JP3208704B2 - Confirmation frame control method in fiber channel / asynchronous transfer mode converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an asynchronous transfer mode (hereinafter referred to as "ATM") for N ports having a fiber channel (hereinafter referred to as "FC") interface located at remote locations.
Regarding a communication method for communication via a network, particularly, FC / FC for full-duplex communication in service classes 1 and 2 in which a confirmation frame must be returned for data frame transmission.
The present invention relates to a confirmation frame control method for an ATM conversion device.

[0002]

2. Description of the Related Art An FC / ATM converter for connecting a FC and an ATM network to provide a service has just recently been developed. The FC / ATM converter is disposed between an N port having an FC interface and an ATM network. When an FC frame is received from the N port, the FC / ATM converter segments the ATM frame into ATM cells and transmits the ATM cells to the ATM network. When receiving ATM cell from opposite N port via FC
The frame is reassembled and transmitted to the N port. Therefore, a large amount of data can be transmitted bidirectionally in full-duplex communication.

On the other hand, FC standards (for example, ANS
I: American National Stand
As an X3T11 standard of the “ard Institute”, a transmission standard between N ports is defined. According to this transmission standard, in the service classes 1 and 2, it is obliged to return a confirmation frame from the N port on the receiving side in response to the transmission of a data frame from the N port on the transmitting side. Therefore, the transmission N port cannot transmit the next data frame until the confirmation frame can be received from the reception N port.

[0004]

The communication between the N ports is performed using the above-described FC / ATM converter.
When applied to communication via a TM network, it takes time to transmit a large amount of data frames in both directions. The reason for this is that a confirmation frame is added after the transmission data queue in the FC / ATM converter, and the transmission data queue is kept waiting, so that a delay time occurs.

Generally, FC is used as a channel interface between a CPU (central processing unit) and a data storage device in a high-speed information processing device such as a supercomputer or the like, and its transmission speed is as high as 1.0625 Gbps, for example. In contrast, the public network AT
The communication speed of the M network is, for example, 622.08 Mbps, which is relatively low. Therefore, a data frame transmitted from the N port to the ATM network is temporarily stored in a buffer in the FC / ATM converter, and then waits for a segmentation order.

Therefore, when the N port attempts to return an acknowledgment frame for a data frame received from the opposite N port, the N port is placed after the data frame waiting for segmentation stored in the buffer in the FC / ATM converter. The confirmation frame is added, and all the data frames stored before that are converted into cells and
It is made to wait in the above buffer until transmission to the TM is completed. As a result, the arrival of the confirmation frame at the opposite N port is delayed, and the transmission of the next data frame is waited at the opposite N port. As a result, the time until the transmission of all data is completed is delayed.

FIG. 3 is a diagram showing such a data frame delay situation, in which N ports 110A and 110B are connected to each FC.
/ ATM converters 120A and 120B and ATM network 10
9 shows a timing example in a case where full-duplex communication of a data frame is performed via a “0”. Here, focusing on the FC / ATM converter 120B, this converter 120B
The data frame DATA0 is transmitted from the N port 110A via the C / ATM converter 120A and the ATM network 100.
And N port 110 in the order in which the confirmation frame ACK was received.
Transfer to B side. Confirmation frame A at N port 110B
As soon as CK is received, the next data frame DATA1
To the N port 110A side.

In the FC / ATM converter 120B, an acknowledgment frame ACK for the completion of the reception of the data frame DATA0 is attached after the queue of the data frame DATA1, stored in a buffer, and waited. That is, a delay due to the queue occurs. Both FC / ATM converters 12
If such a queue delay occurs at 0A and 120B, half-duplex communication will occur if the transmission start timing of data frames in both directions is worst. That is, one N
A situation occurs in which the transmission of the data frame of the other N port waits until the port finishes transmitting the data frame, and the data transmission efficiency is reduced.

Accordingly, the present invention minimizes the data frame transmission waiting time in an FC / ATM converter provided between an N port having an FC interface and an ATM network and performing full-duplex communication. To improve the data transmission efficiency.

[0010]

SUMMARY OF THE INVENTION In order to solve such a problem, the present invention is provided between an N port having an FC interface and an ATM network.
When a frame is received, it is segmented into ATM cells and AT
A first transmitting unit for transmitting to the M network, and a counterpart N via the ATM network.
An FC / ATM converter comprising a second transmission unit for reassembling an ATM cell from a port into an FC frame upon transmission to the N port and storing the received FC frame in the first transmission unit. A first buffer, a first
Confirmation frame from frames stored in buffer
And first detection means for detecting the transfer of
A second buffer configured to store a data frame in the reassembled FC frame, a third buffer configured to store a confirmation frame in the reassembled FC frame, and a second and a third buffer. the selection means for selecting either one of a buffer, and a second detecting means which detects the number of accumulated frames a second buffer, and a second buffer by constantly selecting <br/>-option means Let me choose the second buff
And send the data frame in the
The data frame in the second buffer based on the transmission.
Is detected by the second detection means ,
And N-ports for transmission of the data frame to N-ports.
Counter N port returned from the port and stored in the first buffer
Over preparative confirmation frame addressed transfer is a third buffer is selected by the selection means is detect <br/> by the first detection means
Cause the confirmation frame in the third buffer to be transmitted to the N port
It is provided with a control means that. Therefore, when a confirmation frame that arrives mixedly with data frames received from the opposite N port is detected, the confirmation frame is suspended until all received data frames are transmitted to the N port. Does not send the next data frame. Further, after the confirmation frame from the N port to the opposite N port has been transmitted to the ATM network, the pending confirmation frame is transmitted to the N port, so that the transmission of the confirmation frame causes the next data frame to be transmitted from the N port. Even if transmitted, the confirmation frame from the N port has already been transmitted to the ATM network, and therefore does not wait in the transmission data queue (that is, the first buffer).

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 shows an FC / ATM to which the present invention is applied.
FIG. 3 is a block diagram illustrating a configuration of a conversion device. This FC / A
As described with reference to FIG. 3, the TM conversion device (hereinafter, conversion device) is disposed between the N port 110 and the ATM network 100, and upon receiving an FC frame from the N port 110, is segmented into ATM cells. While transmitting to the ATM network 100, the AT from the opposite N port via the ATM network 100
When the M cell is received, it is reassembled into an FC frame and transmitted to the N port 110.

Referring to FIG. 1, the converter 120 is configured as follows. That is, 1 is an input terminal to which an FC frame from the FC is input, 2 is an FC frame receiver for receiving the FC frame, 3 is a first buffer for storing the received FC frame, and 4 is a received frame as an ATM cell. Segmentation means for segmentation, 5 an ATM cell transmitter for transmitting the segmented ATM cells, and 6 an output terminal for outputting the ATM cells. Then, the FC frame receiver 2, the first buffer 3, the segmentation means 4 and the ATM cell transmitter 5
Is constituted by the transmission means 10.

Next, 11 is an input terminal for inputting an ATM cell from the ATM network, and 12 is an ATM terminal for receiving the ATM cell.
A cell receiver, 13 is reassembly means for reassembling a received ATM cell into an FC frame, 14 is a second buffer for storing a data frame in the reassembled FC frame, and 15 is a cell in the reassembled FC frame. A buffer for storing the confirmation frames of the first and second selectors, 16 is a selector for switching the output of the second and third buffers, 1
7 is an FC for transmitting the output frame of the selector 16 to the FC side.
A frame transmitter 18 is an output terminal of the FC frame. The ATM cell receiver 12, the reassembly means 13, the second buffer 14, the third buffer 15, the selector 16, and the FC frame transmitter 17 constitute a second transmission means 20.

Next, reference numeral 21 denotes first detection means for detecting a confirmation frame output from the first buffer 3, and reference numeral 22 denotes second detection for detecting the number of data frames stored in the second buffer 14. Means 23 is control means for controlling one of the two inputs of the selector 16 to be selected and output based on the detection result of the first detection means 21 and the detection result of the second detection means 22.

Now, the conversion apparatus 1 configured as described above.
20 will be described. FC from N port 110
When a frame enters input terminal 1, this FC frame
The signal is received by the C frame receiver 2 and converted from an optical signal to an electric signal. Here, one character of the FC frame of the optical signal is composed of a 10-bit code. The FC frame receiver 2 converts this 10-bit code into a corresponding 8-bit code electric signal.

The converted FC frame is temporarily stored in the first buffer 3 for speed adjustment, is segmented into 48 bytes by the segmentation means 4 according to the order of reception, and is further provided with an ATM header of 5 bytes. The header includes a VPI (virtual path identifier) and a VCI (virtual connection identifier). Finally, an 8-byte trailer and padding bytes are added as needed. The ATM cell generated in this manner is converted from an electric signal into an optical signal by an ATM cell transmitter 5,
It is transmitted to the TM network 100.

On the other hand, an ATM cell input to the input terminal 11 from the ATM network 100 is received by the ATM cell receiver 12 and converted from an optical signal to an electric signal. Then, the header and trailer are removed by the reassembly means 13 to restore the FC frame. Here, the data frame in the FC frame is stored in the second buffer 14, and the confirmation frame in the FC frame is stored in the third buffer 15.
The frame type of the FC frame, whether it is a data frame or a confirmation frame, can be identified by a corresponding field in the header of the FC frame.

The selector 16 selects one of the outputs of the second and third buffers. Normally, the second buffer 14 is selected and a data frame is output. The output frame of the selector 16 is converted from an 8-bit code into a 10-bit code by the FC frame transmitter 17, further converted from an electric signal into an optical signal, and transmitted to the N port 110 via the output terminal 18 as an FC frame. .

The above description is an example in the case of the AAL5 protocol, but this is not always necessary. In this example, the FC frame receiver 2 and the FC frame transmitter 17
In addition, some of the FC standards FC-0 (physical layer), FC-1 (code layer), and FC-2 (signaling and framing layer) are implemented.

Next, the processing operation of the data frame and the confirmation frame in the present converter will be described. In FIG. 1, the first detection unit 21 notifies the control unit 23 when detecting a confirmation frame from the FC frames output from the first buffer 3. The second detector 22 checks whether or not there is a data frame in the second buffer 14 and notifies the controller 23 of the result. Control means 23
Is notified from the second detecting means 22 that there is no more data frame in the second buffer 14, the first detecting means 21 notifies that the transfer of the confirmation frame to the segmentation means 4 has been completed. Wait until
When the transfer of the confirmation frame to the segmentation means 4 is notified, the input of the selector 17 is changed to the third.
The confirmation frame stored in the third buffer 15 is connected to the output of the buffer 15 of the
And sends this confirmation frame to the FC frame transmitter 1.
7 to the N port 110 side.

Next, FIG. 2 is a timing chart showing a detailed processing operation of the data frame and the confirmation frame in the present converter. The operation of the main part of the present invention will be described with reference to this timing chart. Note that this example is an example of full-duplex communication. Data frames are transmitted in groups of n from the N port 110A, and an acknowledgment frame ACK is returned from the opposite N port 110B.
Then, upon receiving the confirmation frame ACK, the N port 110A next collects n data frames and transmits the data frame to the opposing N auto 110B. Such a transmission operation is repeatedly performed on both N ports 110A and 110B.

In FIG. 2, two converters 120A and 120B are described with the ATM network 100 interposed therebetween. However, since the operations of both converters 120A and 120B are the same, the converter 120B is used for convenience of explanation. An example will be described. First, the FC data frame DATA0 is transmitted from the N port 110A. This data frame DA
TA0 is composed of n (n is an integer) frames as described above. The converter 120A converts the data frame DATA0 into ATM cells and transmits the ATM cells to the ATM network 100. As described above, since the transmission speed of the ATM network 100 is lower than the transmission speed of the FC, the transmission duration of the ATM cell is longer than the transmission duration of the FC frame.

Data frame DAT of N port 110A
Independently of the transmission of A0, a confirmation frame ACK for a data frame (not shown) transmitted from N port 110B to N port 110A is transmitted in data frame D.
It is transmitted from the N port 110A while being mixed with ATA0.
The timing at which the acknowledgment frames ACK are mixed differs depending on the start timing of data transmission in both directions, and the timing shown in FIG.

When the acknowledgment frame ACK arrives at the converter 120A, it is held in a transmission data queue (that is, the first buffer 3) and is output to the ATM network 100 in the order of input in the converter 120A. In the conversion device 120B, A
This confirmation frame ACK during reception of the data frame DATA0 via the TM network 100 is stored in the third buffer 15. That is, in this case, as described above, the second
, The input side of the selector 16 is connected to the output of the second buffer 14 by the control means 23, and the data frame DATA0 stored in the second buffer 14 is detected. Is transmitted to the N port 110B via the FC frame transmitter 17 and the output terminal 18, and the acknowledgment frame ACK remains suspended in the third buffer 15.

Here, in the conversion device 120B, the second
When all of the data frames DATA0 in the buffer 14 have been transmitted and become empty, the second detector 22 notifies the controller 23 that the second buffer 14 has become empty. On the other hand, when the reception of the data frame DATA0 from the conversion device 120B is completed, the N port 110B returns a confirmation frame ACK to the N port 110A. The acknowledgment frame ACK is received by the conversion device 120B, detected by the first detection unit 21, and notified to the control unit 23.

Then, the control means 23 controls the selector 16 so that its input side is connected to the output of the third buffer 15, and the confirmation frame ACK stored in the third buffer 15
Is transmitted to the N port 110B via the ATM network 100. As a result, the N port 110B transmits the next data frame to the N port 110A. In this case, since the confirmation frame ACK transmitted from the N port 110B has already been transmitted, the data frame queue does not interfere with the confirmation frame. This means that N port 1
This is because the next data frame is not transmitted from the N port 110B side because the confirmation frame ACK to be transmitted to the 10B side is suspended.

In the N port 110B, the confirmation frame AC
When K is received, the data frame DATA1 is transmitted to the N port 110A. Upon receiving the confirmation frame ACK, N port 110A transmits the next data frame DATA2 to N port 110B. Here, the number n of units of the data frame is represented by the data DATA0, DATA
If the same value is set for 1, DATA2, as can be seen from FIG. 2, the data transmission timings in both directions are thereafter periodically repeated in synchronization with each other, and the confirmation frame does not stop.
In this way, the queue of transmitted data frames (ie,
The acknowledgment frame ACK is not kept waiting in the first buffer 3), so that the transmission time of all data frames can be reduced to about half that in the example of FIG. 3, and the data transmission efficiency can be greatly improved.

As described above, when the data frame DATA and the acknowledgment frame ACK are received in a mixed manner, the acknowledgment frame ACK is temporarily held until all the received data frames have been transmitted. After transferring the ACK to the opposing converter,
The pending confirmation frame ACK is transferred to the N port. As a result, the confirmation frame is not held in the queue of the transmission data frame, and the time required for transmitting all the data frames can be reduced.

[0029]

As described above, according to the present invention, when a data frame and an acknowledgment frame are mixedly received from the opposite N port, the acknowledgment frame is temporarily held and all the received data frames are received. After the transmission of all data frames is completed and the confirmation frame for the data frame from the N port connected to itself is transmitted to the opposite N port, the pending confirmation frame is transmitted. Since the transfer is made to the N port connected to itself, the acknowledgment frame is not held in the queue of the transmission data frame, so that the time required for transmitting all the data frames can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a timing chart showing transmission timings of a data frame and a confirmation frame of the converter.

FIG. 3 is a timing chart showing transmission timings of a data frame and a confirmation frame of the conventional device.

[Explanation of symbols]

2 ... FC frame receiver, 3 ... first buffer, 4 ... segmentation means, 5 ... ATM cell transmitter, 12 ...
ATM cell receiver, 13 ... reassembly means, 14 ... second buffer, 15 ... third buffer, 16 ... selector,
17 ... FC frame transmitter, 21 ... First detection means, 2
2 ... second detection means, 23 ... control means, 100 ... ATM
Network, 110A, 110B ... N port, 120A, 120
B: FC / ATM converter.

Claims (1)

(57) [Claims] 1. An asynchronous transfer mode network provided between an N port having a fiber channel interface and an asynchronous transfer mode network. When a fiber channel frame is received from the N port, it is segmented into asynchronous transfer mode cells and transmitted to the asynchronous transfer mode network. A fiber channel / asynchronous system comprising: a first transmitting unit; and a second transmitting unit that reassembles a fiber channel frame when receiving an asynchronous transfer mode cell from an opposite N port via the asynchronous transfer mode network and transmits the frame to the N port. a transfer mode converter, the first transmission unit, first detects the transfer of confirmation frame and a first buffer for storing a fiber channel frame received, from the frame stored in the first buffer Rutotomoni a first detecting means, the second transmission unit has been reassembled file One of the second buffer for storing the data frame in the channel channel frame, the third buffer for storing the confirmation frame in the reassembled fiber channel frame, and one of the second and third buffers is selected. Selecting means;
A second detecting means for detecting the number of frames stored in the second buffer, and the selecting means always selects the second buffer.
And the data frame in the second buffer to the N port
Transmitting, and based on said transmission, a second buffer
The data frame is lost within is detected by said second detection means, and N Po of the data frame
The first buffer returned from N port for transmission to
Confirmation frame addressed to the opposite N port stored in the
When detected by the first detection means, the selection means
Third probability in the buffer by selecting a third buffer from
A control method for a confirmation frame in a fiber channel / asynchronous transfer mode converter, comprising a control unit for transmitting a confirmation frame to an N port .