rfc2571.txt

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3.1.1.1.  snmpEngineID

   Within an administrative domain, an snmpEngineID is the unique and
   unambiguous identifier of an SNMP engine. Since there is a one-to-one
   association between SNMP engines and SNMP entities, it also uniquely
   and unambiguously identifies the SNMP entity within that
   administrative domain.  Note that it is possible for SNMP entities in
   different administrative domains to have the same value for
   snmpEngineID.  Federation of administrative domains may necessitate
   assignment of new values.

3.1.1.2.  Dispatcher

   There is only one Dispatcher in an SNMP engine. It allows for
   concurrent support of multiple versions of SNMP messages in the SNMP
   engine. It does so by:

      -  sending and receiving SNMP messages to/from the network,

      -  determining the version of an SNMP message and interacting with
         the corresponding Message Processing Model,

      -  providing an abstract interface to SNMP applications for
         delivery of a PDU to an application.

      -  providing an abstract interface for SNMP applications that
         allows them to send a PDU to a remote SNMP entity.







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RFC 2571           Architecture for SNMP Frameworks             April 1999


3.1.1.3.  Message Processing Subsystem

   The Message Processing Subsystem is responsible for preparing
   messages for sending, and extracting data from received messages.

   The Message Processing Subsystem potentially contains multiple
   Message Processing Models as shown in the next figure.

   * One or more Message Processing Models may be present.

   +------------------------------------------------------------------+
   |                                                                  |
   |  Message Processing Subsystem                                    |
   |                                                                  |
   |  +------------+  +------------+  +------------+  +------------+  |
   |  |          * |  |          * |  |          * |  |          * |  |
   |  | SNMPv3     |  | SNMPv1     |  | SNMPv2c    |  | Other      |  |
   |  | Message    |  | Message    |  | Message    |  | Message    |  |
   |  | Processing |  | Processing |  | Processing |  | Processing |  |
   |  | Model      |  | Model      |  | Model      |  | Model      |  |
   |  |            |  |            |  |            |  |            |  |
   |  +------------+  +------------+  +------------+  +------------+  |
   |                                                                  |
   +------------------------------------------------------------------+

3.1.1.3.1.  Message Processing Model

   Each Message Processing Model defines the format of a particular
   version of an SNMP message and coordinates the preparation and
   extraction of each such version-specific message format.

3.1.1.4.  Security Subsystem

   The Security Subsystem provides security services such as the
   authentication and privacy of messages and potentially contains
   multiple Security Models as shown in the following figure















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RFC 2571           Architecture for SNMP Frameworks             April 1999


   * One or more Security Models may be present.

   +------------------------------------------------------------------+
   |                                                                  |
   |  Security Subsystem                                              |
   |                                                                  |
   |  +----------------+  +-----------------+  +-------------------+  |
   |  |              * |  |               * |  |                 * |  |
   |  | User-Based     |  | Other           |  | Other             |  |
   |  | Security       |  | Security        |  | Security          |  |
   |  | Model          |  | Model           |  | Model             |  |
   |  |                |  |                 |  |                   |  |
   |  +----------------+  +-----------------+  +-------------------+  |
   |                                                                  |
   +------------------------------------------------------------------+

3.1.1.4.1.  Security Model

   A Security Model specifies the threats against which it protects, the
   goals of its services, and the security protocols used to provide
   security services such as authentication and privacy.

3.1.1.4.2.  Security Protocol

   A Security Protocol specifies the mechanisms, procedures, and MIB
   objects used to provide a security service such as authentication or
   privacy.

3.1.2.  Access Control Subsystem

   The Access Control Subsystem provides authorization services by means
   of one or more (*) Access Control Models.

   +------------------------------------------------------------------+
   |                                                                  |
   |  Access Control Subsystem                                        |
   |                                                                  |
   |  +---------------+   +-----------------+   +------------------+  |
   |  |             * |   |               * |   |                * |  |
   |  | View-Based    |   | Other           |   | Other            |  |
   |  | Access        |   | Access          |   | Access           |  |
   |  | Control       |   | Control         |   | Control          |  |
   |  | Model         |   | Model           |   | Model            |  |
   |  |               |   |                 |   |                  |  |
   |  +---------------+   +-----------------+   +------------------+  |
   |                                                                  |
   +------------------------------------------------------------------+




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RFC 2571           Architecture for SNMP Frameworks             April 1999


3.1.2.1.  Access Control Model

   An Access Control Model defines a particular access decision function
   in order to support decisions regarding access rights.

3.1.3.  Applications

   There are several types of applications, including:

      -  command generators, which monitor and manipulate management
         data,

      -  command responders, which provide access to management data,

      -  notification originators, which initiate asynchronous messages,

      -  notification receivers, which process asynchronous messages,
         and

      -  proxy forwarders, which forward messages between entities.

   These applications make use of the services provided by the SNMP
   engine.

3.1.3.1.  SNMP Manager

   An SNMP entity containing one or more command generator and/or
   notification receiver applications (along with their associated SNMP
   engine) has traditionally been called an SNMP manager.






















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RFC 2571           Architecture for SNMP Frameworks             April 1999


   * One or more models may be present.

                       (traditional SNMP manager)
   +-------------------------------------------------------------------+
   | +--------------+  +--------------+  +--------------+  SNMP entity |
   | | NOTIFICATION |  | NOTIFICATION |  |   COMMAND    |              |
   | |  ORIGINATOR  |  |   RECEIVER   |  |  GENERATOR   |              |
   | | applications |  | applications |  | applications |              |
   | +--------------+  +--------------+  +--------------+              |
   |         ^                ^                 ^                      |
   |         |                |                 |                      |
   |         v                v                 v                      |
   |         +-------+--------+-----------------+                      |
   |                 ^                                                 |
   |                 |     +---------------------+  +----------------+ |
   |                 |     | Message Processing  |  | Security       | |
   | Dispatcher      v     | Subsystem           |  | Subsystem      | |
   | +-------------------+ |     +------------+  |  |                | |
   | | PDU Dispatcher    | |  +->| v1MP     * |<--->| +------------+ | |
   | |                   | |  |  +------------+  |  | | Other      | | |
   | |                   | |  |  +------------+  |  | | Security   | | |
   | |                   | |  +->| v2cMP    * |<--->| | Model      | | |
   | | Message           | |  |  +------------+  |  | +------------+ | |
   | | Dispatcher  <--------->+                  |  |                | |
   | |                   | |  |  +------------+  |  | +------------+ | |
   | |                   | |  +->| v3MP     * |<--->| | User-based | | |
   | | Transport         | |  |  +------------+  |  | | Security   | | |
   | | Mapping           | |  |  +------------+  |  | | Model      | | |
   | | (e.g RFC1906)     | |  +->| otherMP  * |<--->| +------------+ | |
   | +-------------------+ |     +------------+  |  |                | |
   |          ^            +---------------------+  +----------------+ |
   |          |                                                        |
   |          v                                                        |
   +-------------------------------------------------------------------+
   +-----+ +-----+       +-------+
   | UDP | | IPX | . . . | other |
   +-----+ +-----+       +-------+
      ^       ^              ^
      |       |              |
      v       v              v
   +------------------------------+
   |           Network            |
   +------------------------------+








SNMPv3 Working Group        Standards Track                    [Page 21]

RFC 2571           Architecture for SNMP Frameworks             April 1999


3.1.3.2.  SNMP Agent

   An SNMP entity containing one or more command responder and/or
   notification originator applications (along with their associated
   SNMP engine) has traditionally been called an SNMP agent.
   +------------------------------+
   |           Network            |
   +------------------------------+
      ^       ^              ^
      |       |              |
      v       v              v
   +-----+ +-----+       +-------+
   | UDP | | IPX | . . . | other |
   +-----+ +-----+       +-------+              (traditional SNMP agent)
   +-------------------------------------------------------------------+
   |              ^                                                    |
   |              |        +---------------------+  +----------------+ |
   |              |        | Message Processing  |  | Security       | |
   | Dispatcher   v        | Subsystem           |  | Subsystem      | |
   | +-------------------+ |     +------------+  |  |                | |
   | | Transport         | |  +->| v1MP     * |<--->| +------------+ | |
   | | Mapping           | |  |  +------------+  |  | | Other      | | |
   | | (e.g. RFC1906)    | |  |  +------------+  |  | | Security   | | |
   | |                   | |  +->| v2cMP    * |<--->| | Model      | | |
   | | Message           | |  |  +------------+  |  | +------------+ | |
   | | Dispatcher  <--------->|  +------------+  |  | +------------+ | |
   | |                   | |  +->| v3MP     * |<--->| | User-based | | |
   | |                   | |  |  +------------+  |  | | Security   | | |
   | | PDU Dispatcher    | |  |  +------------+  |  | | Model      | | |
   | +-------------------+ |  +->| otherMP  * |<--->| +------------+ | |
   |              ^        |     +------------+  |  |                | |
   |              |        +---------------------+  +----------------+ |
   |              v                                                    |
   |      +-------+-------------------------+---------------+          |
   |      ^                                 ^               ^          |
   |      |                                 |               |          |
   |      v                                 v               v          |
   | +-------------+   +---------+   +--------------+  +-------------+ |
   | |   COMMAND   |   | ACCESS  |   | NOTIFICATION |  |    PROXY  * | |
   | |  RESPONDER  |<->| CONTROL |<->|  ORIGINATOR  |  |  FORWARDER  | |
   | | application |   |         |   | applications |  | application | |
   | +-------------+   +---------+   +--------------+  +-------------+ |