Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-03-30
2003-05-27
Kizou, Hassan (Department: 2662)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S412000, C370S413000, C370S415000, C370S417000, C370S422000, C370S428000, C370S468000, C370S474000
Reexamination Certificate
active
06570876
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a packet switch and a switching method, more particularly to a packet switch and a switching method for switching variable length packets by controlling transmission of packets according to the priority of respective packets. More concretely, the present invention relates to a packet switch and a switching method suitable for switching variable length packets in the Internet, as well as intranets, and capable for transmitting the variable length packets by controlling a bandwidth thereof.
(2) Description of the Related Art
The packet communication is a communication method for transmitting and receiving data in a form of a packet comprising a predetermined format of header and a data block obtained by dividing transmission data into blocks each having a proper length, for example, 48 byte to 1.5 Kbytes in length. A packet switch adopts a so-called stored and forward switching method, in which switching of communication data is carried out after the communication data as stored temporarily in the switch, so that it is able to apply a variety of control to the packets passing through the switch.
In the case of the Internet coming into wide use rapidly in recent years, data is communicated as variable length packets with an IP (Internet Protocol) header respectively. Therefore, a packet switching technique is essential to each node for connecting a network to another. An inter-networks connecting apparatus (node apparatus) such as a router is also provided with the packet switching function even if it is not called a “packet switch” actually. Consequently, in the present invention, every network apparatus provided with the packet switching function, including the node apparatus having such a specific name as router, will be referred to as a packet switch.
As a prior art related to such the packet switching, a router is disclosed in Japanese Unexamined Patent Publication No.7-135512. The prior art intends to provide a router with a function for controlling the transfer of received packets according to the priority thereof and a function for controlling the discard of packets performed when a buffer congestion occurs. According to the prior art, packets received by a packet receiving unit are queued in a buffer memory by a priority control unit according to the transmission priority and the discard priority of each packet, then they are transmitted to a packet transmission unit according to the order of the transmission priority. The priority control unit refers to a mapping table based on the transmission priority information and the protocol information included in the header of each received packet to obtain the processing priority and the discard priority corresponding to the received packet, and stores the packet in one of queues prepared corresponding to the discard priority for each processing priority. Stored packets are output sequentially according to the order of descending processing priority. When the free area capacity of the buffer memory goes under a predetermined threshold value, discard control of the stored packets is carried out to avoid congestion. In this discard control, packets with higher discard priority are discarded from queues according to the order of ascending processing priority until the free area capacity of the buffer memory reaches a target threshold value.
In the case of the above related art, only one type of the mapping table is referred for queuing packets. The transmission priority and the discard priority of each packet are defined in the mapping table corresponding to the priority information and the protocol information included in the header of each of received packets. Consequently, in the case of the related art, it is difficult to control a bandwidth for each packet flow and to provide peculiar packet switching services depending on, for example, the source or destination network of those packets in a node apparatus connecting a plurality of networks such as the Internet.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a packet switch and a packet switching method that can control a bandwidth of each of variable length packet flows.
It is another object of the present invention to provide a packet switch and a packet switching method that can guarantee the bandwidth previously reserved for each of variable length packet flows by a communication service contract.
It is still another object of the present invention to provide a packet switch and a packet switching method that can perform both bandwidth control and priority control for each variable length packet flow.
It is further another object of the present invention to provide a packet switch and a packet switching method that can perform both bandwidth control and priority control according to the communication protocol of variable length packets.
In order to achieve the above objects, the packet switch of the present invention comprises a plurality of input port interfaces, a plurality of output port interfaces, and a packet switching unit for switching each of variable length packets received from the input port interfaces to one of the output port interfaces corresponding to the destination address of the packet, wherein each of the output port interfaces comprises a buffer memory for storing transmission packets, a transmission priority controller configured so as to classify the transmission packets received from the packet switching unit based on a predetermined algorithm and queue each of those transmission packets according to transmission priority thereof into one of a plurality of queue groups, each of which is assigned an individual bandwidth, a transmission packet read-out controller for accessing the queue groups of the buffer memory cyclically to read out transmission packets from each of those queue groups according to the order of descending transmission priority while guaranteeing the bandwidth assigned to each queue group, and a packet transmission circuit for transmitting the transmission packets read out by the transmission packet read-out controller to an output port associated with the output port interface.
According to an embodiment of the present invention, the transmission priority controller is, for example, provided with means for identifying communication service contract and transmission priority related to each of transmission packets according to the header information of the transmission packet received from the packet switching unit, thereby to queue the transmission packet in a queue corresponding to the identified transmission priority in a queue group corresponding to the identified communication service contract.
More concretely, the transmission priority controller includes, for example, a first management table for defining the identifier of the queue group corresponding to the combination of a source network address and a destination network address and a second management table for defining a transmission priority corresponding to the combination of a communication protocol and a packet priority, thereby to identify a queue group corresponding to each of the transmission packets by referring to the first management table based on the source network address and the destination network address included in the header of the transmission packet, and to identify the transmission priority of the transmission packet by referring to the second management table based on the communication protocol information and the packet priority information included in the header of the transmission packet.
According to another embodiment of the present invention, the transmission priority controller identifies a queue group corresponding to each of the transmission packets based on the protocol information included in the header of the transmission packet, then queues the transmission packet in one of the queues in the identified queue group. In this case, for example, the object of switching is an IP packet which is identified by the protocol o
Kizou Hassan
Logsdon Joe
LandOfFree
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