BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing a single ring network 100;
FIG. 2 is an explanatory drawing showing an example of a format of a variable-length packet transmitted on the single ring network 100;
FIG. 3 is an explanatory drawing showing a relation between a probe packet 140 issued by a master node 110 and a hop count report packet 150 issued by a slave node 120;
FIG. 4 is a flowchart showing a process for receiving/transmitting the probe packet 140 and issuing the hop count report packet 150 respectively by the slave node 120;
FIG. 5 is a flowchart showing the operation for coping with a fault by the master node 110;
FIG. 6 is a flowchart showing the operation of a sub-master node;
FIG. 7 is a block diagram showing a node appliance 900 with which the ring is provided;
FIG. 8 is a flowchart showing the operation for coping with a fault by the master node 110 including the sub-master node;
FIG. 9 is a block diagram showing a ring manager 930;
FIG. 10 is a block diagram showing a packet transfer unit 920;
FIG. 11 is an explanatory drawing showing a format of retrieval result information 800 stored in a packet transfer database 922 in transferring the packet;
FIG. 12 is a flowchart showing a process for transferring the hop count report packet 150 by the slave node 120;
FIG. 13 is a block diagram showing the single ring network 100 on which multiple faults occur;
FIG. 14 is a block diagram showing a ring network equivalent to a second embodiment;
FIG. 15 is an explanatory drawing showing an example of multiple faults;
FIG. 16 is an explanatory drawing showing the change of topology in a fourth embodiment;
FIG. 17 is a flowchart showing the operation for coping with a fault by a master node 110 in the fourth embodiment; and
FIG. 18 is a flowchart showing the operation for coping with a fault on a ring by a master node 110 including a sub-master node in a fifth embodiment.