Abstract: A network system includes a plurality of networks, a first internetwork apparatus having a plurality of first ports each connected to the plurality of networks, a second internetwork apparatus having a plurality of second ports each connected to the plurality of networks, and a data transmission path connected to the first and second internetwork apparatuses to transmit data mutually between the first and second internetwork apparatuses. In the normal state, each of the plurality of first ports is caused to be able to transmit and receive data to and from one of the plurality of networks and the plurality of second ports are caused not to be able to receive data from the plurality of networks and to be able to transmit data to the plurality of networks.

Abstract: A packet routing apparatus holds at the least one policy condition, and at the least one label corresponding to the respective policy condition. The packet routing apparatus receives a packet, and determines whether any layer information included in the packet information matches any policy conditions. If at the least one layer information matches any policy condition, a label corresponding to this policy condition is extracted. The packet routing apparatus attaches the label to the packet and transmits the packet.

Abstract: A network system includes a plurality of networks, a first internetwork apparatus having a plurality of first ports each connected to the plurality of networks, a second internetwork apparatus having a plurality of second ports each connected to the plurality of networks, and a data transmission path connected to the first and second internetwork apparatuses to transmit data mutually between the first and second internetwork apparatuses. In the normal state, each of the plurality of first ports is caused to be able to transmit and receive data to and from one of the plurality of networks and the plurality of second ports are caused not to be able to receive data from the plurality of networks and to be able to transmit data to the plurality of networks.

Abstract: A network system includes a plurality of networks, a first internetwork apparatus having a plurality of first ports each connected to the plurality of networks, a second internetwork apparatus having a plurality of second ports each connected to the plurality of networks, and a data transmission path connected to the first and second internetwork apparatuses to transmit data mutually between the first and second internetwork apparatuses. In the normal state, each of the plurality of first ports is caused to be able to transmit and receive data to and from one of the plurality of networks and the plurality of second ports are caused not to be able to receive data from the plurality of networks and to be able to transmit data to the plurality of networks.

Abstract: A network system includes a plurality of networks, a first internetwork apparatus having a plurality of first ports each connected to the plurality of networks, a second internetwork apparatus having a plurality of second ports each connected to the plurality of networks, and a data transmission path connected to the first and second internetwork apparatuses to transmit data mutually between the first and second internetwork apparatuses. In the normal state, each of the plurality of first ports is caused to be able to transmit and receive data to and from one of the plurality of networks and the plurality of second ports are caused not to be able to receive data from the plurality of networks and to be able to transmit data to the plurality of networks.

Abstract: A network system has a plurality of networks. A first internetwork apparatus has a plurality of first ports each connected to the plurality of networks and a second internetwork apparatus has a plurality of second ports each connected to the plurality of networks. A data transmission path is connected to the first and second internetwork apparatuses to transmit data therebetween. In the normal state, each of the plurality of first ports is able to transmit and receive data to and from one of the plurality of networks while the plurality of second ports are able to transmit, but not receive data from the plurality of networks. A failure occurring in one of the plurality of first ports and a route therefrom to one of the plurality of networks is detected.

Abstract: A packet routing apparatus holds at the least one policy condition, and at the least one label corresponding to the respective policy condition. The packet routing apparatus receives a packet, and determines whether any layer information included in the packet information matches any policy conditions. If at the least one layer information matches any policy condition, a label corresponding to this policy condition is extracted. The packet routing apparatus attaches the label to the packet and transmits the packet.

Abstract: An ATM switch and a congestion control method are provided to handle connection setup requests from other ATM devices. In the ATM switch, a congestion detecting process detects congestion of a class that has a number of the connection setup requests stored by class in the buffer equal to T(x), a predetermined number of the connection setup requests to be stored for each of the classes. A message discarding process discards the received connection setup request if it belongs to the congested class. Furthermore, a priority control method for receiving connection setup requests is provided to establish connections more efficiently. A branching process detects a port to which the connection setup request is inputted, identifies a priority class which corresponds to the port using a priority table, and stores the connection setup request in one of queues which are provided for each priority class.

Abstract: A network system includes a plurality of networks, a first internetwork apparatus having a plurality of first ports each connected to the plurality of networks, a second internetwork apparatus having a plurality of second ports each connected to the plurality of networks, and a data transmission path connected to the first and second internetwork apparatuses to transmit data mutually between the first and second internetwork apparatuses. In the normal state, each of the plurality of first ports is caused to be able to transmit and receive data to and from one of the plurality of networks and the plurality of second ports are caused not to be able to receive data from the plurality of networks and to be able to transmit data to the plurality of networks.

Abstract: A network system includes a plurality of networks, a first internetwork apparatus having a plurality of first ports each connected to the plurality of networks, a second internetwork apparatus having a plurality of second ports each connected to the plurality of networks, and a data transmission path connected to the first and second internetwork apparatuses to transmit data mutually between the first and second internetwork apparatuses. In the normal state, each of the plurality of first ports is caused to be able to transmit and receive data to and from one of the plurality of networks and the plurality of second ports are caused not to be able to receive data from the plurality of networks and to be able to transmit data to the plurality of networks.

Abstract: A Local Area Network (LAN) is disclosed in which each node includes means for receiving clock signal information from an external network, which may by way of example be another LAN or a wide area network (WAN), and for generating therefrom clock signals for each node of the local network to accommodate synchronous information exchanges with the external network. Any one of the nodes of the local LAN network may act as a Control Node, and any one of the remaining nodes upon instruction from the Control Node may act as a primary Transmission Node for generating clock signals based upon the external network clock signals for all of the nodes of the local LAN network.

Abstract: In a buffer management system for communication apparatus, the statistical information to be collected at each station such as the number of occurences of receiver buffer busy state is counted at regular time intervals for a preset time duration, and if it becomes in excess of a predetermined number, the ratio in size of transmitter buffer area to receiver buffer area is changed in accordance with the buffer busy state number such that the size of the receiver buffer area becomes larger.

Abstract: In a loop communication system in which a plurality of stations connected to a pair of loop transmission lines comprised of a main transmission line and a preparatory transmission line communicate with each other through the loop transmission lines, one of the transmission lines has to be looped back to the other when failures occur in both the transmission lines by escaping from a point at which the failures occur. When the master station sequentially transmits loop back command signals to slave stations connected to the loop transmission lines, it takes into consideration the number of slave stations present between the master station and an interrogated slave station inclusive thereof so as to vary the monitoring time in accordance with a turn around time required for the master station to receive a response signal sent from the interrogated slave station being in receipt of a loop back command signal, thereby reducing the time for loop back.