Abstract: In a bandwidth management apparatus that outputs packets by observing the bandwidth set value predetermined for each destination, provisions are made to prevent a situation where the contracted bandwidth cannot be provided due to influences from packets destined for other destinations. When performing bandwidth management using token buckets provided one for each destination, each token bucket is updated by setting the upper limit token value higher when any packet is stored in the corresponding queue than when no packets are stored; this serves to prevent a situation where even when a packet has already arrived at the queue, the packet cannot be output because a packet is being output from some other queue and, as a result, unconsumed tokens are discarded at the next update time.

Abstract: A multicast packet readout control method is disclosed. An input multicast packet is temporarily stored in a multicast queue of a packet buffer. The multicast packet is read from the multicast queue, and converted into a unicast packet addressed to each of the destinations of the multicast packet. The converted unicast packet is stored in a unicast queue of the packet buffer. The converted unicast packet is then read from the unicast queue and transmitted to the destination.

Abstract: A data communication apparatus has a data retainer, a retain state manager, a guaranteed bandwidth manager, a surplus bandwidth manager managing outputting of output data having a destination retained in the data retainer to an output line on a per-destination basis when the output data is outputted to the output line with the use of a surplus bandwidth that is a surplus over a sum of guaranteed bandwidths, and a scheduler scheduling outputting of data retained in the data retainer to the output line, based on results of managements by the guaranteed bandwidth manager and the surplus bandwidth manager and a retain state managed by the retain state manager. The apparatus manages the bandwidth with improved accuracy at the time of communication using a surplus bandwidth.

Abstract: In a packet transmission method and device, when a received packet is written in a packet buffer, an address of the packet buffer is stored as a read address for each destination corresponding to a physical port and storing information of the received packet. The read address of a destination designated by the received packet information is read and saved when the received packet is read out of the packet buffer in accordance with a scheduling control. Then, the saved read address is taken out in accordance with an arbitration control and a received packet corresponding to the saved read address is read from the packet buffer.

Abstract: A data communication apparatus has a data retainer, a retain state manager, a guaranteed bandwidth manager, a surplus bandwidth manager managing outputting of output data having a destination retained in the data retainer to an output line on a per-destination basis when the output data is outputted to the output line with the use of a surplus bandwidth that is a surplus over a sum of guaranteed bandwidths, and a scheduler scheduling outputting of data retained in the data retainer to the output line, based on results of managements by the guaranteed bandwidth manager and the surplus bandwidth manager and a retain state managed by the retain state manager.

Abstract: In a packet transmission method and device, when a received packet is written in a packet buffer, an address of the packet buffer is stored as a read address for each destination corresponding to a physical port and storing information of the received packet. The read address of a destination designated by the received packet information is read and saved when the received packet is read out of the packet buffer in accordance with a scheduling control. Then, the saved read address is taken out in accordance with an arbitration control and a received packet corresponding to the saved read address is read from the packet buffer.

Abstract: In a bandwidth management apparatus that outputs packets by observing the bandwidth set value predetermined for each destination, provisions are made to prevent a situation where the contracted bandwidth cannot be provided due to influences from packets destined for other destinations. When performing bandwidth management using token buckets provided one for each destination, each token bucket is updated by setting the upper limit token value higher when any packet is stored in the corresponding queue than when no packets are stored; this serves to prevent a situation where even when a packet has already arrived at the queue, the packet cannot be output because a packet is being output from some other queue and, as a result, unconsumed tokens are discarded at the next update time.

Abstract: A multicast packet readout control method is disclosed. An input multicast packet is temporarily stored in a multicast queue of a packet buffer. The multicast packet is read from the multicast queue, and converted into a unicast packet addressed to each of the destinations of the multicast packet. The converted unicast packet is stored in a unicast queue of the packet buffer. The converted unicast packet is then read from the unicast queue and transmitted to the destination.