Node apparatus and RPR network

An RPR network duplicated by system 0 ring and system 1 ring by system each including a plurality of node apparatuses and transmission lines, said RPR network comprising:

• a normal mode processing section provided in each node apparatus for sending in the normal operation mode packets to each of other nodes to a packet transmission ring which is either said system 0 ring or system 1 ring;
• a center node processing section provided in each of said node apparatuses for determining, when a node receives packets functions as a center node receiving the largest volume of packets, a node as a target node, which is a node with the packet transmission ring for the packet to said center node in the normal operation mode to be changed, based on a volume of packets from slave nodes, which are other nodes, and transmitting a target command for instructing the target node to change the packet transmission ring;
• and
• a target node processing section provided in each node apparatus for changing, when said target command transmitted from said center node is received, said packet transmission ring for packets to the center node having transmitted said target command and transiting to dynamic band change mode.