Patent ID: 8031640
Filing Date: 2011-10-04
Classification: H04L

Abstract:
1. A packet transmission apparatus composing a ring network, the packet transmission apparatus comprising: a first-layer processor to process a first packet received from outside of the ring network and to process a second packet to be transmitted to the outside of the ring network; a second-layer processor to transmit a third packet received from the first-layer processor to the ring network with a second-layer header added to the third packet, wherein the second-layer header includes information for allowing the third packet to go around the ring network, and to forward a fourth packet received from the ring network on the ring network depending on a second-layer header of the fourth packet or to pass the fourth packet to the first-layer processor after deleting the second-layer header from the fourth packet; and an address translation table associating a multicast destination address and a flag in conjunction with a pair of an offset value and a virtual network identifier, the flag indicating whether an own node belongs to a virtual network specified by the virtual network identifier, wherein, the second-layer processor has a virtual network Protocol Identifier (PID) table containing a plurality of different PIDs and offset values, each of the plurality of PI Ds being associated with one of the offset values, the plurality of PIDs specifying virtual network packets, if the third packet received from the first-layer processor includes a PID and a virtual network identifier, the second-layer processor extracts from the virtual network PID table an offset value corresponding to the PID of the third packet, searches the address translation table based on the extracted offset value and the virtual network identifier of the third packet for a corresponding multicast destination address, and forwards the third packet on the ring network with a second-layer header added to the third packet, the second-layer header including the corresponding multicast destination address, and if the fourth packet received from the ring network carries the multicast destination address stored in the address translation table and a corresponding flag indicates that the own node does not belong to the virtual network, the second-layer processor does not pass the fourth packet to the first-layer processor.