Patent ID: 7221647

Claim:
A packet data transfer controlling method in a packet communication apparatus, said apparatus having: a switch unit having a scheduler for scheduling packet transfer between a plurality of input ports and a plurality of output ports; a plurality of ingress interfaces each coupled to one of said input ports for selectively transferring packets received from an input line to said switch unit; and a plurality of egress interfaces each coupled to one of said output ports for transmitting packets received from said switch unit to an output line, wherein each of said ingress interfaces has a plurality of pairs of a first storing unit and a second storing unit, and a control unit for selecting one of said pairs, and said switch unit having a plurality of third storing units each associated with one of said input ports so as to temporarily store packet data transferred from one of said ingress interfaces to the input port, said method comprising the steps of: storing, by each of said ingress interfaces, packet data received from said input line in one of said first storing units, selectively and shifting a first data portion including destination information of the packet data from the first storing unit to one of said second storing units, which is paired with the first storing unit; controlling, by each of said control units, one of said second storing units so as to transfer the first data portion to one of said third storing units, but leaving the same data in the second storing unit; selecting, by said scheduler, at least one of said third storing units that stores the first data portion allowed to be transferred to one of said output ports; controlling, by each of said control units, in response to a predetermined control signal from said scheduler, one of said first storing units, which is paired with said second storing unit from which said first data portion has been transferred, so as to transfer a remaining portion of the packet data to one of said third storing units selected by said scheduler; transferring, by said switch unit, the first data portion and remaining portion output from said selected third storing unit to one of said output ports specified by the destination information of the first data portion; and controlling, by each of said control units that could not receive said predetermined control signal, another of said second storing units so as to transfer the first data portion to one of said third storing units, thereby to replace the previous first data portion with the new first data portion in the third storing unit.