Hitachi, Ltd.

Hitachi Communication Technologies, Ltd.

Minoru Nagai

Hiroaki Miyata

Takashi Yokoyama

Migaku Ota

Kozo Ikegami

Yoshitaka Sakamoto

Shigehiro Onizawa

A data transmission device includes a unit that changes the number and combination of optical communication paths forming a virtual communication path. The data transmission device has functions of forming a virtual communication path by connecting only the number of optical communication paths satisfying a required bandwidth and of turning off operation circuits forming unconnected optical communication paths.

Data transmission device

A packet forwarding apparatus (LSW) having a frame segmentation function of converting a extended Ethernet frame such as a MAC-in-MAC frame into a plurality of fragment frames when a payload length of the received frame exceeds a standard MTU size communicable in an Ethernet network to be a forwarding destination, by segmenting the received frame into a plurality of data blocks having a size not longer than the MTU size, and a frame assembling function of restoring an original extended frame from a series of fragment frames received from the Ethernet network.

Packet forwarding apparatus suitable for forwarding extended frame

Any or unique VLAN ID is dynamically assigned to a user terminal connected to a network, and communication by the assigned VLAN ID is enabled. A connection request from a user terminal is directed to L2GWs by a tagged VLAN frame having a common VLAN ID on the network. The L2GWs determine whether the connection request can be met, obtain a VLAN ID that can be assigned to the user terminal from a VLAN ID management server, configure themselves to communicate by the assigned VLAN ID, and report the VLAN ID to the user terminal. The user terminal performs subsequent communication by the reported VLAN ID. L2SWs monitor communication between the user terminal and the L2GWs and configure themselves to allow communication between the user terminal and the L2GWs by the VLAN ID assigned to the user terminal.

Dynamic VLAN ID assignment and packet transfer apparatus

When multicast distribution is performed on a network where a point-to-point connection is made between user terminals and a multicast router, the multicast router is protected from load due to response reports, join requests, or leave statements sent from the user terminals simultaneously. If the user terminals send response reports simultaneously, a Layer 2 switch disposed between the user terminals and the multicast router limits response reports sent to the multicast router. The Layer 2 switch prevents response reports sent from the same user terminal from being discarded consecutively, by sending a response report sent from the same user terminal to the multicast routerwith priority in the next join confirmation event. If the user terminals send join requests or leave statements simultaneously, the Layer 2 switch limits the join requests or leave statements sent to the multicast routerin the same manner. The Layer 2 switch further enlarges a transmission buffer thereof at the multicast router side, so that the packets can be stored in the buffer.

Growing community of inventors

Fujisawa, Japan

Minoru Nagai