Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-02-24
2001-01-09
Pham, Chi H. (Department: 2731)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S338000, C370S402000
Reexamination Certificate
active
06172982
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a communication control system used in a packet communication network and a method of controlling communication in the packet communication network in which a wired sub-network and a plurality of radio sub-networks are connected by learning type bridges.
Generally, in a packet communication network having a plurality of sub-networks, it is known to, when connecting sub-networks to each other, connect them using a bridge apparatus having a learning function (for example, JP-A-140034/1990).
In such a bridge system, a bridge apparatus has a learning table, a bridge for performing a relay of a packet registers a source address included in the packet and a received sub-network number in the learning table, and when a destination address included in the packet is registered in the learning table, the bridge transmits the packet to the registered sub-network. However, in case that the registered sub-network is a sub-network that has received the packet, the packet is discarded.
On the other hand, when the destination address is not registered in the learning table, the packet is simultaneously transmitted to all sub-networks connected to the bridge.
In case that the packet is not transmitted in a predetermined time interval from a terminal having a corresponding address, a set of the address and sub-network that are registered in the learning table is deleted due to out of time.
By means of the bridge system having such a learning function, simultaneous transmission of the packet to the sub-networks in which terminals do not exist (are not located) can be reduced and it become to be easy to structure a large scale network.
By the way, in the network in which a wired sub-network and a plurality of radio sub-networks are connected using the above-described bridge, in case that a terminal connected to, or located in one radio sub-network and conducting communication moves to other radio sub-networks, since an address of the terminal is registered together with the wired sub-network number in the bridge connecting the radio sub-network to which the terminal moves, to the wired sub-network, the packet transmitted to the terminal is not transmitted to a side of the radio sub-networks. And then, if the terminal that has moved (the said terminal) transmits the packet and the learning table is changed or if the set of the address and sub-network is deleted from the learning table due to out of time as mentioned above, the bridge becomes to start transmission of the packet transmitted to the terminal, to the side of the radio sub-network.
In the above-mentioned bridge system, when the terminal connected to one radio sub-network and conducting communication moves to other radio sub-networks, if the contents of the learning table of the bridge are not changed or deleted, the packet transmitted to the terminal is not transmitted to the side of the radio sub-networks, and as a result, there is a problem that reconnection during movement of the terminal needs time.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide a communication control system and a method of controlling communication in a packet communication network that are capable of conducting the reconnection for a short time during the movement of the terminal.
The objective of the present invention is achieved by a communication control system in a packet communication network having a plurality of radio sub-networks. The radio sub-networks are connected to a wired sub-network by learning type bridges, respectively. The communication control system includes a radio terminal for communicating with the radio sub-networks, and the radio terminal includes first means for detecting whether or not the terminal moves from one of the radio sub-networks to other radio sub-networks, and second means for transmitting a dummy packet when movement between the radio sub-networks is detected.
In accordance with present invention, the dummy packet is a packet that does not need a response packet.
Moreover, for example, the learning type bridges include transmission means for transmitting a control packet to the sub-networks on a radio side, which includes sub-network discriminating signals that are different for each of the learning type bridges, and the first means detects the movement between the radio sub-networks when the sub-network discriminating signals included in a received control packet are different from a previously received sub-network discriminating signals.
Also, the first means is adapted to detect movement between the radio sub-networks when a registration discriminating signal is not registered in the radio terminal.
Further, in case that each of the radio sub-networks uses radio channels that are different from each other, the radio terminal selects the radio channels in accordance with a predetermined radio channel selecting procedure and the first means detects the movement between the radio sub-networks when the radio channels are different from each other.
The objective of the present invention is also achieved by a method of controlling communication in a packet communication network is provided, in which the packet communication network has a plurality of radio sub-networks, the radio sub-networks are connected to a wired sub-network by learning type bridges, respectively, and packet communication network includes a radio terminal for communicating with said radio sub-networks. The method includes steps of detecting whether or not the radio terminal moves from one of the radio sub-networks to other radio sub-networks, and transmitting a dummy packet when movement of the radio terminal between the radio sub-networks is detected.
In this manner, according to the present invention, since the radio terminal (mobile terminal) transmits the dummy packet for changing the learning table of the bridge when the radio terminal detects the movement between the radio sub-networks, it is possible to reduce time necessary for the reconnection, and as a result, to mitigate a packet loss.
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C. Perkins, “IP Mobility Support”, RFC2002, Oct. 1996.
Ishii Kenichi
Osawa Tomoki
NEC Corporation
Pham Brenda H.
Pham Chi H.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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