Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-04-08
2001-03-06
Chin, Wellington (Department: 2731)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S474000
Reexamination Certificate
active
06198746
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data transmission system, and more particularly to a data transmission system in which cell retransmission can be avoided when a packet is divided into a plurality of cells in an ATM adaptation layer (AAL) of an ATM (asynchronous transfer mode) communications system.
2. Description of the Related Art
The technique on the loss detection control system of an ATM cell is disclosed in Japanese Laid Open Patent Disclosure (JP-A-Heisei 8-186571: a first conventional example). In this loss detection control system, when an EOP (End Of Packet) cell which is the last cell does not arrive for a predetermined time of period, the EOP cell is determined to have been lost. Thus, the cell loss can be detected in a shorter time period, compared with the case where cell loss is detected by an upper level application. Also, the invalid suspension by a buffer memory for the assembly of cells can be prevented.
Also, the technique on a cell discard control system is disclosed in Japanese Laid Open Patent Disclosure (JP-A-Heisei 4-372245: a second conventional example). In this cell discard control system, when a cell of a data packet is discarded, the discard of the other cells of the data packet is variably controlled, considering the service class. Thus, efficient communication is made possible in accordance with an upper level application.
However, in the above-mentioned conventional examples, only the case which the discard of a cell has occurred is considered. It is not solved at all to reduce the possibility of the discard of cell. This is because the problems such as the short detection time of cell discard and the influence to the upper level layer due to the cell discard are only considering.
In addition, a cell retransmission control system is described in Japanese Laid Open Patent Disclosure (JP-A-Heisei 6-121001). In the cell retransmission control system, a procedure of cell retransmission in an AAL (ATM Adaptation Layer) is simplified to avoid retransmission of an unnecessary cell.
In Japanese Laid Open Patent Disclosure (JP-A-Heisei 7-250082), there is described an AAL type 1 processing unit in which any delay time is not generated even if a phase proceeding is generated due to switching and underflow is not generated even if a phase delay is generated due to the switching.
Also, in Japanese Laid Open Patent Disclosure (JP-A-Heisei 8-116326), there is described a cell assembling unit in which a delay buffer section outputs a cell to a payload accumulating section with a delay time during which the cell is analyzed such that the cell assembling unit can be constructed with a small size.
Also, in Japanese Laid Open Patent Disclosure (JP-A-Heisei 7-87099), an error control method is described in which reliable data communication is made possible with high through-put and low latency in an AAL type 5.
Also, in Japanese Laid Open Patent Disclosure (JP-A-Heisei 8-46629), an ATM network interface module is described in which throughput in an upper layer can be improved by adding hardware of as a small quantity as possible.
Also, in Japanese Laid Open Patent Disclosure (JP-A-Heisei 8-237282), a congestion control system in a packet communication system is described in which data such as the number of accumulated ATM cells and the number of discarded ATM cells are monitored to see a buffer state and whether an ATM cell should be discarded is determined based on such data.
SUMMARY OF THE INVENTION
The present invention is accomplished in view of the above-mentioned problems. Therefore, an object of the present invention is to provide a data transmission system in which it can be avoided that a packet is discarded due to loss or discard of an EOP cell.
Another object of the present invention is to provide a data transmission system in which traffic increase in a transmission network due to retransmission of a packet and complicated control for the retransmission of the packet can be avoided when an EOP cell is discarded or lost.
In order to achieve an aspect of the present invention, a data transmission system connected to a communication network, includes a packet disassembling section for disassembling a data packet into non-final cells with a predetermined data length for a cell stream, and for adding a final cell after the non-final cells for the cell stream, and a cell transmitting section for sequentially transmitting the non-final cells and a plurality of the final cells to the communication network as the cell stream.
The cell transmitting section may include a transmitting section for transmitting the cell stream to the communication network, a distinguishing section for distinguishing the final cell, and for supplying the non-final cells to the transmitting section, and a copy generating section for generating a copy of the final cell. Here, the transmitting section sequentially transmits the non-final cells and a plurality of the copies of the final cell to the communication network as the cell stream.
In this case, the copy generating section may include a memory for storing the copy of the final cell, and a copying section for generating the copy of the final cell to store in the memory. Here, the transmitting section reads the copy of the final cell from the memory plural times after having transmitted the non-final cells, and transmits the read copies of the final cell to the communication network.
In the data transmission system of the present invention, the communication network may be an ATM (asynchronous transfer mode) communication network, and the cells may be ATM cells, and the final cell may be an EOP (end of packet) cell.
In order to achieve another aspect of the present invention, a data transmission system connected to a communication network, includes a packet disassembling section for disassembling a data packet into non-final cells with a predetermined data length for a cell stream, and for adding a final cell after the non-final cells for the cell stream, and a cell transmitting for sequentially transmitting the non-final cells and a plurality of the final cells to the communication network as the cell stream, when the data packet has a data length longer than a predetermined length.
The cell transmitting section may include a transmitting section for transmitting the cell stream to the communication network, a determining section for determining whether the data packet is longer than the predetermined length, a distinguishing section for distinguishing the final cell, and for supplying the non-final cells to the transmitting section when it is determined by the determining section that the data packet has a data length longer than a predetermined length, and a copy generating section for generating a copy of the final cell, when the transmitting section sequentially transmits the non-final cells and a plurality of the copies of the final cell to the communication network as the cell stream.
In this case, it is desirable that the distinguishing section supplies the non-final cells and the final cell to the transmitting section when it is determined by the determining section that the data packet has a data length shorter than a predetermined length. Here, the transmitting section sequentially transmits the non-final cells and the final cell to the communication network as the cell stream.
Alternatively, the copy generating section may include a memory for storing the copy of the final cell, and a copying section for generating the copy of the final cell to store in the memory. Here, the transmitting section reads the copy of the final cell from the memory plural times after having transmitted the non-final cells, and transmits the read copies of the final cell to the communication network.
In the data transmission system of the present invention, the communication network may be an ATM (asynchronous transfer mode) communication network, and the cells may be ATM cells, and the final cell may be an EOP (end of packet) cell.
In order to achieve still another aspect of the presen
Chin Wellington
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
Yao Kwang B.
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