Abstract:
A method is provided for controlling a network element from a client at a remote work station connectable to the network, the network, element is registered for attributes to be tracked, and attributes associated with the network element are polled only if the client requests the monitoring of the network element.

Description:
A microfiche appendix is included in this application. 
     BACKGROUND OF THE INVENTION 
     This invention relates, generally, to a method for controlling a network element and, more particularly, to a method for remotely controlling the network by communications through the network. 
     Network management systems in which network elements, or management agents, are remotely controlled from a remote, management work station by means of communications between the management work station and the managed network elements sent through the network are known. Such known network management systems employ a special communication protocol for communications between the remote work station running a management program and an element management server that contains a management information base that defines the interface between the work station and the network elements. 
     Known systems such as (Hewlett Packard HP-OV NNM or DM, Sun Microsystems Solstice) present an interface where the client application must poll the network element when status is needed. In these systems, the polling may not be coordinated and is replicated for each client, if each client is interested in the same attributes. Also, each of the clients receive the full results for each polling cycle (even if there was no change from the last cycle), increasing the bandwidth used to communicate between the client application and the network element, as well as creating additional processing overhead due to the replicated polling at the network element. 
     SUMMARY OF THE INVENTION 
     A method is provided for controlling a network element from a remote work station connectable to the network. The method provides for registering the network element for attributes to be tracked, and polling for attributes associated with the network element only if the client requests the monitoring of the network element. Changes in attributes are reported when the client requests notification of changes in attributes. For attributes polled for a plurality of clients, changes in the attributes to one of the plurality of clients requesting notification of changes in the attributes are reported. 
     The method further provides for polling once for a plurality of clients that registers for the same attributes and reporting asynchronously changes in the attributes to a plurality of clients. 
     Another aspect of the invention provides for running an object oriented program at the remote work station to control an object associated with the controllable network element, translating interface operations generated by the work station during the running of the object oriented program to corresponding translated interface operations in an object oriented language associated with the object being controlled, and connecting the corresponding translated interface operations through the network to an object server to control the object associated with the network element in accordance with the translated interface operations. 
     These and other features and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing advantageous features will be described in detail and other advantageous features of the invention will be made apparent from the detailed description of the preferred embodiment of the invention that is given with reference to the several figures of the drawings, in which: 
     FIG. 1 is a functional block diagram of the preferred embodiment of a management system using the preferred network element control method of the present invention; 
     FIG. 2 is a functional block diagram of the preferred embodiment of the translating interface shown as a single functional block in FIG. 1; 
     FIG. 3 is a functional block diagram illustrating the interface with the controlled network element that is visible to object oriented client management application at the work station of FIG. 1; 
     FIG. 4 is a table of a plurality of service objects that interact with the client management application run at the work station of FIG. 1; 
     FIG. 5 is a table of a plurality of call back functions performed at the translating interface of FIG. 2; 
     FIG. 6 is a table of the different fundamental data types capable of being translated by the translating interface of FIG. 2 in accordance with the invention. 
     FIG. 7 is a block diagram showing the relationship between client application-specific service object, and the internal service representative of managed object instances; 
     FIG. 8 is a table summarizing filter criteria that is valid for each event category; and 
     FIG. 9 is a table defining specific exceptions with an EMAPI exception code containing one of the listed values. 
    
    
     DETAILED DESCRIPTION 
     This invention provides an application programming interface (API) and protocol that provides for efficient communication between a distributed client application and an element management server independent of the communication protocol to the network element. The Element Management Application Programming Interface (EMAPI) provides the following benefits over known management system. The invention has application in the management of a telecommunication network element. For more information regarding such a management of a telecommunication network element refer to commonly owned U.S. patent application Ser. No. 09/088,463, entitled “Method for Computer Internet Remote Management of a Telecommunication Network Element” by William E. Barker, Lisa M. Connelly, Marvin A. Eggert, Michael P. Foley, Kenneth R. Macfarlane, Philip M. Parsons, Girish Rai, Jerome E. Rog, and Kurt A. Vangsness, filed on May 31, 1998, now U.S. Pat. No. 6,363,481 the disclosure of which is hereby incorporated by reference. 
     Efficient use over low bandwidth connections. Client applications register for network element information they wish to track and after an initial set of data only receive incremental updates (deltas) when there are changes. 
     Centralized polling of attributes. Attributes are only polled if a client exists that has registered to monitor the attribute. If multiple clients register for the same attribute(s), the polling is not repeated for the clients-only a single polling cycle is performed. 
     The invention is used in an operations, administration and maintenance system  20  as shown in FIG.  1 . The system  20  includes a PC or workstation  22 , an element management server (EMS)  24 , an interface  26  in accordance with the invention, located between the workstation  22  and an object server  25 . An application processor  28  is connected to the element management server  24 . 
     The workstation  22  includes a web browser  30  which is the interface to the client and is a host for JAVA applets  32  and web browser HTML  35  which is a hypertext markup language. 
     The system  20  operates on a cluster computing environment, and leverages off-the-shelf technology to enable additional customers visible features, while extending to subsequent releases and other projects, with minimal increased cost. System  20  is provided through the web browser interface and a SNMP based element management platform. 
     A client executes application s via web pages at the workstation  22 . The client makes requests for various views of the network status by making selections through the web browser  30 . The web browser requests pages from the web server  50  which transmits HTML pages that contain instructions to load and run the appropriate JAVA applet  32 . Once the applet starts, it communicates with the object server  25  through the interface  26  to perform initialization and to request initial configuration and status information that is appropriate for the current requested view. The JAVA applet  32  then registers with the object server  25  for subsequent notifications of changes to configuration and status that it requires to keep the view up to date. The client may perform commands to request various maintenance operations on the network element(s)  38 . These commands are converted into appropriate requests through the interface  26  and perform operations on the object server  25 . The commands are then translated into SNMP and are transmitted to the network element(s)  38  through the SNMP library  33 . Acknowledgements and command responses from the network element(s)  38  are transmitted through the SNMP library  33 , are converted to events by the object server  25  and transmitted to origination JAVA applet  32  through the use of callbacks defined by the interface  26 . 
     In one embodiment of the invention, as shown in FIG. 3, client applications in JAVA applets  32  include an active alarm list browser, a system alarm survey and a network element detailed status display. Client applications communication with the web server  50  via the interface  26  in accordance with the invention, to the element manager through a distributed object request architecture such as COBRA. The interface  26  provides a constant interface to all managed objects in the network, and hides the implementation details associated with the element manager platform. 
     The interface  26  (EMAPI) is the definition of objects, attributes and operations that comprise the protocol used between client applications and the server to manage network elements. The EMAPI uses the industry standard CORBA to provide distribution of the objects and their operations and to allow for the implementation of the client and server to be in different programming languages and on different computer architectures. 
     The client interface to the server and the managed object attributes is described in the interface  26  and managed object notation provides a consistent model of all managed objects in the network, hiding the implementation details associated with the element manager platform from client applications, thus clients do not need to know the underlying protocol to the network elements. Managed objects specific logic is encapsulated within the managed object instead of scattered throughout various applications thus simplifying client application development. 
     Each physical, selected non-physical and logical component in the network is modeled as a managed object, which the Server makes visible to distributed client applications through the facilities of the Common Object Request Broker Architecture (CORBA). EM clients need only be concerned about the attributes and operations defined for each application managed object, and not the details of network-level protocol and the server infrastructure required to support object services. 
     EMAPI Object Definition 
     FIG. 3 illustrates all of the interfaces visible to client applications which does not depict process or processor boundaries, which are made transparent by the client and server object request brokers (ORBs). Application services are provided through object interfaces formally defined in the CORBA Interface Definition Language (IDL). The IDL specification of the interfaces described in this document is provided in the Appendix A. 
     The service objects resident on the server with which client applications will interact are shown in FIG.  4 . 
     Client applications which register for real-time status updates or notification of events, alarms or configuration changes must provide a reference to a local callback object which the server will use to propagate information asynchronously. The callback interfaces defined in the interface  26  are shown in FIG.  5 . Classes which implement these interfaces must be defined and instantiated in client code. 
     Data Representation 
     There are several fundamental data types defined in the interface  26 , which fall into one of the two categories shown in FIG.  6 . 
     Session Management 
     Each EM client session is logically associated with a unique login-host combination. Multiple client applications may be associated with the same session, though only one need be registered for the session to be considered active. Session and application identifiers are assigned by the User Session Manager to track resources used by the client, and in future releases, to correlate client access permissions with operation requests. Applications may or may not cross process boundaries. For example, multiple instances of the EMS Command Line Interface (CLI) application registered with the same login and host name will share the same session id, but each process is associated with a different application id. In the EMS Graphical User Interface, all application frames execute in the same process space (albeit in different Threads), yet each frame is associated with a distinct application id. Note that each client application is required to independently register a periodic heartbeat to validate for the Server that its associated resources are still needed. 
     The UserSession service object provides the following interfaces: 
     startApplication 
     This method must be invoked for each client application initialization. 
     stopApplication 
     A client invokes this method to notify the Server that a target application is terminating, and its associated resources should be released. 
     stop 
     This method may be used to deregister all applications associated with the same session identifier. 
     heartbeat 
     This method must be invoked at least every UserSession::HeartbeatPeriod seconds to avoid a timeout condition which, when detected by a Server audit, will result in the release of all resources utilized by an application. 
     Refer to the description of interface UserSession in the attachment for additional details. 
     Managed Objects 
     A managed object (MO) is an abstract representation of a physical or logical resource which may be managed by the EMS, such as a network element, maintenance unit or data link. The EM Server will implement one application-specific service object for each type of physical or logical resource to be managed. Each of these service objects defines a set of attributes which identify managed object properties, as well as the operations which may be performed on a specified managed object instance. (The decision to provide access to instance information through a single “service object” stems from the fact that current ORB implementations become unstable when managing very large numbers of remote references.) FIG. 7 depicts the relationship between Client, application-specific service object, and the internal Server representation of managed object instances. 
     Each managed object service class is uniquely identified by a ClassCode. Each managed object instance is uniquely identified by an InstId. Any object instance in the system may be uniquely referenced by a managed object identifier (Oid), which is the combination of ClassCode and InstId. 
     Managed object status information is reported by a service object as a sequence of attribute code-value pairs. Each attribute value is defined as a union of all of the interface  26  fundamental data types described in FIG.  6 . 
     Configuration information is reported as a sequence of ConfigData structures, which are defined to contain: 
     network element instance id 
     managed object instance id 
     a managed object key list reported as a sequence of attribute-value pairs—when length is greater than 0, the key list specifies the associated logical identifiers (LogicalIds) 
     Each managed object service class must implement the MO interface, which defines the following configuration and status services: 
     viewConfig 
     A client uses this method to obtain the current EMS view of the managed object configuration for a specified network element instance. Note that the reserved instance identifier AnyInstance may be used to obtain configuration information for all network elements. 
     notifyConfig 
     A client may also register for an initial view of managed object configuration information and notification of subsequent changes via callback. The initial view is returned with a notification type CONFIG_NIT. Subsequent changes are reported with type CONFIG_CREATE or CONFIG_DELETE. 
     cancelNotify 
     A client uses this method to cancel registration for managed object configuration notifications associated with a specified client application. 
     getPersistent 
     A client may use this method to retrieve the set of attribute codes (SeqAttrCode) identifying all “persistent” data maintained by this service object. Values for persistent attributes of each managed object instance are stored and kept current irrespective of any client requests. 
     getAttrSpec 
     A client may use this method to retrieve the name and codes of all attributes defined for a target service class (currently used for debugging only). 
     getKeySpec 
     A client may use this method to retrieve the set of codes (SeqAttrCode) identifying the attribute(s) which represents the logical identifier(s) of any instance of the target class. 
     viewStatus 
     A client may invoke this method to obtain the EMS view of the current values for a specified set of persistent attributes for a specified managed object instance. 
     getStatus 
     A client may use this method to register for a snapshot of current status information. This interface differs from the previous one in that the requested attribute list may specify any managed object attribute codes—not just those associated with persistent data, and the information is returned via client status callback (StatusCB). 
     startUpdate 
     A client may also register for an initial view and notification of any updates to a list of selected attributes for a specified managed object instance. In this case, an initial view is reported via client callback with a notification type STATUS_INIT. Subsequent changes are reported with type STATUS_CHANGE. Note that managed object instance deletions are reported only through configuration change notification to avoid a potential flurry of client status callbacks when a network element is unequipped. 
     stopUpdate 
     A client uses this method to cancel registration for managed object status updates associated with a specified client application. 
     getInst 
     A client may use this method to obtain a managed object instance identifier for a specified network element instance id and managed object key list. 
     Note that each method requires a client session application identifier (SessionAppId) to validate user access. In the case of configuration or status change notification registration, this identifier is also used to keep track of the additional server resources utilized while the client application is active. 
     Refer to the description of interfaces MO, ConfigCB &amp; StatusCB in the attachment for additional details. 
     Network Element Level Managed Objects 
     Each network-element level managed object must also implement the NEMO interface which defines additional network-element level configuration services: 
     viewNEconfig 
     A client may invoke this method to obtain the current EMS view of the network element configuration. 
     notifyNEconfig 
     A client may also register for an initial view of network element-level managed object configuration information and notification of subsequent changes via callback. The initial view is returned with a notification type CONFIG_INIT. Subsequent changes are reported with type CONFIG_CREATE or CONFIG_DELETE. 
     cancelNEnotify 
     A client application should use this method to cancel registration for network element managed object configuration updates. 
     getNEinst 
     A client may invoke this method to retrieve the NEMO instance identifier of the network element associated with a specified logical id. 
     getLogicalId 
     A client may invoke this method to retrieve the logical identifier of the network element associated with a specified NEMO instance id. 
     getContainment 
     A client may invoke this method to obtain a sequence of containment information for the target NEMO, where each entry in the sequence contains the name, class code and CORBA reference to a contained service class object. 
     Note that each method requires a client session application identifier to validate user access. In the case of configuration change notification registration, this identifier is also used to keep track of the additional server resources utilized while the client application is active. 
     Refer to the description of interfaces NEMO &amp; NEconfigCB in the attachment for additional details. 
     Descriptive Entity Objects 
     Application objects of this type are defined to provide type and attribute information for abstract entities, such as data communicated between the EMS and network elements which are not part of a managed object description (e.g. SNMP trap definitions and command groups). Descriptive entity objects provide no implementation—they are defined in application-specific IDL and known by client applications at compile time. 
     Event Distributor 
     An event is reported as a combination of the following: 
     1. A header, which contains information of most general interest: 
     Time of the event 
     Event category defined to be one of the following: 
     Alarm Set 
     Alarm Clear 
     Command Acknowledgment 
     Command Response 
     Configuration Change 
     Informational Message 
     Initialization 
     State Change 
     Network element object identifier 
     Network element alarm level—meaningful only for alarm set 
     Maintenance unit object identifier (if applicable) 
     Maintenance unit alarm level—meaningful only for alarm set 
     A command identifier (CmdId) defined as a user session id &amp; command sequence number—meaningful only for command acknowledgment &amp; response 
     2. Event data defined as a sequence of structures which contain: 
     A ClassCode of a managed object, network element or descriptive entity 
     A sequence of attribute code-value pairs 
     Client applications may request a copy of the event stream, as processed by the event distributor, filtered on information specified in the event header. Filter wildcards are implemented with “out-of-band” values: 
     Any Category 
     Any Class 
     Any Instance 
     Any Alarm 
     Any Cmd 
     The table in FIG. 8 summarizes which filter criteria are valid for each event category: 
     The event distributor processes filters by examining the specified category and AND&#39;ing together valid criteria. Clients may simulate OR operations by registering multiple filters. 
     The EvtDist service object implements the following client interfaces: 
     RegisterFilter 
     A client uses this method to register an event filter. A filter identifier is returned. 
     CancelFilter 
     A client invokes this method to remove a specified event filter, using the filter id returned from the associated registration. 
     Note that each method requires a client session application identifier to validate user access. 
     Refer to the description of interfaces EvtDist &amp; EventCB in the attachment for additional details. 
     Alarm Manager 
     Alarm information is reported as a sequence of AlarmData structures which contain: 
     The ClassCode of a managed object which defines a network-element specific alarm record. 
     Note that in the first release of the EMS, only one network element active alarm table is defined (ApActiveAlarms). 
     A sequence of alarm records, each of which contains an alarm instance identifier and sequence of attribute code-value pairs. 
     Client applications may request a copy of all active alarms filtered on any combination of the following: 
     Network element 
     Maintenance unit 
     Alarm level 
     Similar to the interfaces provided by the event distributor, out-of-band values may be used to represent wildcards. 
     Since managed object instance information may not be available at the time an alarm is reported, the actual alarm filter criteria are specified in terms of logical identifiers. Logical ids are integer values which represent the logical numbers of devices and interfaces (e.g. AP  4 ). The correlation between logical ids and managed object instance identifiers is provided in the configuration information made available by each managed object service object, and through the utility method getInst. Refer to the section on Managed Objects for additional details. 
     The following AlarmManager client interfaces are written specifically for the Active Alarm List application: 
     RequestAlarms 
     A client invokes this method to register a filter for active alarms. 
     ChangeFilter 
     A client may invoke this method to change filter criteria. 
     RefreshAlarms 
     A client may invoke this method to refresh the active alarm list. 
     CancelAlarms 
     A client should invoke this method to de-register a filter. 
     All operations except for de-registration return all active alarms filtered on the specified criteria. Also, each of these methods requires a valid client session application identifier to validate user access, and to keep track of the additional server resources which may be utilized while each client is active. 
     The following AlarmManager interface may be used by any client application (e.g. CLI): 
     opAlarm 
     Through client implementations of event callbacks used to process command acknowledgements and responses (the same EventCB reference may be used in both cases), this method returns either a list of all active alarms in the system or just those associated with a target network element. 
     Refer to the description of interfaces AlarmManager, AlarmCB &amp; EventCB in the attachment for additional details. 
     Exceptions 
     Exceptions are used for consistent and structured error handling in both the EM Server and Client. 
     The CORBA specification defines many system exceptions: 
     BAD_PARAM 
     INV_OBJREF 
     NO_PERMISSION 
     BAD_OPERATION 
     OBJ_ADAPTER 
     ♦♦♦ 
     Refer to “The Common Object Request Broker: Architecture and Specification” for an exhaustive list of mnemonics and the associated exception descriptions. 
     Vendor-specific object request broker exceptions are also defined (using the Minor identifier of the SystemException): 
     NO_IT_DAEMON_PORT 
     LICENCE_EXPIRED 
     ♦♦♦ 
     Currently, the EMS uses Iona&#39;s Orbix product. Refer to the “Orbix 2.3c Reference Guide” for an exhaustive list of mnemonics and the associated exception descriptions. 
     In most cases, exceptions will be treated as fatal errors by Client code resulting in application termination. 
     An interface  26 -specific exception is also defined as an Exception Code containing one of the following values shown in FIG.  9 . 
     GLOSSARY 
     Alarm The description of an alarmed notification. 
     Attribute A property of a managed object (e.g. alarm state). 
     Attribute Code An integer value which uniquely identifies an attribute of a given managed object. 
     Class Code An integer value which uniquely identifies a managed object class. 
     Configuration Generic term which has one of two meanings depending on its context: 
     Information With respect to a managed object class, this term applies to the identification of all instances of the class, either for a specific network element or for all network elements in the system. With respect to a managed object instance, this term may apply to one or more attributes which are associated with database values, such as the primary/alternate role of a duplex component. 
     CORBA Common Object Request Broker Architecture 
     EMAPI Element Management Application Programming Interface 
     EMS Element Management System 
     Event The description of a spontaneous occurrence, such as alarm notification, command acknowledgment or configuration change. 
     Instance Identifier An integer value which uniquely identifies an instance of a given managed object. 
     Interface Operation Generic term for distributed service request. The target method may be defined in the Element Management Application Programming Interface (e.g. status registration) or in an application-specific derivation of a managed object (e.g. command execution). 
     Logical Identifier An integer value which represents the logical number of a device or interface (e.g. AP  4 ). Note that there is no direct correlation between a logical id and instance id. 
     Managed Object An abstract representation of a physical or logical resource which may be managed by the EMS (e.g. network element, maintenance unit, data link). 
     ORB Object Request Broker 
     Object Identifier The combination of managed object class code and instance identifier which uniquely identifies any managed object instance in the system. 
     Persistent Attribute Information stored and kept current irrespective of any client request (e.g. maintenance state). 
     Service Object Any EM Server object which provides services to client applications. 
     Session Each client must establish a session at initialization—for which a unique session identifier is assigned—that will be used to validate access permissions, to correlate client requests and to keep track of Server resources utilized in behalf of any applications associated with the session. 
     Status Information Current attribute values for a managed object instance.