Abstract: A communication scheme capable of guaranteeing the order of packets in the communication media exchange during the communication so as to be able to continue the communication smoothly even after the communication media exchange is disclosed. The source host transmits a first check packet through the first communication path and stops transmission of user data packets upon transmitting the first check packet, while the destination host transmits the first check packet through the second communication path upon receiving the first check packet through the first communication path while transmitting a second check packet through the first communication path, and stops transmission of user data packets upon transmitting the second check packet.

Abstract: An L2 integrated access (L2IA) system is constructed from: L2IA subscribers for supporting communications between user terminals using various communication media, each L2IA subscriber having an L2IA identifier for uniquely identifying each L2IA subscriber within the L2 integrated access system and a terminal ID for uniquely identifying each L2IA subscriber within each communication medium associated with each L2IA subscriber; and an L2IA relay network formed by relay units to be connected with the L2IA subscribers through various communication media and relaying communications between the L2IA subscribers through the L2IA relay network, each relay unit being provided in correspondence to one communication medium such that at least one relay unit is provided in correspondence to each communication medium, and each relay unit having an L2IA relay ID for uniquely identifying each relay unit within the L2IA relay network and a terminal ID for uniquely identifying each relay unit within each communication medium

Abstract: A packet multiplexer capable of realizing the optimization of a communication path automatically, without requiring a user to explicitly specify for it, is disclosed. The packet multiplexer is formed by a plurality of first communication interfaces for terminating a plurality of C-plane and U-plane pairs on one side of the packet multiplexer, a second communication interface for terminating a single C-plane and a plurality of U-planes on another side of the packet multiplexer, a connection interface for multiplexing the C-plane and U-plane pairs terminated at the first communication interfaces into the single C-plane and the plurality of U-planes terminated at the second communication interface, and a control unit for controlling multiplexing of U-planes by the connection interface according to signaling through C-planes, such that a cut-through is made within the packet multiplexer between two U-planes terminated at the first communication interfaces that form a loop.