JPH09116561A - Confirmation frame transfer system in fc/arm network converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve data transmission efficiency by generating a confirmation frame to N-port and sending the frame when a data frame addressed to an opposite N-port from the N port is detected so as to send the data frame continuously to an ATM network without interruption. SOLUTION: The converter is made up of a data frame detector 3 counting number of frames, an ACK detector 4 detecting a confirmation frame in the process of converting an input ATM cell from an opposite N port into an FC frame, an ACK generator 5 generating and transmitting the confirmation frame to be sent to the N port, and a controller 6 controlling each section. Then the data frame detector 3 detects the data frames to count the number and its reported to the controller 6. The controller 6 monitors a idle state of a memory 12 and when idle memory is in existence, generation of the confirmation frame to the ACk generator 5 is commanded and a switch 24 is selected to give the confirmation frame to an FC frame transmitter 25, from which the frame is sent to the N port.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to communication between N ports having Fiber Channel (hereinafter, FC) interfaces arranged at a distance from each other via an asynchronous transfer mode network (hereinafter, referred to as an ATM network). In particular, F
Confirmation in the FC / ATM network conversion device that improves the transmission efficiency by preventing the increase of the transmission time of the data frame due to the waiting for the confirmation frame to be returned in the service in which the confirmation frame belonging to the C standard class 1 and class 2 must be returned. This relates to a frame transfer method.

[0002]

2. Description of the Related Art Conventionally, connection between an FC network and an ATM network has not been made publicly, and no conventional example is found. However, in the FC standard (ANSI standard X3T11), there is a definition of a data frame transmission procedure between N ports.
It is mandatory to return a confirmation frame. This is to prevent overflow of the opposite receiving buffer, and to suppress the transmission of data frames on the transmitting side so as not to exceed the value EE called the end_end_credit number reserved in advance.

The above-mentioned N port means a Node port provided in each of the terminals 110 and 120 as shown in FIG. 7, for which an exchange for exchanging data from each of the terminals 110 and 120 is performed. The port provided in the device 100 is called an F port. In FIG. 7, T
X and RX are a transmission terminal and a reception terminal, respectively. Here, the above-mentioned value "EE" indicates a value of the size represented by the number of frames in the reception buffer. The larger this value, the more data frames can be transmitted at one time.

Further, the number of data frames Nr received in the opposite direction is inserted and notified in the header of the confirmation frame. When the number of transmitted data frames is Ns, the N port on the transmission side is allowed to calculate the number of spare frames of the opposite reception buffer by the equation (1) and further transmit the number of data frames equal to the value. It EE-Ns + Nr [frame] (1) Here, in the state of Nr <Ns, Ns-Nr frames among the transmitted data frames Ns are still on the transmission path and have not arrived at the opposite N port. Becomes
Then, at some point of time when the confirmation frame is received, Nr = N
When s is reached, the data frame shown in Expression (2) can be newly transmitted. EE-Ns + Nr = EE [frame] (2) Here, the data frame can be transmitted only up to the reserved number EE at a time, and the next data frame cannot be transmitted before the confirmation frame is received.

[0005]

If such a conventional technique is directly applied to the transmission method via the ATM network,
It takes a long time to transmit a large number of data frames.
The reason is that since the confirmation frame passes through the ATM network, the delay due to the transmission path cannot be ignored, the time for waiting for the confirmation frame increases, and the data frame cannot be transmitted during that time. The longer the distance, the longer the transmission line delay, and proportionally the longer the time required to complete the transmission of all data frames.

An example will be described. The data to be transmitted is divided, and one frame is the maximum frame length of FC 21
Suppose it is 48 bytes. If this is further converted into an ATM cell, one frame will have a header, (2148 bytes / 48 bytes) x 53 bytes = 238
It becomes 5 [bytes / frame] (rounds up the decimal point of the quotient). Here, if the number of EEs is 1000 frames, 1000 frames can be continuously transmitted at one time. 1000 frames are 2385 bytes × 1000 frames = 2385 kbytes on the ATM line.

When the ATM line speed is 2.4 Gbps, the time of 1000 frames is 2385 kbytes × 8 bits / 2.4 GHz = 8 ms. That is, the time for transmitting 1000 frames is 8 ms. Distance between two N ports is 500 km
Then, the time required for the 1000th data frame to arrive reaches the speed of light in the optical fiber by 180,0.
Approximating as 00 km / s, it is 500 km / (180,000 km / s) = 2.8 ms, and it also takes 2.8 ms until the confirmation frame corresponding thereto arrives. Therefore, the total waiting time before transmitting the next data frame is 5.6 ms.
(= 2.8 ms + 2.8 ms). In other words, 8ms
After transmitting for a while, it will wait for 5.6 ms.

Therefore, the line utilization rate becomes 8 ms / (8 ms + 5.6 ms) = 59%, which is lowered to 59%. That is, 59% of the time the data is transmitted on the ATM line, the idle cells are wastefully transmitted during the remaining 41% of the time. This results in inefficient operation of resources such as ATM lines and exchanges. Actually, in addition to the transmission line delay, the processing time of the N port, the switching equipment in the ATM network, the conversion device, etc. is added, so that the total required time increases, and the line utilization rate becomes lower than the above value. And the longer the distance,
Since the waiting time for the confirmation frame increases, there is a problem that the line usage rate further decreases.

Therefore, the present invention aims to improve the transmission efficiency. That is, the N port connected to this device can immediately transmit the next data frame without waiting for the confirmation frame from the opposite N port.

[0010]

In order to solve such a problem, the present invention provides a data frame detecting means for detecting a data frame from an N port and a confirmation for generating a confirmation frame to be transmitted to the N port. The frame generating means, the transfer blocking means for blocking the transfer of the confirmation frame from the opposite N port to the N port, and the confirmation frame generating means when the data frame is detected by the data frame detecting means, control the confirmation frame by N. The control means for transmitting to the port is provided. That is, the device itself creates and transmits a confirmation frame for the N port connected to the device. Therefore, it is not necessary for the N port to wait for a confirmation frame from the opposite N port, and the data frame can be continuously transmitted through the ATM network without interruption, thus improving the transmission efficiency.

Further, the control means is provided with confirmation frame detection means for detecting a confirmation frame from the opposite N port, and the control means stops the operation of the confirmation frame generation means and confirms when the final data frame is detected by the data frame detection means. The confirmation frame generation means is operated when the confirmation frame for the final data frame is detected by the frame detection means. That is, when the final data frame is detected from the N port side, the generation of the confirmation frame is stopped, and when the confirmation frame for this final data frame is detected from the opposite N port side, the confirmation frame is generated and transmitted to the N port. As a result, it is possible to prevent unnecessary confusion on both N-port sides during data transfer. Further, a memory for temporarily storing the received data frame is provided, and the control means controls the confirmation frame generation means to control the confirmation frame by N when the data frame in the memory is transmitted to the opposite N port and a vacancy occurs. It is designed to be sent to the port. Therefore, when the memory is partially empty, the confirmation frame is sent to the N port. As a result,
The data frame transfer efficiency at the N port is further improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an FC / ATM network conversion device (hereinafter referred to as a conversion device) to which the present invention is applied. In the figure, this device inputs from the FC frame / ATM cell converter 1 which converts the FC frame input from the FC frame input terminal Fin into an ATM cell and outputs from the ATM cell output terminal Aout, and from the ATM cell input terminal Ain. ATM cell / FC for converting ATM cells back to FC frames and outputting from FC frame output terminal Fout
The frame converter 2 and the data frame detector 3 which detects a data frame input from an N port (not shown) and counts the number of frames, and the process of converting an input ATM cell from an opposite N port (not shown) into an FC frame It is composed of an ACK detector 4 for detecting a frame, an ACK generator 5 for generating and transmitting a confirmation frame to be transmitted to the N port, and a controller 6 for controlling each of the above parts. Here, the abbreviation ACK of the ACK detector 4 is the ACK (Acknowledge) of the confirmation frame defined in the FC standard.
ge).

Next, FIG. 2 shows a concrete configuration example of the FC frame / ATM cell converter 1 and the ATM cell / FC frame converter 2 described above. In FIG. 2, FC frame /
The ATM cell converter 1 includes an FC frame receiver 11, a memory 12, a segmentation device 13, and an ATM cell transmitter 14. Also, ATM cell / FC
The frame converter 2 includes an ATM cell receiver 21, a reassembly device 22, a memory 23, a switch 24, and an FC.
And a frame transmitter 25.

Here, in the FC frame input from the N port to the FC frame input terminal Fin, 1 byte is 10 bytes.
It is a so-called 10-bit code displayed in bits.
This is a code designed to maintain DC balance and facilitate clock extraction. The FC frame is optically / electrically converted by the FC frame receiver 11, and then 1 byte is reverse-code converted into an 8-bit code. The data speed of the FC interface and the speed of the ATM line are different, and the speed of the FC interface is generally higher than the speed of ATM. Therefore, it is necessary to adjust the time, and the FC frame is once written and stored in the memory 12 at the speed of the FC interface. Thereafter, the FC frames are read from the memory 12 at the speed of the ATM line in the order of input, and the read FC frames are divided by the segmentation unit 13 into 48-byte ATM cells.
A 5-byte header is added to each cell. The last cell is padded by the required number of bytes so that it becomes 53 bytes, and finally a trailer of 8 bytes is added to form a cell.

The above description is for a protocol called AAL5 (ATM adaptation layer 5), but this protocol is not necessarily required. In this conversion process, the segmentation unit 13 causes the VP corresponding to the destination address (Destination_ID) included in the FC frame header in the cell header.
I (virtual path identifier) and VCI (virtual channel identifier)
Is set. VPI, VCI and destination address (opposite N
The correspondence with the port address) is determined in advance, and the correspondence information is held inside the device. Then, these cells are electrically / optically converted by the ATM cell transmitter 14 and then transmitted from the output terminal Aout to the ATM line.

On the contrary, the cell input from the ATM line through the terminal Ain is optically / electrically converted by the ATM cell receiver 21 to extract the cell. Then, the reassembly unit 22 removes the cell header, trailer, and padding, and restores the original FC frame transmitted by the opposing N port. The restored FC frame is temporarily stored in the memory 23 at the speed of the ATM line for speed adjustment. The accumulated FC frames are read from the memory 23 in the order of input at the FC frame speed, and the switch 2
4 and is guided to the FC frame transmitter 25. Then, the FC frame transmitter 25 converts one byte into a 10-bit code, and after electrical / optical conversion, is transmitted to the N port as an FC frame. The FC frame transmitter 25
And FC frame receiver 11, FC-0 of FC layer
(Physical layer), FC-1 (code layer), and FC-2
(A protocol layer).

Now, the generation of the confirmation frame showing the essential part of the present invention will be described with reference to FIG. The frames input to the FC frame receiver 11 include control frames in addition to data frames. The control frame has an instruction and a response to the instruction, but since the header content is different from that of the data frame, they can be identified. The data frame detector 3 detects a data frame among them, counts the number, and reports it to the controller 6. The controller 6 monitors the free space of the memory 12, and when the free space is made, instructs the ACK generator 5 to create a confirmation frame and switches the switch 24 to pass the confirmation frame to the FC frame transmitter 25. The passed confirmation frame is transmitted to the N port.

Upon receiving this confirmation frame, the N port immediately transmits the next data frame. Since the distance between the N port and the conversion device is short, the transmission delay of the confirmation frame is negligibly small as compared with the delay due to the ATM line. Then, after a certain time has elapsed, a confirmation frame indicating a response to the data frame from the opposite N port A
It is input to the ATM cell receiver 21 through the TM network. This confirmation frame is detected by the ACK detector 4 and notified to the controller 6. Here, if this confirmation frame is directly transferred to the N port, the N port sends the ACK
It will be confusing because a total of two confirmation frames will be received by the generator 5. To avoid this, the confirmation frame from the opposite N port causes the switch 24 to stop and F
It is not passed to the C frame transmitter 25 and is not transferred to the N port. In this way, the operation of the N port is guaranteed.

By the way, the confirmation frame has an identifier (sequential_I
The same identifier as in D) is copied and inserted in the header. In addition, the sequential_count in the header of the data frame is updated one frame at a time, and the confirmation_frame includes a sequential_count for each received data frame.
The maximum value in the count is entered, and the value is equal to the sequential_count of the last received data frame among the received data frames. Here, when the data frame detector 3 receives the final data frame, the data frame detector 3 reports the sequential_count of the data frame to the controller 6. Incidentally, the final data frame can be identified because the final frame identification bit indicating that this is the final data frame of the sequence is set in the control bit field in the header.

In this case, the controller 6 does not activate the ACK generator 5. This is because, if it is activated, a confirmation frame is generated and transmitted to the N port, and the N port determines that all data frames have been received by the opposite N port. Then, even if the present apparatus sends a confirmation frame for the final data frame without waiting for the final confirmation frame from the opposite N port, a cell loss occurs for some reason in the ATM network and a data frame is sent to the opposite N port. If the section does not arrive, the opposite N port will naturally notify it with a confirmation frame, but since the final confirmation frame has already been transmitted to the transmitting side, it is overwritten and notified. Because there is no.

In another tentative example, when the transmitting N port immediately starts the next sequence and transmits a command frame for it to arrive at the opposing N port,
If the port was in the process of creating a confirmation frame for a previous data frame, the corresponding N port may be confused and consider the instruction frame abnormal and reject it. Therefore, in order to prevent such confusion, the controller 6 performs control for stopping the confirmation frame as described above with respect to the final confirmation frame.

The final data frame is assigned a maximum sequential_count in the sequence. In the confirmation frame from the opposite N port, the maximum sequential_count in the received data frames is written in the header, so that the confirmation frame for the final data frame can be detected. That is, if the sequential_ID and the sequential_count detected by the ACK detector 4 from the confirmation frame match the one detected by the data frame detector 3, it is the final confirmation frame for the final data frame. When the final confirmation frame from the opposite N port is detected, the controller 3 activates the ACK generator 5 to generate and transmit the confirmation frame to the N port. Then, when this confirmation frame is received by the N port, the transmission of a series of data frames ends and the sequence ends.

Next, FIG. 6 is a sequence diagram showing an example of the operation of each part of the system when the present invention is not applied. In this example, the data frame is transmitted from the transmission N port A to the reception N port E, and the conversion device B → A
The case where the transmission is performed in the order of the TM network C and the conversion device D is shown. Here, in FIG. 6, the description of the transmission N port A corresponds to the N port described above, and the description of the reception N port E corresponds to the opposite N port described above. .

In FIG. 6, the conversion device B transmits "n1" data frames from the transmission N port A, which passes through the ATM network C and the reception conversion port D through the opposite conversion device D. Is reached at the receiving N port E,
Acknowledge frames ACK_n1 indicating "1" receptions are generated. Then, in this case, the confirmation frame ACK_n1 is transmitted N via the conversion device D → ATM network C → conversion device B.
Until it reaches the port A, the transmission N port A cannot wait to transmit the next "n2" data frames and is waiting. Further, even in the conversion device B on the transmission N port A side, the reception buffer (that is, the memory 12) waits until the next data frame is input even though the reception buffer (that is, the memory 12) has finished transmitting n1 data frames and is empty. No choice but was.

When the ATM network C has such a delay, the time for waiting for the confirmation frame increases with respect to the time for transmitting the data frame, and the transmission efficiency deteriorates.
In the present invention, the reception buffer is prevented from waiting without being emptied. The operation of the main part of the present invention will be described in more detail below with reference to the sequence diagram of FIG. First, “n1” data frames are transmitted from the transmission N port A at one time and accumulated in the reception buffer of the conversion apparatus B. Here, the reception buffer corresponds to the memory 12 in FIG.

In this example, as described above, the data rate of the FC interface is higher than the data rate of the ATM network C. Therefore, when the data frame is transferred from the converter B to the ATM network C, the time length is extended and the time required for output is longer than the time required for input. A confirmation frame ACK for notifying that "n1" data frames have been received from the conversion device B when the transmission of all "n1" data frames from the conversion device B has ended.
_N1 is transmitted to the transmitting N port A side. “N1” of this confirmation frame ACK_n1 is written in the header of the confirmation frame as described above. The value is represented by 16 bits and is in the range of "1" to "65,535". At this point, although there are some "n1" data frames that have not arrived at the reception N port E, transmission N
The port A immediately collects the next data frame "n2" and transmits it to the conversion device B. “N2” may or may not be equal to “n1”.

The conversion device B starts transmission to the ATM network C immediately after receiving "n2" data frames. When all “n2” pieces have been transmitted, the confirmation frame AC
K_n2 is transmitted to the transmission N port A. The same operation is performed thereafter, and when the transmission N port A finally transmits "ni" number of data frames, the data frame is transmitted to the opposite reception N port E via the ATM network C, and finally received from the reception N port E. A confirmation frame is returned. This final confirmation frame is AT
When reaching the converter B via the M network C, the converter B
Is a final confirmation frame and a confirmation frame AC indicating that “ni” data frames have been received
K_ni is generated and transmitted to the transmission N port A. In this case, the controller 6 controls the switch 24 so that the FC frame transmitter 25 can directly input the confirmation frame ACK_ni from the opposite reception port E via the memory 23 and transmit it to the transmission N port A. . Thus, when the transmitting N port A receives this confirmation frame, the data transmission of all the data frames is completed.

Confirmation frames other than the final confirmation frame from the reception N port E are terminated in this device (conversion device B) and are not transferred to the transmission N port A, but these confirmation frames in the middle are used in this device. It is also possible to check its normality. If, in these confirmation frames,
If the receiving N port E has notified that an error has been detected, since the final confirmation frame has not been transmitted yet, it is possible to reprint the error information in the confirmation frame to the transmitting N port A and notify it. is there.

In the sequence of FIG. 3 described above, the conversion device B
The confirmation frame is generated after the reception buffer of is completely empty, that is, after all the received data frames have been transmitted, but it is not necessary to wait until it is completely empty. It is also possible to detect the condition and generate a confirmation frame as soon as it becomes available. FIG. 4 is a diagram showing an example of such a sequence. Here, FIG. 4 shows a part of the sequence of FIG. 3, and the other sequences are the same as those of FIG.

In the sequence of FIG. 4, converter B receives "n1" data frames at a time. Of these, "n
At the time point of transmitting "0", the reception buffer is vacant for "n0" frames, so that "n0" can be further received, and "n0" confirmation frames ACK_ indicating reception has been completed.
Returns n0. At this point, not all “n1” data frames have been received. The transmitting N port A can immediately transmit "n0" data frames after transmitting "n1" data frames. In this way, it is not necessary to wait until the conversion device B has transmitted all the data frames, and the transmission efficiency can be further improved.

Further, as can be seen by comparing the sequences shown in FIGS. 3 and 4 with the sequence of the conventional example of FIG. 6, the size of the receive buffer in the present invention is the same as that of the conventional example of FIG. However, there is also an advantage that it does not increase the scale of hardware.
It should be noted that although the above description has been limited to the transmission of the data frame, naturally, it is necessary to establish the connection via the ATM network C before the transmission of the data frame. After the end of transmission of the data frame, if there is no other data frame or command frame to be transmitted, the connection is released. This is shown in the sequence diagram of FIG. This portion is not changed by the confirmation frame transfer method of the present invention.

Each operation of establishing and releasing a connection will be described with reference to the sequence diagram of FIG. At first,
A login request (command frame) is transmitted from the transmission N port A to the reception N port E, and reaches the reception N port E via the ATM network C. Receive N If port E is ready, send login permission (response frame) N
It is returned to the port A via the ATM network C. The connection is established when this response frame is detected by the transmission N port A. After that, the data frame transmission sequence described in FIGS. 3 and 4 is started. When the data frame transmission is completed, the transmission N port A
A logout request (instruction frame) is issued from the same, and after arriving at the receiving N port E in the same manner, a logout acknowledgment (response frame) is returned from the receiving N port E, and when this is detected by the transmitting N port A, the connection is established. Is released.

In this way, the receiving N port E is ready for receiving at the time of establishing the connection. Therefore, even if the conversion device B transmits a confirmation frame to the transmission N port A before receiving the confirmation frame from the reception N port E, and the transmission N port A continues to transmit further data frames after receiving the confirmation frame, the reception N Since the port E is already prepared for reception, the data frame is surely received. In other words, the conversion device B generates a confirmation frame by itself after transmitting the reception N port E after recognizing that the reception N port E is ready for reception.
Since the data frame is transmitted to the port A and is not arbitrarily performed independently from the reception N port E, the transmission data frame is not rejected from the reception N port E due to unprepared reason.

As described above, in the transmission N port, the time interval from the end of transmission of a series of data frames to the transmission of the next series of data frames is narrowed, and the transfer time of the entire data frame is shortened. can do. The reason is that, as described above, the conversion device creates and returns a confirmation frame, so that the data frame passes through the ATM network and reaches the opposite reception N port.
This is because the transmitting N port does not have to stop transmitting the next data frame and wait until the confirmation frame from the opposite receiving N port arrives via the ATM network.

[0035]

As described above, according to the present invention, N
When a data frame addressed to the opposite N port is detected from the port, a confirmation frame is generated and transmitted to the N port. Therefore, the N port does not have to wait for the confirmation frame from the opposite N port, and the data frames are continuous. As a result, the ATM network can be transmitted without interruption, thus improving the data transmission efficiency. Also, when the final data frame is detected from the N port side, the generation of the confirmation frame is stopped, and when the confirmation frame for this final data frame is detected from the opposite N port side, the confirmation frame is generated and transmitted to the N port. Therefore, it is possible to avoid unnecessary confusion on both N-port sides during data transfer. In addition, when the data frame in the memory that temporarily stores the data frame is transmitted to the opposite N port and a vacancy occurs, the confirmation frame is transmitted to the N port, so that the memory is partially emptied. Since the confirmation frame is transmitted to the N port, the data frame transfer efficiency at the N port is further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a conversion device to which the present invention is applied.

FIG. 2 is a block diagram showing a detailed configuration of the conversion device.

FIG. 3 is a sequence diagram showing an operation of each unit of a system including the conversion device.

FIG. 4 is a sequence diagram showing another operation example in the system.

FIG. 5 is a sequence diagram showing an operation of establishing and releasing a connection in the above system.

FIG. 6 is a sequence diagram showing the operation of the conventional system.

FIG. 7 is a diagram illustrating N ports handled in the present invention.

[Explanation of symbols]

1 ... FC frame / ATM cell converter, 2 ... ATM cell / FC frame converter, 3 ... data frame detector, 4
... ACK detector, 5 ... ACK generator, 6 ... Controller, 11 ... FC frame receiver, 12, 23 ... Memory,
13 ... Segmentation device, 14 ... ATM cell transmitter, 21 ... ATM cell receiver, 22 ... Reassembly device,
24 ... Switch, 25 ... FC frame transmitter, Fin ...
FC frame input terminal, Fout ... FC frame output terminal, Ain ... ATM cell input terminal, Aout ... ATM cell output terminal.

Claims (3)

[Claims] 1. An ATM network which is arranged between an N port having an FC interface which is a fiber channel interface and an ATM network which is an asynchronous transfer mode network. When an FC frame is received from the N port, it is segmented into an ATM cell. FC / ATM network conversion including first transmitting means for transmitting to the N port and second transmitting means for reassembling into an FC frame when an ATM cell is received from the opposite N port via the ATM network and transmitting to the N port An apparatus, comprising: a data frame detecting means for detecting a data frame from FC frames transmitted from the N port; a confirmation frame generating means for generating a confirmation frame to be transmitted to the N port; From the transfer frame to the N port by the transfer blocking means and the data frame detecting means. Check frame transfer method in FC / ATM network conversion device characterized by comprising a control means for transmitting the control to confirm frame the confirmation frame generating means to the N ports when a data frame is detected. 2. The confirmation frame detecting means according to claim 1, further comprising a confirmation frame detecting means for detecting a confirmation frame from the opposite N port, wherein the control means includes a confirmation frame generating means when the final data frame is detected by the data frame detecting means. A confirmation frame transfer system in an FC / ATM network conversion device, characterized in that when the confirmation frame detecting means detects a confirmation frame for the final data frame, the confirmation frame generating means is operated. 3. The memory according to claim 1, further comprising a memory for temporarily storing the received data frame,
The control unit controls the confirmation frame generation unit to transmit a confirmation frame to the N port when a vacancy occurs due to the data frame in the memory being transmitted to the opposite N port. Confirmation frame transfer method in ATM network conversion device.