JPH0378339A - Duplex control system for inter-local area network bridge device - Google Patents

Duplex control system for inter-local area network bridge device

Info

Publication number
JPH0378339A
JPH0378339A JP1215189A JP21518989A JPH0378339A JP H0378339 A JPH0378339 A JP H0378339A JP 1215189 A JP1215189 A JP 1215189A JP 21518989 A JP21518989 A JP 21518989A JP H0378339 A JPH0378339 A JP H0378339A
Authority
JP
Japan
Prior art keywords
bridge device
brg
active
local area
instruction
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP1215189A
Other languages
Japanese (ja)
Other versions
JPH07121015B2 (en
Inventor
Hideji Hagiwara
萩原 秀治
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NEC Corp
Original Assignee
NEC Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by NEC Corp filed Critical NEC Corp
Priority to JP1215189A priority Critical patent/JPH07121015B2/en
Publication of JPH0378339A publication Critical patent/JPH0378339A/en
Publication of JPH07121015B2 publication Critical patent/JPH07121015B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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  • Detection And Prevention Of Errors In Transmission (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)
  • Small-Scale Networks (AREA)

Abstract

PURPOSE:To facilitate device switching by providing a control means giving a non-acivating instruction to a bridge device when the fault of the bridge device in the midst of operation is detected and giving an activating instruction to the bridge device which is not in operation. CONSTITUTION:When the bridge device (BRG) 1 cannot execute a normal action, CPU 3 rewrites activating/non-activating information stored in a control information storage circuit (MGM) 33 and changes information of BRG 1 from active to non-active. Then, a central control circuit (CC) 32 transmits the non-activating instruction to BRG 1 which is in an active state till then through a control information transmission/reception circuit (RSC) 31 and a control bus (CBS) 6. BRG 1 stores it in an active/inactive information storage circuit (MEM) 17 and a control circuit (CTL) 15 gives the instruction to an A-side transmission/ reception circuit (RSA) 11 and a B-side transmission/reception circuit (RSB) 12 and closes respective transmission gates. On the other hand, BRG 2 receiving the activating instruction opens the transmission gates of RSA 21 and RSB 22. Thus, the active/inactive systems of BRG 1 and 2 easily is switched.

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明はローカルエリアネットワーク間ブリッジ装置の
二重化制御方式に関する。
DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a redundant control system for a bridge device between local area networks.

〔従来の技術〕[Conventional technology]

従来、2つのローカルエリアネットワーク間で必要なデ
ータを通過させる二重化されたブリッジ装置では、一方
のブリッジ装置が故障した時には人手によってこの故障
装置を系から切りはなして他方の正常なブリッジ装置を
起動していた。
Conventionally, in a duplex bridge device that passes necessary data between two local area networks, when one bridge device fails, the failed device is manually disconnected from the system and the other normal bridge device is activated. was.

〔発明が解決しようとする課題〕[Problem to be solved by the invention]

上述した従来のローカルエリアネットワーク闇ブリッジ
装置の二重化制御方式は、一方のブリッジ装置が故障し
た時に保守者が手動で他方の正常なブリッジ装置に切り
換えるので、故障が発生してから正常装置が稼働するま
での時間が非常に多くかかっていた。また、故障したブ
リッジ装置の故障前の状態が失われてしまうという欠点
があった。
In the conventional redundant control method for local area network network bridge devices described above, when one bridge device fails, the maintenance person manually switches to the other normal bridge device, so the normal device starts operating after the failure occurs. It took a very long time. Another drawback is that the state of the failed bridge device before the failure is lost.

〔課題を解決するための手段〕[Means to solve the problem]

本発明のローカルエリアネットワーク間ブリッジ装置の
二重化制御方式は、2つのローカルエリアネットワーク
間で必要なデータを通過させる二重化されたブリッジ装
置において、前記ブリッジ装置のヘルスチェックを行い
、運用中のブリッジ装置の障害を検出したときこのブリ
ッジ装置に不活性化指示を行うと共に非運用中のブリッ
ジ装置に活性化指示を行う制御手段を備えることを特徴
とし、前記各ブリッジ装置はその活性/不活性状態を記
憶する活性/不活性情報記憶回路と、フィルタリング情
報や運用時に収集した統計データを記憶する運用情報記
憶回路と、外部制御手段からの活性化/不活性化指示情
報に従って前記活性/不活性情報記憶回路の内容を書き
替えると共にブリッジ機能の実行の可否を制御する制御
回路とを備えている。
The redundant control method for a bridge device between local area networks of the present invention performs a health check of the bridge device in a redundant bridge device that passes necessary data between two local area networks, and checks the health of the bridge device in operation. The present invention is characterized by comprising control means for instructing the bridge device to deactivate and instruct non-operating bridge devices to activate when a failure is detected, and each bridge device stores its activated/deactivated state. an activation/inactivation information storage circuit that stores filtering information and statistical data collected during operation, and an activation/inactivation information storage circuit that stores activation/inactivation instruction information from an external control means. The controller includes a control circuit that rewrites the contents of , and controls whether or not the bridge function can be executed.

〔実施例〕〔Example〕

次に、本発明について図面を参照して説明する。 Next, the present invention will be explained with reference to the drawings.

第1図は本発明のローカルエリアネットワーク間ブリッ
ジ装置の二重化制御方式の一実施例を示すブロック図で
ある。
FIG. 1 is a block diagram showing an embodiment of a redundant control method for a bridge device between local area networks according to the present invention.

第1図において、本実施例は二重化されたブリッジ装置
(以下BRG)1.2と、BRGI、2を制御する中央
処理装置(以下CPU)3とで構成される。
In FIG. 1, this embodiment is comprised of a duplex bridge device (hereinafter referred to as BRG) 1.2 and a central processing unit (hereinafter referred to as CPU) 3 that controls the BRGI and 2.

BRGI、2はA側口−カルエリアネットワーク(以下
LANA)4とB側口−カルエリアネットワーク(以下
LANB)5の2つのローカルエリアネットワークの間
のデータの受は渡しを行うための装置である。BRGI
、2は制御バス(以下CBS)6を介してCPU3に接
続されており、CPU3はBRGI、2の活性状態およ
び不活性状態の制御を行う。
BRGI 2 is a device for receiving and passing data between two local area networks, A-side local area network (hereinafter referred to as LANA) 4 and B-side local area network (hereinafter referred to as LANB) 5. . BRGI
, 2 are connected to a CPU 3 via a control bus (hereinafter referred to as CBS) 6, and the CPU 3 controls the active and inactive states of BRGI, 2.

BRGIはA側送受信回路(以下R3A)11゜B測道
受信回路(以下R3B)12.制御情報送受信回路(以
下RSC)13.フィルタ回路(以下FIL)14.制
御回路(以下CTL)15゜運用情報記憶回路(以下O
PM>16.活性/不活性情報記憶回路(以下MEM)
17から構成されており、CTL15はR5Al 1.
R5B12゜R3Cl3.OMP16.MEM17の制
御を行う。BRGIはR3AIIを介してLANA4と
接続し、R3B12を介してLANB5と接続し、R2
O1Bを介してCB56と接続している。
BRGI has an A-side transmitting/receiving circuit (hereinafter referred to as R3A) 11°B road surveying receiving circuit (hereinafter referred to as R3B) 12. Control information transmitting/receiving circuit (hereinafter referred to as RSC) 13. Filter circuit (hereinafter referred to as FIL) 14. Control circuit (hereinafter referred to as CTL) 15° Operational information storage circuit (hereinafter referred to as O
PM>16. Active/inactive information storage circuit (hereinafter MEM)
CTL15 is composed of R5Al 1.
R5B12°R3Cl3. OMP16. Controls the MEM17. BRGI connects to LANA4 via R3AII, connects to LANB5 via R3B12, and connects to R2
It is connected to CB56 via O1B.

R3AIIはFIL14を介してR5B12と接続し、
F I L14はCTL15を介してOPMI6と接続
され、OPMI 6に記憶されている運用情報を用いて
データのフィルタリングを行う。
R3AII is connected to R5B12 via FIL14,
The FI L 14 is connected to the OPMI 6 via the CTL 15 and uses operational information stored in the OPMI 6 to filter data.

またR3AIIとR5B12はそれぞれCTL15を介
してMEM17と接続され、CTL15はMEM17に
記憶されている活性/不活性情報を用いて活性時にはR
3Al 1.R3B 12にデータの送信を許可し、不
活性時には送信を禁止する制御を行う。
In addition, R3AII and R5B12 are each connected to MEM17 via CTL15, and CTL15 uses the activation/inactivation information stored in MEM17 to R3AII and R5B12 when activated.
3Al 1. Control is performed to allow R3B 12 to transmit data, and to prohibit transmission when it is inactive.

BRG2はBRGIと同様にR3A21.R3B22.
  R3C23,FIL24.CTL25゜OPM26
.MEM27から構成され、BRGIと同様の機能を有
する。
BRG2 is R3A21. similar to BRGI. R3B22.
R3C23, FIL24. CTL25°OPM26
.. It is composed of MEM27 and has the same functions as BRGI.

CPU3はR5C31,中央制御回路(以下CC)32
.管理情報記憶回路(以下MGM)3Bから構成され、
CC32はR3C31とMGM33に接続されている。
CPU3 is R5C31, central control circuit (hereinafter referred to as CC) 32
.. Consists of a management information storage circuit (hereinafter referred to as MGM) 3B,
CC32 is connected to R3C31 and MGM33.

R5C31はCB56を介してBRGl、2のR3Cl
3,23と接続されている。CC32はMGM33の管
理情報に従ってR5C31,CB56を介してBRGI
、2を監視する。
R5C31 via CB56 BRGl, 2 R3Cl
It is connected to 3 and 23. CC32 transmits BRGI via R5C31 and CB56 according to the management information of MGM33.
, 2.

次に、本実施例の動作について説明する。Next, the operation of this embodiment will be explained.

CPU3はBRGI、2の二重化制御を初期設定から運
用時において制御する。初期設定時には、CPU3がM
GM33からBRGI、2に対する活性又は不活性情報
のデイフォルト値およびLANA4とLANB5間を通
過させるフィルタリング情報を読み出して、CC32に
指示してこれをBRGI、2にそれぞれ送出する。
The CPU 3 controls the redundancy control of the BRGI 2 from initial setting to during operation. At the time of initial setting, CPU3 is set to M.
The default value of active or inactive information for BRGI, 2 and the filtering information to be passed between LANA 4 and LANB 5 are read from GM 33, and the CC 32 is instructed to send them to BRGI, 2, respectively.

ここでBRGIを活性にし、BRG2を不活性にする場
合を例にとって説明する。BRGIではCPU3から送
出された活性化指示とフィルタリング情報をR2O13
で受信し、CTL15を介してMGM17とOPMI 
6にそれぞれ活性′化指示情報とフィルタリング情報を
記憶する0次いでCTL15はOPMI6からフィルタ
リング情報を読み出してFIL14を制御する。また、
CTL15はMEMl7から活性化指示情報を読み出し
てR3Al 1.R5B12の送信ゲートを開き、BR
GIのブリッジ機能を活性状態にする。
Here, an example will be explained in which BRGI is activated and BRG2 is inactivated. In BRGI, the activation instruction and filtering information sent from CPU3 are sent to R2O13.
received by MGM17 and OPMI via CTL15.
Then, the CTL 15 reads out the filtering information from the OPMI 6 and controls the FIL 14. Also,
CTL15 reads activation instruction information from MEM17 and activates R3Al1. Open the transmission gate of R5B12 and BR
Activate the GI bridge function.

従ってLANA4を流れるデータはR3AIIで受信さ
れてFIL14に送られる。FIL14では受信データ
がLANB5に流す必要のあるデータか否かを・判断し
、データ通過個数等の必要なデータをCTL1’5を介
してOPMI6に記憶した後、BRGIを通過させるデ
ータであればR3B 12を介してLANB5に送出す
る。またBRGIを通過させないデータであればFIL
14からR3B12へはデータを送らない。なお、LA
NB5を流れるデータも同様にBRGIで処理されて必
要に応じてR3AIIからLANA4に送出される。
Therefore, data flowing through LANA4 is received by R3AII and sent to FIL14. FIL14 judges whether or not the received data needs to be sent to LANB5, and after storing necessary data such as the number of passed data in OPMI6 via CTL1'5, if the data is to be passed through BRGI, it is sent to R3B. 12 to LANB5. Also, if the data does not pass through BRGI, FIL
No data is sent from R3B14 to R3B12. In addition, L.A.
Data flowing through NB5 is similarly processed by BRGI and sent from R3AII to LANA4 as necessary.

一方、BRG2はCPU3から送出された不活性化指示
とフィルタリング情報をR2O23で受信し、CTL2
5を介してそれぞれMEM27とOPM26に記憶する
。次いでCTL25はOPM26からフィルタリング情
報を読み出してF I L24を制御する。また、CT
L25はMEM27から不活性情報を読み出してR3A
21、R3B22の受信ゲートを開き、送信ゲートを閉
じてBRG2のブリッジ機能を不活性状態にする。
On the other hand, BRG2 receives the deactivation instruction and filtering information sent from CPU3 at R2O23, and CTL2
5 to the MEM 27 and OPM 26, respectively. The CTL 25 then reads filtering information from the OPM 26 and controls the FI L 24. Also, CT
L25 reads the inactivation information from MEM27 and sends it to R3A.
21. Open the reception gate of R3B22 and close the transmission gate to deactivate the bridge function of BRG2.

従ってLANA4を流れるデータはR5A21で受信さ
れてF I L24へ送られる。F I L24では受
信データがLANB5に流す必要のあるデータか否かを
判断し、データ通過個数等の必要なデータをCTL25
を介してOPM26に記憶した後、BRG2を通過させ
るデータであればR3B22へ送るが、R5B22の送
信ゲートが閉じているのでLANB5へデータは送出さ
れない。また、BRG2を通過させないデータであれば
F I L24からR5B22へデータは送らない、な
お、LANB5を流れるデータも同様にBRG2内で処
理される。
Therefore, data flowing through LANA4 is received by R5A21 and sent to FI L24. The FI L24 determines whether the received data is data that needs to be sent to the LANB5, and sends necessary data such as the number of data passages to the CTL25.
If the data is to be passed through BRG2, it will be sent to R3B22, but since the transmission gate of R5B22 is closed, the data will not be sent to LANB5. Further, if the data is not allowed to pass through BRG2, the data is not sent from FI L24 to R5B22. Furthermore, data flowing through LANB5 is similarly processed within BRG2.

以上説明したように本実施例では、初期設定時からの活
性状態のブリッジ装置(BRGl)と不活性状態のブリ
ッジ装置(BRG2)との違いはMEMl 7とMEM
27に記憶している内容のみであり、OPMI6.26
に記憶しているフィルタリング情報や運用時に収集され
るデータ通過個数等の統計データは同一である。従って
二重系の系切換えが発生しても、上述の収集データが失
われることはなく、非常に短い時間で系を切り換えるこ
とができる。
As explained above, in this embodiment, the difference between the bridge device (BRG1) in the active state from the initial setting and the bridge device (BRG2) in the inactive state is MEM17 and MEM1.
It is only the contents stored in OPMI6.27.
The filtering information stored in the server and statistical data such as the number of data passes collected during operation are the same. Therefore, even if a duplex system is switched, the above-mentioned collected data will not be lost, and the system can be switched in a very short time.

次に運用時の系切換え動作について説明する。Next, the system switching operation during operation will be explained.

運用時において、CPU3のCC32はBRGl、2の
CTL15,25に対して動作の正常性を確認するため
にヘルスチェックコマンドを送出する。CTL15.2
5はこのヘルスチェックコマンドをR5Cl3,23か
ら受は取ると、RGI、2内の動作の正常性をそれぞれ
確認してCC32に応答を返す。CC32はこの応答の
内容を解析してBRGI、2の正常性を判断する。
During operation, the CC 32 of the CPU 3 sends a health check command to the CTLs 15 and 25 of the BRGs 1 and 2 to confirm the normality of their operations. CTL15.2
When 5 receives this health check command from R5Cl3 and 23, it confirms the normality of the operations in RGI and 2, and returns a response to CC32. CC32 analyzes the content of this response and determines the normality of BRGI,2.

なおCC32は上記のヘルスチェックコマンドを定期的
に送出してBRGI、2の動作を監視する。
Note that the CC 32 monitors the operation of the BRGI 2 by periodically sending out the above health check command.

もし、例えばBRGIが故障等により正常動作を行えな
くなると、CPU3はMGM33内に記憶している活性
/不活性情報の書替えを行ってBRGIの情報を活性か
ら不活性に変更する。次いでCC32は現在まで活性状
態であったBRGlにR3C31,CB56を介して不
活性化指示を送出する。BRGIではR2O13がこの
不活性化指示を受信し、CTL15を介してMEMl7
にこれを記憶する。CTL15はR3AIIとR3B1
2に指示してそれぞれの送信ゲートを閉じる。従ってB
RGIのブリッジ機能は不活性状態になる0次いで、C
PU3は同様にBRG2に活性化指示を送出する。BR
G2ではR5A21とR3B22の送信ゲートを開いて
ブリッジ機能を不活性状態から活性状態とする。これに
より、BRGI、2の活性/不活性の系切換えが行われ
BRG2が運用状態となる。
If, for example, the BRGI becomes unable to operate normally due to a failure or the like, the CPU 3 rewrites the active/inactive information stored in the MGM 33 to change the BRGI information from active to inactive. Next, CC32 sends a deactivation instruction to BRG1, which has been in the active state until now, via R3C31 and CB56. In BRGI, R2O13 receives this inactivation instruction and MEMl7 via CTL15.
Remember this. CTL15 is R3AII and R3B1
2 to close each transmission gate. Therefore B
The RGI bridge function becomes inactive when 0 then C
PU3 similarly sends an activation instruction to BRG2. B.R.
In G2, the transmission gates of R5A21 and R3B22 are opened to change the bridge function from an inactive state to an active state. As a result, BRGI2 is switched between active and inactive, and BRG2 becomes operational.

〔発明の効果〕〔Effect of the invention〕

以上説明したように本発明によれば、二重化されたロー
カルエリアネットワーク間ブリッジ装置の系切換えを中
央処理装置によって制御し、且つ活性状態のブリッジ装
置と不活性状態のブリッジ装置における相違をローカル
エリアネットワークに対する出力ゲートのオン・オフ状
、態のみとすることにより、系切換え前に活性状態だっ
たブリッジ装置のデータが失われることがないのでデー
タの複写や初期設定手順が不要となり、即座に活性/不
活性状態を切り換えられるという効果がある。
As explained above, according to the present invention, the central processing unit controls the system switching of the bridge devices between duplicated local area networks, and the difference between the bridge devices in the active state and the bridge devices in the inactive state is controlled by the local area network. By setting only the on/off state of the output gate for the system, the data of the bridge device that was active before system switching is not lost, so there is no need to copy data or initial setting procedures, and it can be activated / activated immediately. It has the effect of being able to switch between inactive states.

間ブリッジ装置の二重化制御方式の一実施例を示すブロ
ック図である。
FIG. 2 is a block diagram illustrating an embodiment of a duplex control method for an inter-bridge device.

1.2・・・ブリッジ装置(BRG)、3・・・中央処
理装置(CPU)、4・・・A側口−カルエリアネット
ワーク(LANA) 、5・・・B側口−カルエリアネ
ットワーク(LANB)、6・・・制御バス(CBS)
、11.21・・・A測道受信回路(R3A)、12.
22・・・B測道受信回路(RSB)、13゜23.3
1・・・制御情報送受信回路(R3C)14.24・・
・フィルタ回路(FIL)、15゜25・・・制御回路
(CTL)、16.26・・・運用情報記憶回路(○P
M) 、17.27・・・活性/不活性情報記憶回路(
MEM) 、32・・・中央制御回路(CC)、33・
・・管理情報記憶回路(MGM)。
1.2...Bridge device (BRG), 3...Central processing unit (CPU), 4...A side entrance - Cal Area Network (LANA), 5...B side entrance - Cal Area Network ( LANB), 6...Control bus (CBS)
, 11.21...A road survey receiving circuit (R3A), 12.
22...B road survey receiving circuit (RSB), 13°23.3
1... Control information transmitting/receiving circuit (R3C) 14.24...
・Filter circuit (FIL), 15°25... Control circuit (CTL), 16.26... Operation information storage circuit (○P
M), 17.27...active/inactive information storage circuit (
MEM), 32... central control circuit (CC), 33.
...Management information storage circuit (MGM).

Claims (2)

【特許請求の範囲】[Claims] (1)2つのローカルエリアネットワーク間で必要なデ
ータを通過させる二重化されたブリッジ装置において、
前記ブリッジ装置のヘルスチェックを行い、運用中のブ
リッジ装置の障害を検出したときこのブリッジ装置に不
活性化指示を行うと共に非運用中のブリッジ装置に活性
化指示を行う制御手段を備えることを特徴とするローカ
ルエリアネットワーク間ブリッジ装置の二重化制御方式
(1) In a duplex bridge device that passes necessary data between two local area networks,
The present invention is characterized by comprising a control means that performs a health check on the bridge device and, when a failure is detected in the bridge device in operation, instructs the bridge device to deactivate and instructs the bridge device in non-operation to activate. A redundant control method for bridging equipment between local area networks.
(2)各ブリッジ装置はその活性/不活性状態を記憶す
る活性/不活性情報記憶回路と、フィルタリング情報や
運用時に収集した統計データを記憶する運用情報記憶回
路と、外部制御手段からの活性化/不活性化指示情報に
従って前記活性/不活性情報記憶回路の内容を書き替え
ると共にブリッジ機能の実行の可否を制御する制御回路
とを備える請求項(1)記載のローカルエリアネットワ
ーク間ブリッジ装置の二重化制御方式。
(2) Each bridge device has an activation/inactivation information storage circuit that stores its activation/inactivation state, an operation information storage circuit that stores filtering information and statistical data collected during operation, and activation from an external control means. A redundant local area network bridging device according to claim 1, further comprising a control circuit that rewrites the contents of the activation/inactivation information storage circuit according to deactivation instruction information and controls whether or not a bridge function can be executed. control method.
JP1215189A 1989-08-21 1989-08-21 Redundant control method of bridge device between local area networks Expired - Lifetime JPH07121015B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP1215189A JPH07121015B2 (en) 1989-08-21 1989-08-21 Redundant control method of bridge device between local area networks

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1215189A JPH07121015B2 (en) 1989-08-21 1989-08-21 Redundant control method of bridge device between local area networks

Publications (2)

Publication Number Publication Date
JPH0378339A true JPH0378339A (en) 1991-04-03
JPH07121015B2 JPH07121015B2 (en) 1995-12-20

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0646039A (en) * 1992-07-23 1994-02-18 Nec Corp Optical fiber medium connector
JPH08256173A (en) * 1995-03-17 1996-10-01 Nec Corp System and device for inter-lan connection
JPH09149072A (en) * 1995-11-20 1997-06-06 Nec Commun Syst Ltd Duplicate lan bridge system
US6370653B1 (en) 1997-11-28 2002-04-09 Hitachi, Ltd. Internetwork route calculation execution method and apparatus

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63138832A (en) * 1986-12-01 1988-06-10 Hitachi Ltd Gateway backup system
JPS641350A (en) * 1987-06-23 1989-01-05 Hitachi Ltd Gateway backing-up system
JPH01202046A (en) * 1988-02-06 1989-08-15 Mitsubishi Electric Corp Transmitter

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63138832A (en) * 1986-12-01 1988-06-10 Hitachi Ltd Gateway backup system
JPS641350A (en) * 1987-06-23 1989-01-05 Hitachi Ltd Gateway backing-up system
JPH01202046A (en) * 1988-02-06 1989-08-15 Mitsubishi Electric Corp Transmitter

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0646039A (en) * 1992-07-23 1994-02-18 Nec Corp Optical fiber medium connector
JPH08256173A (en) * 1995-03-17 1996-10-01 Nec Corp System and device for inter-lan connection
JPH09149072A (en) * 1995-11-20 1997-06-06 Nec Commun Syst Ltd Duplicate lan bridge system
US6370653B1 (en) 1997-11-28 2002-04-09 Hitachi, Ltd. Internetwork route calculation execution method and apparatus

Also Published As

Publication number Publication date
JPH07121015B2 (en) 1995-12-20

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