JP2004120672A - Data exchange apparatus using preamble, switching hub and media converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To exchange operation management data or the like in economical configuration by making possible a data exchange at a physical layer level with connected equipment such as a switching hub or a media converter. <P>SOLUTION: When sending the operation management data to a media converter 2, a switching hub 1 sends a MAC frame wherein contents of a preamble are replaced with the operation management data to the media converter 2. In the media converter 2, operation management data (such as operation management data indicating a status of the media converter 2) are created according to the contents of the preamble (operation management data) in the MAC frame. Then, a MAC frame wherein the contents of the preamble are replaced with the operation management data is transmitted to the switching hub 1. Besides, the media converter 2 returns the contents of the preamble in the MAC frame to a regular preamble value and then transmits it from a port P4 to external equipment. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technology for exchanging data between connected devices, and more particularly to a data exchange technology for enabling data exchange at a PHY (physical layer) level with an economical configuration by using a preamble portion of a MAC frame. About.
[0002]
[Prior art]
Exchange of operation management data between connected devices such as switching hubs and media converters has conventionally been performed (for example, see Patent Document 1). By exchanging the operation management data, for example, the state of the media converter (operating, abnormal occurrence, etc.) is managed in the switching hub, and the state (operation mode, etc.) of the media converter is controlled from the switching hub. Becomes possible.
[0003]
Meanwhile, when exchanging operation management data and the like according to the world standard IEEE802.3, conventionally, operation management data is exchanged using a data area of a MAC (Media Access Controller) frame. FIG. 6 shows the format of the MAC frame. As shown in the figure, the MAC frame includes a preamble, a frame start code, a destination MAC address, a source MAC address, a frame length / type, data, and a frame check code.
[0004]
[Patent Document 1]
JP 2001-94585 A
[0005]
[Problems to be solved by the invention]
As described above, conventionally, since operation management data is exchanged using the data area of the MAC frame, the configuration for assembling the MAC frame, the configuration for storing the MAC frame, and the MAC frame A configuration for processing is required. Therefore, there is a problem that the configuration is complicated and the cost is high. This problem will be described with reference to FIG. FIG. 7 is a block diagram showing a configuration that must be provided in a media converter that exchanges operation management data using a data area of a MAC frame. As shown in the figure, in order to exchange operation data using the data area of the MAC frame, in addition to the basic configuration of the media converter such as the PHY units 711 and 712, the RJ45 connector 714, and the optical module 715, Therefore, MAC units 719 and 720 for processing the MAC frame, a packet memory bridge 718 for storing the MAC frame data, a CPU 713 for creating the MAC frame, and a memory 717 for a work area of the CPU 713 are required. . For this reason, the configuration becomes complicated and expensive. In FIG. 7, reference numeral 716 denotes an operation management unit.
[0006]
Therefore, an object of the present invention is to enable data exchange at a physical layer level without using a data area of a MAC frame, thereby enabling operation management data and the like to be exchanged between connected devices in an economical configuration. Is to do so.
[0007]
[Means for Solving the Problems]
A data exchange device using the preamble of the present invention achieves the above object,
The first connection device is
A first control circuit unit that replaces the contents of the preamble portion of the MAC frame with other data and transmits the replaced MAC frame to the second connection device;
The second connection device includes:
A second control circuit unit for extracting the contents of the preamble part in the MAC frame sent from the first connection device and returning the contents of the preamble part in the MAC frame to a normal preamble value It is characterized by having.
[0008]
In addition, the data exchange device using the preamble of the present invention,
The second control circuit unit includes:
A configuration in which the content of the preamble portion in the MAC frame is replaced with other data, and the replaced MAC frame is transmitted to the first connection device;
The first control circuit unit includes:
The content of the preamble portion in the MAC frame sent from the second connection device is extracted, and the content of the preamble portion in the MAC frame is returned to a normal preamble value.
[0009]
More specifically, a data exchange device using the preamble of the present invention
Switching hub
A first preamble change circuit that replaces the contents of the preamble portion in the MAC frame with operation management data and transmits the replaced MAC frame to the media converter;
A first preamble detection circuit for extracting the contents of a preamble portion in the MAC frame sent from the media converter;
A first preamble correction circuit for returning a content of a preamble portion in the MAC frame sent from the media converter to a normal preamble value,
Wherein the media converter is
A second preamble change circuit for replacing the contents of the preamble portion in the MAC frame with operation management data and transmitting the replaced MAC frame to the switching hub;
A second preamble detection circuit for extracting the contents of a preamble portion in the MAC frame sent from the switching hub;
A second preamble correction circuit for returning the content of the preamble portion in the MAC frame sent from the switching hub to a normal preamble value.
[0010]
In addition, the data exchange device using the preamble of the present invention,
The switching hub,
A first operation management unit that outputs operation management data for state inquiry for inquiring the state of the media converter to the first preamble change circuit;
The first preamble change circuit includes:
A configuration in which the content of the preamble part in the MAC frame transmitted to the media converter is replaced with operation management data for status inquiry output by the first operation management unit,
Wherein the media converter is
When operation management data for status inquiry is extracted by the second preamble detection circuit, operation management data for status display indicating the status of the media converter is output to the second preamble change circuit. Operation management department,
The second preamble changing circuit includes:
The content of the preamble portion in the MAC frame transmitted to the switching hub is replaced with operation management data for status display output by the second operation management unit.
[0011]
In addition, the data exchange device using the preamble of the present invention,
The first operation management unit includes:
A configuration for outputting operation management data for a state change instruction for changing the state of the media converter to the first preamble change circuit,
The first preamble change circuit includes:
The content of the preamble part in the MAC frame transmitted to the media converter is replaced with operation management data for state change instruction output by the first operation management unit,
The second operation management unit includes:
When the operation management data for the state change instruction is extracted by the second preamble detection circuit, the state of the own media converter is changed according to the operation management data for the state change instruction, and thereafter, the completion of the state change is confirmed. Having a configuration to output operation management data for the state change completion notification to the second preamble change circuit,
The second preamble changing circuit includes:
The content of the preamble portion in the MAC frame transmitted to the switching hub is replaced with operation management data for status change completion notification output from the second operation management unit.
[0012]
[Action]
When transmitting operation management data and the like to the second connected device, the first connected device replaces the contents of the preamble portion of the MAC frame with the operation management data and transmits the replaced MAC frame to the second connected device. I do. The second connection device extracts the contents of the preamble portion (operation management data and the like) in the MAC frame and returns the contents of the preamble portion in the MAC frame to a normal preamble value. Conversely, when transmitting operation management data and the like from the second connected device to the first connected device, the second connected device replaces the contents of the preamble portion of the MAC frame with the operation management data and the like, and The MAC frame is transmitted to the first connection device. The first connection device extracts the contents of the preamble (operation management data and the like) in the MAC frame and returns the contents of the preamble portion in the MAC frame to a normal preamble value.
[0013]
As described above, the first and second connected devices have a configuration in which the content of the preamble portion in the MAC frame is replaced with operation management data and the like, and a configuration in which the content of the preamble portion in the MAC frame (operation management data and the like) is extracted. A configuration may be provided in which the contents of the preamble portion in the MAC frame are returned to the normal preamble value, and as in the media converter shown in FIG. Since it is not necessary to provide the packet memory bridge 718, the CPU 713, and the memory 717 serving as a work area of the CPU 713, the configuration can be simplified and the cost can be reduced. In addition, since there is a configuration in which operation management data and the like in the MAC frame are returned to the normal preamble value, there is no problem with synchronization at all.
[0014]
Further, for example, when the first and second operation devices are a switching hub and a media converter, respectively, data to be transmitted from the switching hub to the media converter is transmitted to the operation management data for status inquiry for inquiring the status of the media converter or media. This can be operation management data for a state change instruction for changing the state of the converter.
[0015]
In the media converter, if the data extracted from the MAC frame is operation management data for status inquiry, a MAC frame including operation management data for status display indicating the status of the media converter is used instead of the preamble part. Send to switching hub. Also, in the media converter, when the data extracted from the MAC frame is operation management data for state change instruction, after changing the state of its own media converter according to the operation management data, it is determined that the state change is completed. The MAC frame including the operation management data for the status change completion notification shown in place of the contents of the preamble portion is transmitted to the switching hub.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
FIG. 1 is a block diagram of an embodiment of a data exchange device using a preamble according to the present invention, which comprises a switching hub 1 and a media converter 2.
[0018]
As shown in FIG. 1, the switching hub 1 includes a packet switching mechanism 91 for switching a packet, a CPU 96 for performing a routing process and the like, a memory 94 for storing and holding data, and a console terminal for external management (not shown). ), And eight interface cards # 1 to # 8.
[0019]
The interface card # 1 includes a packet forwarding mechanism 92 for transferring packets, MAC units 111 and 112 and PHY units 211 and 212 for processing packets, and exchange of operation management data using a MAC frame preamble unit. It outputs operation management data to the control circuit units 311 and 312 in accordance with instructions from the control circuit units 311 and 312 for enabling, and processes the operation management data passed from the control circuit units 311 and 312. The operation management unit 511 and the optical modules 411 and 412 are mounted. The media converter 2 is connected to the port P1 of the ports P1 and P2 of the interface card # 1. The other interface cards # 2 to # 8 have the same configuration as the interface card # 1.
[0020]
FIG. 2 is a block diagram showing a detailed configuration example of the control circuit unit 311 in the switching hub 1 shown in FIG. 1 and showing a connection relationship between the control circuit unit 311 and its peripheral parts.
[0021]
The control circuit unit 311 detects a preamble part in the MAC frame from the MAC unit 111 to the PHY unit 211, and transfers the MAC frame to the preamble change circuit 32. The preamble detection circuit 31 and the operation management unit 511 A data input circuit 35 that receives data and passes it to the preamble change circuit 32, and a preamble change that changes the contents of the preamble portion in the MAC frame detected by the preamble detection circuit 31 according to the operation management data passed from the data input circuit 35. And a circuit 32. Further, the control circuit unit 311 detects the preamble portion in the MAC frame from the PHY unit 211 to the MAC unit 111 and passes the content to the data output circuit 36, and passes the MAC frame to the preamble correction circuit 33. The circuit 34, the data output circuit 36 that passes the data passed from the preamble detection circuit 34 to the operation management unit 511, and the contents of the preamble portion in the MAC frame detected by the preamble detection circuit 34 are returned to the normal preamble value. After that, a preamble correction circuit 33 for transmitting to the MAC unit 111 is provided.
[0022]
FIG. 3 is a block diagram showing a configuration example of the media converter 2 shown in FIG. As shown in the figure, the media converter 2 includes an RJ45 connector 614 for receiving an electric signal from a category 5 cable, PHY units 611 and 612, an optical module 615 for converting an electric signal into an optical signal, and a MAC frame preamble. A control circuit unit 613 for enabling the exchange of operation management data using the unit and an operation management unit 616 are provided. The port P3 of the media converter 2 is connected to the port P1 of the switching hub 1.
[0023]
The control circuit unit 613 has the same function as the control circuit unit 311 shown in FIG. 2, and includes a preamble detection circuit 61, a preamble change circuit 62, a preamble correction circuit 63, a preamble detection circuit 64, a data input circuit 65 and a data output circuit 66. The operation management unit 616 has a function of performing operation settings for the PHY units 611 and 612 in accordance with the data from the data output circuit 66 and passing operation management data indicating the state of the own media converter 2 to the data input circuit 65.
[0024]
Description of operation of the embodiment
Next, the operation of this embodiment will be described in detail. First, an operation when transmitting operation management data from the port P1 of the switching hub 1 to the media converter 2 will be described.
[0025]
The transmission of the operation management data is performed using the preamble portion of the communication data (MAC frame) from the packet forwarding mechanism 92 in FIG. The communication data (MAC frame) is sent from the packet forwarding mechanism 92 to the MAC unit 111, and after recalculation of the frame check code and the like, MII TXD <0-3> (transmission data), TX_EN (transmission enable) ), TX_ER (transmission error) to the control circuit unit 311.
[0026]
The preamble detection circuit 31 in the control circuit unit 311 detects a preamble part in the MAC frame, and passes the MAC frame and information indicating the preamble part to the preamble change circuit 32.
[0027]
When the operation management data is not passed from the data input circuit 35, the preamble change circuit 32 uses the MAC frame from the preamble detection circuit 31 as it is at the timing of the MII standard as TXD <0-3> (transmission data), TX_EN (Transmission enable), and transmit to the PHY section 211 as TX_ER (transmission error). On the other hand, when the operation management data is passed from the data input circuit 35, the contents of the preamble portion of the MAC frame are replaced with the operation management data passed from the data input circuit 35, and the MAC frame after the replacement is replaced. Are transmitted to the PHY unit 211 as TXD <0-3> (transmission data), TX_EN (transmission enable), and TX_ER (transmission error) at the timing of the MII standard.
[0028]
Here, the operation management data is passed from the data input circuit 35 to the preamble change circuit 32 in the following cases. When the network administrator or the like wants to know the status of the media converter 2 or wants to change the status of the media converter 2, a status collection instruction or a status change content (for example, a PHY unit 612 is changed to the loop-back mode, etc.). When a state collection instruction or a state change instruction is input via the console I / O 95, the CPU 96 passes the instruction to the operation management unit 511. As a result, the operation management unit 511 creates operation management data according to the instruction given from the CPU 96 and passes it to the data input circuit 35. For example, when a status collection instruction is passed from the CPU 96, operation management data for a status inquiry is created, and when a status change instruction is passed, the operation management data for a status change instruction according to the content of the change is created. create. The size of the operation management data created by the operation management unit 511 is 7 bytes, which is the same size as the MAC frame preamble portion. The data input circuit 35 passes the data passed from the operation management unit 511 to the preamble change circuit 32.
[0029]
The PHY unit 211 performs processing in the physical layer, such as decoding, on the MAC frame transmitted from the preamble change circuit 32. The optical module 411 converts the MAC frame output from the PHY unit 211 from an electrical signal into an optical signal. The signal is converted into a signal and transmitted to the media converter 2 via the port P1.
[0030]
The MAC frame transmitted from the port P1 of the switching hub 1 is input to the port P3 of the media converter 2 in FIG. 3, is converted from an optical signal to an electric signal by the optical module 615, and is input to the PHY unit 612 as received data. You. The PHY unit 612 performs processing of the physical layer such as decoding, and performs control in the MAC frame format via MII RXD <0-3> (reception data), RX_DV (reception enable), and RX_ER (reception error). It is sent to the circuit unit 613.
[0031]
The preamble detection circuit 64 in the control circuit unit 613 detects a preamble part in the MAC frame passed from the PHY unit 612 (detects the first seven bytes as a preamble part), and outputs the contents of the detected preamble part as data. Send to circuit 66. At the same time, the MAC frame and information indicating the detected preamble portion are sent to the preamble correction circuit 63.
[0032]
The data output circuit 66 passes the contents of the preamble portion sent from the preamble detection unit 64 to the operation management unit 616. As a result, the operation management unit 616 determines whether or not the content of the preamble part passed from the data output circuit 66 is operation management data as shown in the flowchart of FIG. 4 (step S41). That is, if the content passed from the data output circuit 66 is not a regular preamble value, it is determined to be operation management data, and if it is a regular preamble value, it is determined not to be operation management data.
[0033]
If it is determined that the data is not operation management data (NO in step S41), the process ends. On the other hand, if it is determined that the data is operation management data (YES in step S41), a process corresponding to the contents of the operation management data is performed (step S42). Now, for example, when the operation management data is operation management data for state inquiry, the operation management unit 616 determines the state of the media converter 2 (for example, operating, stopped, operation of the PHY units 611 and 612). The operation management data for displaying the status indicating the mode is generated and passed to the data input circuit 65. Further, for example, when the operation management data is operation management data for a state change instruction for instructing the operation mode of the PHY unit 612 to be in the loopback mode, the PHY unit 612 via the MDIO / MDC interface. After the operation mode is changed to loopback, operation management data for a state change completion notification indicating that the operation mode change is completed is created and passed to the data input circuit 65. Note that the size of the operation management data created by the operation management unit 616 is 7 bytes, which is the same as the size of the preamble part.
[0034]
On the other hand, the preamble correction circuit 63 replaces the contents of the preamble portion of the MAC frame passed from the preamble detection circuit 64 with a regular preamble value of the IEEE802.3 standard. The MAC frame whose preamble portion has been corrected by the preamble correction circuit 63 is transmitted to the PHY unit 611 via the MII, and transmitted to an external device (not shown) connected to the port P4 via the RJ45 connector 614. Here, the preamble correction circuit 63 replaces the contents of the preamble portion of the MAC frame with a regular preamble value, so that the MAC frame sent from the switching hub 1 is replaced with the contents of the preamble portion in the operation management data. The replacement does not cause any synchronization problems.
[0035]
Next, the operation when the operation management data is transmitted from the media converter 2 to the switching hub 1 will be described.
[0036]
Transmission of operation management data from the media converter 2 to the switching hub 1 is performed using a preamble portion of communication data (MAC frame) transmitted from an external device (not shown) connected to the port P4. The MAC frame input to the port P4 is sent to the PHY unit 611 via the RJ45 connector 614, and is subjected to physical layer processing. TXD <0-3> (transmission data), TX_EN (transmission enable), TX_ER (transmission An error) signal is sent to the control circuit unit 613.
[0037]
The preamble detection circuit 61 in the control circuit unit 613 detects a preamble part in the MAC frame, and passes the MAC frame and information indicating the preamble part to the preamble change circuit 62.
[0038]
When the operation management data is not passed from the data input circuit 65, the preamble change circuit 62 uses the MAC frame from the preamble detection circuit 61 as it is at the timing of the MII standard as TXD <0-3> (transmission data), TX_EN (Transmission enable) and transmit to the PHY section 612 as TX_ER (transmission error). On the other hand, when the operation management data is passed from the data input circuit 65, the contents of the preamble portion of the MAC frame are replaced with the operation management data passed from the data input circuit 65, and the MAC frame after the replacement is replaced. Are transmitted to the PHY unit 612 as TXD <0-3> (transmission data), TX_EN (transmission enable), and TX_ER (transmission error) at the timing of the MII standard. Here, the operation management data is passed from the data input circuit 65 to the preamble change circuit 62 when the operation management unit 616 performs the process of step S42 in FIG. At this time, the operation management data passed from the data input circuit 65 includes the above-described operation management data for state display, operation management data for state change completion notification, and the like.
[0039]
The PHY unit 612 performs processing in the physical layer such as decoding on the MAC frame sent from the preamble change circuit 62, and the optical module 615 converts the MAC frame from the PHY unit 612 from an electric signal to an optical signal. The data is converted and transmitted to the switching hub 1 via the port P3.
[0040]
The MAC frame transmitted from the port P3 of the media converter 2 is input to the port P1 of the switching hub 1, converted from an optical signal to an electrical signal by the optical module 411, and input to the PHY unit 211 as received data. The PHY unit 211 performs processing of the physical layer such as decoding, and controls in the MAC frame format via MII RXD <0-3> (reception data), RX_DV (reception enable), and RX_ER (reception error). It is sent to the circuit unit 311.
[0041]
The preamble detection circuit 34 in the control circuit unit 311 detects a preamble part in the MAC frame passed from the PHY unit 211, and sends the content of the detected preamble part to the data output circuit 36. At the same time, the information indicating the MAC frame and the detected preamble portion is sent to the preamble correction circuit 33.
[0042]
The data output circuit 36 passes the contents of the preamble portion sent from the preamble detection circuit 34 to the operation management unit 511. As a result, as shown in the flowchart of FIG. 5, the operation management unit 511 determines whether or not the content of the preamble portion passed from the preamble detection circuit 34 is operation management data (step S51).
[0043]
If it is determined that the data is not operation management data, that is, if the content of the preamble portion is a regular preamble value defined in IEEE802.3 (NO in step S51), the process ends. On the other hand, when it is determined that the operation management data is the operation management data (YES in step S51), the operation management data is transmitted to the CPU 96 (step S52), and the process is terminated. Here, the operation management data transmitted to the CPU 96 includes the operation management data for status display described above and the operation management data for notification of completion of status change. The operation management data for displaying the status is a response from the media converter 2 to the status collection instruction output by the CPU 96, and the operation management data for notifying the status change completion is output from the media converter 2 in response to the status change instruction output from the CPU 96. Response. Therefore, the CPU 96 can manage the state of the media converter 2 based on the operation management data for displaying the state, and based on the operation management data for notifying completion of the state change, the state of the media converter 2 indicates the state instructed. It can be confirmed that it has been changed.
[0044]
On the other hand, the preamble correction circuit 33 corrects the content of the preamble portion of the MAC frame passed from the preamble detection circuit 34 to a normal preamble value of the IEEE802.3 standard. The MAC frame corrected by the preamble correction circuit 33 is transmitted to the MAC unit 111 via the MII, transmitted from the MAC unit 111 to the packet forwarding mechanism 92 in FIG. 1, and processed in the switching hub 1. . Here, the preamble correction circuit 33 replaces the contents of the preamble portion of the MAC frame with a regular preamble value, so that the MAC frame sent from the media converter 2 is replaced with the operation management data in the preamble portion. Even if they are used, no synchronization problems occur.
[0045]
【The invention's effect】
As described above, according to the present invention, it is possible to exchange data at the physical layer level without using the data area of the MAC frame. Can be replaced. In other words, according to the present invention in which data exchange is performed at the physical layer level using the preamble portion of the MAC frame, a first control circuit that replaces the content of the preamble portion in the MAC frame with operation management data or the like is provided to the connection device on the transmission side. Operation management by merely providing a second control circuit unit for extracting the contents of the preamble part in the MAC frame and returning the contents of the preamble part in the MAC frame to a normal preamble value in the connection device on the receiving side. Since data and the like can be exchanged, operation management data and the like can be exchanged with a simple and economical configuration as compared with a media converter or the like that exchanges data using the data area of the MAC frame shown in FIG. Becomes possible.
[0046]
Further, the present invention has a configuration in which the content of the preamble portion in the MAC frame is returned to the normal preamble portion, so that there is no problem in synchronization at all.
[Brief description of the drawings]
FIG. 1 is a block diagram of an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration example of a control circuit unit 311 in the switching hub 1 and showing a connection relationship between the control circuit unit 311 and peripheral parts thereof.
FIG. 3 is a block diagram illustrating a configuration example of a media converter 2.
FIG. 4 is a flowchart illustrating a processing example of an operation management unit 616;
FIG. 5 is a flowchart illustrating a processing example of an operation management unit 511;
FIG. 6 is a diagram showing a format of a MAC frame.
FIG. 7 is a diagram showing an example of a configuration that a media converter can take when exchanging operation management data using a data area of a MAC frame.
[Explanation of symbols]
1. Switching hub
# 1 to # 8: Interface card
91: Packet switching mechanism
92: Packet forwarding mechanism
94… Memory
95 ... Console I / O
96 ... CPU
111, 112 ... MAC unit
211, 212 ... PHY section
311, 312: Control circuit unit
31 ... Preamble detection circuit
32 ... Preamble change circuit
33 ... Preamble correction circuit
34 ... Preamble detection circuit
35 ... Data input circuit
36 ... Data output circuit
411, 412: Optical module
511: Operation management unit
2. Media converter
611, 612 ... PHY section
613: control circuit section
61: Preamble detection circuit
62: Preamble change circuit
63: Preamble correction circuit
64: Preamble detection circuit
65 Data input circuit
66 Data output circuit
614 ... RJ45 connector
615 ... Optical module
616: Operation Management Department

Claims (10)

The first connection device is
A first control circuit unit that replaces the contents of the preamble portion of the MAC frame with other data and transmits the replaced MAC frame to the second connection device;
The second connection device includes:
A second control circuit unit for extracting the contents of the preamble part in the MAC frame sent from the first connection device and returning the contents of the preamble part in the MAC frame to a normal preamble value A data exchange device using a preamble. A data exchange device using the preamble according to claim 1,
The second control circuit unit includes:
A configuration in which the content of the preamble portion in the MAC frame is replaced with other data, and the replaced MAC frame is transmitted to the first connection device;
The first control circuit unit includes:
A preamble for extracting the contents of the preamble portion in the MAC frame sent from the second connection device and returning the contents of the preamble portion in the MAC frame to a normal preamble value. A data exchange device that uses. A data exchange device using the preamble according to claim 2,
A data exchange device using a preamble, wherein the other data is operation management data. Switching hub
A first preamble change circuit that replaces the contents of the preamble portion in the MAC frame with operation management data and transmits the replaced MAC frame to the media converter;
A first preamble detection circuit for extracting the contents of a preamble portion in the MAC frame sent from the media converter;
A first preamble correction circuit for returning a content of a preamble portion in the MAC frame sent from the media converter to a normal preamble value,
Wherein the media converter is
A second preamble change circuit for replacing the contents of the preamble portion in the MAC frame with operation management data and transmitting the replaced MAC frame to the switching hub;
A second preamble detection circuit for extracting the contents of a preamble portion in the MAC frame sent from the switching hub;
A data exchange device using a preamble, comprising: a second preamble correction circuit for returning a content of a preamble portion in the MAC frame sent from the switching hub to a normal preamble value. A data exchange device using a preamble according to claim 4,
The switching hub,
A first operation management unit that outputs operation management data for state inquiry for inquiring the state of the media converter to the first preamble change circuit;
The first preamble change circuit includes:
A configuration in which the content of the preamble part in the MAC frame transmitted to the media converter is replaced with operation management data for status inquiry output by the first operation management unit,
Wherein the media converter is
When operation management data for status inquiry is extracted by the second preamble detection circuit, operation management data for status display indicating the status of the media converter is output to the second preamble change circuit. Operation management department,
The second preamble changing circuit includes:
A data exchange device using a preamble, wherein the content of a preamble portion in a MAC frame transmitted to the switching hub is replaced with operation management data for status display output by the second operation management unit. . A data exchange device using a preamble according to claim 5,
The first operation management unit includes:
A configuration for outputting operation management data for a state change instruction for changing the state of the media converter to the first preamble change circuit,
The first preamble change circuit includes:
The content of the preamble part in the MAC frame transmitted to the media converter is replaced with operation management data for state change instruction output by the first operation management unit,
The second operation management unit includes:
When the operation management data for the state change instruction is extracted by the second preamble detection circuit, the state of the own media converter is changed according to the operation management data for the state change instruction, and thereafter, the completion of the state change is confirmed. Having a configuration to output operation management data for the state change completion notification to the second preamble change circuit,
The second preamble changing circuit includes:
Data using a preamble, wherein the content of the preamble portion in the MAC frame transmitted to the switching hub is replaced with operation management data for status change completion notification output by the second operation management unit. Exchange equipment. Replace the contents of the preamble part of the MAC frame with other data, extract the replaced MAC frame, extract the contents of the preamble part in the received MAC frame, and convert the contents of the preamble part in the MAC frame to a regular preamble value. A switching hub comprising a control circuit unit for transmitting data to a media converter having a configuration for returning. The switching hub according to claim 7,
Wherein the media converter is
Having a configuration in which the content of the preamble part in the MAC frame is replaced with other data, and the replaced MAC frame is transmitted to the switching hub;
The control circuit unit,
A switching hub having a configuration for extracting the contents of a preamble portion in the MAC frame sent from the media converter and returning the contents of the preamble portion in the MAC frame to a normal preamble value. When the content of the preamble portion in the MAC frame is replaced with other data and the MAC frame is transmitted from the switching hub having a configuration for transmitting the replaced MAC frame, the content of the preamble portion in the MAC frame is extracted. And a control circuit for returning the content of the preamble portion in the MAC frame to a normal preamble value. The media converter according to claim 9,
The switching hub,
A structure for extracting the content of the preamble portion in the MAC frame sent from the media converter and returning the content of the preamble portion in the MAC frame to a normal preamble value,
The control circuit unit,
A media converter having a configuration in which the contents of a preamble portion in a MAC frame are replaced with other data, and the replaced MAC frame is transmitted to the switching hub.

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