A method that uses a SNMP (Simple Network Management Protocol)/MIB (Management Information Base) is known as a method of managing various devices (referred to as “network devices” below) connected on a network. (With regard to the details of SNMP/MIB, see “Introduction to TCP/IP Network Management; Aiming at Practical Management”, by M. T. Rose, translated by Takeshi Nishida, published by Toppan Printing Co., Ltd., Aug. 20, 1992, First Edition.)
In accordance with SNMP network management techniques, a network management system includes at least one network management station (NMS), several managed nodes each of which includes an agent, and a network management protocol used in order that a network management station or agent may exchange management information. Using network management software at a network management station, a user can acquire data related to a management target via the network and can change the data by communicating with agent software at the managed node.
A method using FTP (File Transfer Protocol) is available as a method of uploading or downloading a large quantity of data between terminals on the network. FTP is defined by RFC (Request for Comments) 959 as a standard for performing file transfer. Specifically, according to RFC 959, the FTP communication model, data type, file structure, transfer mode and FTP commands, etc., are defined, and file transfer is carried out by establishing two sessions, namely a control session for transferring a control command and a data session for transferring data, between clients and a server.
In general, if status-change information is actively reported from a management target such as a printer, TRAP-PDU is used according to the SNMP protocol. (For the details of the TRAP-PDU structure, see Marshall T. Rose, “This Simple Book”, Prentice-Hall, 1991.)
In accordance with the above, TRAP-PDU is employed in a case where status-change information relating to errors such as paper jamming is reported from, e.g., a printer. That is, in a case where an error has occurred in a printer, the printer transmits error information to the network management station by TRAP-PDU. The network management station that has received the error information displays the event, such as occurrence of the error, on a display using characters or figures, thereby making it possible to notify the user of the error information received.
The protocol used when the status of a printer or the like is monitored by such event notification is not limited to the above-mentioned SNMP protocol. For example, with the SNMP protocol, a packet can be received via a specific port by network management software in order to receive TRAP-PDU. There is also a protocol through which any port can be used at receipt of an event by registering event reception ports with the printer.
As mentioned above, a method using FTP (File Transfer Protocol) is available as a method of uploading or downloading a large quantity of data between terminals on the network. FTP is defined by RFC (Request for Comments) 959 as a standard for performing file transfer. Specifically, according to RFC 959, the FTP communication model, data type, file structure, transfer mode and FTP commands, etc., are defined, and file transfer is carried out by establishing two sessions, namely a control session for transferring a control command and a data session for transferring data, between a client and server.
By way of example, FTP is used also in a case where a large quantity of data is sent and received between a network device management system such as an FTP client and a network device such as an FTP server. In this case, the network device management system uses FTP to update or download a large quantity of data, with respect to the network device to be managed, and can acquire resources within the network device or change these resources. Types of resources are font data, calibration data and log information, etc.
In a case where software (network management software) for performing the above-described network device management is used in a decentralized environment, the general practice is to adopt a system configuration that is based upon a client/server system that employs a server application having a network device management function and a client application launched at each terminal.
For example, RFC 1057 RPC (Remote Procedure Call) has been defined as a standard in a case where process-to-process communication is performed between different terminals using a client application and server application. With RPC, a function group that provides a network service is prepared on the server side, and functions provided by the server are called by a client process at a separate terminal on the network in a manner similar to the functions within the local machine.
The flow of process-to-process communication in RPC is as follows: First, the client calls the RPC function, which has been prepared at the server, as a service request directed to the server. At this time, a data packet in which the function calling information has been stored is sent from the client to the server and execution of the client program is suspended. Upon receiving the data packet, the server dispatches the called function, extracts the argument of the function, then executes the service based upon the argument and sends the result back to the client. The client resumes program execution after it has received the result of the function.
It should be noted that XDR (External Data Representation), which is a standard data representation method over a network, is used to send and receive data between a client and server. A conversion from internal data representation to the XDR format is referred to as “serialization”, and a conversion from the XDR format to the internal data representation is referred to as “de-serialization”. The transceive data created is increased or decreased depending upon the data size of the argument of the function.
In a case where end of a print job by a printer connected via a network is sensed in a client-server-type network device management system, two methods are available, namely a method of reporting print-job change information (event information) from a printer actively, and a method of acquiring log information, which relates to a printing-completed job, periodically using a file transfer protocol such as FTP. The event information or log information is sent and received using process-to-process communication.
However, with the conventional network device management system of the above-described kind, the log-information acquisition essentials, such as the intervals of the log-information acquisition request to the device and the acquisition protocol, differ for every device managed. As a result, the client application based upon the network management software involves a complicated operation.
In a case where the client application based upon the network management software senses a change in the job of a network device, such as the completion of a print job by a managed printer, in the conventional network device management system of the above-described kind, the job-change sensing method is used selectively, such as sensing by acquisition of event information or sensing by acquisition of log information, in accordance with the type of network device managed. This means that the operation of the client application is complicated.
Further, in data communication between a client application and a server application with the conventional network device management system, a large amount of log information is sent and received. A problem that arises is an increase in traffic in process-to-process communication.