmp group of the
        Internet-standard MIB, together with all information relevant
        to the fifth network interface attached to the managed device.
        In addition, the MIB view attributed to the SNMPv2 context
        ricky includes the number of octets received on the fourth
        attached network interface.
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        RFC 1445       Administrative Model for SNMPv2      April 1993
             Context    Type        Family Name        Family Mask
             lucy       included    system             ''H
             lucy       included    { ifEntry 0 2 }    'FFA0'H
             lucy       excluded    { ifSpeed 2 }      ''H
             ricky      included    icmp               ''H
             ricky      included    { ifEntry 0 5 }    'FFA0'H
             ricky      included    { ifInOctets 4 }   ''H
                   Table 8: More Elaborate View Definitions
        While, as suggested by the examples above, a wide range of MIB
        view configurations are efficiently supported by the
        abbreviated representation of [4], prudent MIB design can
        sometimes further reduce the size and complexity of the most
        likely MIB view definitions.  On one hand, it is critical that
        mechanisms for MIB view configuration impose no absolute
        constraints either upon the access policies of local
        administrations or upon the structure of MIB namespaces; on
        the other hand, where the most common access policies are
        known, the configuration costs of realizing those policies may
        be slightly reduced by assigning to distinct portions of the
        registration hierarchy those MIB objects for which local
        policies most frequently require distinct treatment.
        4.4.  Proxy Configuration
        This section presents examples of SNMPv2 proxy configurations.
        On one hand, foreign proxy configurations provide the
        capability to manage non-SNMP devices.  On the other hand,
        native proxy configurations allow an administrator to shift
        the computational burden of rich management functionality away
        from network devices whose primary task is not management.  To
        the extent that SNMPv2 proxy agents function as points of
        aggregation for management information, proxy configurations
        may also reduce the bandwidth requirements of large-scale
        management activities.
        The example configurations in this section are simplified for
        clarity: actual configurations may require additional parties
        in order to support clock synchronization and distribution of
        secrets.
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        4.4.1.  Foreign Proxy Configuration
        This section presents an example configuration by which a
        SNMPv2 management station may manage network elements that do
        not themselves support the SNMPv2.  This configuration centers
        on a SNMPv2 proxy agent that realizes SNMPv2 management
        operations by interacting with a non-SNMPv2 device using a
        proprietary protocol.
        Table 9 presents information about SNMPv2 parties that is
        recorded in the SNMPv2 proxy agent's local database of party
        information.  Table 10 presents information about proxy
        relationships that is recorded in the SNMPv2 proxy agent's
        local database of context information.  Table 11 presents
        information about SNMPv2 parties that is recorded in the
        SNMPv2 management station's local database of party
        information.  Table 12 presents information about the database
        of access policy information specified by the local
        administration.
 Identity        groucho             chico               harpo
                 (manager)           (proxy agent)       (proxy dst)
 Domain          snmpUDPDomain       snmpUDPDomain       acmeMgmtPrtcl
 Address         1.2.3.4, 2002       1.2.3.5, 161        0x98765432
 Auth Prot       v2md5AuthProtocol   v2md5AuthProtocol   noAuth
 Auth Priv Key   "0123456789ABCDEF"  "GHIJKL0123456789"  ""
 Auth Pub Key    ""                  ""                  ""
 Auth Clock      0                   0                   0
 Auth Lifetime   300                 300                 0
 Priv Prot       noPriv              noPriv              noPriv
 Priv Priv Key   ""                  ""                  ""
 Priv Pub Key    ""                  ""                  ""
           Table 9: Party Information for Proxy Agent
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        RFC 1445       Administrative Model for SNMPv2      April 1993
        Context     Proxy Destination    Proxy Source    Proxy Context
        ducksoup    harpo                n/a             n/a
                Table 10: Proxy Relationships for Proxy Agent
             Identity          groucho              chico
                               (manager)            (proxy agent)
             Domain            snmpUDPDomain        snmpUDPDomain
             Address           1.2.3.4, 2002        1.2.3.5, 161
             Auth Prot         v2md5AuthProtocol    v2md5AuthProtocol
             Auth Priv Key     "0123456789ABCDEF"   "GHIJKL0123456789"
             Auth Pub Key      ""                   ""
             Auth Clock        0                    0
             Auth Lifetime     300                  300
             Priv Prot         noPriv               noPriv
             Priv Priv Key     ""                   ""
             Priv Pub Key      ""                   ""
              Table 11: Party Information for Management Station
        Target     Subject    Context     Privileges
        chico      groucho    ducksoup     35 (Get, GetNext & GetBulk)
        groucho    chico      ducksoup    132 (Response & SNMPv2-Trap)
                Table 12: Access Information for Foreign Proxy
        As represented in Table 9, the proxy agent party operates at
        UDP port 161 at IP address 1.2.3.5 using the party identity
        chico; and, the example manager operates at UDP port 2002 at
        IP address 1.2.3.4 using the identity groucho.  Both groucho
        and chico authenticate all messages that they generate by
        using the protocol v2md5AuthProtocol and their distinct,
        private authentication keys.  Although these private
        authentication key values ("0123456789ABCDEF" and
        "GHIJKL0123456789") are presented here for expository
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        RFC 1445       Administrative Model for SNMPv2      April 1993
        purposes, knowledge of private keys is not normally afforded
        to human beings and is confined to those portions of the
        protocol implementation that require it.
        The party harpo does not send or receive SNMPv2 protocol
        messages; rather, all communication with that party proceeds
        via a hypothetical proprietary protocol identified by the
        value acmeMgmtPrtcl.  Because the party harpo does not
        participate in the SNMPv2, many of the attributes recorded for
        that party in the local database of party information are
        ignored.
        Table 10 shows the proxy relationships known to the proxy
        agent.  In particular, the SNMPv2 context ducksoup refers to a
        relationship that is satisfied by the party harpo.  (The
        transport domain of the proxy destination party determines the
        interpretation of the proxy source and proxy context
        identities - in this case, use of the acmeMgmtPrtcl indicates
        that the proxy source and context identities are ignored.)
        In order to interrogate the proprietary device associated with
        the party harpo, the management station groucho constructs a
        SNMPv2 GetNext request contained within a SnmpMgmtCom value
        which references the SNMPv2 context ducksoup, and transmits it
        to the party chico operating (see Table 11) at UDP port 161,
        and IP address 1.2.3.5.  This request is authenticated using
        the private authentication key "0123456789ABCDEF".
        When that request is received by the party chico, the
        originator of the message is verified as being the party
        groucho by using local knowledge (see Table 9) of the private
        authentication key "0123456789ABCDEF".  Because party groucho
        is authorized to issue GetNext (as well as Get and GetBulk)
        requests with respect to party chico and the SNMPv2 context
        ducksoup by the relevant access control policy (Table 12), the
        request is accepted.  Because the local database of context
        information indicates that the SNMPv2 context ducksoup refers
        to a proxy relationship, the request is satisfied by its
        translation into appropriate operations of the acmeMgmtPrtcl
        directed at party harpo.  These new operations are transmitted
        to the party harpo at the address 0x98765432 in the
        acmeMgmtPrtcl domain.
        When and if the proprietary protocol exchange between the
        proxy agent and the proprietary device concludes, a SNMPv2
        Galvin & McCloghrie                                  [Page 35]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        Response management operation is constructed by the SNMPv2
        party chico to relay the results to party groucho again
        referring to the SNMPv2 context ducksoup.  This response
        communication is authenticated as to origin and integrity
        using the authentication protocol v2md5AuthProtocol and
        private authentication key "GHIJKL0123456789" specified for
        transmissions from party chico.  It is then transmitted to the
        SNMPv2 party groucho operating at the management station at IP
        address 1.2.3.4 and UDP port 2002 (the source address for the
        corresponding request).
        When this response is received by the party groucho, the
        originator of the message is verified as being the party chico
        by using local knowledge (see Table 11) of the private
        authentication key "GHIJKL0123456789".  Because party chico is
        authorized to issue Response communications with respect to
        party groucho and SNMPv2 context ducksoup by the relevant
        access control policy (Table 12), the response is accepted,
        and the interrogation of the proprietary device is complete.
        It is especially useful to observe that the local database of
        party information recorded at the proxy agent (Table 9) need
        be neither static nor configured exclusively by the management
        station.  For instance, suppose that, in this example, the
        acmeMgmtPrtcl was a proprietary, MAC-layer mechanism for
        managing stations attached to a local area network.  In such
        an environment, the SNMPv2 party chico would reside at a
        SNMPv2 proxy agent attached to such a LAN and could, by
        participating in the LAN protocols, detect the attachment and
        disconnection of various stations on the LAN.  In this
        scenario, the SNMPv2 proxy agent could easily adjust its local
        database of party information to support indirect management
        of the LAN stations by the SNMPv2 management station.  For
        each new LAN station detected, the SNMPv2 proxy agent would
        add to its local database of party information an entry
        analogous to that for party harpo (representing the new LAN
        station itself), and also add to its local database of context
        information an entry analogous to that for SNMPv2 context
        ducksoup (representing a proxy relationship for that new
        station in the SNMPv2 domain).
        By using the SNMPv2 to interrogate the local database of party
        information held by the SNMPv2 proxy agent, a SNMPv2
        management station can discover and interact with new stations
        as they are attached to the LAN.
        Galvin & McCloghrie                                  [Page 36]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        4.4.2.  Native Proxy Configuration
        This section presents an example configuration that supports
        SNMPv2 native proxy operations - indirect interaction between
        a SNMPv2 agent and a management station that is mediated by a
        second SNMPv2 (proxy) agent.
        This example configuration is similar to that presented in the
        discussion of SNMPv2 foreign proxy above.  In this example,
        however, the party associated with the identity harpo receives
        messages via the SNMPv2, and, accordingly interacts with the
        SNMPv2 proxy agent chico using authenticated SNMPv2
        communications.
        Table 13 presents information about SNMPv2 parties that is
        recorded in the SNMPv2 proxy agent's local database of party
        information.  Table 14 presents information about proxy
        relationships that is recorded in the SNMPv2 proxy agent's
        local database of context information.  Table 11 presents
        information about SNMPv2 parties that is recorded in the
        SNMPv2 management station's local database of party
        information.  Table 15 presents information about the database
        of access policy information specified by the local
        administration.
        Galvin & McCloghrie                                  [Page 37]
        RFC 1445       Administrative Model for SNMPv2      April 1993
             Identity          groucho              chico
                               (manager)            (proxy agent)
             Domain            snmpUDPDomain        snmpUDPDomain
             Address           1.2.3.4, 2002        1.2.3.5, 161
             Auth Prot         v2md5AuthProtocol    v2md5AuthProtocol
             Auth Priv Key     "0123456789ABCDEF"   "GHIJKL0123456789"
             Auth Pub Key      ""                   ""
             Auth Clock        0                    0
             Auth Lifetime     300                  300
             Priv Prot         noPriv               noPriv
             Priv Priv Key     ""                   ""
             Priv Pub Key      ""                   ""
             Identity          harpo                   zeppo
                               (proxy dst)          (proxy src)
             Domain            snmpUDPDomain        snmpUDPDomain
             Address           1.2.3.6, 161         1.2.3.5, 161
             Auth Prot         v2md5AuthProtocol    v2md5AuthProtocol
             Auth Priv Key     "MNOPQR0123456789"   "STUVWX0123456789"
             Auth Pub Key      ""                   ""
             Auth Clock        0                    0
             Auth Lifetime     300                  300
             Priv Prot         noPriv               noPriv
             Priv Priv Key     ""                   ""
             Priv Pub Key      ""                   ""
                 Table 13: Party Information for Proxy Agent
        Context     Proxy Destination    Proxy Source    Proxy Context
        ducksoup    harpo                zeppo           bigstore
        bigstore    groucho              chico           ducksoup
                Table 14: Proxy Relationships for Proxy Agent
        Galvin & McCloghrie                                  [Page 38]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        Target     Subject    Context     Privileges
        chico      groucho    ducksoup     35 (Get, GetNext & GetBulk)
        groucho    chico      ducksoup    132 (Response & SNMPv2-Trap)
        harpo      zeppo      bigstore     35 (Get, GetNext & GetBulk)
        zeppo      harpo      bigstore    132 (Response & SNMPv2-Trap)
                Table 15: Access Information for Native Proxy
        As represented in Table 13, the proxy agent party operates at
        UDP port 161 at IP address 1.2.3.5 using the party identity
        chico; the example manager operates at UDP port 2002 at IP
        address 1.2.3.4 using the identity groucho; the proxy source
        party operates at UDP port 161 at IP address 1.2.3.5 using the
        party identity zeppo; and, the proxy destination party
        operates at UDP port 161 at IP address 1.2.3.6 using the party
        identity harpo.  Messages generated by all four SNMPv2 parties
        are authenticated as to origin and integrity by using the
        authentication protocol v2md5AuthProtocol and distinct,
        private authentication keys.  Although these private
        authentication key values ("0123456789ABCDEF",
        "GHIJKL0123456789", "MNOPQR0123456789", and
        "STUVWX0123456789") are presented here for expository
        purposes, knowledge of private keys is not normally afforded
        to human beings and is confined to those portions of the
        protocol implementation that require it.
        Table 14 shows the proxy relationships known to the proxy
        agent.  In particular, the SNMPv2 context ducksoup refers to a
        relationship that is satisfied when the SNMPv2 party zeppo
        communicates with the SNMPv2 party harpo and references the
        SNMPv2 context bigstore.
        In order to interrogate the proxied device associated with the
        party harpo, the management station groucho constructs a
        SNMPv2 GetNext request contained with a SnmpMgmtCom value
        which references the SNMPv2 context ducksoup, and transmits it
        to the party chico operating (see Table 11) at UDP port 161
        and IP address 1.2.3.5.  This request is authenticated using
        the private authentication key "0123456789ABCDEF".
        When that request is received by the party chico, the
        originator of the message is verified as being the party
        groucho by using local knowledge (see Table 13) of the private
        Galvin & McCloghrie                                  [Page 39]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        authentication key "0123456789ABCDEF".  Because party groucho
        is authorized to issue GetNext (as well as Get and GetBulk)
        requests with respect to party chico and the SNMPv2 context
        ducksoup by the relevant access control policy (Table 15), the
        request is accepted.  Because the local database of context
        information indicates that the SNMPv2 context ducksoup refers
        to a proxy relationship, the request is satisfied by its
        translation into a corresponding SNMPv2 GetNext request
        directed from party zeppo to party harpo referencing SNMPv2
        context bigstore.  This new communication is authenticated
        using the private authentication key "STUVWX0123456789" and
        transmitted to party harpo at the IP address 1.2.3.6.
        When this new request is received by the party harpo, the
        originator of the message is verified as being the party zeppo
        by using local knowledge of the private authentication key
        "STUVWX0123456789".  Because party zeppo is authorized to
        issue GetNext (as well as Get and GetBulk) requests with
        respect to party harpo and the SNMPv2 context bigstore by the
        relevant access control policy (Table 15), the request is
        accepted.  A SNMPv2 Response message representing the results
        of the query is then generated by party harpo to party zeppo
        referencing SNMPv2 context bigstore.  This response
        communication is authenticated as to origin and integrity
        using the private authentication key "MNOPQR0123456789" and
        transmitted to party zeppo at IP address 1.2.3.5 (the source
        address for the corresponding request).
        When this response is received by party zeppo, the originator
        of the message is verified as being the party harpo by using
        local knowledge (see Table 13) of the private authentication
        key "MNOPQR0123456789".  Because party harpo is authorized to
        issue Response communications with respect to party zeppo and
        SNMPv2 context bigstore by the relevant access control policy
        (Table 15), the response is accepted, and is used to construct
        a response to the original GetNext request, indicating a
        SNMPv2 context of ducksoup.  This response, from party chico
        to party groucho, is authenticated as to origin and integrity
        using the private authentication key "GHIJKL0123456789" and is
        transmitted to the party groucho at IP address 1.2.3.4 (the
        source address for the original request).
        When this response is received by the party groucho, the
        originator of the message is verified as being the party chico
        by using local knowledge (see Table 13) of the private
        Galvin & McCloghrie                                  [Page 40]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        authentication key "GHIJKL0123456789".  Because party chico is
        authorized to issue Response communications with respect to
        party groucho and SNMPv2 context ducksoup by the relevant
        access control policy (Table 15), the response is accepted,
        and the interrogation is complete.
        4.5.  Public Key Configuration
        This section presents an example configuration predicated upon
        a hypothetical security protocol.  This hypothetical protocol
        would be based on asymmetric (public key) cryptography as a
        means for providing data origin authentication (but not
        protection against disclosure).  This example illustrates the
        consistency of the administrative model with public key
        technology, and the extension of the example to support
        protection against disclosure should be apparent.
             Identity          ollie                stan
                               (agent)              (manager)
             Domain            snmpUDPDomain        snmpUDPDomain
             Address           1.2.3.4, 161         1.2.3.5, 2004
             Auth Prot         pkAuthProtocol       pkAuthProtocol
             Auth Priv Key     "0123456789ABCDEF"   ""
             Auth Pub Key      "0123456789abcdef"   "ghijkl0123456789"
             Auth Clock        0                    0
             Auth Lifetime     300                  300
             Priv Prot         noPriv               noPriv
             Priv Priv Key     ""                   ""
             Priv Pub Key      ""                   ""
               Table 16: Party Information for Public Key Agent
        The example configuration comprises a single SNMPv2 agent that
        interacts with a single SNMPv2 management station.  Tables 16
        and 17 present information about SNMPv2 parties that is by the
        agent and manager, respectively, while Table 5 presents
        information about the local access policy that is known to
        both manager and agent.
        Galvin & McCloghrie                                  [Page 41]
        RFC 1445       Administrative Model for SNMPv2      April 1993
             Identity          ollie                stan
                               (agent)              (manager)
             Domain            snmpUDPDomain        snmpUDPDomain
             Address           1.2.3.4, 161         1.2.3.5, 2004
             Auth Prot         pkAuthProtocol       pkAuthProtocol
             Auth Priv Key     ""                   "GHIJKL0123456789"
             Auth Pub Key      "0123456789abcdef"   "ghijkl0123456789"
             Auth Clock        0                    0
             Auth Lifetime     300                  300
             Priv Prot         noPriv               noPriv
             Priv Priv Key     ""                   ""
             Priv Pub Key      ""                   ""
        Table 17: Party Information for Public Key Management Station
        As represented in Table 16, the example agent party operates
        at UDP port 161 at IP address 1.2.3.4 using the party identity
        ollie; the example manager operates at UDP port 2004 at IP
        address 1.2.3.5 using the identity stan.  Both ollie and stan
        authenticate all messages that they generate as to origin and
        integrity by using the hypothetical SNMPv2 authentication
        protocol pkAuthProtocol and their distinct, private
        authentication keys.  Although these private authentication
        key values ("0123456789ABCDEF" and "GHIJKL0123456789") are
        presented here for expository purposes, knowledge of private
        keys is not normally afforded to human beings and is confined
        to those portions of the protocol implementation that require
        it.
        In most respects, the interaction between manager and agent in
        this configuration is almost identical to that in the example
        of the minimal, secure SNMPv2 agent described above.  The most
        significant difference is that neither SNMPv2 party in the
        public key configuration has knowledge of the private key by
        which the other party authenticates its transmissions.
        Instead, for each received authenticated SNMPv2 communication,
        the identity of the originator is verified by applying an
        asymmetric cryptographic algorithm to the received message
        together with the public authentication key for the
        originating party.  Thus, in this configuration, the agent
        knows the manager's public key ("ghijkl0123456789") but not
        its private key ("GHIJKL0123456789"); similarly, the manager
        knows the agent's public key ("0123456789abcdef") but not its
        Galvin & McCloghrie                                  [Page 42]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        private key ("0123456789ABCDEF").
        Galvin & McCloghrie                                  [Page 43]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        5.  Security Considerations
        In order to participate in the administrative model set forth
        in this memo, SNMPv2 implementations must support local, non-
        volatile storage of the local database of party information.
        Accordingly, every attempt has been made to minimize the
        amount of non-volatile storage required.
        Galvin & McCloghrie                                  [Page 44]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        6.  Acknowledgements
        This document is based, almost entirely, on RFC 1351.
        Galvin & McCloghrie                                  [Page 45]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        7.  References
        [1]  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.
        [2]  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S.,
             "Protocol Operations for version 2 of the Simple Network
             Management Protocol (SNMPv2)", RFC 1448, SNMP Research,
             Inc., Hughes LAN Systems, Dover Beach Consulting, Inc.,
             Carnegie Mellon University, April 1993.
        [3]  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S.,
             "Structure of Management Information for version 2 of the
             Simple Network Management Protocol (SNMPv2)", RFC 1442,
             SNMP Research, Inc., Hughes LAN Systems, Dover Beach
             Consulting, Inc., Carnegie Mellon University, April 1993.
        [4]  McCloghrie, K., and Galvin, J., "Party MIB for version 2
             of the Simple Network Management Protocol (SNMPv2)", RFC
             1447, Hughes LAN Systems, Trusted Information Systems,
             April 1993.
        [5]  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S.,
             "Transport Mappings for version 2 of the Simple Network
             Management Protocol (SNMPv2)", RFC 1449, SNMP Research,
             Inc., Hughes LAN Systems, Dover Beach Consulting, Inc.,
             Carnegie Mellon University, April 1993.
        [6]  Galvin, J., and McCloghrie, K., "Security Protocols for
             version 2 of the Simple Network Management Protocol
             (SNMPv2)", RFC 1446, Trusted Information Systems, Hughes
             LAN Systems, April 1993.
        [7]  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S.,
             "Management Information Base for version 2 of the Simple
             Network Management Protocol (SNMPv2)", RFC 1450, SNMP
             Research, Inc., Hughes LAN Systems, Dover Beach
             Consulting, Inc., Carnegie Mellon University, April 1993.
        Galvin & McCloghrie                                  [Page 46]
        RFC 1445       Administrative Model for SNMPv2      April 1993
        8.  Authors' Addresses
             James M. Galvin
             Trusted Information Systems, Inc.
             3060 Washington Road, Route 97
             Glenwood, MD 21738
             Phone:  +1 301 854-6889
             EMail:  galvin@tis.com
             Keith McCloghrie
             Hughes LAN Systems
             1225 Charleston Road
             Mountain View, CA  94043
             US
             Phone: +1 415 966 7934
             Email: kzm@hls.com
        Galvin & McCloghrie                                  [Page 47]
/data/webs/external/dokuwiki/data/pages/rfc/rfc1445.txt · Last modified: 1993/04/30 22:08 (external edit)