To assure high reliability required for a communication carrier network and at the same time provide an inexpensive high-functional packet relay device.
The packet relay device includes multiple interface parts that send and receive data packets, two packet switches of active and standby systems to sort the received data packet to the interface parts corresponding to the addresses of the data packets, and a device control part that controls the multiple interface parts to send and receive control signals between operation devices connected to the outside. The interface parts receive control commands from the device control part. When the command instructs insertion of the diagnosis packet, the diagnosis packet is generated at a predetermined-fixed cycle and is inserted into the stream of data packets. If the diagnosis packet sent from other interface part via a packet switch does not come continuously over a predetermined number of monitoring cycles, the packet switch is controlled to switch the systems.
WATANABE YOSHIHIDE
URAHATA SATOYUKI
SAITO MASAHIRO
SUZUKI AKINORI
TAKASE MASAYOSHI
SUGANO TAKAYUKI
RYU ISAMU
NTT COMM KK
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