JP3950865B2 - ATM communication system - Google Patents

Description

The present invention relates to an ATM communication system for transmitting data in an asynchronous transfer mode, and more particularly to an ATM communication system characterized by data retransmission processing.

  When data is transmitted using ATM (Asynchronous Transfer Mode) cells, some ATM cells in a plurality of ATM cells constituting one set of data are discarded in the middle of the transmission path. There is. In the case where a loss due to this occurs, a proposal has been made so far that the receiving side can apparently receive the ATM cell correctly by inserting a dummy cell in place of the discarded ATM cell (for example, a patent). Reference 1). If a dummy cell is inserted in place of the discarded ATM cell as in the first proposal, one piece of data itself is received formally correctly on the receiving side.

  However, since the ATM transmission apparatus on the receiving side receives data having some errors, there is a problem that the reliability of the received data cannot be maintained. In other words, such a communication method is suitable for transmission / reception of streaming data such as video and audio data in which high-speed data transmission is given priority over data reliability, but is suitable for transmission of data where reliability is important. Not.

  Therefore, in order to reliably transmit important data to a destination, data in which a transmission error has occurred is generally retransmitted. Also for data transmission using ATM cells, retransmission processing can be performed using a TCP (Transmission Control Protocol) protocol. In the TCP protocol, when data transmitted to a destination reaches the destination correctly, an ACK (ACKnowledgement) signal is returned to the source as a message indicating that communication has arrived without error. If this retransmission method is adopted, it is assumed that a transmission error has occurred when the ACK signal does not return even after a sufficient time has elapsed for the ACK signal to return, and the transmission source retransmits the data to the destination. It has become.

  The data to be retransmitted includes not only data that has not reached the destination, but also data that has arrived in an incomplete state due to the influence of noise or the like. Adopting the TCP protocol in this way ensures the arrival of data and its integrity. For this reason, the TCP protocol is employed for error processing even when data is transmitted using ATM cells.

  However, when the TCP protocol is employed, there is a problem that efficient communication cannot be performed because it is necessary to take a certain amount of time until the data is retransmitted. Therefore, it takes a long time until data is actually retransmitted, resulting in a significant reduction in throughput.

In order to solve such a problem, a procedure of a retransmission process that is more efficient than a retransmission process based on the TCP protocol has been proposed (see, for example, Patent Document 2). In this second proposal, the receiving side is provided with a counter for detecting the number of the ATM cell in which the loss has occurred, so that the number of the ATM cell in which the loss has occurred is notified to the transmitting side and The ATM cell is requested to be retransmitted. As described above, since retransmission processing is performed in the ATM layer without waiting for the reply of the ACK signal, it is possible to shorten the time until actual retransmission is performed, and to improve the throughput.
JP-A-4-265034 (paragraphs 0005 and 0006, FIG. 1) JP-A-10-65675 (paragraph 0019, FIG. 1)

  By the way, there are various types of data to be transmitted using ATM cells, and there is data that requires high immediacy such as streaming data such as television broadcasting. However, if any data instructed from the receiving side is to be retransmitted without considering the characteristics of the data to be retransmitted as in the second proposal, a delay occurs in the data itself. As a result, for example, there may be a problem in displaying the current time or reproducing the melody. In addition, the transmission efficiency of the entire ATM cell is impaired.

Accordingly, an object of the present invention is to quickly retransmit data in a predetermined unit transmitted by an ATM cell that needs to be retransmitted or an ATM cell including the ATM cell when an error occurs in transmission of the ATM cell. By doing so, an object is to provide an ATM communication system that enables efficient transmission of the entire ATM cell.

According to the first aspect of the present invention, (a) an ATM cell transmitting means for sequentially transmitting ATM cells and a data storing means for storing a set of data that is a base before assembling the ATM cells transmitted by the ATM cell transmitting means. When the retransmission request data requesting retransmission is sent from the receiving side of the ATM cell transmitted by the ATM cell transmitting means to the specific batch of data transmitted by the ATM cell, the corresponding batch from the data storage means. And when this is a set of data using the TCP protocol, retransmission necessity determining means for determining that retransmission is necessary, and retransmission when the retransmission necessity determining means determines that retransmission is required. A transmission side device comprising data retransmission means for retransmitting a set of data requested by an ATM cell; An ATM cell receiving means for receiving an ATM cell sent from the ATM cell transmitting means of the transmitting side device, and a data assembling means for assembling the above-mentioned set of original data from the ATM cell received by the ATM cell receiving means; The error detection means for detecting when an error occurs in the ATM cell received by the ATM cell receiving means, and the ATM cell receiving means receives the ATM cell before the ATM cell in which the error detection means detects that a transmission error has occurred. Of the group of data assembled by the data assembling means based on the ATM cell, the data specifying means for specifying the newest data and the data specified by the data specifying means among the data stored in the data storage means. Next to the group of data, the group of data transmitted by the ATM cell transmission means is re-transmitted. A reception side device comprising: a retransmission request data generation unit for generating retransmission request data for requesting a retransmission request; and a retransmission request data transmission unit for transmitting the retransmission request data generated by the retransmission request data generation unit to the transmission side device. It is provided in the communication system.

That is, according to the first aspect of the present invention, it is possible to determine whether or not retransmission is necessary, and to request retransmission in a unit of a group of data as transmission data before being assembled into an ATM cell to be transmitted by the transmission side apparatus. To do. The receiving side device is provided with data assembling means for assembling the original batch of data from the received ATM cell, and when the error detecting means detects a transmission error of the ATM cell, the assembled batch of data. The newest of these is identified. In other words, the group of data sent by the transmission side device is specified immediately before the group of data that is the source of the ATM cell in which the transmission error has occurred. Then, retransmission request data for requesting retransmission of the batch of data transmitted next to the specified batch of data is generated, and this is transmitted to the transmission side device. On the other hand, the transmission side device is provided with data storage means for storing a set of data as a transmission data before assembling into an ATM cell to be transmitted, and when this retransmission request data is received, the retransmission is performed. The requested batch of data is retrieved from this data storage means. When this is a set of data using the TCP protocol, it is determined that retransmission is necessary, and the set of data is retransmitted. As a result, when it is discriminated whether or not retransmission is necessary for each set of data that is the basis of the ATM cell, it is possible to cope with this distinction without determining whether or not retransmission is required by the ATM cell. Can be retransmitted.

As described above, in the present invention, when the receiving side detects an ATM cell transmission error, the receiving side requests the transmitting side to retransmit a set of data transmitted by the ATM cell or the ATM cell including the ATM cell. The transmission side searches for a corresponding group of data from the data storage means, determines that retransmission is necessary when this is the above-described group of data using the TCP protocol , and performs retransmission. As a result, when an error occurs in the transmission of the ATM cell, the retransmission can be performed quickly, and the ATM cell can be efficiently transmitted in order to suppress the retransmission of the ATM cell or data that does not need to be retransmitted.

  Hereinafter, the present invention will be described in detail with reference to examples.

  FIG. 1 shows an outline of an ATM communication system according to an embodiment of the present invention. The ATM communication system 101 includes an ATM network 102, a first communication terminal 103 that transmits ATM cells via the ATM network 102, and a second communication terminal 104 that receives ATM cells.

  The first communication terminal 103 is provided with a first data processing unit 111 that performs various data processing, and a first ATM processing unit 112 that performs processing related to ATM cells using a predetermined ATM protocol. In addition, a first packet processing unit 113 that performs packet processing such as packet generation and data extraction as a unit of transmission and reception using various communication protocols that belong to a layer higher than the ATM layer such as the TCP protocol is provided. . Further, a first AAL processing unit 114 that performs AAL (ATM Adaptation Layer) processing such as packet disassembly and assembly is provided.

  The first packet processing unit 113 includes a first packet transmission processing unit 121 that stores data received from the first data processing unit 111 in a packet, and first data processing by extracting data from the received packet. A first packet reception processing unit 122 to be passed to the unit 111 is provided. Also provided is a packet storage queue 123 for temporarily storing packets, a packet storage processing unit 124 for storing packets in the packet storage queue 123, and a retransmission packet generation unit 125 for generating packets to be retransmitted. It has been.

  The first AAL processing unit 114 performs AAL protocol transmission processing on the packet to be transmitted received from the first packet processing unit 113, disassembles the packet, and stores it as data stored in the ATM cell payload. A first AAL transmission processing unit 126 for generating the cell data is provided. Also, a first AAL reception processing unit 127 is provided that assembles the original packet from the received cell data and passes the assembled packet to the first packet processing unit 113.

  The first ATM processing unit 112 generates an ATM cell based on the cell data received from the first AAL processing unit 114, and sends it to the second communication terminal 104 using a predetermined ATM protocol. A first ATM transmission processing unit 128 that performs the transmission processing is provided. In addition, the ATM cell received from the second communication terminal 104 is subjected to reception processing using a predetermined ATM protocol, and the cell data is extracted and passed to the first AAL reception processing unit 127. A reception processing unit 129 is provided. Further, it is detected whether the cell data extracted from the received ATM cell is a retransmission request cell requesting retransmission of the packet or a normal cell as a normal cell, and the retransmission is performed in accordance with the detection result. A request cell detector 130 is provided. In the case of a retransmission request cell, information that can identify a packet included in the retransmission request cell is passed to the retransmission packet generation unit 125, and in the case of a normal cell, cell data is passed to the first AAL reception processing unit 127. It will be.

  On the other hand, the second communication terminal 104 also performs processing related to ATM cells using the same predetermined ATM protocol as the first data processing unit 111 and the second data processing unit 141 that similarly performs various data processing. A second ATM processing unit 142 is provided. A second packet processing unit 143 that performs packet processing according to various communication protocols belonging to a layer higher than the ATM layer and a second AAL processing unit 144 that performs AAL processing are provided.

  The second packet processing unit 143 extracts the data from the received packet and passes it to the second data processing unit 141 and the data received from the second data processing unit 141. A second packet transmission processing unit 152 that performs packet processing to be stored in the packet is provided.

  The second AAL processing unit 144 is provided with a second AAL transmission processing unit 156 that decomposes the packet received from the second packet processing unit 143 and generates cell data to be stored in the payload of the ATM cell. . The second AAL transmission processing unit 156 performs AAL protocol transmission processing on the packet received from the second packet reception processing 152, and the packet is broken down into cells. The disassembled cell is transferred to the second ATM transmission processing unit 158 of the second ATM processing unit 142. The second AAL processing unit 144 includes a second AAL reception processing unit 157 that assembles the original packet from the cell data stored in the received ATM cell and passes the assembled packet to the second packet processing unit 143. It has been.

  The second ATM processing unit 142 uses a predetermined ATM protocol for the cell data received from the second AAL processing unit 144 or the retransmission request cell described below in the second ATM processing unit 142. A second ATM transmission processing unit 158 that performs transmission processing to the first communication terminal 103 is provided. In addition, the ATM cell received from the first communication terminal 103 is subjected to reception processing using a predetermined ATM protocol, and the second detects the loss of the ATM cell transmitted from the first communication terminal 103. An ATM reception processing unit 159 is provided. When detecting the loss of the ATM cell, the second ATM reception processing unit 159 outputs a retransmission request cell generation request. The retransmission request cell generation request is input to the retransmission request cell generation unit 160. When there is a retransmission request cell generation request from the second ATM reception processing unit 159, the retransmission request cell generation unit 160 receives information from the second packet reception processing unit 151 that can identify the packet in the most recently received packet. Then, a retransmission request cell as a cell for a retransmission request to which this information is added is generated and passed to the second ATM transmission processing unit 158. Here, the information that can identify the packet includes, for example, a header checksum value of the IP (Internet Protocol) protocol and a sequence number of the TCP protocol. The second ATM reception processing unit 159 passes this cell to the second AAL reception processing unit 157 when the loss of the ATM cell is not detected. The second AAL reception processing unit 157 performs AAL protocol reception processing on the cell received from the second ATM reception processing unit 159, and the cell is assembled into a packet. The assembled packet is transferred to the second packet reception processing unit 151.

  Processing when data is transmitted from the first communication terminal 103 to the second communication terminal 104 in the ATM communication system 101 as described above will be described.

  The first data processing unit 111 of the first communication terminal 103 passes the data to be transmitted to the second communication terminal 104 to the first packet transmission processing unit 121. The first packet transmission processing unit 121 first converts the received data into a packet in a format corresponding to the application software that generated the data.

  Communication using ATM has a feature that even if the required communication speed differs for each data to be transmitted, it can be efficiently transferred at a speed suitable for each data. Further, even if the protocol applied in the higher layer than the ATM layer is different for each data to be transmitted, there is a feature that various processes by each protocol can be realized. The first packet processing unit 113 uses a so-called streaming protocol used in streaming, which is a technique for reproducing data while receiving it, in addition to the TCP protocol described above.

  In such streaming protocols such as the UDP (User Datagram Protocol) protocol, retransmission processing is not performed, but header processing of streaming packets such as UDP packets, which are transmission units, is simple and can be transferred at high speed. There is. In other words, the streaming protocol is applied to data that is required to reach the destination as quickly as possible rather than the reliability related to the arrival of the data at the destination, and is adopted by many application softwares like the TCP protocol. .

  In the first packet transmission processing unit 121, for example, data that needs to ensure the reachability of data to the destination, such as data created by e-mail or application software for document creation, is converted into a TCP packet. It has become so. For example, data that is required to reach the destination as fast as possible, such as streaming video data and music data, is converted into a UDP packet that is not retransmitted. When the first packet transmission processing unit 121 receives a series of data to be converted into a TCP packet from the first data processing unit 111, the first packet transmission processing unit 121 determines the position in the series of data when generating the TCP packet. The sequence number to be indicated is described in the header area. Specifically, the total number of bits of data transmitted before the TCP packet in a series of data is described.

  The first packet transmission processing unit 121 further converts these generated packets into IP packets that are transmission / reception units in the IP (Internet Protocol) protocol. At this time, in the header area of the IP packet, the IP address of the second communication terminal 104 is described as the destination, and a checksum value for checking whether or not a transmission error has occurred in the IP packet on the receiving side. Described. The generated IP packet is passed to the packet storage processing unit 124.

  The packet storage processing unit 124 passes the IP packet received from the first packet transmission processing unit 121 to the first AAL transmission processing unit 126 and stores it in the packet storage queue 123. The packet storage queue 123 stores IP packets by a certain amount of data, and if a new IP packet is stored and exceeds a certain amount of data, the stored IP packet The oldest one is deleted. That is, a new one of the transmitted IP packets is preferentially stored in the packet storage queue 123. This is the case when the IP packet needs to be retransmitted to the second communication terminal 104. Is for. The certain amount of data is an amount for reliably storing data that may be subject to retransmission, and is determined with a predetermined margin in the frequency of retransmission.

  The first AAL transmission processing unit 126 disassembles the IP packet received from the packet storage processing unit 124 and generates cell data of ATM cells. At this time, the cell data is added with information necessary for assembling the decomposed IP packet on the receiving side, a sequence number for detecting the loss of the ATM cell from the missing number, and the like. The IP packet is broken down to 48 bytes. The generated cell data is passed to the first ATM transmission processing unit 128.

  The first ATM transmission processing unit 128 generates an ATM cell destined for the second communication terminal 104 storing the received cell data, and sends it to the ATM network 102.

  When the second ATM reception processing unit 159 of the second communication terminal 104 receives the ATM cell sent from the first ATM transmission processing unit 128 via the ATM network 102, the header error control described in the header area is received. Based on HEC (Header Error Control), whether or not a transmission error has occurred in the ATM cell is detected. Further, the sequence number described in the cell data stored in the received ATM cell is confirmed, and it is detected whether or not there is a loss in the ATM cell sent out by the first ATM transmission processing unit 128 immediately before the ATM cell. . That is, the ATM cell loss is detected by confirming whether or not the sequence numbers of the ATM cells received subsequently correspond to each other.

  If it is determined that a transmission error of the received ATM cell or a loss of the ATM cell that should have been received (hereinafter referred to as a transmission error) has not occurred, the second ATM reception processing unit 159 starts the header from the ATM cell. The area is removed and only the cell data is passed to the second AAL reception processing unit 157. The second AAL reception processing unit 157 assembles the original IP packet from the received cell data based on the added information, and passes it to the second packet reception processing unit 151. The second packet reception processing unit 151 passes the data stored in the received IP packet to the second data processing unit 141, and stores packet specification information as information that can specify the IP packet in a storage area (not shown). Memorize it in the form of overwriting. This packet specifying information is a checksum value described in the header area of the IP packet.

  On the other hand, when the second ATM reception processing unit 159 detects the occurrence of an ATM cell transmission error, the second ATM reception processing unit 159 sends a retransmission request cell generation request to the retransmission request cell generation unit 160. When the retransmission request cell generator 160 receives this signal, the packet specifying information stored in the second packet reception processor 151, that is, a packet indicating the IP packet received immediately before by the second packet reception processor 151. Get specific information. Then, a retransmission request cell in which the packet identification information is stored in the payload is generated and passed to the second ATM transmission processing unit 158. At this time, the specific data for detecting the retransmission request cell on the first communication terminal 103 side is also described in a predetermined area of the payload.

  The second ATM transmission processing unit 158 generates an ATM cell destined for the first communication terminal 103 storing the received retransmission request cell, and sends it to the ATM network 102.

  In addition, the second data processing unit 141, the second packet transmission processing unit 152, and the second AAL transmission processing unit 156 include the first data processing unit 111, the first packet transmission processing unit 121, and the first AAL. The same processing as that of the transmission processing unit 126 is performed. Then, the second ATM transmission processing unit 158 also generates an ATM cell destined for the first communication terminal 103 for the cell data received from the second AAL transmission processing unit 156 and sends it to the ATM network 102. To do.

  When the first ATM reception processing unit 129 of the first communication terminal 103 receives the ATM cell sent from the second ATM transmission processing unit 158 via the ATM network 102, the first ATM reception processing unit 129 removes the header area from the ATM cell and receives the cell. Only the data is passed to the retransmission request cell detection unit 130.

  The retransmission request cell detection unit 130 determines whether the received data is a retransmission request cell generated by the retransmission request cell generation unit 160. This determination is performed by confirming whether or not specific data is described in a predetermined area of the cell data. If it is determined that the cell data is not the retransmission request cell but is composed of only normal data generated by the second AAL transmission processing unit 156 of the second communication terminal 104, the first AAL reception is performed as it is. The data is passed to the processing unit 127. The first AAL reception processing unit 127, the first packet reception processing unit 122, and the first data processing unit 111 are the second AAL reception processing unit 157, the second packet reception processing unit 151, and the second data processing. The same processing as that of the unit 141 is performed.

  On the other hand, when it is determined that the received data is the retransmission request cell generated by the retransmission request cell generation unit 160 of the second communication terminal 104, the retransmission request cell detection unit 130 extracts the packet identification information, The packet is sent to the packet generator 125.

  When receiving the packet specifying information, the retransmission packet generating unit 125 searches the packet storage queue 123 for the IP packet indicated by the packet specifying information. Specifically, the checksum value of each IP packet stored in the packet storage queue 123 is sequentially compared with the packet specifying information. When the IP packet indicated by the packet specifying information is specified, the IP packet sent next to the IP packet is taken out from the packet storage queue 123. Then, based on the protocol number described in the header area of the extracted IP packet, it is determined whether or not the stored packet is a TCP packet. If it is a TCP packet, retransmission is required. Therefore, this IP packet is transferred to the first AAL transmission processing unit 126 in order to perform this processing.

  The first AAL transmission processing unit 126 receives the IP packet from the retransmission packet generation unit 125 as is received from the packet storage processing unit 124 and appropriately divides it into 48-byte cell data. The data is sent to the ATM transmission processing unit 128. Based on this, the first ATM transmission processing unit 128 generates an ATM cell and transmits it to the second communication terminal 104 via the ATM network 102.

  Note that the second packet processing unit 143 appropriately performs TCP packet retransmission processing according to the TCP protocol. However, since retransmission processing at the ATM layer is performed by the second ATM processing unit 142, even if a transmission error occurs in the ATM cell, retransmission processing by the TCP protocol is hardly performed.

  As described above, according to this embodiment, the transmission protocol detects a transmission error and dynamically sends a retransmission request to the transmission side. Therefore, the TCP protocol performs retransmission after a timeout occurs on the transmission side. Compared to the above, a higher-speed retransmission process can be realized. Also, this retransmission request is made in the ATM layer below the transport layer to which the TCP protocol belongs, and the ATM layer does not specify which packet has a transmission error. Can be performed at high speed. Further, various processes in the upper layer than the ATM layer can be realized as usual. Further, the transmission side determines whether it is necessary to retransmit a packet in which a transmission error has occurred, and in the case of the embodiment, retransmission is performed only in the case of a TCP packet. Can be prevented from decreasing due to retransmission. In addition, for example, the streaming protocol is usually passed to the higher-layer protocol in the order of arrival at the receiving side, and when the data is retransmitted later, the data is out of order and retransmitted to an inappropriate position. Data can be prevented from being inserted.

<Modification of the present invention>

  In the embodiment described above, the packet storage processing unit, the packet storage queue, the retransmission packet generation unit, and the retransmission request cell detection unit are provided only in the transmission side communication terminal, and the retransmission request cell generation unit is provided only in the reception side communication terminal. The case where it is provided has been described. However, many communication terminals used in actual communication perform both transmission and reception. In the modification of the present invention, a case will be described in which these communication units are commonly provided in a normal communication terminal having no distinction between the transmission side and the reception side.

  FIG. 2 shows a configuration of a third communication terminal used in the ATM communication system according to the modification of the present invention. The third communication terminal 303 corresponds to the first communication terminal 103 and the second communication terminal 104 in FIG. 1 of the embodiment. The third communication terminal 303 performs packet processing, a third data processing unit 311 that performs various data processing, a third ATM processing unit 312 that performs processing related to ATM cells using a predetermined ATM protocol, and the like. A third packet processing unit 313 and a third AAL processing unit 314 that performs AAL processing are provided.

  Similar to the first packet processing unit 113 in FIG. 1, the third packet processing unit 313 includes a third packet transmission processing unit 321, a third packet reception processing unit 322, a packet storage queue 323, and a packet storage. A processing unit 324 and a retransmission packet generation unit 325 are provided. The third AAL processing unit 314 is provided with a third AAL transmission processing unit 326 and a third AAL reception processing unit 327 in the same manner as the first AAL processing unit 114 and the second AAL processing unit 144 in FIG. It has been. The third ATM processing unit 312 includes a third ATM transmission processing unit 328 and a third ATM reception processing in the form of a combination of the first ATM processing unit 112 and the second ATM processing unit 142 of FIG. 329, a retransmission request cell generation unit 360, and a retransmission request cell detection unit 330 are provided. Since each of these processing units performs the same processing as the corresponding processing unit in FIG. 1, description thereof will be omitted.

  By having such a configuration in both communication terminals that perform communication, the effect of the communication system of the embodiment can also be exhibited in bidirectional communication.

  In the embodiment, the packet identification information is the checksum value of the header area of the IP packet. However, the present invention is not limited to this. For example, information on the area corresponding to the sequence number of the TCP packet or the checksum of the TCP packet Information on an area corresponding to the value may be used. Furthermore, although the TCP packet has been described as a packet that needs to be retransmitted, other packets may be retransmitted. In addition, an attribute relating to the necessity of retransmission of data or the importance of arrival at the reception side of data may be stored in the transmission side apparatus, and the presence or absence of retransmission may be determined based on this.

  In the embodiment, the IP packet is stored in the packet storage queue 123 by a certain amount of data. However, the latest IP packet that has been transmitted may be stored within a certain time. In addition, the data to be stored may be in any other data format as long as the corresponding ATM cell can be retransmitted, or the ATM cell itself may be stored for a certain amount or for a certain time. Good.

  Furthermore, in the embodiment, retransmission in units of IP packets when an error occurs has been described. However, retransmission may be requested from the transmission side in units of ATM cells, and the corresponding ATM cell may be retransmitted to the reception side. In this case, if a serial number is attached to the ATM cell and sent to the receiving side, it can be requested to the transmitting side when the ATM cell in which the loss has occurred is determined on the receiving side. In the present invention, since the receiving side requests data retransmission without particularly entering the data contents, the serial number itself may be missing in some cases, and there may be no loss of ATM cells. In such a case, the transmission side does not transmit the missing ATM cell, which is the same as when retransmission is requested for a type of ATM cell that does not require retransmission.

It is a block diagram showing the structure of the ATM communication system by one Example of this invention. It is a block diagram showing the structure of the 3rd communication terminal used with the ATM communication system by the modification of this invention.

Explanation of symbols

101 ATM communication system 102 ATM network 103, 104, 303 Communication terminal 111, 141, 311 Data processing unit 112, 142, 312 ATM processing unit 113, 143, 313 Packet processing unit 114, 144, 314 AAL processing unit 121, 151, 321 Packet transmission processing unit 122, 152, 322 Packet reception processing unit 123, 323 Packet storage queue 124, 324 Packet storage processing unit 125, 325 Retransmission packet generation unit 126, 156, 326 AAL transmission processing unit 127, 157, 327 AAL reception Processing unit 128, 158, 328 ATM transmission processing unit 129, 159, 329 ATM reception processing unit 130, 330 Retransmission request cell detection unit 160, 360 Retransmission request cell generation unit

Claims (3)

ATM cell transmitting means for sequentially transmitting ATM cells, data storage means for storing a set of data before assembling the ATM cells transmitted by the ATM cell transmitting means, and ATM transmitted by the ATM cell transmitting means When retransmission request data for requesting retransmission is sent from a cell receiving side to a specific set of data transmitted by an ATM cell, the corresponding data set is retrieved from the data storage means, and this is the TCP protocol. The retransmission necessity determination means for determining that retransmission is necessary when the data is a set of data using the data, and the batch of data requested for retransmission when the retransmission necessity determination means determines that the retransmission is required. A transmission-side device comprising data retransmission means for retransmitting data by ATM cell;
An ATM cell receiving means for receiving an ATM cell transmitted from the ATM cell transmitting means of the transmitting side device, and a data assembly for assembling the original batch of data from the ATM cell received by the ATM cell receiving means Means, an error detecting means for detecting when an error occurs in the ATM cell received by the ATM cell receiving means, and the ATM cell before the ATM cell in which the error detecting means detects that a transmission error has occurred. The data specifying means for specifying the newest data among a set of data assembled by the data assembling means based on the ATM cell received by the receiving means, and the data specifying among the data stored by the data storage means Next, the ATM cell transmission means transmits a set of data specified by the means. Retransmission request data generation means for generating retransmission request data for requesting retransmission of a batch of data, and retransmission request data transmission means for transmitting the retransmission request data generated by the retransmission request data generation means to the transmission side device. An ATM communication system comprising: a receiving side device . 2. An ATM communication system according to claim 1, wherein said data storage means is means for storing a predetermined amount of said batch of data to be transmitted from the latest data. 2. The ATM communication system according to claim 1 , wherein the data storing means is means for storing the batch of data to be transmitted from the latest data to a past portion of a predetermined time .

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