Rogue Packet Removal Operation - GE PCIE-5565PIORC* Hardware Reference Manual

2.8 Rogue Packet Removal Operation

28 PCIE-5565PIORC Reflective Memory Board
A rogue packet is a packet that does not belong to any node on the network.
Recalling the basic operation of Reflective Memory, one node originates a packet
on the network in response to a memory write from the host. The packet is
transferred around the network to all nodes until it returns to the originating
node. It is a requirement that the originating node remove the packet from the
network. If, however, the packet is erroneously altered as it passes through
another node, or if the originating node begins to malfunction, then the
originating node may fail to recognize the packet as its own and will not remove it
from the network. In this case, the packet will continue to traverse the network as
a "rogue packet."
Rogue packets are extremely rare. A rogue packet could be created when turning
a node's power on or off while connected to a 5595 Hub. It could also occur when
connecting or disconnecting fiber cables. A rogue packet might be created if any
node in the network overflows a network FIFO. Their existence could indicate a
malfunctioning board due to true component failure, or due to operation in an
overly harsh environment. Normally, the solution is to isolate and replace the
malfunctioning board and/or improve the environment. However, some users
prefer to tolerate sporadic rogue packets rather than halt the system for
maintenance provided the rogue packets are removed from the network.
To provide tolerance for rogue packet faults, the RFM‐5565 contains circuitry that
allows it to operate as one of two Rogue Masters. A rogue master marks each
packet as it passes through from another node. If the same packet returns to the
rogue master a second time, the Rogue Master recognizes that it is a rogue packet
and removes it from the network (after the rogue packet has affected every node).
When a rogue packet is detected, a rogue packet fault flag is set in the LISR. The
assertion of the rogue packet fault bit may optionally assert a PCI interrupt to
inform the host that the condition exists.
Two rogue masters, Rogue Master 0 and Rogue Master 1, are provided to cross
check each other. Rogue Master 0 is enabled by placing switch S1 position 5 in the
ON position. Rogue Master 1 is enabled by placing switch S1 position 6 in the ON
position. Just as two boards in a network should not have the same node ID, two
boards in the same network should not be set as the same Rogue Master.
Otherwise, one of the two will erroneously remove packets marked by the other.