JPH03192936A - Optical lan controller - Google Patents

Abstract

PURPOSE:To easily detect the occurrence of a fault by receiving a frame sent from a present equipment and checking a frame checking sequence(FCS) of the received frame. CONSTITUTION:n-Set of work stations (11-1)-(11-n) are connected to an optical branching coupler 13 via optical LAN controllers (12-1)-(12-n) respectively with optical fiber cables (14-1)-(14-n). The work stations 11 are connected in a radial shape physically around the optical branching coupler 13 to form path type optical LAN logically. Then a sent FCS and a received FCS in the loopback signal of a frame generated from its own equipment 12 are collated, the result is stored statistically and it is checked from the work stations 11. Thus, fast troubleshooting of a fault and a fault occurring location on the network are easily estimated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical local area network, and more particularly to an optical LAN control device for connecting a station and a local area network.

[Conventional technology]

When transmitting data using a bus type optical LAN, a frame with a destination address added is output and then transmitted to all workstations through optical fibers. Each workstation captures only frames to which an address indicating its own device is added. In this way, the transmission function in a bus-based optical LAN is realized on the terminal device side.

Generally, it is controlled by the optical LAN control device of the workstation.

In a conventional optical LAN control device using such a bus system, the physical layer receives frames from the trunk transmission line. The destination address of the frame is MAC (Medium Acc
esSControl) Reception of data from the physical layer continues only when the sublayer control unit recognizes the physical address or broadcast address indicating the own device. The received data is stored in memory and then transmitted to the workstation.

On the other hand, if the destination address indicated by the received data does not match the address of the device itself, the subsequently received data is discarded without being stored in the memory.

[Problem to be solved by the invention]

In this way, the conventional bus type optical LAN control device 1...
The transmitted , t: 7 frames are distributed to all workstations by an optical branching/coupling device, and are also returned to the own device for reception. However, since the destination of the frame transmitted from the own device indicates the address of another device, the frame is discarded without being stored in memory. Therefore, even if there is a fault in a transmission medium such as an optical cable between the own device and the optical branch/coupler, it cannot be easily detected. In particular, in the case of optical fiber cables, continuity tests and level measurements in the event of a failure are
Specialized measuring equipment is required and faults are generally more difficult to diagnose than with electrical cables.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical LAN control device that can easily detect the occurrence of a failure.

[Means to solve the problem]

The optical LAN control device according to claim 1 includes (i) a frame check sequence generating means for generating and adding a frame check sequence to data to be transmitted; and (ii) a source address for recognizing a source address from a received frame. recognition means; (iii) frame check sequence inspection means for inspecting the frame check sequence of the received frame; and (1v) if the source recognized by the source address 1m means is the own device, a frame check sequence generation means generates (v) a counting means for counting the number of times the comparison results in the comparing means are inconsistent; ing.

That is, the optical LAN control apparatus according to the first aspect of the present invention is configured to receive a frame transmitted from the own apparatus and perform a frame check sequence inspection means for the frame.

The optical LAN control device according to claim 2 is the invention according to claim 1, further comprising: (i) test frame transmitting means for sequentially transmitting a plurality of test frames to the network;
) an error rate calculation means for calculating an error rate from the count value of the counting means due to the transmission of the test frame from the test frame transmission means, and (iii) if the error rate calculated by the error rate calculation means exceeds a predetermined value, and a fault notification means for notifying one workstation of a fault and rejecting subsequent transmission requests.

That is, the optical LAN control device according to the second aspect of the present invention is configured to automatically detect the occurrence of a failure by transmitting a test frame.

In the optical LAN control device according to claim 3, in the invention according to claim 2, in the case of the CSMA/CD method, the error rate calculation means calculates the error rate in consideration of the number of times collisions of test frames occur. ing.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples.

FIG. 1 shows the configuration of a LAN system using an optical LAN control device according to an embodiment of the present invention.

Each of n workstations 11-1, 11-2,...
... 11-n are optical LAN control devices 12-, respectively.
The optical fiber cables 14-L..., 14n are connected to the optical branch/coupler 13 via L..., 12-n. These workstations 11 are physically connected radially around the optical branching coupler 13, and logically constitute a bus-type optical LAN.

The optical LAN control device 12-1 is the workstation 11
Workstation interface 16, LLC (Logical Link Conn.
trol) layer control unit 17, transmission/reception memory 18 and MA
A C layer control section 19 is provided.

The LLC layer control unit 17 performs logical transmission control at the data link level in order to transmit data from the workstation 11-1 to the network or to receive frames addressed to the workstation 11-1.

The MAC layer control unit 19 executes transmission/reception control depending on the physical medium to the optical network, and provides a function for constructing a bus-type LAN using an optical fiber transmission line.

FIG. 2 shows the circuit configuration of the MAC layer control section in blocks.

The MAC layer control unit 19 includes a MAC layer controller 21. The MAC layer controller 21 is configured to control data transmission and reception together with the LLC layer control section 17.

The MAC layer control unit 19 includes a source address addition unit 22 that reads data stored in the transmission/reception memo +718 and adds the address of its own device, which is the transmission source, to the data. The transmitted data with the source address added is the first
After being temporarily buffered in the FIF◯ buffer 23, the data is converted into serial data by a parallel-to-serial converter 24 and supplied to a frame assembler 26.

The MAC layer control section 12-1 includes an Fe2 (frame check sequence) generation section 27.

The FC3 generating section 27 generates an FCS code used for error detection in transmission data, and supplies it to the frame assembling section 26 and the comparator 28. The frame assembly afs 26 assembles a frame from the transmission data and FCS code serially supplied from the parallel-serial converter 24 and supplies it to the encoding circuit 29. The encoding circuit 29 converts the transmission data encapsulated into a frame into a transmission line code system such as a CMI code or Manchester code, and supplies the converted data to an electro-optic converter 31 . The electro-optical converter 31 converts the signal converted into the transmission path code system from an electrical signal to an optical signal, and sends it to the network via the optical fiber cable 14-1 (Fig. 1). .

On the other hand, from the optical branching coupler 13 to the optical fiber cable 14-
The optical signal supplied via 1 is converted into an electrical signal by an opto-electrical converter 32 and supplied to a clock extraction circuit 33 and a decoding circuit 34. Clock extraction circuit 33 extracts a timing signal from the received signal and supplies it to decoding circuit 34 . The decoding circuit 34 decodes the received signal based on the timing signal and supplies it to the frame decomposition section 36.

The frame decomposition unit 36 detects the beginning and end of the frame, separates only the data, and supplies the separated data to the FC3 inspection unit 37 and the serial-parallel conversion unit 38. The FC8 inspection unit 37 monitors the data until the end of the frame, calculates Fe2, and supplies the value to the MAC layer controller 21 and the comparator 28. On the other hand, the received data serially supplied to the serial-parallel converter 38 is converted into parallel data,
Destination address after being puffed into the second FIFO buffer 39! ! ! The information is supplied to the identification unit 41 and the source address recognition unit 42. The destination address recognition unit 41 checks the destination address of the received frame, and if it matches the network address indicating the own device, sends a reception instruction signal 43.
is output to the MAC layer controller 21. The source address recognition unit 42 is configured to supply a source matching signal 44 to the comparator 28 when the source address of the received frame matches the network address of the device itself.

The comparator 28 receives the source matching signal 44 and compares Fe2, which is added to the last transmitted frame and is supplied from the FC3 generator 27, with Fe2 calculated by the FC3 checker 37. If the two do not match, a mismatch signal 46 is supplied from the comparator 28 to a statistical counter 47, which is counted up.

Next, the operation of detecting a failure in the optical LAN control device configured as described above will be explained.

Data from workstation 11-1 is transmitted via optical LAN.
A control device adds a source address and an FCS code to each frame and transmits it to the network. The transmitted frame is distributed by the optical branch/coupler 13 to other workstations 11-2, .

Now, the received signal from the optical branching coupler 13 is sent to the opto-electrical converter 3.
2, the second FIFO buffer 39 via the decoding circuit 34, the frame analysis section 36, and the serial/parallel return section 38.
shall have been supplied to.

The received signal stored in the second FIFO buffer 39 is
It is supplied to the destination address recognition unit 41. If the frame is destined for the own device, the destination address recognition unit 41 supplies a reception instruction signal 43 to the MAC layer stiffness controller 21. When the MAC layer stiffness controller 21 receives the transmission instruction signal 43, it transfers the received data from the second FIFO buffer 39 to the transmission/reception memory 18.

If the destination address does not match the network address of the device itself, reading from the second FIFO buffer 39 is not performed, and the received data is distorted here. Even in this case, the FC3 inspection unit 37 monitors the data until the end of the frame, calculates Fe2, and supplies the result to the MAC layer stiffness controller 21 comparator 28.

When the comparator 28 receives the source matching signal 44 from the source address recognizing section 42, the comparator 41 compares Fe2 added to the last transmitted frame with Fe2 calculated by the FC3 checking section 37. If the frame sent from the own device is returned normally by the optical branching coupler 13, Fe
2 matches.

On the other hand, if a failure occurs in the optical transmission line, the transmitting section after the frame assembling section 26 of the own device, or the receiving section before the frame disassembling section 36, Fe2 will not match. If Fe2 does not match, the comparator 28 supplies a mismatch signal 46 to the statistical counter 47 and adds "1" to its count value. If this failure is not temporary, the value of this statistical counter 42 will steadily increase. Workstation 11 is LLC
By monitoring the value of this statistical counter 42 through the layer control unit 17, failures can be easily discovered.

The LLC layer control unit 17 periodically scans the count value of the statistical counter 42 and automatically performs fault diagnosis when the count value reaches a predetermined value of the monitoring system.

FIG. 3 shows the flow of automatic fault diagnosis performed by the LLC layer control unit 17.

The LLC layer control unit clears the value of the statistical counter 42 to zero (step (2)) and sets the counter value of the frame number counter to 100 (step (2)).

Then, 100 test frames without a destination are sequentially transmitted at time intervals that are sufficiently larger than the propagation delay time of the optical transmission line medium (steps ① to ②).

This test frame is also returned to the own device through the optical branching coupler 13. The own device recognizes the frame as having its own network address as the source address, so
A comparison is made between the last transmitted Fe2 and the received Fe2. As a result of the comparison, if both FCs 5 do not match, the statistical counter 42 is updated. The data portion of the test frame may be generated randomly or may be prepared in advance so as to generate data with different FC3O values for each frame.

After sending 100 test frames (step ■:
Y), read the value of the statistical counter 42 (step ■)
, determine whether the value is "θ" or not (Step 2), and check the number of failures. If there is no failure occurrence count (step ◯; Y), that is, if all verifications are successful, the self-diagnosis process is ended without doing anything, and the process returns to the original process.

On the other hand, if there is a number of failures (Step ■; N), generate a self-diagnosis error message (Step ■), and notify the workstation of this (Step [Co., Ltd.]).
. At the same time, step ■) will switch to transmission prohibition mode.
, rejecting further transmission requests from the workstation.

When a collision occurs in the CSMA/CD (carrier detection multiple access/equilibrium detection) method, the number of collisions is counted, and a value is determined in consideration of the number of collisions when determining the number of mismatches in matching.

〔Effect of the invention〕

In this way, according to the invention as claimed in claim 1, the transmitted Fe2 and the received Fe2 are collated in the return signal of the frame generated by the own device, and the results are statistically accumulated. By checking from the station, it is possible to discover faults on the network early and easily detect faults when they occur.

Further, according to the second aspect of the invention, network reliability can be improved by automatically diagnosing a fault and actively notifying an upper layer such as a workstation of the fault based on the result.

[Brief explanation of drawings]

The drawings are for explaining one embodiment of the present invention, and among them, Fig. 1 is a system configuration diagram of a LAN using an optical LAN control device, Fig. 2 is a circuit diagram of a MAC layer control unit, and Fig. 3 is a circuit diagram of a MAC layer control unit. is a flowchart showing the flow of performing self-failure diagnosis. 11... Workstation, 12...
・Optical LAN control device, 13... Optical branching coupler, 14... Optical fiber cable, 17...
・LLC layer control unit, 18... Transmission/reception memory, 19... MAC layer control unit, 22... Source address addition unit, 7...
・FC3 generation unit, 28... Comparator, 7...
...FC3 inspection section, 2... Source address recognition section, 7...
statistics counter.

Claims (1)

[Claims] 1. Frame check sequence generation means for generating and adding a frame check sequence to data to be transmitted; Source address recognition means for recognizing a source address from a received frame; and Source address recognition means for recognizing a source address from a received frame; a frame check sequence inspection means for inspecting a frame check sequence; and when the source recognized by the source address recognition means is the own device, a frame check sequence value generated by the frame check sequence generation means and the frame check sequence inspection means; An optical LAN control device comprising: a comparison means for comparing a frame check sequence value obtained from a received frame with a frame check sequence value obtained from a received frame; and a counting means for counting the number of times the comparison result in the comparison means does not match. 2. A test frame transmitting means for sequentially transmitting a plurality of test frames to the network; an error rate calculating means for calculating an error rate from the count value of the counting means by transmitting test frames from the test frame transmitting means; 2. The optical LAN control according to claim 1, further comprising failure notification means for notifying a workstation of a failure and rejecting subsequent transmission requests when the error rate calculated by the rate calculation means exceeds a predetermined value. Device. 3. The optical LAN control device according to claim 2, wherein in the CSMA/CD method, the error rate calculation means calculates the error rate by taking into account the number of times collisions of test frames occur.