| 摘要 |
A multicast communications system that updates multicast trees in a reliable way to prevent transmitted packets from being dropped or reversed before they reach their destinations. When a transmitting device sending multicast packets has moved from an initial access point to a new access point, a trigger data generator produces and sends trigger data to a network control server. This trigger data includes a sequence number of a particular packet as a trigger condition that initiates a change from an initial multicast tree to a new multicast tree. A trigger data distributor then sends the trigger data to both the initial and new access points. In packet routing devices, an update processor maintains the initial multicast tree until a packet having the sequence number specified in the trigger data is received and forwarded. After that, the update processor replaces the initial multicast tree with the new multicast tree.
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