rfc1445.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

          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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          RFC 1445       Administrative Model for SNMPv2      April 1993


          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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          RFC 1445       Administrative Model for SNMPv2      April 1993


          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