JP2002094542A - Inter-lan connection system and its loopback test system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inter-LAN connection system that can effectively carry out a loopback test from a communication company to a termination point of a subscriber in the case of connecting a user LAN to a broadband LAN of the communication enterprise via an optical fiber transmission line. SOLUTION: An optical conversion bridge 40 of the enterprise transmits a start packet whose length is shorter than a packet length of an Ethernet (R) frame to a subscriber side optical conversion repeater 50 via the optical fiber transmission line 20 in the case of conducting a loopback test. Thus, the optical conversion repeater 50 sets its electric physical layer termination section 510 with respect to the user LAN to a loopback state and transmits a reply packet in response to the start packet to the optical conversion bridge 40. The optical conversion bridge 40 receiving the reply packet transmits a test packet with a length equal to that of the Ethernet frame to the optical conversion repeater 50 via the optical fiber transmission line 20. The test packet is looped back at the electric physical layer termination section 510 of the optical conversion repeater 50 and looped back to the optical conversion bridge 40 via the optical fiber transmission line 20. The result is indicated by a blinked LED 429 or reported to a remote controller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inter-LAN connection system and a loop-back test method thereof, and more particularly to an inter-LAN connection system for transmitting an Ethernet frame and a loop-back test method.

[0002]

2. Description of the Related Art In recent years, wide area LANs based on LAN (local area network) technology have been constructed in each region, and WANs (wide area networks) connecting these with a high-speed and broadband backbone network have become nationwide. It is being developed and is being put to practical use. An optical fiber is applied as the transmission line base, so-called FTTO (fib
er to the office) or FTTH (fiber to the ho
Network services that have been extended to user connections called me) have been provided.

As is well known, an OSI (open systems in OSI) is used as an inter-LAN connecting device for connecting LANs.
A bridge that connects at a data link layer level of a terconnection) model, a router that connects at a network layer level, and a gateway that connects at a higher level than the transport layer are known. In particular, since the bridge-type LAN connection is connected via a common data link layer, TCP / IP (transmission control
LANs can be connected by inexpensive devices regardless of higher-level protocols such as l protocol / internet protocol).

[0004]

By the way, the user LA
When N is connected to a wide area LAN of a communication carrier as described above via an optical fiber transmission line, the responsibility point of the communication carrier is positioned at a terminal point inside the house of the optical fiber transmission line,
A maintenance and monitoring function up to the terminal point is required. However, the conventional LAN connection device as described above does not have a sufficient maintenance and monitoring function, and its development has been desired. In particular, when a bridge type termination device is applied, there is a disadvantage that a broadcasting frame is passed. For example, when a loopback test is performed, a control packet or a test packet is transmitted to each L.
There is a possibility that a packet that has passed to the AN side and that has flowed out to another network may adversely affect communication.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been developed in such a manner that a user LAN is connected to a wide area LA of a communication carrier.
It is an object of the present invention to provide a LAN-to-LAN connection system that can perform LAN-to-LAN connection using an inexpensive device to N, and that can more effectively perform an optical fiber transmission line test, and a loopback test method therefor.

[0006]

According to the present invention, there is provided an inter-LAN connection system for solving the above-mentioned problems, which is performed by a user LA.
N (10) and a wide area LAN (30) of a communication carrier through an optical fiber transmission line (20).
A first optical conversion device (40) for performing electrical / optical conversion of a predetermined data frame transmitted between the optical fiber transmission line and the optical frame and transferring the data frame by medium access control;
A second optical conversion device (50) installed in the user's home for converting the data frame transmitted between the user LAN and the optical fiber transmission line into an optical signal and transferring the data frame by medium access control; The first optical conversion device transmits a control packet for controlling a loopback test with the second optical conversion device, which is discarded during transfer processing in the second optical conversion device. And a test control unit (414) for transmitting a test packet similar to the data frame to perform a loopback test, wherein the second optical conversion device performs a user operation based on the control packet from the first optical conversion device. Loop control for setting a physical layer termination point with the LAN in a loopback state, returning a test packet received via the optical fiber transmission line to the first optical conversion device, and performing loopback control Characterized in that it comprises a stage (512).

In this case, the control packet may be a packet formed to have a shorter packet length than the shortest packet length of the data frame to be transferred in the second optical conversion device.

The control packet is a packet having the same length as the packet length of the data frame to be transferred in the second optical conversion device, and may be a packet in which an error is included in the data check. .

[0009] In this case, the first light conversion device has a wide area LA.
N, an electric physical layer terminating means (402) for terminating the electric physical layer connected to the optical fiber, an optical physical layer terminating means (412) for terminating the optical physical layer connected to the optical fiber transmission line, and MAC switch (404, 408) for transferring a data frame according to its MAC address
And inserting a control packet from the test control means between the MAC switch and the optical physical layer terminating means into a transmission path to the second optical conversion device, and responding to the control packet from the second optical conversion device. And a control packet insertion detecting means (410) for detecting the packet from the receiving path, and inserting the test packet from the test controlling means into the transmission path to the second optical conversion device between the MAC address and the electric physical layer terminating means. It is preferable to include a test packet insertion detecting means (406) for detecting a test packet looped back from the second optical conversion device from a reception path.

The test control means of the first optical conversion device generates at least a control packet and a test packet including a start packet and a stop packet at the time of a loopback test, respectively.
A packet detecting means (442) for detecting a response packet to the start packet and a loop-backed test packet; and a packet comparing means (444) for comparing whether or not the looped-back test packet matches the transmitted test packet. ) And a notifying means (440) for notifying the result to the outside.

[0011] The second optical conversion device is a user LAN.
An electrical physical layer terminating means (510) for terminating the electrical physical layer connected to the optical fiber transmission line, an optical physical layer terminating means (502) for terminating the optical physical layer connected to the optical fiber transmission line, and data between these terminating means. A MAC switch (506, 508) for transferring the frame according to the MAC address;
First between the MAC switch and the optical physical layer termination means
Control packet insertion detecting means for detecting the control packet from the optical conversion device from the receiving path and supplying the control packet to the loop control means, and inserting the response packet from the loop control means into the transmission path to the first optical conversion device ( 504).

Further, the loop control means of the second optical conversion device includes at least a packet detection means (542) for respectively detecting a control packet including a start packet and a stop packet from the first optical conversion device, and a packet detection means. A packet generating means (536) for generating a response packet when detecting a start packet, and setting the electric physical layer terminating means to a loopback state when receiving the start packet by the packet detecting means, and receiving a stop packet. And a loop setting canceling means (532) for canceling the loop-back state when this occurs.

On the other hand, the loopback test method according to the present invention is a loopback test method in an inter-LAN connection system for connecting a user LAN and a wide area LAN of a communication carrier via an optical fiber transmission line. A first optical conversion device is provided on the side for converting a predetermined data frame to be transmitted between the wide area LAN and the optical fiber transmission line into an optical signal and transferring the data frame by medium access control. A second optical converter for converting the data frame transmitted between the user LAN and the optical fiber transmission line into an optical signal and transferring the data frame by medium access control; A startup packet that instructs the second optical conversion device to perform a loopback test and is discarded after the detection is transmitted to the optical fiber transmission line. The second optical conversion device, which has received the start packet, sets the electric physical layer terminal point with the user LAN in a loopback state, and is a response packet responding to the start packet and detecting the response packet. A response packet to be discarded later is transmitted to the first optical conversion device via the optical fiber transmission line, and the first optical conversion device receiving the response packet transmits a test packet similar to a predetermined data frame to the first optical conversion device. The test packet is transmitted to the second optical conversion device via the path, and the test packet is returned to the second optical conversion device at the end point of the electro-physical layer with the user LAN at the second optical conversion device which has received the test packet, and again transmitted through the optical fiber transmission line. The first optical conversion device loops back the test packet, and the loop-backed test packet is received by the first optical conversion device and transmitted. Compared whether back test packet matches characterized by notifying the result to the outside.

In this case, when the first optical conversion device terminates the loopback test, the second optical conversion device sends the stop packet discarded after the detection to the second optical conversion device via the optical fiber transmission line. The second optical converter receives the stop packet and transmits to the device to return to a state in which normal data communication can be performed, and the second optical conversion device releases the loopback state of the electric physical layer terminal point with the user LAN to enable normal data communication. It is good to return to the state.

[0015] In these cases, the start packet, the response packet, and the stop packet are packets formed to have a shorter packet length than the shortest packet length of the data frame to be transferred in the first and second optical conversion repeaters. Good.

The start packet, the response packet, and the stop packet are packets having the same length as the packet length of the data frame to be transferred in the first and second optical conversion devices. The packet may be included.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a LAN connection system and a loopback test system according to the present invention; FIG. 1 shows an embodiment of an inter-LAN connection system according to the present invention. As shown in FIG. 2, for example, a LAN-to-LAN connection system according to the present embodiment connects a user LAN 10 to a carrier network such as a wide area LAN 30 of a communication carrier via an optical fiber transmission line 20. In the present embodiment, the bridge type LAN connection system including the optical fiber transmission line 20, the optical conversion bridge 40 connected to the station side, and the optical conversion repeater 50 connected inside the house is an interface. is there. In particular, in the present embodiment, the optical conversion repeater 5 on the inside of the house via the optical fiber transmission line 20 from the optical conversion bridge 40 on the office side.
0, a start packet SP shorter than the packet length of the Ethernet frame is supplied, and a test packet TP having a packet length similar to that of the Ethernet frame is sent to perform a remote loopback test. The main feature is that it has functions.

The details of each unit will be described.
0 is a 10Base-T or 100Base-T Ethernet LAN to which a plurality of data terminals such as personal computers are connected in this embodiment. In this embodiment, 10Mbp is set according to a bandwidth contract with a communication carrier.
s to 100 Mbps is selected, and the LAN connection system of this embodiment selects a wide area LAN.
30. The user LAN 10 is connected to an optical conversion repeater 50 via a hub or a router 100. On the other hand, the wide area LAN 30 is, for example, several Gbps.
s is a high-speed broadband Ethernet-based LAN having a transmission bandwidth of, for example, a plurality of user LANs for each region.
A WAN (wide area network) for accommodating 10 and further connecting to each area via a 100 Gbps class backbone network is formed. This wide area LAN 30 is connected to an optical conversion bridge 40 via a router 300.

The routers 100 and 300 are switches at the network layer level, and for example, IP (Internet protocol) in an Ethernet frame transmitted in the present embodiment.
ol) An inter-LAN connection device that distributes routes according to addresses. As shown in FIG. 5, the Ethernet frame has a preamble PA indicating a synchronization signal, an 8-bit frame start delimiter SFD, and a destination MAC (media access control) address DA indicating the next adjacent destination.
And a source MAC address SA representing a source address
, Length type LT indicating data length or data type, variable length transmission data DT of 46 to 1500 octets including an IP header, and destination MAC address DA
Pad PA that is added when the length from data to data DT is less than 64 octets and is adjusted to a length of 64 octets
D and a frame check sequence FCS for error detection of a frame such as a CRC (cyclic redundancy check) code. The LAN connection system according to the present embodiment is a bridge-type LAN connection system that transfers each Ethernet frame based on an Ethernet header including a destination MAC address DA, a source MAC address SA, and a length type LT. .

More specifically, the optical conversion bridge 40 according to the present embodiment is installed on the telecommunications carrier side, and is connected to the Ethernet frame from the router 300 of the wide area LAN 30 and the user LAN 10 transferred through the optical fiber transmission line 20 from the user LAN 10. This is a MAC bridge for mutually transferring the Ethernet frame according to the MAC address. In the present embodiment, the Ethernet frame is connected between the optical transmission line such as a twisted pair from the router 300 and the optical fiber transmission line 20 and converted into an electrical / optical signal. This is a first optical conversion device that performs medium access control. More specifically, as shown in FIG. 1, the optical conversion bridge (MC2) 40 of the present embodiment includes an electrophysical layer terminator (PHY-E) 402 and a first MAC switch 4
04, the test packet insertion detection unit 406, and the second MA
C switch 408 and control packet insertion detecting section 410
, An optical physical layer termination unit (PHY-O) 412, and a control unit 4
14 is included. The electrophysical layer termination unit 402
0 is a layer 1 termination circuit that terminates Ethernet frames transmitted and received between
100Base-T connector and this connector and PH
It includes a transformer for matching with the Y chip, and a PHY chip for performing processing such as frame waveform shaping. In particular,
In the present embodiment, at the time of the loopback test, the control unit 41
4 includes a loopback mode in which the PHY chip forms a return path so that the test packet is not transmitted to the outside under control. The PHY chip and the first MAC switch 404 are connected by two lines, a forward line and a return line.

The first MAC switch 404 is a transfer processing unit for transferring a frame according to the MAC address of the Ethernet frame. In the present embodiment, the first MAC switch 404 cooperates with the second MAC switch 408 to cope with the wide area LAN 3 as described later.
It is a band control unit that limits the band of data flowing out to the 0 side. The first MAC switch 404 and the second MAC switch 408 are connected via a test packet insertion detection unit 406 by a forward line and a return line, respectively. The test packet insertion detection unit 406 inserts the test packet generated by the control unit 414 during the loop-back test of the remote loop and the self-loop into the outward route, and sends the loop-backed test packet to the control unit 414 from the return route. A switch (SW-T) 420 provided on the outward route from the first MAC switch 404 to the second MAC switch 408, and a first switch from the second MAC switch 408 to the first MAC switch 408. MAC switch 4
04 and a detection line 422 commonly connected to the return line to 04.

The second MAC switch 408 is connected to the first M
Like the AC switch 404, the transfer unit is a transfer processing unit that transfers a frame according to the MAC address of an Ethernet frame. In the present embodiment, the first MAC switch 404
Is a band control unit that limits the band of data flowing out to the wide area LAN 30 in cooperation with. In other words, when the operating frequency is determined by the oscillator common to the first MAC switch 404 and the writing and reading of data to and from the buffer are controlled, when the data band flowing from the user LAN 10 exceeds the contracted band, Execute the process of discarding the frame. The second MAC switch 408 is connected to the optical-physical-layer terminating unit 412 via a control packet insertion detection unit 410 via a forward line and a return line.

The control packet insertion detecting section 410 inserts the control packet generated by the control section 414 during the remote loopback test into the forward line, and detects the response packet from the optical conversion repeater 50 from the return line. A switch (SW-C) 424 provided on the outward route from the second MAC switch 408 to the optical physical layer termination unit 412, and a switch from the optical physical layer termination unit 412 to the MAC switch 408. And a detection line 424 commonly connected to the return line. Optical Physical Layer Terminator (PHY-O) 41
Reference numeral 2 denotes a layer 1 termination circuit for terminating an Ethernet frame transmitted / received to / from the optical fiber transmission line 20. More precisely, a line interface with the optical fiber transmission line 20 including an electric / optical conversion circuit; PHY that performs processing such as waveform shaping of frames converted into electrical signals
Including chips. In particular, the PHY chip is set to the loopback mode during the self-loop test among the loopback tests.

On the other hand, the control section 414 is a test control section mainly for controlling each section at the time of a loopback test. In this embodiment, the control section 414 depresses the test switches 427 and 428 or receives a signal from a remote control device (not shown). A loopback test is performed by control. The result is an LED (light emi
This is notified by blinking of the tting diode 429 or notification to the remote control device. FIG. 3 shows functional blocks of the control unit 414. In this figure, a switch detection unit 430 is a unit that detects on / off of a switch at the time of a self-loop or a remote loop test, and outputs the result to a PHY setting unit 432, a MAC switch setting unit 434,
Packet generation unit 436, timer setting unit 438, and LE
It is supplied to the D control unit 440, respectively. PHY setting unit 43
2 for remote loop test and self loop test,
A control unit that sets the electrical physical layer terminating unit 402 to full duplex and isolated mode so that packets do not flow to the wide area LAN 30, and sets the optical physical layer terminating unit 412 to loopback mode in the case of a self-loop test. . When switch-off is detected or when a time-out signal is received from the timer setting unit 438, each mode is returned to the normal mode. The MAC switch setting unit 434 sets the first MAC switch 404 to all two when the switch-on is detected in both the self-loop and the remote loop.
Set to heavy mode. The second MAC switch 408 is
It is always set to full duplex mode.

The packet generator 436 generates a control packet and a test packet for controlling the optical conversion repeater 50 including a start packet and a stop packet in the case of a remote loop test, and generates only a test packet in the case of a self-loop. A timer setting unit 438
Each packet is generated in a predetermined order in accordance with a timing signal from the CPU or an instruction from the packet detection unit 442. For example, as shown in FIG. 6, the test packet is formed in the same format as that of the Ethernet frame, a broadcast address representing a broadcast is given as its destination MAC address DA, and the address of its own device is given as a source MAC address SA. The data DA is provided with a pattern of, for example, 64 bytes by repeating "11001100". The control packet is formed to have a shorter packet length than the Ethernet frame. For example, as shown in FIG. 7, a broadcast address indicating a broadcast is assigned as a destination MAC address DA, and an address of the own device is assigned as a source MAC address SA. Then, the start-up packet as the data DA is, for example, 4 bytes by repeating “0001”.
And the stop packet is "0011"
Is repeated to provide a 4-byte pattern. In this embodiment, the start packet is transmitted at a predetermined interval up to 10 times.

Returning to FIG. 3, the timer setting unit 438 supplies the start-up packet and the test packet transmission timing to the packet generation unit 436, and further, the packet detection unit 44.
2 is a timer circuit for setting a time-out period of a start ACK packet and a test packet in the second embodiment. The LED control unit 440 is a control circuit that controls the blinking of the LED 429 at the time of the loopback test. In this embodiment, when switch-on is detected, the yellow LED indicating that the test is being performed is turned on. The green LED is turned on when it is determined that the test packet is normal. At the end of the test, both LEDs are turned off.

On the other hand, the packet detection unit 442 is a detection circuit that detects a start-up ACK packet from the optical conversion repeater 50 and detects a test packet that has been looped back during a remote loop test. The detection result is sent to the packet generation unit 436 and the timer setting unit 43.
8 and the detected test packet is compared with the packet comparison unit 4
Transfer to 44. Similarly, in the case of the self-loop test, the test packet is transferred to the packet comparing section 444. The packet comparing unit 444 is a comparing circuit that compares whether or not the test packet sent from the packet generating unit 436 matches the looped-back test packet. As a result, if they match, the LED control unit 440 and the remote controller A signal indicating normality is sent to the control device.

Returning to FIG. 1, the optical conversion repeater (MC1) 50 according to the present embodiment is installed in the user's home and is transmitted over the Ethernet frame from the router 100 of the user LAN 10 via the optical fiber transmission line 20 and the wide area. A MAC bridge for mutually transferring an Ethernet frame from the LAN 30 according to the MAC address;
In the present embodiment, the second optical conversion device performs the electrical / optical conversion of the Ethernet frame between the electrical transmission line such as the twisted pair from the router 100 and the optical fiber transmission line 20 to control the medium access. More specifically, as shown in the figure, the optical conversion repeater 50 of the present embodiment includes an optical physical layer terminator (PHY-O) 502 and a control packet insertion detector 5
04, a first MAC switch 506, and a second MAC switch 506.
Switch 508 and electrophysical layer termination (PHY-E) 5
10 and a control unit 512. Optical physical layer termination (PH
YO) 502 is a layer 1 for terminating an Ethernet frame transmitted and received with the optical fiber transmission line 20.
More specifically, it includes a line interface with the optical fiber transmission line 20 including an electric / optical conversion circuit, and a PHY chip for performing processing such as waveform shaping of a frame converted into an electric signal. Particularly in the present embodiment,
The PHY chip is set to the loopback mode during the self-loop test among the loopback tests. The PHY chip is connected to the first MAC switch 506 via a control packet insertion detection unit 504 by way of a forward route and a return route.

The control packet insertion detection unit 504 detects a start packet from the optical conversion bridge 40 from the outward line during the remote loopback test, and inserts the start ACK packet generated by the control unit 512 into the return line. This is a part unique to the present embodiment, and is a detection line 520 commonly connected to an outward line from the optical physical layer terminating unit 502 to the first MAC switch 506, and from the first MAC switch 504 to the optical physical layer terminating unit 502. And a change-over switch (SW-C) 522 provided on the return line of. The first MAC switch 506 is a transfer processing unit that transfers a frame according to the MAC address of the Ethernet frame. In the present embodiment, the first MAC switch 506 cooperates with the second MAC switch 508 to transmit the user L
10Base-T and 100Ba depending on the band of AN10
Switching of se-T is performed. From 10Base-T to 1
In the case of a contract band up to 00Base-T, all are set to 100Base-T. The first MAC switch 506 and the second MAC switch 508 are connected by a forward line and a return line.

The second MAC switch 508 has a first M
Like the AC switch 506, the transfer unit is a transfer processing unit that transfers a frame according to the MAC address of the Ethernet frame. In the present embodiment, the transfer unit is a first MAC switch 504.
10 Bass according to the bandwidth of the user LAN 10 in cooperation with
Switching between e-T and 100Base-T is performed. Second
The MAC switch 508 is connected to the electrophysical layer terminating unit 510 by a forward line and a return line. The electro-physical layer terminating unit 510 is a layer 1 terminating circuit for terminating an Ethernet frame transmitted / received between the router 100 and, more precisely, a 10 / 100Base-T connector and a connector between the connector and the PHY chip. Transformer that matches the data and PH that performs processing such as frame waveform shaping
Y chip. In particular, the present embodiment includes a loopback mode in which a loopback path is formed by a PHY chip under the control of the control unit 512 so that a test packet is not transmitted to the outside under the control of the control unit 512 during a loopback test.

The control unit 512 is a loop control unit that performs a loop-back control during a remote loop test from the optical conversion bridge 40 and a self-loop test.
The loop-back control of the remote loop test is executed by receiving the start packet from the optical conversion bridge 40, or the control of the self-loop test is executed by pressing the self-test switch 524. At this time, the LED 526 is turned on or blinks to notify the outside that the loopback test is being performed.
FIG. 4 shows functional blocks of the control unit 512. In this figure, a switch detection unit 530 is a unit that detects on / off of a switch at the time of a self-loop test, and outputs the result to a PHY setting unit 532, a MAC switch setting unit 534, a packet generation unit 536, a timer setting unit. 5
38 and the LED control unit 540. P
The HY setting unit 532 sets the electric physical layer termination unit 510 to the loopback mode in the case of the remote loop test, and sets the electric physical layer termination unit 510 and the optical physical layer termination unit 502 to the loopback mode in the case of the self-loop test. Is a control unit to be set. When the switch-off is detected in the case of the self-loop test or in the time-out signal from the timer setting unit 538, the mode is returned to the normal mode, and in the case of the remote loop test, the mode is detected by detecting the stop packet from the packet detection unit 542. Return to normal mode. The MAC switch setting unit 534 sets the second MAC switch 508 to the full-duplex mode when switch-on is detected in both the self-loop and the remote loop, or when the packet detection unit 530 detects a start-up packet. It is a control unit to perform. First MAC switch 50
6 is always set to the full duplex mode.

The packet generation unit 536 is a packet generation circuit that generates a startup ACK packet when the packet detection unit 542 detects a startup packet and generates a test packet in the case of a self-loop test, and a timer setting unit 538. Each packet is generated in accordance with a timing signal from the CPU or an instruction from the packet detection unit 542. The start ACK packet is formed to have a shorter packet length than the Ethernet frame, and as shown in FIG. 7, a broadcast address indicating broadcast is added as a destination MAC address DA, and the address of the own device is set as a source MAC address SA. Then, a 4-byte pattern by repeating, for example, “0010” is provided as the data DA.

Returning again to FIG. 4, the timer setting section 538
Is a timing generation circuit that supplies the transmission timing of the start ACK packet and the test packet to the packet generation unit 536. In particular, in the present embodiment, the packet detection unit 530 detects the second start packet in the remote loop test. In this case, a timing signal instructing generation of a start ACK packet is supplied. A timer circuit that supplies a timeout signal to the PHY setting unit 532 and the MAC switch setting unit 534 when a predetermined time has elapsed from the detection of the first activation packet to the detection of the second activation packet. The LED control unit 540 is a control circuit that controls the blinking of the LED 526 during a loopback test. In the present embodiment, when a switch-on is detected or when a start-up packet is received, a yellow LED indicating that the test is in progress is performed. It turns on, and turns on a green LED when the packet comparison unit 544 determines that the test packet is normal during the self-loop test. At the end of the test, both LEDs are turned off.

On the other hand, the packet detector 542 is a detection circuit that detects a start packet and a stop packet from the optical conversion bridge 40 during a remote loop test, or detects a test packet during a self-loop test. Particularly, in the present embodiment, when the second start packet is detected, the result is sent to the PHY setting unit 532 and the MAC switch setting unit 53.
4. The data is supplied to the packet generation unit 536 and the timer setting unit 538. Similarly, in the case of the self-loop test, a test packet looped back is detected, and the packet comparison unit 544 is detected.
Transfer to The packet comparing unit 544 is a comparing circuit that compares whether or not the test packet sent from the packet generating unit 536 matches the looped-back test packet. As a result, when they match, the LED control unit 540 normally operates. Is provided.

Next, the loopback test method according to the present embodiment will be described with reference to FIGS. 8 to 10 together with the operation of the LAN connection system. First, when the remote loop test is performed, the optical carrier 40
The switch is turned on via the remote loop test switch 428 or remote control. As a result, in the optical conversion bridge 40, as shown in FIG. 9, the control unit 414 detects the switch-on in step S10, and proceeds to step S12. In step S12,
The electrophysical layer termination 402 is set to full duplex and isolated mode, and the first MAC switch 404 is set to
Double mode. Next, in step S14, the timing of the inter-packet gap is set, and
At 16, the counter indicating the transmission of the first start packet is set to "1", and at step S18, the yellow LED 429 is turned on. Next, step S2
At 0, the first activation packet is generated and transmitted.

Next, the timing of the inter-packet gap is taken again in step S22, and the counter is incremented in step S24, and it is determined whether or not the value is "9" in step S26, that is, whether the start packet has been transmitted ten times. Judge and further step S28
It is determined whether or not a start ACK packet has been received. If the activation ACK packet has not been received, the process returns to step S20, generates and transmits the activation packet again, and repeats steps S20 to S28. That is, in this case, the transmission of the activation packet up to ten times is repeated from the transmission of the activation packet to the reception of the activation ACK packet at a timing of the packet gap. Incidentally, when the counter becomes N = “9”, step S29 is performed.
Then, it is determined whether a timeout or switch-off has occurred. The start packet generated in step S20 is transmitted from the electric physical layer terminating unit 412 to the optical fiber transmission line 20 via the changeover switch 424.
Is supplied to the optical conversion repeater 50 via the.

Next, in the optical conversion repeater 50, the start packet from the optical conversion bridge 40 is transmitted to the optical fiber transmission line 20.
Is received by the optical physical layer terminating unit 502 via the control unit 512, the start packet subjected to the optical-electrical conversion is detected by the control unit 512 via the detection line 520 of the control packet insertion detecting unit 504. At this time, the start packet is transmitted from the outbound route to the first MAC.
The switch 506 is also supplied to the MAC switch 50
In No. 6, since the data length is shorter than the normal frame, it is discarded and does not pass downstream. The control unit 512 of the optical conversion repeater 50 that has received the start packet determines whether or not the first start packet has been received in step S50 as shown in FIG. In S52, time counting is started. At this time, the switch detection of the test switch 524 in the self-loop is masked in step S54. Next, in step S56, it is determined whether or not a predetermined time T1 in consideration of the inter-packet gap, that is, a time to reach the second start packet has elapsed. If the time T1 has not elapsed, step S58
It is determined whether or not the next start packet has been received. If the next start packet has not been received, step S
56 and step S58 are repeated. Step S
When the predetermined time T1 elapses at 56, step S
The process proceeds to 60, the timer is cleared, and the process returns to step S50. When the second start packet is received in step S58, the process proceeds to step S62, in which the second MAC switch 508 is set to full duplex, and the electric physical layer terminating unit 510 is set to the loopback mode.

Next, in step S64, the yellow LE
D526 is turned on to notify the outside that the remote loop test is being performed, and the process proceeds to step S66. In step S66, a start ACK packet is generated and transmitted. Thereby, the start ACK packet is transmitted to the control packet insertion detecting unit 5.
The signal is transmitted from the changeover switch 522 of No. 04 to the optical conversion bridge 40 via the optical fiber transmission line 20 through the optical physical layer conversion unit 502. In the optical conversion bridge 40, the starting AC
The K-packet is subjected to optical-electrical conversion in the optical physical layer terminating unit 412 and is taken into the control unit 414 via the detection line 426 of the control packet insertion detecting unit 410. In this case as well, the start ACK packet is supplied to the second MAC switch 408, but is discarded because the packet length is shorter than a normal frame, and does not pass upstream. The control unit 414 that has received the activation ACK packet returns to the state shown in FIG.
In step S28, it is determined whether or not a startup ACK packet has been received.
Proceed to step S30. In step S30, a waiting time for the inter-packet gap is counted, and when the time elapses, a test packet is generated and transmitted in step S32. In this case, a timeout time, for example, a time for looping back the test packet a plurality of times is set in step S34, and it is determined whether the timeout time has elapsed in step S36 or whether the switch has been turned off. If No is determined in step S36, it is determined in step S38 whether a test packet has been received. If the test packet has not been received, the process returns to step S30, and steps S30 to S38 are repeated.

As a result, the test packet generated in step S32 is
From the second switch 420 to the optical conversion repeater 50 via the optical fiber transmission 20. In the optical conversion repeater 50, the test packet is subjected to optical-electrical conversion in the optical physical layer terminating unit 502, and reaches the electric physical layer terminating unit 510 through the MAC switches 506 and 508. Electrophysical layer termination 5
In 10, the arriving test packet is looped back, is subjected to the return path, is subjected to electro-optical conversion at the optical physical layer terminating section 502 through the MAC switches 508 and 506, and is looped back to the optical conversion bridge 40 via the optical fiber transmission path 20. Is done. At this time, the optical conversion repeater 50 loops back the test packet in step S68 as shown in FIG. 10, and proceeds to step S70 to wait for the reception of the stop packet.

On the other hand, in the optical conversion bridge 40, the test packet that has been looped back is subjected to optical-electrical conversion in the optical physical layer terminating unit 412, and is further subjected to the second MAC switch 4.
When the test packet is output to the return path through 08, the test packet looped back by the detection line 422 of the test packet insertion detection unit 406 is supplied to the control unit 414. Thus, returning to FIG. 9 again, when a test packet is detected in step S38, the process proceeds to step S40, and it is determined whether the received test packet and the transmitted test packet match. At this time, if it is determined that the test packets do not match, the process proceeds to step S42 and the green L
If the ED 429 is on, it is turned off, and in step S44, the remote control device is notified that the loopback is not normal, and the process returns to step S30.
If it is determined in step S40 that the test packets match, the process proceeds to step S46, where the green LED 42
9 is turned on, and in step S48, the remote control device is notified that loopback is normal,
It returns to step S30. Next, steps S30 to S48 are repeated in the same manner as described above, and step S3
When the switch is turned off for a predetermined time in step 6, the process proceeds to step S80 to generate and transmit a stop packet. Next, in step S82, the timing time of the inter-packet gap is counted, and in step S84
Then, the MAC switches 404 and 408 and the electric physical layer terminating unit 402 are returned to the normal mode, and the LED is turned off in step S86, and the light conversion bridge 4 is turned off.
The remote loop test state at 0 is released.

On the other hand, the stop packet is transmitted to the changeover switch 42.
4 through the optical physical layer terminator 412 and further to the optical conversion repeater 50 via the optical fiber transmission line 20. In the optical conversion repeater 50, when the control unit 512 receives a stop packet from the optical physical layer terminating unit 502 via the detection line 520, the process proceeds from step S70 to step S70 in FIG.
Proceeding to 72, the second MAC switch 506 and the electrophysical layer termination unit 510 are set to the normal mode. Next, the time count is cleared in step S74, and the LED is turned off in step S76, and the loopback test ends.

Next, FIG. 11 shows a flowchart of the self-loop test. In the self-loop test, the optical conversion bridge 40 and the optical conversion repeater 50 perform the same operation. Therefore, for example, when the optical conversion bridge 40 is described, first, in step S90, the self-loop test switch 427 or the control of the remote control device is performed. When the switch is turned on, the process proceeds to step S92, in which the first MAC switch 404 is set to the full-duplex mode, the electrical physical layer terminating unit 402 is set to the isolated mode, and the optical physical layer terminating unit 412 is set to the loopback mode. Set each. Next, in step S94, the timing of the inter-packet gap is set, and the process proceeds to step S9.
At 6, the yellow LED 429 is turned on. Next, the process proceeds to step S98, and after the elapse of the inter-packet gap,
In step S100, a test packet is generated. As a result, the test packet is inserted into the outgoing line via the changeover switch 420 and is supplied from the second MAC switch 408 to the optical physical layer terminating unit 412. Optical physical layer termination 4
At 12, the test packet from the outward route is looped back and supplied to the return route, and is output from the second MAC switch 408 to the return route. As a result, a test packet by the self-loop is detected by the control unit 414 via the detection line 422 of the test packet insertion detection unit 406.

At this time, the control unit 414 determines in step S9
8 to step S106 are repeated, and step S1
When a test packet is detected at 06, step S1
In step 08, it is determined whether the transmitted test packet matches the test packet received by the self-loop.
If the results do not match, the green LED 429 is turned off in step S110, and an error is notified to the remote control device in step S112. If a packet match is detected in step 108, step S114
In step S116, the green LED 429 is turned on.
Notifies the remote control device that the self-loop is normal. Next, steps S98 to S116 are repeated in the same manner as above, and if a timeout or switch-off is detected in step S104, the process proceeds to step S118, where the MAC switch 404,
408 is returned to the normal state, and the electrical physical layer termination section 402 and the optical physical layer termination section 410 are returned to the normal state. Next, the LED 429 is turned off, and the self-loop test ends.

As described above, according to the LAN connection system of the present embodiment and the loopback test method thereof, the user LAN 10 is connected to the wide area of the communication carrier by using the inexpensive bridge type optical conversion bridge 40 and optical conversion repeater 50. It can be connected to the LAN 30. In this case, the optical conversion bridge 40 from the station side provides the optical conversion repeater 5 inside the house.
A loopback test to zero can be effectively performed. In particular, since a control packet such as a start-up packet and a start-up ACK packet uses a packet shorter than the packet length of a normal Ethernet frame, a broadcast address packet used in a loopback test is transmitted to the user LAN 10 or the wide area LAN 30 or another network. It is possible to perform a reliable test without leaking to other devices and without adversely affecting other traffic. Therefore, it is possible to quickly detect a failure of the optical fiber transmission line 20 and the optical conversion repeater 50 inside the house, improve the quality of the maintenance, and provide an excellent service to the user.

In the above embodiment, as shown in FIG. 6, a packet shorter than the minimum packet length of the Ethernet frame is applied as the control packet. However, the present invention is not limited to this. The control packet may be such that it is detected by the control unit of the bridge and then discarded by the MAC switch. For example, as shown in FIG. 12, a frame may be formed in the same manner as a normal Ethernet net frame, and a CRC bit error may be inserted as the frame check sequence FCS. In this case, the broadcast address is assigned as the destination address DA, the own device address is assigned as the source address, and the data DA is added to the start packet by repeating, for example, “0001”.
A byte pattern is given, a response packet is given a 64 byte pattern by repeating, for example, “0010”, and a stop packet is given, for example, “0”.
A pattern of 64 bytes is provided by repeating “011”. As for the CRC bit, it is preferable to invert the result obtained by operating these data using a generator polynomial to generate a data error.

In the above-described embodiment, the case where two MAC switches are applied to the optical conversion bridge 40 and the optical conversion repeater 50 for band limitation has been described as an example. Including those to which the above MAC switch is applied. In the above embodiment, the optical fiber transmission line 20 has a transmission bandwidth of 100 Mbps.
In the present invention, any transmission band may be applied.

[0047]

As described above, according to the LAN connection system of the present invention, a wide area L is installed on a communication carrier side.
A first optical conversion device for performing electrical / optical conversion of a predetermined data frame transmitted between the AN and the optical fiber transmission line and transferring the data frame by medium access control; A second method for converting a data frame transmitted between the optical fiber transmission line and the optical frame into an optical signal and transferring the data frame by medium access control.
The first optical conversion device transmits a control packet for controlling a loop-back test having a shorter packet length than a data frame transferred to the second optical conversion device via an optical fiber transmission line. And a test control unit for transmitting a test packet having a packet length similar to that of the data frame to perform a loop-back test.
The physical layer termination point with the user LAN is set in a loopback state based on the control packet from the first optical conversion device, and the test packet received via the optical fiber transmission line is returned to the first optical conversion device. Inexpensive bridge-type LAN-to-LAN connection that enables effective execution of a loop-back test from an optical conversion device on the telecommunications carrier side to an optical conversion device on the inside of the home because it includes a loop control unit that performs loop-back control can do.

According to the LAN connection system of the second aspect of the present invention, the control packet is a packet formed to have a shorter packet length than the shortest packet length of the data frame to be transferred in the second optical conversion device. Therefore, after detecting the control packet in the second optical conversion device, it can be effectively discarded separately from other data frames to be transferred, and it is possible to prevent extra packets from leaking to the user LAN side. .

According to the LAN connection system of the third aspect of the present invention, the control packet is a packet having the same length as the packet length of the data frame to be transferred in the second optical conversion device. Since the packet includes an error in the check, after detecting the control packet in the second optical conversion device, the data error can be checked and effectively discarded, and an extra packet to the user LAN side can be transmitted. Outflow can be prevented.

According to the inter-LAN connecting device according to the fourth aspect of the present invention, the first optical conversion device terminates the electric physical layer connected to the wide area LAN, and the optical fiber transmission line. An optical physical layer terminating means for terminating the connected optical physical layer, a MAC switch for transferring a data frame between the terminating means according to the MAC address,
A control packet from the test control means is inserted into a transmission path to the second optical conversion device between the MAC switch and the optical physical layer terminating device, and a response packet from the second optical conversion device to the control packet is received. A control packet insertion detecting means for detecting from the path, and a test packet from the test control means between the MAC address and the electro-physical layer terminating means, inserted into a transmission path to the second optical conversion device and transmitted from the optical conversion repeater. Since it includes the test packet insertion detecting means for detecting the looped-back test packet from the receiving path, it is possible to effectively exchange control packets with the optical conversion device inside the house and loop back the test packets. In particular, the control packet is blocked by the MAC switch from passing to the wide area LAN side and is discarded, so that the outflow thereof has no adverse effect.

According to the LAN connection system according to the fifth aspect of the present invention, the test control means of the first optical conversion device includes at least a control packet and a test packet including a start packet and a stop packet for a loopback test. A packet generation unit for generating a packet; a packet detection unit for detecting a response packet to the start packet and a test packet looped back; and comparing whether the test packet looped back matches the transmitted test packet. Since the packet comparing means and the notifying means for notifying the result to the outside are included, the start and stop of the second optical conversion device at the time of the loopback test can be effectively controlled, and the loopback test is performed. The test result by the packet can be effectively reported.

According to the inter-LAN connection system according to claim 6 of the present invention, the second optical conversion device terminates the electrical physical layer connected to the user LAN, the optical fiber transmission line, Optical physical layer terminating means for terminating the connected optical physical layer, a MAC switch for transferring a data frame between these terminating means according to the MAC address, and a first optical switch between the MAC switch and the optical physical layer terminating means. Control packet insertion detecting means for detecting a control packet from the conversion device from its reception path and supplying the control packet to the loop control means, and inserting a response packet from the loop control means into a transmission path to the first optical conversion device. Therefore, it is possible to effectively exchange control packets with the optical conversion device on the provider side and loop back test packets. In particular, since the control packet is blocked by the MAC switch from passing to the user LAN side and is discarded, the outflow thereof has no adverse effect.

According to the LAN connection system according to claim 7 of the present invention, the loop control means of the second optical converter transmits at least the control packet including the start packet and the stop packet from the first optical converter. A packet detecting means for detecting, a packet generating means for generating a response packet when a start packet is detected by the packet detecting means, and a loopback state of the electrophysical layer terminating means when the start packet is received by the packet detecting means. And a loop setting canceling means for canceling the loopback state when receiving the stop packet, so that the start and stop from the first optical conversion device can be effectively controlled during the loopback test. The loopback control of the test packet at that time can be reliably performed.

On the other hand, according to the loop-back test method of the present invention, the communication carrier transmits a predetermined data frame to be transmitted between the wide area LAN and the optical fiber transmission line to the electric / electrical transmission line.
A first optical converter for optically converting the data frame and transferring the data frame by medium access control is prepared, and the data frame transmitted between the user LAN and the optical fiber transmission line is electrically / optically converted inside the user's house. An optical conversion repeater for transferring the data frame by the medium access control is prepared, and a start packet for instructing the second optical conversion device from the optical conversion bridge to perform a loopback test shorter than the packet length of the predetermined data frame is transmitted to the optical fiber. The second optical conversion device, which has transmitted the transmission packet via the transmission path and received the activation packet, sets the electrophysical layer termination point with the user LAN in a loopback state, and responds to the activation packet with a predetermined data frame packet. A response packet shorter than the length is transmitted to the first optical conversion device via the optical fiber transmission line, and the response packet is received. Transmits a first same packet length of the test packet and the predetermined data frame in the optical conversion apparatus to a second optical converter through an optical fiber transmission line,
In the second optical converter receiving the test packet, the test packet is looped back at the end point of the electric physical layer with the user LAN, and looped back to the first optical converter via the optical fiber transmission line. The first optical conversion device receives the transmitted test packet, compares the transmitted test packet with the looped-back test packet, and reports the result to the outside, so that the control packet and the test packet are transmitted. Is user LAN or wide area L
Without being sent to the AN, the test packet can be effectively looped back in the system and the test can be performed reliably and effectively.

According to the loopback test method according to the ninth aspect of the present invention, when the first optical conversion bridge ends the loopback test, the stop packet shorter than the packet length of the predetermined data frame is transmitted through the optical fiber. Second through the road
To the normal optical transmission device and returns to the normal transmission state, and upon receiving the stop packet, the first optical conversion device releases the loopback state of the termination point of the electric physical layer with the user LAN to enable normal data communication. Since the state returns to the normal state, it is possible to effectively return to the state in which normal data communication can be performed after the loopback test.

According to the loopback test method according to claim 10 of the present invention, the start packet, the response packet, and the stop packet are further longer than the shortest packet length of the data frame to be transferred in the first and second optical conversion devices. Since the packet is formed to have a short packet length, the control packet can be effectively discarded after being detected by the first and second optical converters, separately from other data frames to be transferred. Outflow of unnecessary packets can be prevented.

According to the loopback test method of the present invention, the start packet, the response packet, and the stop packet have the same length as the packet length of the data frame to be transferred in the first and second optical conversion devices. Since the packet is a packet having an error included in the data check, the data error is checked and effectively discarded after the control packet is detected in the first and second optical conversion devices. It is possible to prevent extra packets from flowing to the LAN side.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of an inter-LAN connection system according to the present invention.

FIG. 2 is a diagram showing a network configuration to which the LAN connection system according to the embodiment of FIG. 1 is applied;

FIG. 3 is a functional block diagram illustrating a functional configuration of a control unit of the optical conversion bridge according to the embodiment of FIG. 1;

FIG. 4 is a functional block diagram showing a functional configuration of a control unit of the optical conversion repeater according to the embodiment of FIG.

FIG. 5 is a diagram showing an example of a format of an Ethernet frame applied to the embodiment of FIG. 1;

FIG. 6 is a diagram showing a format example of a test packet applied to the embodiment of FIG. 1;

FIG. 7 is a diagram showing a format example of a control packet applied to the embodiment of FIG. 1;

FIG. 8 is a sequence diagram illustrating a procedure of a loopback test method applied to the embodiment of FIG. 1;

FIG. 9 is a flowchart showing a flow of a loopback test method applied to the embodiment of FIG. 1;

FIG. 10 is a flowchart showing a flow of a loopback test method applied to the embodiment of FIG. 1;

FIG. 11 is a flowchart showing a flow of a loopback test method applied to the embodiment of FIG. 1;

12 is a diagram showing another example of a control packet applied to the inter-LAN connection system and its loopback test method according to the embodiment of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 User LAN 20 Optical fiber transmission line 30 Wide area LAN 40 Optical conversion bridge (first optical conversion device) 50 Optical conversion repeater (second optical conversion device) 402, 510 Electrophysical layer terminating sections 404, 408, 506, 508 MAC switch 412,502 Optical physical layer termination unit 414 512 Control unit 428,524 Test switch

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04L 29/14 H04L 13/00 315A H04Q 1/20 F term (Reference) 5K002 AA05 AA06 DA04 DA32 EA05 FA01 5K019 AA08 AC09 BA56 CC15 CC16 5K030 GA14 HB06 HB11 HB28 HC01 HD07 JA08 JA10 JL03 LB02 MC02 MC09 5K033 AA05 CB03 CB08 CC01 DA01 DA06 DB19 DB20 DB22 EA02 EA03 EA07 5K035 AA07 BB03 CC06 DD02 EE02 GG10 GG08 GG08 GG08 GG08 GG08 GG08 GG08

Claims (11)

[Claims] 1. A user LAN and a wide area LAN of a communication carrier
Between the LAN and the optical fiber transmission line, the system connects between the LAN and the optical fiber transmission line. A first optical conversion device for performing optical / optical conversion and transferring the data frame by medium access control, and an electrical / optical conversion for a data frame installed in a user's home and transmitted between a user LAN and an optical fiber transmission line. And a second optical conversion device for transferring the data frame by medium access control, wherein the first optical conversion device controls a loopback test with the second optical conversion device. Transmitting a control packet discarded during the transfer processing in the second optical conversion device through the optical fiber transmission line, and further transmitting a packet similar to a data frame. Test control means for transmitting a test packet to perform a loopback test, wherein the second optical conversion device loops a physical layer termination point with a user LAN based on a control packet from the first optical conversion device. An inter-LAN connection system comprising: a loop control unit that sets a back state and returns a test packet received via an optical fiber transmission line to the first optical conversion device to perform loop-back control. 2. The inter-LAN connection system according to claim 1, wherein the control packet has a packet length shorter than a shortest packet length of a data frame to be transferred in the second optical conversion device. An inter-LAN connection system, characterized in that: 3. The inter-LAN connection system according to claim 1, wherein the control packet is a packet having the same length as a packet length of a data frame to be transferred in the second optical conversion device. An inter-LAN connection system characterized in that the packet includes an error in the data check. 4. The inter-LAN connection system according to claim 1, wherein the first optical conversion device terminates an electro-physical layer connected to a wide area LAN. An optical physical layer terminating means for terminating an optical physical layer connected to an optical fiber transmission line, a MAC switch for transferring a data frame between the terminating means according to the MAC address, the MAC switch and the optical physical layer termination Means for inserting a control packet from the test control means into a transmission path to the second optical conversion device and detecting a response packet from the second optical conversion device to the control packet from the reception path. Control packet insertion detecting means, and a test packet from the test control means between the MAC address and the electro-physical layer terminating means. A test packet insertion detecting means for detecting a test packet inserted into a transmission path to the conversion apparatus and looped back from the second optical conversion apparatus, from the reception path. 5. The inter-LAN connection system according to claim 4, wherein the test control means of the first optical conversion device includes at least a control packet and a test packet including a start packet and a stop packet at the time of a loopback test. Respectively, a packet detecting means for detecting a response packet to the start packet and a looped-back test packet, and a packet for comparing whether the looped-back test packet matches the transmitted test packet. An inter-LAN connection system comprising a comparing unit and a notifying unit for notifying the result to the outside. 6. The inter-LAN connection system according to claim 1, wherein the second optical conversion device terminates an electro-physical layer connected to a user LAN. An optical physical layer terminating means for terminating an optical physical layer connected to an optical fiber transmission line, a MAC switch for transferring a data frame between the terminating means according to the MAC address, the MAC switch and the optical physical layer termination Means for detecting a control packet from the first optical conversion device from its receiving path and supplying the control packet to the loop control device, and transmitting a response packet from the loop control device to the first optical conversion device. L including control packet insertion detecting means for inserting the control packet into the transmission path.
AN connection system. 7. The inter-LAN connection system according to claim 6, wherein the loop control means of the second optical conversion device transmits at least a control packet including a start packet and a stop packet from the first optical conversion device. A packet detection unit for detecting the packet, a packet generation unit for generating a response packet when the start-up packet is detected by the packet detection unit, and the electrophysical layer termination unit when the start-up packet is received by the packet detection unit. A LAN setting system for setting a loopback state and canceling the loopback state when a stop packet is received. 8. A user LAN and a wide area LAN of a communication carrier
Is a loopback test method in an inter-LAN connection system for connecting a LAN and an optical fiber transmission line via an optical fiber transmission line. A first optical converter for optically converting the data frame and transferring the data frame by medium access control is prepared, and the data frame transmitted between the user LAN and the optical fiber transmission line is electrically / optically converted inside the user's house. A second optical conversion device for transferring the data frame by medium access control, and a start packet instructing a loopback test from the first optical conversion device to the second optical conversion device; The start packet to be discarded is transmitted via the optical fiber transmission line, and the second optical converter receiving the start packet transmits the power to the user LAN. A physical layer termination point is set to a loop-back state, and a response packet that responds to the start-up packet to the first optical conversion device and that is discarded after the detection is transmitted via the optical fiber transmission line. The first optical conversion device that has received the response packet transmits a test packet similar to a predetermined data frame to the second optical conversion device via the optical fiber transmission line, and the second optical conversion device that has received the test packet In the optical conversion device, the test packet is looped back at the end point of the electrophysical layer with the user LAN, and looped back to the first optical conversion device via the optical fiber transmission line. The first optical conversion device compares the test packet received and transmitted with the looped-back test packet and reports the result to the outside. Loopback test method in LAN connecting system, characterized in that. 9. The loopback test method according to claim 8, wherein the first optical conversion device, when ending the loopback test, outputs a stop packet discarded after the detection by the second optical conversion device. The data is transmitted to the second optical conversion device via the optical fiber transmission line to return to a state in which normal data communication is possible, and the second optical conversion device receiving the stop packet transmits the termination point of the electrophysical layer with the user LAN. A loop-back test method in an inter-LAN connection system, wherein a loop-back setting is canceled to return to a state in which normal data communication is possible. 10. The loopback test method according to claim 8, wherein the start packet, the response packet, and the stop packet are shorter than a shortest packet length of a data frame to be transferred in the second optical conversion device. A loopback test method in an inter-LAN connection system, wherein the packet has a shorter packet length. 11. The loopback test system according to claim 8, wherein the start packet, the response packet, and the stop packet are the same as the packet length of a data frame to be transferred and processed in the second optical conversion device. Characterized in that the packet has a data check length and an error is included in the data check.
N-to-N connection system.