GB2244628A - Node apparatus in a local area network - Google Patents
Node apparatus in a local area network Download PDFInfo
- Publication number
- GB2244628A GB2244628A GB9108286A GB9108286A GB2244628A GB 2244628 A GB2244628 A GB 2244628A GB 9108286 A GB9108286 A GB 9108286A GB 9108286 A GB9108286 A GB 9108286A GB 2244628 A GB2244628 A GB 2244628A
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- Prior art keywords
- subsystem
- duplicated
- control section
- node apparatus
- switching
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
- G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
- G06F11/16—Error detection or correction of the data by redundancy in hardware
- G06F11/20—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements
- G06F11/2002—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements where interconnections or communication control functionality are redundant
- G06F11/2005—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements where interconnections or communication control functionality are redundant using redundant communication controllers
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
- G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
- G06F11/16—Error detection or correction of the data by redundancy in hardware
- G06F11/20—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements
- G06F11/2002—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements where interconnections or communication control functionality are redundant
- G06F11/2007—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements where interconnections or communication control functionality are redundant using redundant communication media
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
- G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
- G06F11/16—Error detection or correction of the data by redundancy in hardware
- G06F11/20—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements
- G06F11/202—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements where processing functionality is redundant
- G06F11/2038—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements where processing functionality is redundant with a single idle spare processing component
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
- G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
- G06F11/16—Error detection or correction of the data by redundancy in hardware
- G06F11/20—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements
- G06F11/202—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements where processing functionality is redundant
- G06F11/2043—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements where processing functionality is redundant where the redundant components share a common memory address space
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
- G06F11/22—Detection or location of defective computer hardware by testing during standby operation or during idle time, e.g. start-up testing
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
- G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
- G06F11/16—Error detection or correction of the data by redundancy in hardware
- G06F11/20—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements
- G06F11/2015—Redundant power supplies
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
- G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
- G06F11/16—Error detection or correction of the data by redundancy in hardware
- G06F11/20—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements
- G06F11/202—Error detection or correction of the data by redundancy in hardware using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements where processing functionality is redundant
- G06F11/2023—Failover techniques
- G06F11/2025—Failover techniques using centralised failover control functionality
Landscapes
- Engineering & Computer Science (AREA)
- Theoretical Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Quality & Reliability (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Computer Hardware Design (AREA)
- Data Exchanges In Wide-Area Networks (AREA)
- Hardware Redundancy (AREA)
- Safety Devices In Control Systems (AREA)
Abstract
A node apparatus (10) included in a local area network having duplicated communication paths comprises duplicated subsystems (11, 12). Each of these subsystems monitors its own operation state. The node apparatus further comprises shared memories (17, 18), each memory storing therein operation state monitoring information on the operation state of its own subsystem and continuously enabling the opposite subsystem to store the operation state monitoring information therein. Duplicately arranged switching control sections (15, 16) switch a master operation to the opposite subsystem when a failure occurs in either one of the subsystems. The switching of the master operation can take place even when a failure occurs in one of the switching control sections (15, 16). Power supplies (19, 20) are also duplicated. <IMAGE>
Description
The present invention relates to a node apparatus contained in a local area network.
A local area network (LAN) is utilized as a network for making high speed data transfer in a middle distance (several tens km at its maximum) range. In general, this local area network is composed of node apparatuses for performing reproduction, repeating and processing of signals; transmission paths for connecting these node apparatuses with each other; and terminal devices connected to the respective node apparatuses.
Some of the LANs employ duplicated communication paths, and the node apparatuses employed therein comprise duplicated subsystems.
Fig. 1 is a functional block diagram showing an arrangement of a conventional node apparatus as a first example thereof. In a node apparatus 8 shown in Fig. 1, reference numeral 1 indicates a first subsystem and reference numeral 2 denotes a second subsystem. With such first and second subsystems, this node apparatus 8 has a structure of a duplicated internal module. Reference numeral 3 indicates a switching control section for switching the operating/waiting conditions between the first and second subsystems 1 and 2. In the first and second subsystems 1 and 2, reference numerals 4 and 5 denote control sections, and reference numerals 6 and 7 represent shared memories, respectively.Then, the writing of the operation management information is performed commonly via these shared memories 6 and 7 under the control of the control sections 4 and 5 between the first and second subsystems.
The operations of the conventional node apparatus 8 shown in Fig. 1 will be described. In Fig. 1, when a state change occurs in the conventional network, for instance, the control section 4 employed in the first subsystem 1 in operation recognizes this state change and then writes this state change into the shared memory 6.
This state change is simultaneously written into the shared memory 7 employed in the second subsystem 2 which is in the waiting condition. The control section 5 in the second subsystem 2, which is in the waiting cordition, reads the operation management information of the control section 4 in the first subsystem 1 from the shared memory 7, so that both of the first and second subsystems 1 and 2 are allowed always to share the same operation management information.
Next, another operation of the conventional node apparatus 8 in which a failure or fault happens to occur will be described. When a failure or fault happens to occur in the first subsystem 1 in an operation condition, the control section 4 in the first subsystem 1 informs the occurrence of the failure or fault to the switching control section 3, otherwise, the switching control section 3 detects a failure informing signal from the control section 4 in the first subsystem 1. Then, the switching control section 3 operates to stop the operation of the control section 4 in the first subsystem 1 in order to remove it from the redundant arrangement and, at the same time, to switch the control section 5 of the second subsystem 2 to be put into operation.With such a processing operation, the operation of the node apparatus 8 can be continued so that the operation of the network can be executed without any interruption.
As described above, even when one of the duplicated subsystems happens to fail in the conventional node apparatus 8, the operation of the network may be continued without any interruption by virtue of the duplication switching function of the switching control section, namely, such a function that an operation condition of one subsystem in an operating condition, in which a failure has happend to occur, is switched to the other subsystem in a waiting condition.
However, in the above described conventional node apparatus 8, if a failure happens to occur in the switching control section 3 itself which is not duplicated, there is a problem that the intended duplication switching function cannot be performed.
Next, Fig. 2 is a schematic block diagram showing a conventional node apparatus 9 having the above-described duplicated subsystems, as a second example of the conventional node apparatus.
In Fig. 2, the node apparatus 9 comprises a first subsystem 21a, a second subsystem 21b and a switching control section 22 commonly used therefor.
Thus, this node apparatus 9 is duplicated by the first subsystem 21a and second subsystem 21b. The switching control section 22 switches the operating/waiting conditions between the first subsystem 21a and second subsystem 21b. The first subsystem 21a comprises a control section CTa and a shared memory MRa. Similarly, the second subsystem comprises a control section CTb and a shared memory MRb. Reference numeral 23 indicates a central monitoring control apparatus which transmits/ receives connection information and monitoring information via the duplicated communication paths 24a and 2db between the control section CTa and control section CTb employed in this node apparatus 9.
Then, the operation of the above-described conventional node apparatus 9 with the above-explained functional arrangement, upon occurrence of a fault, will now be explained.
Fig. 3 illustrates an operation sequence of this node apparatus 9 when a fault or failure happens to occur therein.
When a failure or fault happens to occur in the first subsystem 21a (time point ta), the first subsystem 21a sends a duplication switching instruction to the switching control section 22 as far as the first subsystem 21a can do so (time point tb). Otherwise, if this procedure of the first subsystem 21a can not be performed appropriately, the switching control section 22 detects a factor which requires the duplication switching operation (time point tb'). Then the switching control section 22 sends an interruption instruction informing a duplication state change to the second subsystem 21b (time point tc).
Then, the second subsystem 21b, which have recognized this interruption instruction, informs this state change to the central monitoring control apparatus 23 (time point td).
As described above, it is possible for the above-described conventional node apparatus 9 having such a functional arrangement to inform a change of the duplicated condition, upon occurrence of a failure
However, in the conventional node apparatus 9, there is another problem that, although the occurrence of a failure is reported to the central monitoring control apparatus 23, the details of the failure and the place, where the failure has actually occurred, cannot be determined.
The present invention has been made in an attempt to solve the above-described problems.
Thus, the present invention proposes to provide such a node apparatus capable of dealing with a failure or fault occurring in a switching control section having a duplication switching function.
According to the present invention, there is provided a node apparatus in a local area network including duplicated communication paths, which node apparatus has duplicated subsystems, each thereof monitoring an operating condition of its own, said duplicated subsystems comprising:
storage means for storing therein operating condition monitoring information obtained by the monitoring operation of each of the duplicated subsystems, and for simultaneously causing the monitoring information to be stored in an opposite subsystem continuously; and
duplicated switching means having an operation switching function to switch an operating condition from a failed subsystem to the other subsystem when one of the duplicated subsystems happens to fail, whereby one subsystem in normal operation in the duplicated subsystems is continuously kept in operation without interrupting the operation switching function.
The present invention will now be further described by way of example with reference to the accompanying drawings, in which:
Fig. 1 is a schematic block diagram showing an arrangement of a conventional node apparatus as a first example thereof;
Fig. 2 is a schematic block diagram showing an arrangement of a conventional node apparatus as a second example thereof;
Fig. 3 schematically illustrates an operation sequence of the second conventional node apparatus;
Fig. 4 is a schematic block diagram showing an arrangement of a node apparatus according to a first embodiment of the present invention;
Fig. 5 is a schematic block diagram showing an arrangement of a node apparatus according to a second embodiment of the present invention; and
Fig. 6 schematically illustrates an operation sequence of the node apparatus according to the second embodiment of the present invention.
Referring to Fig. 4, a first embodiment of the present invention will be described hereunder.
Fig. 4 shows an arrangement of a node apparatus 10 according to the first embodiment of the present invention. In the node apparatus 10 shown in Fig. 4, reference numeral 11 indicates a first subsystem, and reference numeral 12 represents a second subsystem, each of which has a form of a duplicated internal structure module. In each of the first and second subsystems, reference numerals 13 and 14 indicate control sections, and reference numerals 15 and 16 designate switching control sections both of which function as sections capable of switching the operating/waiting conditions between the first and second subsystems 11 and 12, respectively.Reference numerals 17 and 18 indicate shared memories disposed in the first subsystem 11 and second subsystem 12, respectively, through which operation management information is made available commonly to the control sections 13 and 14. Reference numerals 19 and 20 indicate power supply sections used to commonly feed the switching control sections 15 and 16, respectively. These power supply sections supply power to both of the switching control sections 15 and 16 in a parallel mode.
It should be noted that, although the shared memories 17 and 18 and also the control sections 13 and 14 in the first and second subsystems 11 and 12 are energized by the other power supply systems, respectively, which are different from the above-described power supply sections 19 and 20, said power supply systems are not shown.
There is a master/slave relationship between the switching control section 15 of the first subsystem 11 and the switching control section 16 of the second subsystem 12, so that one of these switching control sections 15 and 16 becomes the master to take the initiative in the switching control, and a control section on the same side with the switching control section of the slave side is subordinate to an instruction from the switching control section in the subsystem on the master side, and further the switching control section on the slave side keeps the states of its instructions to the respective control sections always identical with those of the switching control section on the master side.Furthermore, since the respective switching control sections 15 and 16 are always fed by both of the power supply sections 19 and 20, both the switching control sections 15 and 16 can operate even when one of the power supply sections 19 and 20 happens to fail.
The operation of the node apparatus 10 according to the first embodiment of the present invention will be described. In the node apparatus 10 of the first embodiment, it is assumed that the first subsystem 11 is in an operating condition, while the second subsystem 12 is in a waiting condition, and the switching control section 15 of the first subsystem 11 functions as the master, while the switching control section 16 of the second subsystem 12 functions as the slave.
Firstly, a description will be made of a case where the switching control section 15 of the first subsystem 11 happens to fail. Upon occurrence of a failure in the switching control section 15 functioning as the master, the switching control section 16 functioning as the slave in the second subsystem 12, which is always monitoring the state of the switching control section 15 in the opposite subsystem 11, detects this failure with higher priority as compared with other failure factors, and becomes a master switching control section by itself.
At the same time this new master switching control section 16 instructs the old#master switching control section 15 to become a new slave switching control section, and further sends an information of the master/slave change of the switching control sections to the control section 14 of the second subsystem 12. As a result, when such a failure happens to occur in the duplicated subsystems, the control section 13 of the first subsystem 11 receives an instruction of the change of the operating/waiting conditions from the old slave switching control section 16 of the second subsystem 12, whereby the operation of the node apparatus 10 can be continued.
Next, a description will be made of operations at the time when a power supply section for a switching control section happens to fail.
As explained before, even when the switching control sections are duplicated, if power supply sections therefor happen to fail, a satisfactory operation thereof cannot be expected. Therefore, the operation reliability of the subsystems may be improved by employing duplicated power sources belonging to a power system different from that of the other power supply sections for other component units in the subsystems. These duplicated power sources may be constructed to supply power to the abovedescribed duplication switching control sections in a parallel mode to thereby elevate the reliability of the operation of the subsystems. Even when the power supply section 19 for supplying power to the switching control section 15 in the first subsystem 11 happens to fail, for instance, when power supply is interrupted or a voltage drop occurs, since this switching control section 15 is also fed by the power supply section 20 in the second subsystem 12, the setting of the operating/waiting conditions of the first and second subsystems 11 and 12 and the master/slave relationship between the switching control sections 15 and 16 may be maintained in the same state.
Thus, in accordance with the above-described first embodiment, even when one of the switching control sections 15 and 16 happens to fail, the switching to the other switching control section can be performed smoothly. Furthermore, since it is so constructed that each of the power supply sections supplies power to both of the switching control sections 15 and 16 in a parallel mode, even if any one of the power supply sections 19 and 20 for feeding the switching control sections 15 and 16, respectively happens to fail, the operations of the switching control sections are not put into disorder.
Subsequently, a node apparatus 60 according to a second embodiment of the present invention will be described with reference to Figs. 5 and 6.
Fig. 5 is a schematic block diagram showing an arrangement of the node apparatus 60 according to the second embodiment of the present invention.
The node apparatus 60 shown in Fig. 5 comprises a first subsystem 21A and a second subsystem 21B which are provided with the function of the present invention, and also a common switching control section 22. Thus, this node apparatus 60 has a duplicated structure by employing the first subsystem 21A and second subsystem 21B. The switching control section 22 switches the operating/ waiting conditions between the first subsystem 21A and second subsystem 21B. The first subsystem 21A has a control section CTA and a shared memory MRA. The second subsystem 21B has a control section CTB and a shared memory MRB.Reference numeral 30 indicates a central monitoring control apparatus which transmits/receives, through either one of duplicated communication paths 50A and SOB, connection information and monitoring information to and from the control section CTA or the control section
CTB in the node apparatus 60.The shared memories MRA and
MRB are constructed so that communication can be realized between the subsystems 21A and 21B. Furthermore, the control sections CTA and CTB, respectively, have a function for writing the content of a failure into the shared memory MRA or MRB, and also a function for reading the failure content from the shared memory MRA or MRB and informing both an apparatus state and a duplication state to the central monitoring control apparatus 30, upon receipt of an interruption instruction informing a duplication state change (which will be described later).
The operation of the node apparatus 60 having the above-described arrangement according to the second embodiment of the present invention will be explained with reference to Figs. 5 and 6.
Fig. 6 shows an operation sequence of the node apparatus 60 according to the second embodiment of the present invention, in which the abscissa indicates respective component elements and the ordinate represents time "t".
In Figs. 5 and 6, when a failure happens to occur in the first subsystem 21A (time point "tl"), the control section CTA writes information on a failure state into the shared memory MRA and shared memory MRB as far as the control section CTA can do so (time points T2 and T3). Also, the control section CTA sends a duplication switching instruction for switching from the control section CTA to the control section CTB to the switching control section 22 (time point t4). When this procedure can not be performed appropriately, the switching control unit 22 directly detects a factor which requires the duplication switching operation (time point t5). As a consequence, the switching control unit 22 sends an interruption instruction informing a duplication state change to the control section CTB (time point t6).The control section CTB, which has confirmed the above-described interruption instruction, reads out the content of the failure from the shared memory MRB (time point t7), and thereafter the control section CTB produces information on the apparatus state based on the information on the failure state. Then, the control section CTB sends the changed duplication state information together with the apparatus state information to the central monitoring control apparatus 30 (time points t8 and tg) Immediately thereafter, the control section CTB resets the failure state information which has been written in the shared memory MRB (time point t10).
As described above, in the node apparatus 60 according to the second embodiment of the present invention, there is a particular merit that, since a control section, in which a failure has happend to occur, informs the failure state to a new operating control section which has been subjected to the duplication switching operation, and the new operating control section takes over the failure state information and informs it to the central monitoring control apparatus, the place of occurrence of the failure, which has formed a factor for the duplication switching operation can be determined.
As is apparent from the foregoing explanation of the first embodiment, there is obtained a particular advantage that, since the switching control sections, which control the switching operations for the operating/ waiting conditions between the duplicated subsystems in the node apparatus, are also duplicated, even when one of the switching control sections fails, the duplication switching function may be maintained.Furthermore, since the power supply sections for the respective duplicated switching control sections are disposed independently and separately from power supply sections for other component units and besides they are duplicated to be able to supply power to both of the duplicated switching control sections in a parallel mode, an overall normal operation of the node apparatus can be assured even when a failure occurs, and furthermore the reliability of the network system against various failures or malfunctions can be elevated.
As is apparent from the above-described explanation of the second embodiment of the present invention, in the node apparatus 60 of the present invention, a control section on the side, where a failure has occurred, informs the state of the failure through the shared memories to the other control section on the normally operating side, as far as it can recognize the state of the failure, and thereafter it instructs the duplication switching operation.
Further, the other control section on the normally operating side informs the state of the failure to the central monitoring control apparatus. As a consequence, there is obtained a particular advantage that the maintenance of a node apparatus and also a restoration process required in the case of occurrence of a failure therein can be quickly and readily attained.
Claims (5)
1. A node apparatus in a local area network including duplicated communication paths, which node apparatus has duplicated subsystems, each thereof monitoring an operating condition of its own, said duplicated subsystems comprising:
storage means for storing therein operating condition monitoring information obtained by said monitoring operation of each of said duplicated subsystems, and for simultaneously causing said monitoring information to be stored in an opposite subsystem continuously; and
duplicated switching means having an operation switching function to switch an operating condition from a failed subsystem to the other subsystem when one of said duplicated subsystems happens to fail, whereby one subsystem in normal operation in said duplicated subsystems is continuously kept in operation without interrupting the operation switching function.
2. A node apparatus as claimed in Claim 1, wherein each of said duplicated switching means is simultaneously fed by duplicated power supplies which are disposed independently from power supplies for circuit portions other than said duplicated switching means in said duplicated subsystems.
3. A node apparatus as claimed in Claim 1, wherein each of said duplicated subsystems comprises:
a control section for performing at least a condition monitoring operation to monitor a condition of a communication path connected to said duplicated subsystem, controlling communication with another node apparatus, and a condition monitoring operation to monitor operating conditions of respective portions of the node apparatus;
shared memories each thereof continuously writing therein operation management information of its own subsystem under the control of said control section;;
writing means for continuously writing the operation management information of its own subsystem into said shared memory of its own subsystem and simultaneously writing the operation management information in said shared memory of the other subsystem during a normal operating condition, and for writing a failure content of a subsystem, in which a failure has happened to occur, simultaneously with the operation management information, in both said shared memories of said duplicated subsystems upon occurrence of a failure; and
switching control sections for instructing the operation switching to one of said subsystems in normal operation upon inputting at least one of an operation switching instructing command from said control section of a failed subsystem and a failure detection signal indicative of a failure occurring in the failed subsystem.
4. A node apparatus as claimed in Claim 3, wherein said switching control section includes interrupt means for executing interruption to send duplicated condition change information which instructs the operation switching to said control section in the other normally operating subsystem, upon inputting at least one of an operation switching instructing command from said control section of a failed subsystem and a failure detection signal indicative of a failure occurring in the failed subsystem, whereby said control section in the other normally operating subsystem reads from said shared memory of its own subsystem the operation management information and the information on the failure content by the interruption executed by said interrupt means.
5. A node apparatus substantially as hereinbefore described with reference to and as shown in Figure 4 or Figures 5 and 6 of the accompanying drawings.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2105011A JPH043633A (en) | 1990-04-20 | 1990-04-20 | Node equipment |
| JP2133381A JPH0429446A (en) | 1990-05-23 | 1990-05-23 | Node device |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9108286D0 GB9108286D0 (en) | 1991-06-05 |
| GB2244628A true GB2244628A (en) | 1991-12-04 |
| GB2244628B GB2244628B (en) | 1994-11-23 |
Family
ID=26445368
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9108286A Expired - Fee Related GB2244628B (en) | 1990-04-20 | 1991-04-18 | Node apparatus having alternative subsystem switching function |
Country Status (2)
| Country | Link |
|---|---|
| KR (1) | KR950007954B1 (en) |
| GB (1) | GB2244628B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2308045A (en) * | 1995-12-07 | 1997-06-11 | Nec Corp | Communication unit switching apparatus |
| GB2328352A (en) * | 1997-08-12 | 1999-02-17 | Lucent Technologies Uk Limited | Redundant communication network |
| US6230281B1 (en) | 1998-08-26 | 2001-05-08 | Lucent Technologies, Inc. | Geographic redundancy protection method and apparatus for a communications network |
| EP1298861A2 (en) | 2001-09-27 | 2003-04-02 | Alcatel Canada Inc. | System for providing fabric activity switch control in a communications system |
| EP1331759A1 (en) * | 2002-01-24 | 2003-07-30 | Alcatel Canada Inc. | System and method for providing management of communication links connecting components in a network element |
-
1991
- 1991-04-18 GB GB9108286A patent/GB2244628B/en not_active Expired - Fee Related
- 1991-04-18 KR KR1019910006184A patent/KR950007954B1/en not_active IP Right Cessation
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2308045A (en) * | 1995-12-07 | 1997-06-11 | Nec Corp | Communication unit switching apparatus |
| US6021111A (en) * | 1995-12-07 | 2000-02-01 | Nec Corporation | Unit switching apparatus with failure detection |
| GB2308045B (en) * | 1995-12-07 | 2000-07-12 | Nec Corp | Communication unit switching apparatus |
| GB2328352A (en) * | 1997-08-12 | 1999-02-17 | Lucent Technologies Uk Limited | Redundant communication network |
| US6230281B1 (en) | 1998-08-26 | 2001-05-08 | Lucent Technologies, Inc. | Geographic redundancy protection method and apparatus for a communications network |
| EP1298861A2 (en) | 2001-09-27 | 2003-04-02 | Alcatel Canada Inc. | System for providing fabric activity switch control in a communications system |
| EP1298861A3 (en) * | 2001-09-27 | 2009-07-01 | Alcatel Canada Inc. | System for providing fabric activity switch control in a communications system |
| EP1331759A1 (en) * | 2002-01-24 | 2003-07-30 | Alcatel Canada Inc. | System and method for providing management of communication links connecting components in a network element |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9108286D0 (en) | 1991-06-05 |
| GB2244628B (en) | 1994-11-23 |
| KR910019367A (en) | 1991-11-30 |
| KR950007954B1 (en) | 1995-07-21 |
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| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20050418 |