The present invention relates to a protocol conversion system, and in particular, to the system which performs protocol-conversion for data communication between different types of open networks to which different types of protocols are implemented.
At present, under the growing demands for open systems and multi-venders, various types of connection mode of computers have been requested. Particularly, there are strong needs for connections, for example, from a network to another LAN (Local Area Network), or to a remote host computer network. For the connection from a closed network environment to another network environment, connecting devices such as routers are used. For connection with a higher processing performance, protocol conversion systems such as gateways are also used.
Routers perform connection between networks by processing up to the network layer of an OSI reference model to recognize what type of communication devices are connected in a network, and sending information necessary to the party system.
On one hand, gateways, which process all the layers of an OSI reference model, that is, up to an application layer, convert a protocol of data received from a communication network to another protocol of data which can be recognized by other computers.
However, since the foregoing routers cannot process by the transport layer and layers upper than the transport layer, there occurs a problem that the router, in itself, cannot solve cases where data have been lost on the way to a destination.
The gateways convert a protocol of data received from a communication network into another communication protocol and send them to its party protocol. Therefore if an abnormal situation occurs in the party system, it is no longer recognized by the gateways.
Furthermore, owing to the fact that the gateways are protocol conversion systems which process layers up to the application layer, designing the gateways takes a huge amount of work and a long time.
The present invention is provided to overcome the above drawbacks concerning the conventional protocol conversion systems. A first object of the present invention is to take appropriate measures against losses of data on the way in communication. A second object of the present invention is to properly recognize abnormal states which occurred in the party system. A third object of the present invention is to provide a protocol conversion system which raises reliability in the transmission and reception of data.
In the present invention, to achieve the first object concerning the router, the protocol conversion between different types of networks uses a method of replacing headers of communication data. By placing information about the success or failure in data transmission in the header, sending results of the communication data can be recognized.
In order to achieve the above second object relating to abnormalities occurred in gateway systems, the present invention provides a serial interface means intervening between two network systems. The serial interface means has a construction capable of reading the states of one party system.
Furthermore, to achieve the third object of the present invention, there is provided a construction which processes or terminates only both a transport layer and layers lower then the transport layer, instead of processing or terminating layers up to an application layer.
Specifically, there is provided a protocol conversion system intervening between different types of networks and being responsible for sending and receiving communication data therebetween, comprising: a first node performing communication of data based on a first protocol defining a communication system of a first network; a second node performing communication of data based on a second protocol defining a communication system of a second network, said second node including a protocol converting means for adding conversion information for conversion to the first protocol, adding control information for control of the first node, and terminating conversion information for conversion to the second protocol; and a protocol converter for mutually relaying the communication data between the first and second nodes and for controlling the first node, comprising: first communication data processing means for processing the communication data to the first node layer by layer; second communication data processing means for processing the communication data to the second node layer by layer; node control means not only having serial interface means but also having means for controlling the first node using the serial interface means, monitoring a state of the first node, and notifying the second node of a monitored state of the first node; and further protocol converting means for terminating the conversion information for conversion to the first protocol, converting to frames recognized by the first node based on the terminated conversion information, terminating the control information for control of the first node, and adding the conversion information for conversion of the communication data from the first node into the second protocol.
It is preferred that each of said first and second communication data processing means is constructed to terminate only lower layers of a protocol implemented in each processing means.
It is also preferred that said first protocol is an HDLC and said second protocol is a TCP/IP.
It is also preferred that said further protocol converting means includes means for replacing a header composed of a first identifier for identifying a type of the communication data, a second identifier indicating an origin from which the communication data are sent, a third identifier indicating a destination to which the communication data are sent, a fourth identifier indicating sequential information, and a fifth identifier indicating details of the first identifier. By way of example, said further protocol converting means includes means for classifying the communication data by identifying the header.
Further preferably, said node control means includes mean for monitoring the state of the first node through the serial interface means, and means for notifying the second node of the state of the first node when the monitoring means detects changes in the state of the first node. For example, said node control means further includes means for storing information about the monitored state of the first node, and said notifying means is constructed to notify the second node of the state of the first node in response to a request originated from the first node.
Preferably, said first node has means for receiving a physical address sent by the serial interface means and setting the physical address in the first protocol. In this case, said receiving and setting means may be constructed to be performed responsively to a request-to-start of operation sent from the second node.
It is also preferred that said protocol converter further comprises means for determining an abnormal state of a connection with the second node, means for cutting off the connection if the abnormal state is determined, means for performing a reconnection operation with the second node, and means for notifying the first node of the reconnection when the reconnection has been achieved.