JP3693523B2 - Data transfer method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for transferring data between two or more devices on a network including a computer system, and more particularly, to a plurality of devices and a plurality of logical protocols using a single physical transmission line. The present invention relates to a data transfer method suitable for simultaneous operation and for executing data transfer operations in units of frames.
[0002]
[Prior art]
Due to recent advances in optical transmission technology, the data transfer capability (bit rate) between computer systems tends to increase from several megabits / second to several gigabits / second. If the bit rate increases, the actual transfer rate (throughput) tends to increase as the bit rate increases. However, in actuality, simply increasing the bit rate of the transmission path may cause command instructions before and after data transfer. In addition, since there is a processing time represented by an end report, an improvement effect commensurate with an increase in the bit rate cannot be obtained.
[0003]
Conventionally, as a means for efficiently using the high bit rate of the transmission line, for example, in the case of a device capable of simultaneously operating in parallel on the same transmission line as described in JP-A-6-187277, frame multiplexing is used. Multiple nodes on the network, such as those that share links and Fiber Channel known by the American National Standards Institute (ANSI) FC-PH REV4.3 (X3.230-199x FIBRECHANEL Physical and Signing REV4.3) One that multiplexes frames transferred between them is well known.
[0004]
These technologies use a transmission line with a single high-speed bit rate to perform data transfer processing that has been realized by using multiple medium- and low-speed transmission lines by operating multiple devices and multiple protocols simultaneously. To achieve this. As a technique for simultaneously operating a plurality of protocols, for example, an SCSI (Small Computer System Interface-face), HIPPI (High-Performance Parallel Interface), SBCCS (Single Byte Com- Some of them operate at the same time.
[0005]
On the other hand, the transmission distance tends to be several kilometers to several tens of kilometers even without relay, and several hundred kilometers through a relay device. Between data transfer devices, prior to data transfer, the transmission side issues a transmission request to the reception side, and in response to this, the reception side returns a response to the transmission side. Since the response waiting time due to the time increases, a data transfer apparatus that attempts to maintain a high transfer rate even over a long distance connection tends to be equipped with a large-capacity data buffer.
[0006]
[Problems to be solved by the invention]
The above-described multiple data transfer processes that have been realized by using multiple medium / low speed transmission lines by operating multiple devices and multiple protocols simultaneously, can be applied to a transmission line having a single high bit rate. The technology to be realized by using is very effective as a means for efficiently using the bit rate of the high-speed transmission path. However, since one transmission line is shared, there are the following problems.
[0007]
First, the first problem is that if a data transfer device multiplexes multiple devices or multiple protocols at the same time using a transmission line with a single high-speed bit rate, protocols with various transfer speeds Alternatively, since the counterpart device is placed on the same transmission path, there is a high possibility that the transfer operation between the devices that are performing the multiplex operation will affect the transfer operation with another device. This was not a problem in the case of a dedicated transmission line.
[0008]
Of course, it is impossible to achieve a performance where the sum of the maximum transfer speeds in the device operating in a multiplex operation exceeds the bit rate of the transmission path, but within the range where the sum of the maximum transfer speeds is lower than the bit rate of the transmission path, It is desirable to guarantee maximum data transfer performance for all operating devices. However, in order to always manage different maximum transfer rates for device units operating independently of each other and perform appropriate performance allocation, complicated processing is required. If proper performance distribution for each multi-operation device is neglected, data is transferred at an unnecessary data transfer speed to a specific device because a transmission path having a high bit rate is used. Necessary devices may not be able to provide sufficient data transfer rates.
[0009]
For example, each port has a frame storage data buffer, temporarily buffers data from a device connected to a port (source side), and transfers it to a device connected to another port (destination side). There is a dynamic switch that performs multiple operations in units of frames (fabric called ANSI FC-PH). When such a dynamic switch device is interposed and data is transferred simultaneously between a plurality of devices, the data buffer of the dynamic switch device is occupied for a long time for data transfer of one low-speed device. The fact that the buffer is occupied for a long time means that the number of frames that can be multiplexed decreases, so if more and more data is sent to this low speed device, it will be transferred to other medium and high speed devices. As a result, it is difficult to dispatch the data buffer to be used, and as a result, the maximum data transfer is performed for all devices that are operating in multiplex even though the total maximum transfer rate is within the range of the bit rate of the transmission line. Event that performance cannot be guaranteed will occur. For this reason, system performance may be significantly degraded unless different maximum transfer rates are always managed in units of devices operating independently of each other and appropriate performance distribution is performed. However, because of the complexity, the overhead is also large and often not as effective as expected.
[0010]
The second problem is that devices that perform multiple operations are not all assigned the same rating for the system, but when they are operating simultaneously on the same transmission path, transfer with a device with a low priority is a device with a high priority. It may affect the transfer to. This is also a problem that occurs because various devices simultaneously transfer data on the same transmission path.
[0011]
For example, on a transmission line with a bit rate of 100 megabytes / second, if only one device with a maximum of 40 megabytes / second is operating, it will be operating at a maximum performance of 40 megabytes / second. However, if 10 devices with a maximum of 40 megabytes / second are operating simultaneously, it is of course impossible for all 10 devices to operate at a maximum performance of 40 megabytes / second. How many megabytes / second is operating depends on the implementation of the data transfer device, but for most data transfer devices, the overall performance (100 megabytes / second) is the number of simultaneous operation devices (10). The average would be 10 megabytes / second. However, in a realistic system, there should be a mix of important and non-critical devices. Two of the critical devices operated at 40 megabytes / second and the remaining eight devices operated at 2.5 megabytes / second However, system performance often increases. For these important devices, a common workaround is to prepare a dedicated transmission line instead of sharing a transmission line, but it will not be possible to efficiently use the bit rate that will continue to develop in the future. End up.
[0012]
The first object of the present invention is to realize an appropriate performance distribution process, which is complicated in the multiplex operation mentioned in the first problem, by simple control and guarantee the data transfer speed for each data transfer device or It is to provide a means to limit.
The second object of the present invention is to provide means for ensuring the performance of a data transfer band for an important data transfer apparatus that has been damaged by the multiplex operation mentioned in the second problem even if the multiplex operation is performed. It is in.
[0013]
[Means for Solving the Problems]
In the present invention, in order to maintain the maximum performance even in a long distance connection, a large-capacity frame storage data buffer mounted on the data transfer device or the dynamic switch device is provided on the connection destination port frame reception side. Manages allocation and usage of data buffers with entries. A data buffer having multiple entries can include one or more device groups based on, for example, the maximum data transfer rate of the partner data transfer device, the transfer logical protocol of the partner data transfer device, or the importance in the system of the partner data transfer device. The frame transmission side apparatus allocates the reception side of the connection destination port for each group.
[0014]
Specify which entry in the frame storage data buffer of the connection destination port receiving device stores the frame transmitted by the transmitting device so that the sending device manages the frame storage data buffer usage of the frame receiving device The connected port frame receiving side device notifies the frame transmitting side device when the frame storing data buffer of the connected device becomes usable due to the frame processing. The information (RDY) indicating buffer release has an open data buffer identifier.
[0015]
The frame transmission side device includes the port addresses, transfer protocols, and maximum data transfer rates of all the other devices that may transfer data, and the data transfer device or dynamic switch device that is the connection destination port reception side device. A data buffer allocation management table is provided that stores the correspondence with the mounted data buffers and the current use status flags of these data buffers. By referring to the data buffer allocation management table, the frame transmission side device can select the data buffer of the connection destination port reception side device by simple control. The contents of the data buffer allocation management table can be changed by software or an operator. This enables, for example, fine-grained buffer allocation to be adjusted in the system based on the data transfer speed and priority of the data transfer device connected by the system administrator, resulting in effective capital investment and system operation. It becomes.
[0016]
According to the present invention, the above-mentioned two problems that occur when a plurality of devices are operated simultaneously on the same transmission path, which is a means for efficiently using the bit rate of the high-speed transmission path, are solved. A transmission line having a high bit rate that is not high can be regarded as a logical dedicated cable not only in terms of function but also in terms of performance. One dedicated cable for a plurality of cables can reduce the cable cost because the number of physical cables is changed from a plurality of cables to one as compared with a conventional dedicated cable. In addition, a single cable that is functionally and functionally dedicated cable is managed for various service providers while maintaining the chargeable object corresponding to multiple dedicated cable lines so far. Since the number of cables decreases, the total investment effect also increases.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a data transfer method according to the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a diagram showing a system configuration of an embodiment to which a data transfer method of the present invention is applied. In FIG. 1, 10 and 30 to 50 are data transfer devices, 20 is a dynamic switch device (fabric or the like referred to as ANSI FC-PH), 60 to 90 are transmission paths for information transmission, and A to D are dynamic switch devices. 20 Each port Is the address assigned to. In FIG. 1, the number of ports of the dynamic switch device 20 is four, but it is of course not limited to this. Therefore, the number of data transfer devices need not be four. Further, the dynamic switch device 20 may itself be a single data transfer device.
[0018]
The data transfer apparatus 10 includes a transmission frame storage buffer 11, a reception frame storage buffer 12, and a data buffer allocation management table 13. The transmission frame storage buffer 11 stores a frame to be transmitted to the data transfer devices 30, 40, and 50 via the dynamic switch device 20. The reception frame storage buffer 12 stores frames received from the data transfer devices 30, 40, 50 via the dynamic switch device 20. The data buffer allocation management table 13 manages the allocation and usage status of the data buffer 21 corresponding to the connection destination port A of the data transfer device 10 in the dynamic switch device 20 described later to the data transfer devices 30, 40, 50. . Specifically, the port address, the transfer protocol, and the maximum data transfer of all the counterpart devices 30, 40, and 50 that the data transfer device 10 may transfer data to speed Manages allocation buffer number, usage status, etc. The configuration within the data transfer devices 30, 40, 50 is the same as that of the data transfer device 10.
[0019]
The dynamic switch device 20 includes a data buffer and a buffer counter for each port. For convenience of explanation, FIG. 1 shows only the data buffer 21 corresponding to the port A and the buffer counter 22 corresponding to the port B. The data buffer 21 is a kind of received frame storage buffer for storing a frame sent from the data transfer apparatus 10 connected to the port A. In this embodiment, there are 8 entries (# 0 to # 7). Exists. The same applies to the data buffers corresponding to the other ports B to D. The buffer counter 22 is for managing the use status of the received frame storage buffer in the data transfer apparatus 30 to which the port B is connected. The buffer counter 22 has an initial value of 0 and is incremented by 1 when a frame is transmitted to the data transfer device 30 to which the port B is connected. RDY) is decremented by one. The same applies to the buffer counters corresponding to the other ports A, C, and D.
[0020]
FIG. 2 shows a format of a frame exchanged between the data transfer apparatuses 10, 30, 40, and 50 via the dynamic switch apparatus 20, and shows a destination port address field, a source port address field, a frame identification field, and a buffer ID. It consists of fields and data fields. In FIG. 2, the maximum data field is 2 kilobytes, but this is limited to the buffer capacity in one entry of the data buffer (received frame storage buffer) built in the data transfer device or dynamic switch device. 2 kilobytes is a numerical value given as an example, and does not limit the present invention. FIG. 3 notifies the partner device that the buffer (data buffer in the dynamic switch device and buffer for storing received frames in the data transfer device) is opened in the dynamic switch device 20 or the data transfer devices 10, 30, 40, and 50. The link control word (RDY) of the buffer release notification is indicated, and is composed of a link control word identification field and a buffer ID field.
[0021]
4 and 5 show a configuration example of the data buffer allocation management table 13 in the data transfer apparatus 10. The data buffer allocation management table 13 is created based on the system configuration information when the system is started up. The same applies to the data buffer allocation management tables existing in the other data transfer apparatuses 30, 40, and 50.
[0022]
FIG. 4 shows that the number of entries in the data buffer 21 in the dynamic switch device 20 is 8 entries (# 0 to # 7), and all the partner data transfer devices 30 to 50 that may transfer data have the same priority and data transfer. Since the devices 30 and 40 have the protocol SBCCS, the maximum data transfer performance is 40 megabytes / second, the data transfer device 50, the protocol is the SCSI, and the maximum data transfer performance is 10 megabytes / second, the number of entries in the data buffer 21 Are assigned 3 entries for the data transfer device 30 (# 0, # 1, # 2 of the data buffer 21) and 3 entries for the data transfer device 40 (# 3, # 4, # 5 of the data buffer 21). 1 entry for the data transfer device 50 (# 6 of the data buffer 21), 1 entry for the multipurpose (# 7 of the data buffer 21) It is an example of. The multi-purpose buffer is for use in reporting and recovery after failure detection. The in-use flag indicates “0” when the entry is empty, and indicates “1” when the entry is in use.
[0023]
In FIG. 5, the data transfer device 30 has the highest priority, the remaining data transfer devices 40 and 50 have the same priority, the data transfer device 30 has the protocol HIPPI, and the maximum data transfer performance is 75 megabytes / second. 40 and 50 are both SBCCS and the maximum data transfer performance is 40 megabytes / second. Therefore, the allocation of the number of entries in the data buffer 21 of the dynamic switch device 20 is assigned to the 6 entries (data # 0, # 1, # 2, # 3, # 4, # 5) of the buffer 21, two entries of the same group for the data transfer device 40 and the data transfer device 50 (# 6, # 7 of the data buffer 21) In this example, no multi-purpose entry is assigned.
[0024]
As shown in FIGS. 2 and 3, the first feature of the present embodiment is that the stored data buffer information (buffer ID) of the connection destination port in the frame is converted into a link control word (RDY) that means release of the data buffer. Each has open data buffer information (buffer ID). As a result, the frame transmission side can manage whether or not a specific entry of the data buffer in the connection destination port is currently in use.
[0025]
The second feature of this embodiment is that, as shown in FIGS. 4 and 5, the frame transmission side has a table (data buffer allocation management table) for managing allocation of data buffers of connection destination ports. This data buffer allocation management table includes the port addresses, transfer protocols, and maximum data transfer speeds of all the other devices that may transfer data, and the data transfer device or dynamic switch device that is the connection destination port receiving device. Holds the correspondence with the mounted data buffers and the current usage status flags of those data buffers. By referring to this data buffer allocation management table and selecting a data buffer of the connection destination port receiving side device, the frame transmitting side device can realize appropriate performance distribution processing with simple control.
[0026]
The third feature of this embodiment is that the data buffer of the connection destination port is allocated for each final data transfer destination. Depending on the maximum data transfer rate of the destination data transfer device that can execute the transfer operation, the transfer logical protocol of the destination data transfer device, or the importance in the system of the destination data transfer device, the frame for one or more device groups The transmission side device allocates the data buffer of the connection destination port for each final data transfer destination, and further secures the data transfer bandwidth for the specific important device by referring to the data buffer allocation management table of the second feature. A simple performance distribution process can be realized with simple control.
[0027]
The fourth feature of the present embodiment is that the data buffer allocation management table of the second feature can be changed by software or an operator. This makes it possible to adjust fine-grained buffer allocation within the system based on, for example, the data transfer speed and priority of the data transfer device to which the system administrator is connected, resulting in effective capital investment and system operation. It becomes possible.
[0028]
First, based on FIG. 1 to FIG. 4, the data of this embodiment is simply taken from the data transfer device 10 through the dynamic switch device 20 to the data transfer device 30 (data transmission) as an example. An outline of the transfer operation will be described. Of course, it goes without saying that the data transfer operation is actually performed in a unit of frame between the data transfer device 10 and the plurality of data transfer devices 30 to 50 via the dynamic switch device 20.
[0029]
FIG. 6 is a flowchart when the data transfer apparatus 10 operates as a frame transmission side. 7 is a flowchart when the port receives a frame from the data transfer device to which the port is connected in the dynamic switch device 20, and FIG. 8 is a flowchart when the port transmits a frame to the data transfer device 30 to which the port is connected. It is.
[0030]
In FIG. 6, the data transfer device 10 determines whether there is a frame to be transmitted to the partner data transfer device 30, 40, 50 in the transmission frame storage buffer 11, and previously transmitted from the dynamic switch device 20. It is monitored whether a data buffer release notification (RDY) for the frame is received (steps 601 to 606).
[0031]
Now, when it is determined that there is a transmission frame for the data transfer device 30 (step 601), the data transfer device 10 refers to the data buffer allocation management table 13 (step 607), and in the data buffer 21 of the dynamic switch device 20 It is determined whether there is an available buffer in the buffers (# 0, # 1, # 2 in FIG. 4) assigned to the data transfer device 30 (step 608). Here, if there is no usable buffer, transmission of the frame to the data transfer device 30 is suspended.
[0032]
On the other hand, if there is an available buffer, the data transfer apparatus 10 selects the buffer (for example, # 0) (step 609) and sets the corresponding busy flag in the data buffer allocation management table 13 to “1”. (Step 610). If there are a plurality of usable buffers, for example, the one with the smaller number is selected. Next, the data transfer apparatus 10 assembles a transmission frame for the data transfer apparatus 30 in the format shown in FIG. 2 and transmits it to the dynamic switch apparatus 20 via the transmission path 60 (step 611). That is, in FIG. 2, the port address B of the dynamic switch device 20 to which the data transfer device 30 (final frame receiving device) is connected is transferred to the destination port address field in the frame, and the data transfer is transferred to the source port address field. The port address A of the dynamic switch device 20 to which the device 10 (frame transmission device) is connected, the identification information of the frame in the frame identification field, and the buffer number selected in step 609 (for example, FIG. If the currently available buffer number in the table of 4 is 0, # 0) is entered in the data field, and in this example, transfer data of a maximum of 2 kilobytes is entered. When the data transfer device 10 transmits the frame to the dynamic switch device 20, the data transfer device 10 returns to the step immediately after the branch is established (step 612), and executes the next process.
[0033]
In the dynamic switch device 20, the processes of FIGS. 7 and 8 are executed in parallel at each port.
Now, when the port A receives a frame from the connected data transfer apparatus 10 (step 701), the entry (eg, # 0) indicated by the buffer ID field in the received frame in the data buffer 21 corresponding to the port A concerned. Then, the received frame from the data transfer apparatus 10 is temporarily stored (step 702), and a frame transmission request is issued to the port (port B in this example) indicated by the destination address field in the received frame (step 703). . Thereafter, when transmission is permitted from the port B side (step 704), the frame stored in the entry # 0 in the data buffer 21 is transmitted to the port B (step 705). Then, the entry # 0 of the data buffer 21 is released (step 706), and the entry (buffer) # 0 is entered in the buffer ID field for the data transfer apparatus 10 to which the port A is connected. A buffer release notification (RDY) in the format shown in FIG. 6 is transmitted (step 707).
[0034]
On the other hand, when there is a frame transmission request on the port B side (step 801), the buffer counter 22 checks whether there is an available buffer (empty entry) in the reception frame storage buffer in the data transfer device 30 at the connection destination. (Step 802). If there is no usable buffer, the frame transmission request is put on hold until an available buffer is generated. If there is an available buffer in the buffer for storing received frames in the partner data transfer device 30, a transmission permission is issued to the source port side (port A in this example) of the frame transmission request (step 803) and received from the source port side. The frame is transmitted to the data transfer device 30 (step 804), and the buffer counter 22 is incremented by 1 (step 805). When receiving a buffer release notification (RDY) from the data transfer device 30, the port B side decrements the buffer counter 22 by 1 (steps 806 and 807).
[0035]
Returning to the operation of the data transfer apparatus 10 in FIG. 6, when the data transfer apparatus 10 receives a buffer release notification (RDY) from the dynamic switch apparatus 20 in any of steps 602, 604, and 606, the buffer ID field of the RDY The in-use flag corresponding to the corresponding buffer (buffer # 0 in this example) in the data buffer allocation management table 13 is reset by the buffer ID (step 613).
[0036]
As described above, in the data transfer device 10, when the in-use flag corresponding to the selected buffer in the data buffer allocation management table 13 is reset, the buffer, that is, the data buffer of the dynamic switch device 20 is again used thereafter. It is possible to transmit a frame using the 21 entries.
[0037]
Here, the relationship between the number of entries in the data buffer 21 of the dynamic switch device 20 and the data transfer rate when the data transfer device 10 continuously transmits data to the data transfer device 30 will be described. As preconditions, the bit rate of the transmission line 60 and the transmission line 70 is 1062.5 megabits / second (about 100 megabytes / second), the cable length of the transmission line 60 is 10 kilometers, and the propagation delay time of the transmission line 60 is 5 microseconds. / Km, and the number of data bytes in the transmission frame is 2 kilobytes. In this case, 5 microseconds / km × 10 kilometers = 50 microseconds from the time when the data transfer device 10 sends the first byte of the transmission frame to the transmission path 60 until it reaches the dynamic switch device 20, the frame in the dynamic switch device 20 From receiving the first byte of the frame until the last byte of the frame is received, 1 ÷ 100 megabytes / second × 2 kilobytes = 20 microseconds, after the dynamic switch device 20 receives the last byte of the frame, Assuming that the first byte is transferred, from receiving the last byte of the frame to transferring the last byte of the frame to the destination port address B, 1 ÷ 100 megabytes / second × 2 kilobytes = 20 microseconds, destination 5 microseconds / km × 10 km = 50 until the data transfer device 10 is reached after the dynamic switch device 20 transmits the RDY for notifying the release of the data buffer after the frame has been transferred to the transmission port address B It takes microseconds. Therefore, the time during which the in-use flag corresponding to the selected buffer (referred to as buffer # 0) in the data buffer allocation management table 13 is set is 50 microseconds + 20 microseconds + 20 microseconds + 50 microseconds = 140 microseconds. It will be seconds. Since buffer # 0 cannot be used for 140 microseconds, it is necessary to select another buffer and transmit the frame in order to transmit transmission frames continuously. This is because, in order to achieve the maximum data transfer rate of 100 megabytes / second on the transmission line 60 between the data transfer device 10 and the dynamic switch device 20, the data buffer for continuing to transmit frames for 140 microseconds is at least 140 microseconds. Second / 20 microseconds = 7 entries, indicating that the data buffer 21 of the dynamic switching device 20 on the frame receiving side is necessary. In other words, if there are 7 entries of 2 kilobyte data buffers, the data transfer rate can be achieved at 100 megabytes / second, but if 6 entries, 6 entries × 2 kilobytes / 140 microseconds = 85.7 megabytes / second, In the case of 5 entries, 5 entries × 2 kilobytes / 140 microseconds = 71.4 megabytes / second, and the data transfer rate decreases by 14.3 megabytes / second every time one entry is reduced.
[0038]
The present invention uses the characteristic that the data transfer rate increases / decreases as the number of data buffer entries increases / decreases, and implements an appropriate performance allocation process that is complex in a multiplex operation by simple control. It is intended to provide means for guaranteeing or limiting the data transfer rate for the data transfer, and means for ensuring the performance of the data transfer band for important devices that have been impaired by the multiplex operation even if the multiplex operation is performed.
[0039]
Next, an operation example in which the data transfer apparatus 10 performs multiple data transfer simultaneously with a plurality of data transfer apparatuses 30, 40, and 50 will be described. In the first operation example, when the sum of the maximum transfer speeds of the devices (data transfer devices 30, 40, and 50) performing the multiplex operation is lower than the bit rate of the transmission path, the maximum data transfer performance can be guaranteed for each device. Explain things. In the second operation example, when the sum of the maximum transfer speeds of the devices (data transfer devices 30, 40, and 50) that perform multiple operations exceeds the bit rate of the transmission path, the highest priority device (the data transfer device 30 in this example) Explain that the maximum data transfer performance can be guaranteed.
[0040]
[Operation Example 1]
It will be described that the maximum data transfer performance can be guaranteed for each device when the sum of the maximum transfer rates in the devices (data transfer devices 30, 40, 50) operating in a multiplex operation is lower than the bit rate of the transmission path. The contents of the data buffer allocation management table 13 used in this operation example are as shown in FIG.
[0041]
Here, the bit rate of all the transmission lines 60 to 90 is 1062.5 megabits / second, the number of entries in the data buffer 21 of the dynamic switch device 20 is 8 entries, the maximum number of data bytes in one frame is 2 kilobytes, and the data transfer device The maximum data transfer performance of 30 is 40 megabytes / second, the maximum data transfer performance of the data transfer device 40 is 40 megabytes / second, the maximum data transfer performance of the data transfer device 50 is 10 megabytes / second, and the data transfer device 10 is dynamic. It is assumed that simultaneous data transfer operation is performed with these data transfer devices 30, 40 and 50 via the switch device 20.
[0042]
The data transfer device 10 has eight entries in the data buffer 21 of the dynamic switch device 20, all data transfer devices have the same priority, the maximum data transfer rate of the data transfer devices 30, 40, 50, and one data buffer entry. Since the occupation time (busy time) is about 140 microseconds, the number of entries in the data buffer 21 is allocated to 3 entries (# 0, # 1, # 2) for the data transfer device 30 and for the data transfer device 40. 3 entries (# 3, # 4, # 5), 1 entry (# 6) for the data transfer apparatus 50, 1 entry (# 7) for multi-purpose use, and the contents of the data buffer allocation management table 13 shown in FIG. Is created at system startup. The multipurpose buffer (# 7) is prepared exclusively for use in reporting and recovery after failure detection, but is not particularly relevant to the present invention.
[0043]
First, it is assumed that data transfer is started between the data transfer device 10 and the data transfer device 30. Since the data transfer device 10 can determine from the contents of the data buffer allocation management table 13 in FIG. 4 that the buffers available to the data transfer device 30 are # 0 to # 2, the first frame has the buffer # 0. Suppose you use it. After the in-use flag corresponding to buffer # 0 is set in data buffer allocation management table 13, the frame containing buffer # 0 is transmitted. Thereafter, in order to transmit the second frame, the contents of the data buffer allocation management table 13 are read again. Since the buffer # 0 is in use this time, the buffer # 1 is selected, the in-use flag corresponding to the buffer # 1 is set in the data buffer allocation management table 13, and the frame containing the buffer # 1 is transmitted. Thereafter, in order to transmit the third frame, the contents of the data buffer allocation management table 13 are read again. Since buffer # 0 and buffer # 1 are in use this time, buffer # 2 is selected, and the in-use flag corresponding to buffer # 2 is set in data buffer allocation management table 13, and then the frame containing buffer # 2 is selected. Send.
[0044]
Thereafter, in order to transmit the fourth frame, the contents of the data buffer allocation management table 13 are read again. This time, buffers # 0 to # 2 are in use, and all the allocated buffers are in use, so the buffer cannot be selected. In this case, frame transmission is suppressed until a link control word (RDY) for notifying the release of the data buffer from the connection destination port is received. If no failure or the like occurs, RDY of buffer # 0 is returned when about 140 microseconds have elapsed after transmitting the first frame. After resetting the in-use flag of the data buffer allocation management table 13 by this RDY reception, the buffer # 0 is selected to transmit the fourth frame, and the in-use flag corresponding to the buffer # 0 is set in the data buffer allocation management table 13 Then, the frame with buffer # 0 is transmitted.
[0045]
Thereafter, the contents of the data buffer allocation management table 13 are read again in order to transmit the fifth frame. Since the buffers # 0 to # 2 are in use again and all assigned buffers are in use, the buffer # cannot be selected. Therefore, similarly to the above, frame transmission is suppressed until a link control word (RDY) for notifying the release of the data buffer from the connection destination port is received. Similarly, when about 140 microseconds elapses after transmitting the second frame, the RDY of the buffer # 1 is returned. After the reset operation of the in-use flag of the data buffer allocation management table 13 by this RDY reception, the buffer # 1 is selected to transmit the fifth frame, and the in-use flag corresponding to the buffer # 1 is set in the data buffer allocation management table 13 Then, the frame containing buffer # 1 is transmitted.
[0046]
The above operation is repeated in buffers # 0 to # 2 until the final frame transmission. At this time, since the data transfer rate between the data transfer device 10 and the dynamic switch device 20 transmits 3 frames (for 6 kilobytes) in 140 microseconds, 6 kilobytes / 140 microseconds = 42.8 megabytes / second. Thus, the maximum transfer rate of the data transfer device 30 is over 40 megabytes / second.
[0047]
Next, it is assumed that data transfer between the data transfer device 10 and the data transfer device 30 and data transfer between the data transfer device 10 and the data transfer device 40 are started simultaneously. First, the data transfer apparatus 10 reads the contents of the data buffer allocation management table 13 in order to transmit the first frame to the data transfer apparatus 30. At first, since all the buffers # 0 to # 2 corresponding to the data transfer device 30 are usable, the buffer # 0 is selected, and the in-use flag corresponding to the buffer # 0 is set in the data buffer allocation management table 13, and then the buffer A frame with # 0 is transmitted. Since the service of the data transfer device 30 has ended, the service of the data transfer device 40 is now performed. Therefore, the data transfer apparatus 10 reads the contents of the data buffer allocation management table 13 in order to transmit the first frame to the data transfer apparatus 40. At first, since all the buffers # 3 to # 5 corresponding to the data transfer apparatus 40 are usable, the buffer # 3 is selected, and after the busy flag corresponding to the buffer # 3 is set in the data buffer allocation management table 13, the buffer The frame with # 3 is transmitted. When the service of the data transfer device 40 ends, the service returns to the service of the data transfer device 30 again.
[0048]
The data transfer device 10 reads the contents of the data buffer allocation management table 13 to transmit the second frame to the data transfer device 30. Since the buffer # 0 is in use, the buffer # 1 is selected, the in-use flag corresponding to the buffer # 1 is set in the data buffer allocation management table 13, and then the frame containing the buffer # 1 is transmitted. Since the service of the data transfer device 30 has ended, the service of the data transfer device 40 is returned again. Therefore, the data transfer device 10 reads the contents of the data buffer allocation management table 13 in order to transmit the second frame to the data transfer device 40. Since the buffer # 3 is in use, the buffer # 4 is selected, the in-use flag corresponding to the buffer # 4 is set in the data buffer allocation management table 13, and then the frame containing the buffer # 4 is transmitted. Since the service of the data transfer device 40 is completed, the service of the data transfer device 30 is returned to.
[0049]
The data transfer apparatus 10 reads the contents of the data buffer allocation management table 13 to transmit the third frame to the data transfer apparatus 30. Since the buffers # 0 to # 1 are in use, the buffer # 2 is selected, the in-use flag corresponding to the buffer # 2 is set in the data buffer allocation management table 13, and then the frame containing the buffer # 2 is transmitted. Since the service of the data transfer device 30 is completed, the service of the data transfer device 40 is returned to. The data transfer device 10 reads the contents of the data buffer allocation management table 13 in order to transmit the third frame to the data transfer device 40. Since the buffers # 3 to # 4 are in use, the buffer # 5 is selected, the in-use flag corresponding to the buffer # 5 is set in the data buffer allocation management table 13, and then the frame containing the buffer # 5 is transmitted. Since the service of the data transfer device 40 is completed, the service of the data transfer device 30 is returned to.
[0050]
The data transfer device 10 reads the contents of the data buffer allocation management table 13 to transmit the fourth frame to the data transfer device 30. This time, the buffers # 0 to # 2 are in use, all the buffers assigned to the data transfer device 30 are in use, and the buffer cannot be selected. Therefore, the data transfer device 10 ends the service of the data transfer device 30 by waiting for RDY to be returned to any of the buffers # 0 to # 2. Since the service of the data transfer device 30 is completed, the service of the data transfer device 40 is returned to. In order to transmit the fourth frame to the data transfer device 40, the contents of the data buffer allocation management table 13 are read. However, since the buffers # 3 to # 5 are also in use and all the buffers assigned to the data transfer device 40 are in use, the buffer # cannot be selected. By waiting for the RDY to be returned to any of the buffers # 3 to # 5, the service of the data transfer device 40 is terminated.
[0051]
Thereafter, in the data transfer device 10, when RDY is returned and the in-use flag of the data buffer allocation management table 13 of the corresponding buffer is reset, the operation of transmitting the frame waiting for the purpose of using the corresponding buffer is performed. The frame for the transfer device 30 is repeated in the buffers # 0 to # 2, and the frame for the data transfer device 40 is repeated in the buffers # 3 to # 5.
[0052]
At this time, since the data transfer rate between the data transfer device 10 and the dynamic switch 20 is transmitting 6 frames (for 12 kilobytes) in 140 microseconds, 12 kilobytes / 140 microseconds = 85.7 megabytes / second. It becomes. Further, since the distribution to the data transfer device 30 and the data transfer device 40 is 3 frames each, both devices are 42.8 megabytes / second, which is the maximum transfer rate of the data transfer device 30 and the data transfer device 40. It exceeds 40 megabytes / second. Further, the maximum transfer rate is not changed even when the data transfer device 30 is operating alone, and is not affected by the simultaneous operation at all, and the performance distribution is ideal.
[0053]
Next, it is assumed that data transfer between the data transfer device 10 and the data transfer devices 30, 40, and 50 is started simultaneously. First, the data transfer apparatus 10 reads the contents of the data buffer allocation management table 13 in order to transmit the first frame to the data transfer apparatus 30. Since all the buffers # 0 to # 2 corresponding to the data transfer device 30 are usable, the buffer # 0 is selected, and the busy flag corresponding to the buffer # 0 is set in the data buffer allocation management table 13, and then the buffer # 0 is set. Send the inserted frame. Since the service of the data transfer device 30 has ended, the service of the data transfer device 40 is now performed. The data transfer device 10 reads the contents of the data buffer allocation management table 13 in order to transmit the first frame to the data transfer device 31. Since all the buffers # 3 to # 5 corresponding to the data transfer device 31 are usable, the buffer # 3 is selected, and after the busy flag corresponding to the buffer # 3 is set in the data buffer allocation management table 13, the buffer # 3 is set. Send the inserted frame. Since the service of the data transfer device 40 has ended, the service of the data transfer device 50 is now performed. The data transfer device 10 reads the contents of the data buffer allocation management table 13 in order to transmit the first frame to the data transfer device 50. After selecting the buffer # 6 corresponding to the data transfer device 50 and setting the in-use flag corresponding to the buffer # 6 in the data buffer allocation management table 13, the frame containing the buffer # 6 is transmitted. Since the service of the data transfer device 50 is completed, the service of the data transfer device 30 is returned again.
[0054]
The data transfer device 10 reads the contents of the data buffer allocation management table 13 to transmit the second frame to the data transfer device 30. Since the buffer # 0 is in use, the buffer # 1 is selected, the in-use flag corresponding to the buffer # 1 is set in the data buffer allocation management table 13, and then the frame containing the buffer # 1 is transmitted. Since the service of the data transfer device 30 is finished, the service of the data transfer device 40 is started. The data transfer device 10 reads the contents of the data buffer allocation management table 13 in order to transmit the second frame to the data transfer device 40. Since the buffer # 3 is in use, the buffer # 4 is selected, the in-use flag corresponding to the buffer # 4 is set in the data buffer allocation management table 13, and then the frame containing the buffer # 4 is transmitted. Since the service of the data transfer device 40 is completed, the service of the data transfer device 50 is started.
[0055]
The data transfer device 10 reads the contents of the data buffer allocation management table 13 to transmit the second frame to the data transfer device 50. However, since there is only one buffer # 6 for the data transfer device 50 and the buffer # 6 is already in use, the buffer cannot be selected. Therefore, the data transfer apparatus 10 ends the service of the data transfer apparatus 50 by waiting for RDY to be returned to the buffer # 6. Since the service of the data transfer device 50 is completed, the service returns to the service of the data transfer device 30.
[0056]
The data transfer apparatus 10 reads the contents of the data buffer allocation management table 13 to transmit the third frame to the data transfer apparatus 30. Since the buffers # 0 to # 1 are in use, the buffer # 2 is selected, the in-use flag corresponding to the buffer # 2 is set in the data buffer allocation management table 13, and then the frame containing the buffer # 2 is transmitted. Since the service of the data transfer device 30 is finished, the service of the data transfer device 40 is started. The data transfer device 10 reads the contents of the data buffer allocation management table 13 in order to transmit the third frame to the data transfer device 40. Since the buffers # 3 to # 4 are in use, the buffer # 5 is selected, the in-use flag corresponding to the buffer # 5 is set in the data buffer allocation management table 13, and then the frame containing the buffer # 5 is transmitted. Since the service of the data transfer device 40 has been completed, the service of the data transfer device 50 is attempted, but since the service of the data transfer device 50 is already waiting for the RDY return of the buffer # 6, the service returns to the data transfer device 30. .
[0057]
The data transfer device 10 reads the contents of the data buffer allocation management table 13 to transmit the fourth frame to the data transfer device 30. This time, since the buffers # 0 to # 2 are in use and all the buffers assigned to the data transfer device 30 are in use, the buffer # cannot be selected. The service of the data transfer device 30 is terminated by waiting for the message to be returned. Since the service of the data transfer device 30 is finished, the service of the data transfer device 40 is started. The data transfer apparatus 10 reads the contents of the data buffer allocation management table 13 to transmit the fourth frame to the data transfer apparatus 40. However, since the buffers # 3 to # 5 are in use and all the buffers assigned to the data transfer device 40 are in use, the buffer cannot be selected. The service of the data transfer apparatus 40 is terminated by waiting for the return of RDY.
[0058]
Thereafter, in the data transfer device 10, when RDY is returned and the in-use flag of the data buffer allocation management table 13 of the corresponding buffer is reset, the operation of transmitting the frame waiting for the purpose of using the corresponding buffer is performed. The frame for the transfer device 30 is repeated in the buffers # 0 to # 2, the frame for the data transfer device 40 is repeated in the buffers # 3 to # 5, and the frame for the data transfer device 50 is repeated in the buffer # 6.
[0059]
At this time, the data transfer speed between the data transfer device 10 and the dynamic switch device 20 is 7 frames (for 14 kilobytes) transmitted in 140 microseconds, so 14 kilobytes / 140 microseconds = 100 megabytes / second. . The distribution to the data transfer devices 30 to 50 is 32.8 each for the data transfer devices 30 and 40, so both devices are 42.8 megabytes / second, and the data transfer device 50 is 1 frame. Therefore, it is 14.3 megabytes / second, which exceeds the maximum transfer speed of 40 megabytes / second of the data transfer apparatus 30 and the data transfer apparatus 40 and the maximum transfer speed of the data transfer apparatus 50 of 10 megabytes / second. Furthermore, there is no change in the maximum transfer rate of the data transfer devices 30 and 40 when compared to when the data transfer device 30 is operating alone or when the data transfer devices 30 and 40 are operating simultaneously. It is not affected at all by the operation, and the performance distribution is ideal. Further, in the data transfer apparatus 10, there is no need to consider the maximum performance related to the data transfer apparatuses 30 to 50 in the normal processing except for the initial setting of the data buffer allocation management table 13, and only the returned RDY is supported. It only repeats sending the frame that is waiting for the purpose of using the buffer.
[0060]
As described above, when the sum of the maximum transfer rates in the multiplex operation device is lower than the bit rate of the transmission path, the frame transmission side assigns the data buffer on the frame reception side in units of the data transfer device and sets the data An appropriate performance distribution process can be realized only by selecting a data buffer by a very simple process of updating or referring to the buffer allocation management table 13.
[0061]
[Operation example 2]
When the sum of the maximum transfer rates in the devices that operate in multiplex (data transfer devices 30, 40, 50) exceeds the bit rate of the transmission line, it is the maximum for only the highest priority device (data transfer device 30 in this example). Explain that data transfer performance can be guaranteed. The contents of the data buffer allocation management table 13 used in this operation example are as shown in FIG.
[0062]
Here, the bit rate of all the transmission lines 60 to 90 is 1062.5 megabits / second, the number of entries in the data buffer 21 of the dynamic switch device 20 is 8 entries, the maximum number of data bytes in one frame is 2 kilobytes, and the data transfer device The maximum data transfer performance of 30 is 75 megabytes / second (this is different from operation example 1), the maximum data transfer performance of the data transfer device 40 is 40 megabytes / second, and the maximum data transfer performance of the data transfer device 50 is also 40 megabytes / second. It is assumed that the data transfer device 10 performs a simultaneous data transfer operation with these data transfer devices 30, 40, and 50 via the dynamic switch device 20.
[0063]
In the data transfer apparatus 10, the number of entries in the data buffer 21 of the dynamic switch apparatus 20 is 8 entries, the data transfer apparatus 30 has the highest priority, and the remaining data transfer apparatuses 40 and 50 have the same priority and are defined as the same group. , 40 and 50, and the occupied time (busy time) of one entry of the data buffer is about 140 microseconds. Therefore, the number of entries in the data buffer 21 is allocated to 6 entries (buffers) for the data transfer device 30. # 0, # 1, # 2, # 3, # 4, # 5), two entries (buffers #, # 6, # 7) are commonly allocated to the data transfer device 40 and the data transfer device 50, and FIG. A data buffer allocation management table 13 is created when the system is started up.
[0064]
It is assumed that data transfer between the data transfer device 10 and the data transfer devices 30, 40, 50 is started simultaneously. First, the data transfer device 10 reads the contents of the data buffer allocation management table 13 (FIG. 5) in order to transmit the first frame to the data transfer device 30. Initially, since all the buffers # 0 to # 5 corresponding to the data transfer device 30 are usable, the buffer # 0 is selected, and the in-use flag corresponding to the buffer # 0 is set in the data buffer allocation management table 13, and then the buffer A frame with # 0 is transmitted. Since the service of the data transfer device 30 has ended, the service of the data transfer device 40 is now performed. The data transfer device 10 reads the contents of the data buffer allocation management table 13 in order to transmit the first frame to the data transfer device 40. Since all of the buffers # 6 and # 7 corresponding to the data transfer device 40 are usable, the buffer # 6 is selected, and the in-use flag corresponding to the buffer # 6 is set in the data buffer allocation management table 13, and then the buffer # A frame with 6 is transmitted. Since the service of the data transfer device 40 has ended, the service of the data transfer device 50 is now performed. The data transfer device 10 reads the contents of the data buffer allocation management table 13 in order to transmit the first frame to the data transfer device 50. In this example, the data transfer devices 40 and 50 are in the same group, and the buffers # 6 and # 7 are shared by both devices 40 and 50. However, the buffer # 6 has already been used by the data transfer device 40 and is in use. The flag is set. Therefore, the data transfer apparatus 10 selects the buffer # 7, sets a busy flag corresponding to the buffer # 7 in the data buffer allocation management table 13, and then transmits a frame containing the buffer # 7. Since the service of the data transfer device 50 is completed, the service of the data transfer device 30 is returned again.
[0065]
The data transfer device 10 reads the contents of the data buffer allocation management table 13 to transmit the second frame to the data transfer device 30. Since buffer # 0 is in use, buffer # 1 is selected, an in-use flag corresponding to buffer # 1 is set in data buffer allocation management table 13, and then a frame containing buffer # 1 is transmitted. Since the service of the data transfer device 30 is finished, the service of the data transfer device 40 is started. The data transfer device 10 reads the contents of the data buffer allocation management table 13 in order to transmit the second frame to the data transfer device 40. Since the buffers # 6 and # 7 for the data transfer device 40 are already in use, the buffer cannot be selected, and the data transfer is performed by waiting for RDY to be returned to the buffers # 6 and # 7. The service of the device 40 is terminated. Since the service of the data transfer device 40 is completed, the service of the data transfer device 50 is started. The data transfer device 10 reads the contents of the data buffer allocation management table 13 to transmit the second frame to the data transfer device 50. However, as with the previous data transfer device 40, since the buffers # 6 and # 7 for the data transfer device 50 are already in use, the buffer cannot be selected, and RDY is stored in the buffers # 6 and # 7. The service of the data transfer apparatus 50 is terminated by waiting for the return. Since the service of the data transfer device 50 is finished, the service returns to the service of the data transfer device 30.
[0066]
The data transfer apparatus 10 reads the contents of the data buffer allocation management table 13 to transmit the third frame to the data transfer apparatus 30. Since the buffers # 0 and # 1 are in use, the buffer # 2 is selected, the in-use flag corresponding to the buffer # 2 is set in the data buffer allocation management table 13, and the frame containing the buffer # 2 is transmitted. Since the service of the data transfer device 30 is completed, the service of the data transfer device 40 is transferred, but the service of the data transfer device 40 is already waiting for the RDY return of the buffers # 6 and # 7. Is skipped. Since the next data transfer device 50 is also in the same state as the data transfer device 40, the service is skipped and the service returns to the data transfer device 30 again. Thereafter, the fourth to sixth frames for the data transfer device 30 are used by the buffers # 3 to # 5 to transmit frames.
[0067]
Thereafter, in the data transfer apparatus 10, when RDY is returned and the in-use flag in the data buffer allocation management table 13 of the corresponding buffer # is reset, an operation of transmitting a frame waiting for the purpose of using the corresponding buffer # is performed. The frame for the data transfer device 30 is repeated in the buffers # 0 to # 5, and the frame for the data transfer device 40 or the data transfer device 50 is repeated in the buffers # 6 to # 7.
[0068]
At this time, the data transfer rate between the data transfer device 10 and the dynamic switch device 20 is of course 100 megabytes / second, and the distribution to the data transfer devices 30 to 50 indicates that the service probability of the data transfer device 30 is 6/8. Therefore, since the service probability of 75 megabytes / second and the data transfer devices 40 and 50 is 1/8, respectively, it becomes 12.5 megabytes / second, but only one of the data transfer devices 40 and 50 is When operating, the service probability is two-eighth and performance is restored to 25 megabytes / second. As described above, the data transfer device 30 which is an important device for the system can operate simultaneously with the data transfer devices 40 and 50 while securing the maximum transfer speed of 75 megabytes / second, and the data transfer device 10. However, except for the initial setting of the data buffer allocation management table 13, there is no need to consider the maximum performance related to the data transfer devices 30 to 50 in the normal processing, and the corresponding buffer # is used for the returned RDY. It only repeats sending the frame waiting for the purpose.
[0069]
As described above, even when the total maximum transfer rate in a multiplex operation device exceeds the bit rate of the transmission path, the frame transmission side allocates the data buffer on the frame reception side in units of data transfer devices in the initial setting. By simply selecting the data buffer with a simple process of updating or referring to the data buffer allocation management table, the performance can be secured even if the data transfer bandwidth for the critical device that has been damaged by the multiplex operation is performed. can do.
[0070]
In the operation examples 1 and 2, the buffer allocation of the data buffer allocation management table is performed in the above-described operation examples 1 and 2, and the port address, transfer protocol, and maximum data of all the partner devices that the frame transmission side device may transfer data at the time of system initialization. Considering the transfer speed, the correspondence with the data buffer installed in the data transfer device or dynamic switch device that is the connection destination port receiving side device is determined. It is also possible to change from. This makes it possible to adjust fine-grained buffer allocation within the system based on, for example, the data transfer speed and priority of the data transfer device to which the system administrator is connected, resulting in effective capital investment and system operation. It becomes possible.
[0071]
【The invention's effect】
In the present invention, the data transfer operation can be performed in units of frames, and the data transfer system including the data transfer device or the dynamic switch device having the data buffer for storing the frame in the receiving side device is complicated in the multiplex operation. It is possible to realize a certain appropriate performance allocation process with simple control to guarantee or limit the data transfer rate for each device, and to multiplex the data transfer band for important devices that have been damaged by multiplex operation. Even if the operation is performed, the performance can be easily secured.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a data transfer system according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a format of a transfer frame in the present embodiment.
FIG. 3 is a diagram illustrating a format of a buffer release notification (RDY) in the present embodiment.
FIG. 4 is a diagram illustrating a first configuration example of a data buffer allocation management table in the embodiment.
FIG. 5 is a diagram illustrating a second configuration example of the data buffer allocation management table in the embodiment.
FIG. 6 is an example of an operation flowchart of a frame transmission side apparatus according to the present embodiment.
FIG. 7 is an example of an operation flowchart of a frame reception port of the dynamic switch device according to the embodiment.
FIG. 8 is an example of an operation flowchart of a frame transmission port of the dynamic switch device according to the embodiment.
[Explanation of symbols]
10 Data transfer device
11 Transmission frame storage buffer
12 Received frame storage buffer
13 Data buffer allocation management table
20 Dynamic switch device
21 Data buffer (buffer for storing received frames)
22 Buffer counter
30, 40, 50 Data transfer device
60, 70, 80, 90 transmission path
A, B, C, D port

Claims (3)

The receiving side device has multiple entries for the frame storage data buffer for temporarily storing frames received from the transmitting side device, and multiple data transfer operations are performed in units of frames between the transmitting side device and the receiving side device. In the data transfer method to
In the frame transmitted from the transmission side apparatus to the reception side apparatus, a buffer identifier that specifies which entry of the frame storage data buffer included in the reception side apparatus is to be stored is provided.
In the information that the receiving side device notifies the transmitting side device of the release of the data buffer for storing the frame, the buffer identifier of the entry that has been released is included ,
A data transfer method characterized in that , in a transmission side apparatus, whether or not a frame storage data buffer provided in a reception side apparatus is currently in use can be managed for each entry . The data transfer method according to claim 1, wherein
In order to transmit frames to a plurality of counterpart data transfer apparatuses via the receiver apparatus, the transmitter apparatus transmits a buffer of the counterpart data transfer apparatus for each entry of the frame storage data buffer provided in the receiver apparatus. It has a data buffer allocation management table that manages allocation and usage status.
When transmitting a frame, the transmitting side device selects an entry in the data buffer for storing the frame of the receiving side device using the data buffer allocation table and sets the entry in the data buffer allocation table to be in use. If the buffer identifier of the entry is included in the frame to be transmitted and the frame storage data buffer release notification information is received from the receiving side device, the entry in the data buffer allocation table is not used by the buffer identifier included in the information. And a data transfer method. 3. The data transfer method according to claim 2, wherein one or a plurality of device groups are formed on the basis of any or all of the data transfer speed, transfer protocol, and importance of the partner data transfer device. A data transfer method, characterized in that a transmitting side apparatus allocates an entry in a frame storing data buffer of a receiving side apparatus.

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