Therefore, software on Hitachi H8 microprocessor attached to a switch chip process it. So a part of process is achieved maintenance module, on-chip hardware. Moreover the maintenance process owes the performance monitor. The ping and pong packets are utilized to confirm a connection between switches. Ping is a configuration request packet of line involving a physical ID of the sender.
Pong is a acknowledge packet of line.
Switch continually send pong packet when line is off. Once it receive a ping packet from a opposite switch, it becomes to send a pong packet. If it receive a pong packet created by its ping packet at opposite switch, it recognizes the online. Physical ID is a unique number among switches and host computers, and this ID enables to recognize whether the opposite is switch or host computer by the MSB bit. Therefore, switch recognize I am branch and have to increase the virtual channel ID, or not.