path: root/doc/rfc/rfc1445.txt

          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





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          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






































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          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).










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          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.


















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          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.





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          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





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               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.







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          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





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          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





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          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





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          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),







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          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].







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          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.

















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          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).























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          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





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               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





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               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].









































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          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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          (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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               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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          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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          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





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          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.





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          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.


























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               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











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          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





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          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





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          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.








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               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





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          private key ("0123456789ABCDEF").

















































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          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.











































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          6.  Acknowledgements

          This document is based, almost entirely, on RFC 1351.















































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          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.










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          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































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