📄 rfc1095.txt
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The Association Control Service Element (ACSE) is used to establish and release associations between application entities. Before any management operations can be performed using CMIP, it is necessary for the two application entities involved to form an association. Either the manager or the agent can initiate association establishment. ACSE allows the manager and agent to exchange application entity titles for the purpose of identification and application context names to establish an application context. As stated above, an application context defines what service elements (for instance, ROSE and CMISE) may be used over the association. After the association is established, ACSE is not used again until the association is released by the manager or agent.3.3.2. ROSE The Remote Operation Service Element (ROSE) is the ISO equivalent of remote procedure call. ROSE allows the invocation of an operation to be performed on a remote system. The Remote Operation protocol contains an invoke identifier for correlating requests and responses, an operation code, and an argument field for parameters specific to the operation. ROSE can only be invoked once an application association has been established. CMIP uses the transaction-oriented services provided by ROSE for all its requests and responses. CMIP also uses the error response facilities provided by ROSE.3.3.3. CMISE The Common Management Information Service Element (CMISE) is the service element that provides the basic management services. TheWarrier & Besaw [Page 10]RFC 1095 CMOT April 1989 CMISE is a user of both ROSE and ACSE. The CMISE provides both confirmed and unconfirmed services for reporting events and retrieving and manipulating management data. These services are used by manager and agent application entities to exchange management information. Table 1 provides a list of the CMISE services. In addition, the CMISE also provides the ability to issue a series of (multiple) linked replies in response to a single request. +-----------------+-------------------------+ | Service | Type | +-----------------+-------------------------+ | M-INITIALISE | confirmed | | M-TERMINATE | confirmed | | M-ABORT | non-confirmed | | M-EVENT-REPORT | confirmed/non-confirmed | | M-GET | confirmed | | M-SET | confirmed/non-confirmed | | M-ACTION | confirmed/non-confirmed | | M-CREATE | confirmed | | M-DELETE | confirmed | +-----------------+-------------------------+ Table 1. CMISE Service Summary CMIS services can be divided into two main classes: management association services and information transfer services. Furthermore, there are two types of information transfer services: management notification services and management operation services. In addition to the other CMIS services, the CMISE provides facilities that enable multiple responses to confirmed operations to be linked to the operation by the use of a linked identification parameter.3.3.3.1. Management Association Services CMIS provides services for the establishment and release of application associations. These services control the establishment and normal and abnormal release of a management association. These services are simply pass-throughs to ACSE. The M-INITIALISE service is invoked by a CMISE-service-user to establish an association with a remote CMISE-service-user for the purpose of exchanging management information. A reply is expected. (A CMISE-service-user is that part of an application process that makes use of the CMISE.) The M-TERMINATE service is invoked by a CMISE-service-user to releaseWarrier & Besaw [Page 11]RFC 1095 CMOT April 1989 an association with a remote CMISE-service-user in an orderly manner. A reply is expected. The M-ABORT service is invoked by a CMISE-service-user or a CMISE- service-provider to release an association with a remote CMISE- service-user in an abrupt manner.3.3.3.2. Management Notification Services The definition of notification and the consequent behavior of the communicating entities is dependent upon the specification of the managed object which generated the notification and is outside the scope of CMIS. CMIS provides the following service to convey management information applicable to notifications. The M-EVENT-REPORT service is invoked by a CMISE-service-user to report an event about a managed object to a remote CMISE-service- user. The service may be requested in a confirmed or a non-confirmed mode. In the confirmed mode, a reply is expected.3.3.3.3. Management Operation Services The definition of the operation and the consequent behavior of the communicating entities is dependent upon the specification of the managed object at which the operation is directed and is outside the scope of CMIS. However, certain operations are used frequently within the scope of management and CMIS provides the following definitions of the common services that may be used to convey management information applicable to the operations. The M-GET service is invoked by a CMISE-service-user to request the retrieval of management information from a remote CMISE-service-user. The service may only be requested in a confirmed mode. A reply is expected. The M-SET service is invoked by a CMISE-service-user to request the modification of management information by a remote CMISE-service- user. The service may be requested in a confirmed or a non-confirmed mode. In the confirmed mode, a reply is expected. The M-ACTION service is invoked by a CMISE-service-user to request a remote CMISE-service-user to perform an action. The service may be requested in a confirmed or a non-confirmed mode. In the confirmed mode, a reply is expected. The M-CREATE service is invoked by a CMISE-service-user to request a remote CMISE-service-user to create another instance of a managed object. The service may only be requested in a confirmed mode. AWarrier & Besaw [Page 12]RFC 1095 CMOT April 1989 reply is expected. The M-DELETE service is invoked by a CMISE-service-user to request a remote CMISE-service-user to delete an instance of a managed object. The service may only be requested in a confirmed mode. A reply is expected.4. The CMOT Architecture The CMOT (CMIP Over TCP/IP) architecture is based on the OSI management framework [15] and the models, services, and protocols developed by ISO for network management. The CMOT architecture demonstrates how the OSI management framework can be applied to a TCP/IP environment and used to manage objects in a TCP/IP network. The use of ISO protocols for the management of widely deployed TCP/IP networks will facilitate the ultimate migration from TCP/IP to ISO protocols. The concept of proxy management is introduced as a useful extension to the architecture. Proxy management provides the ability to manage network elements that either are not addressable by means of an Internet address or use a network management protocol other than CMIP. The CMOT architecture specifies all the essential components of a network management architecture. The OSI management framework and models are used as the foundation for network management. A protocol-dependent interpretation of the Internet SMI [2] is used for defining management information. The Internet MIB [3] provides an initial list of managed objects. Finally, a means is defined for using ISO management services and protocols on top of TCP/IP transport protocols. Management applications themselves are not included within the scope of the CMOT architecture. What is currently standardized in this architecture is the minimum required for building an interoperable multivendor network management system. Applications are explicitly left as a competitive issue for network developers and providers.4.1. Management Models The following sections indicate how the CMOT architecture applies the OSI managements models and point out any limitations the CMOT architecture has as it is currently defined in this memo.4.1.1. The Organizational Model It is beyond the scope of this memo to define the relations and interactions between different management domains. The current CMOT architecture concerns itself only with the operations and characteristics of a single domain of management. The extension ofWarrier & Besaw [Page 13]RFC 1095 CMOT April 1989 the mechanisms defined here to include multiple domains is left for further study.4.1.2. The Functional Model The CMOT architecture provides the foundation for carrying out management in the five functional areas (fault, configuration, performance, accounting, and security), but does not address specifically how any of these types of management are accomplished. It is anticipated that most functional requirements can be satisfied by CMIS. The greatest impact of the functional requirements in the various areas will likely be on the definition of managed objects.4.1.3. The Information Model There are two different SMI specifications that are important to the CMOT architecture. The first is the SMI currently being defined by ISO [19]. This SMI is important to the CMOT approach because the ISO management protocol CMIP has been designed with the ISO model of management information in mind. The second SMI of importance is the that defined by the IETF MIB working group for use in defining the Internet MIB [3]. This Internet SMI, which is loosely based on a simplified version of the ISO SMI, is important because the managed objects defined for TCP/IP networks to be used by CMOT are defined in terms of it. Thus, in order to make the CMOT architecture complete, it will be necessary to show how the Internet SMI maps into CMIP in such a way as to enable it to convey the management information defined in the Internet MIB. This is done in the section devoted to management information (section 5).4.2. Protocol Architecture The objective of the CMOT protocol architecture is to map the OSI management protocol architecture into the TCP/IP environment. The model presented here follows the OSI model at the application layer, while using Internet protocols at the transport layer. The ISO application protocols used for network management are ACSE, ROSE, and CMIP. Instead of implementing these protocols on top of the ISO presentation, session, and transport layer protocols, the protocol data units (PDUs) for ACSE, ROSE, and CMIP are carried using the Internet transport protocols UDP [20] and TCP [21]. This is made possible by means of the lightweight presentation protocol defined in RFC 1085 [13] that maps ROSE and ACSE onto TCP/UDP/IP. The use of Internet transport protocols is transparent to network management applications, since they are presented with real ISO services.Warrier & Besaw [Page 14]RFC 1095 CMOT April 19894.2.1. The Lightweight Presentation Layer
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