US20030120966A1 - Method for encoding/decoding a binary signal state in a fault tolerant environment - Google Patents
Method for encoding/decoding a binary signal state in a fault tolerant environment Download PDFInfo
- Publication number
- US20030120966A1 US20030120966A1 US10/026,353 US2635301A US2003120966A1 US 20030120966 A1 US20030120966 A1 US 20030120966A1 US 2635301 A US2635301 A US 2635301A US 2003120966 A1 US2003120966 A1 US 2003120966A1
- Authority
- US
- United States
- Prior art keywords
- binary
- frequency
- signals
- signal
- another
- 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.)
- Abandoned
Links
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
- H04L41/06—Management of faults, events, alarms or notifications
- H04L41/0654—Management of faults, events, alarms or notifications using network fault recovery
- H04L41/0663—Performing the actions predefined by failover planning, e.g. switching to standby network elements
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L43/00—Arrangements for monitoring or testing data switching networks
- H04L43/08—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
- H04L43/0805—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters by checking availability
- H04L43/0817—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters by checking availability by checking functioning
Definitions
- the present invention relates to fault tolerant systems and, more particularly, to a method for confirming validity of a control signal for energizing a back-up system in a fault tolerant environment.
- Numerous electronic control systems utilize multiple redundant systems to assure fault tolerance in critical applications.
- One example of such a system is a redundant switching fabric for a communication line card installation.
- a redundant switching fabric for a communication line card installation.
- such systems have two switching fabrics, a primary and a back-up. All of the line cards are connected to the outside world through the switching fabric.
- the primary fabric has a failure, the system has to switch to the backup fabric.
- the switching function resides on each line card and a remote controller provides a binary state signal to each card to let the card know when to switch to the back-up fabric.
- control signal may become tied to one of the binary states and be unable to switch in response to the remote controller. For example, if a binary zero is used to maintain the line cards connected to the primary fabric and the control signal line becomes grounded, the line card will not receive a binary one signal generated by the controller when the binary one signal is used to command a change to the backup fabric.
- control signal could fail into the switch state and cause one or more of the components to switch in error. In particular, a subset of the components might see the switch indication. This is particularly undesirable since it could lead to a partitioning of the system and result in a system failure. This type failure is not amenable to the test mode described below.
- the present invention is directed to a method for use in a fault tolerant environment for assuring that devices within the environment switch between primary and back-up systems in response to remotely generated control signals.
- the inventive system uses a binary code in the form of a pair of different frequency signals, i.e., a binary zero is represented by one frequency and a binary one is represented by another frequency.
- the signals may be continuous or may be sent in timed bursts.
- a receiver is provided to detect the presence of the signals. Since the line cards already have receivers to detect the binary signal, modification to detect a frequency signal requires the addition of minimal components.
- the receiver also includes circuitry for reporting the status of the card and such circuitry can be used to report to the remote controller whether the signals are reaching the line card.
- the signals could be sent in burst format using a single frequency in which the number of bursts could indicate a binary one or a binary zero. For example, if N bursts are received in some unit of time, that could be indicative of one binary state. If 2N burst are received in the same unit of time, that could be indicative of another binary state.
- the receiver could be programmed to look for N changes of frequency per unit of time to indicate one binary state and 2N changes of frequency could be indicative of another binary state.
- the receiver could be programmed to notify the remote controller whenever signals are being received and the absence of signal confirmation at the controller would be indicative of a loss of the control signal. In this way, the system would always know whether or not the control signal is being transmitted to the devices and thereby provide assurance that the redundancy is available.
- FIG. 1 is a simplified illustration of a phone switching system incorporating a redundant switching fabric with which the present invention may be used;
- FIG. 2 is a graph illustrating two forms of control signals.
- FIG. 1 there is illustrated a portion of a communication switching system 10 with which the present invention may be used.
- the system includes a block 12 identified as a remote controller which monitors and directs data flow into a distribution network.
- Data entering block 12 at line 14 is directed into a data distribution block 16 which forwards the data into multiple selected paths, two of which are shown at 18 and 20 coupling the data into a pair of redundant switching fabrics 22 and 24 .
- the switching fabrics couple data signals to and from a set of line cards 26 .
- the line cards are arranged so that each card directs calls to a specific communication line.
- the switching fabric is essentially a back plane connecting the line cards to the communication lines.
- the remote controller monitors operation of the switching fabric and determines whether there is any failure in the fabric. In the event of a failure, the controller 12 provides a DC signal to instruct the line cards to switch their respective inputs and outputs to the back-up fabric. Both the switching fabrics 22 and 24 are arranged to couple output data through a data select block 28 .
- the block 28 functions to pass data from either fabric to an output bus 30 .
- the controller 12 uses a bi-level control signal on a control voltage line to indicate to the line cards 26 which of the fabrics 22 and 24 are to be used to couple data into and out of the system. For example, a signal of zero volts would indicate use of one fabric and a signal of some positive or negative voltage would indicate use of the other of the fabrics.
- a grounded or open control voltage line corresponds to one state of the bi-level control signal. If the controller 12 changes the state of the control signal, the grounded or open control line will prevent the control signal from changing state at the line cards and thus prevent the redundant or back-up fabric from being brought into use, or alternately causing one or more of the line cards to switch states in error, leading to a partitioned system.
- the present invention overcomes the above described problem with the control line signaling by changing the format of the control signal.
- the bi-level control signal is replaced with a signal that has a varying characteristic.
- the control signal may be a dual frequency signal such that a first frequency of the signal indicates selection of a primary fabric (or other device) and a second frequency of the signal indicates selection of a back-up fabric (or other device).
- FIG. 2 at 32 shows a first frequency at A and a second frequency at B.
- the signal could be a multipulse signal in which a first number of pulses per unit of time would indicate selection of a first device and a second number of pulses per unit of time would indicate selection of a second device.
- the line cards 26 could be modified to receive the varying signal and provide a response to the controller 12 confirming receipt of the signal.
- the control voltage line such as the lines 32 and 34
- the control voltage line could be bi-directional signal lines passing through the fabrics 22 and 24 to the respective line cards 26 .
- Each line card could be modified to return a recognizable signal to the controller to indicate to the controller that the control voltage signal was received.
- Various types of signal responsive circuits are known in the art for performing this function.
- the control signal line is shown as a hard-wired line in the drawing, it will be understood that the return signal could be a wireless transmission.
Abstract
A method for use in a fault tolerant environment for assuring that devices within the environment switch between primary and back-up systems in response to remotely generated control signals. In one embodiment, the inventive system uses a binary code in the form of a pair of different frequency signals, i.e., a binary zero is represented by one frequency and a binary one is represented by another frequency. The signals may be continuous or may be sent in timed bursts. At the individual devices, such as the aforementioned line cards, a receiver is provided to detect the presence of the signals. Since the line cards already have receivers to detect the binary signal, modification to detect a frequency signal requires the addition of minimal components. The receiver also includes circuitry for reporting the status of the card and such circuitry can be used to report to the remote controller whether the signals are reaching the line card. Alternately, the signals could be sent in burst format using a single frequency in which the number of bursts could indicate a binary one or a binary zero. For example, if N bursts are received in some unit of time, that could be indicative of one binary state. If 2N burst are received in the same unit of time, that could be indicative of another binary state. In another form, the receiver could be programmed to look for N changes of frequency per unit of time to indicate one binary state and 2N changes of frequency could be indicative of another binary state.
Description
- The present invention relates to fault tolerant systems and, more particularly, to a method for confirming validity of a control signal for energizing a back-up system in a fault tolerant environment.
- Numerous electronic control systems utilize multiple redundant systems to assure fault tolerance in critical applications. One example of such a system is a redundant switching fabric for a communication line card installation. Typically, such systems have two switching fabrics, a primary and a back-up. All of the line cards are connected to the outside world through the switching fabric. In the event that the primary fabric has a failure, the system has to switch to the backup fabric. In this example, the switching function resides on each line card and a remote controller provides a binary state signal to each card to let the card know when to switch to the back-up fabric.
- One potential problem with such systems is that the control signal may become tied to one of the binary states and be unable to switch in response to the remote controller. For example, if a binary zero is used to maintain the line cards connected to the primary fabric and the control signal line becomes grounded, the line card will not receive a binary one signal generated by the controller when the binary one signal is used to command a change to the backup fabric. Another potential problem is that the control signal could fail into the switch state and cause one or more of the components to switch in error. In particular, a subset of the components might see the switch indication. This is particularly undesirable since it could lead to a partitioning of the system and result in a system failure. This type failure is not amenable to the test mode described below. There are solutions to this problem as well, such as running dual redundant signals and then running tests on both of them but such additional redundancy introduces more complexity. One solution to this problem is to periodically run a test mode in which a test signal is sent to each line card and a check is then made to determine if the line card responded to the test signal. While this approach may be suitable in simple systems having only a few devices that need to switch, verifying that each line card in a typical communication system has switched presents a complex problem. Accordingly, it would be desirable to provide a method for continually verifying proper operation of devices in response to control signals in a fault tolerant environment.
- The present invention is directed to a method for use in a fault tolerant environment for assuring that devices within the environment switch between primary and back-up systems in response to remotely generated control signals. In one embodiment, the inventive system uses a binary code in the form of a pair of different frequency signals, i.e., a binary zero is represented by one frequency and a binary one is represented by another frequency. The signals may be continuous or may be sent in timed bursts. At the individual devices, such as the aforementioned line cards, a receiver is provided to detect the presence of the signals. Since the line cards already have receivers to detect the binary signal, modification to detect a frequency signal requires the addition of minimal components. The receiver also includes circuitry for reporting the status of the card and such circuitry can be used to report to the remote controller whether the signals are reaching the line card. Alternately, the signals could be sent in burst format using a single frequency in which the number of bursts could indicate a binary one or a binary zero. For example, if N bursts are received in some unit of time, that could be indicative of one binary state. If 2N burst are received in the same unit of time, that could be indicative of another binary state. In another form, the receiver could be programmed to look for N changes of frequency per unit of time to indicate one binary state and 2N changes of frequency could be indicative of another binary state. In any of the examples, the receiver could be programmed to notify the remote controller whenever signals are being received and the absence of signal confirmation at the controller would be indicative of a loss of the control signal. In this way, the system would always know whether or not the control signal is being transmitted to the devices and thereby provide assurance that the redundancy is available.
- For a better understanding of the present invention reference may be had to the following detailed description taken in conjunction with the accompanying drawing in which:
- FIG. 1 is a simplified illustration of a phone switching system incorporating a redundant switching fabric with which the present invention may be used; and
- FIG. 2 is a graph illustrating two forms of control signals.
- Referring to FIG. 1, there is illustrated a portion of a
communication switching system 10 with which the present invention may be used. The system includes ablock 12 identified as a remote controller which monitors and directs data flow into a distribution network.Data entering block 12 at line 14 is directed into adata distribution block 16 which forwards the data into multiple selected paths, two of which are shown at 18 and 20 coupling the data into a pair ofredundant switching fabrics line cards 26. In the communication system, the line cards are arranged so that each card directs calls to a specific communication line. The switching fabric is essentially a back plane connecting the line cards to the communication lines. In existing systems, the remote controller monitors operation of the switching fabric and determines whether there is any failure in the fabric. In the event of a failure, thecontroller 12 provides a DC signal to instruct the line cards to switch their respective inputs and outputs to the back-up fabric. Both theswitching fabrics output bus 30. - In prior art systems, the
controller 12 uses a bi-level control signal on a control voltage line to indicate to theline cards 26 which of thefabrics controller 12 changes the state of the control signal, the grounded or open control line will prevent the control signal from changing state at the line cards and thus prevent the redundant or back-up fabric from being brought into use, or alternately causing one or more of the line cards to switch states in error, leading to a partitioned system. - The present invention overcomes the above described problem with the control line signaling by changing the format of the control signal. The bi-level control signal is replaced with a signal that has a varying characteristic. By way of example, the control signal may be a dual frequency signal such that a first frequency of the signal indicates selection of a primary fabric (or other device) and a second frequency of the signal indicates selection of a back-up fabric (or other device). FIG. 2 at32 shows a first frequency at A and a second frequency at B. As another example, the signal could be a multipulse signal in which a first number of pulses per unit of time would indicate selection of a first device and a second number of pulses per unit of time would indicate selection of a second device. FIG. 2 at 34 indicates one form of such pulsing. Other variations of this concept could be implemented with the basic theme of a variation in the control signal per unit time being such as to assure that a loss of control signal can be recognized. All of these signals are characterized by having a varying value rather than being set at some fixed value that could be duplicated by inadvertent coupling of the control line to some fixed value.
- In the illustrative example, the
line cards 26 could be modified to receive the varying signal and provide a response to thecontroller 12 confirming receipt of the signal. In one form, the control voltage line, such as thelines fabrics respective line cards 26. Each line card could be modified to return a recognizable signal to the controller to indicate to the controller that the control voltage signal was received. Various types of signal responsive circuits are known in the art for performing this function. Further, while the control signal line is shown as a hard-wired line in the drawing, it will be understood that the return signal could be a wireless transmission. - While the invention has been described in what is presently considered to be a preferred embodiment, various modifications will become apparent to those skilled in the art. It is intended therefore that the invention not be limited to the specific disclosed embodiment but be interpreted within the full spirit and scope of the appended claims.
Claims (5)
1. In a fault tolerant system having a primary device and at least one redundant device, and further having a remote controller for monitoring the status of the devices and providing a control signal to switch from the primary device to the redundant device upon detection of a failure in the primary device, a method of determining validity of the control signal comprising:
continually sending a first signal having a predetermined varying characteristic to at least the primary device from the remote controller; and
sending a second signal having a different varying characteristic to at least the primary device from the remote controller upon detection of a failure of the primary device.
2. The method of claim 1 wherein the varying characteristic comprises a signal frequency.
3. The method of claim 2 wherein the signal frequency is a continuous wave frequency.
4. The method of claim 2 wherein the signal frequency is a selected number of signals per unit of time.
5. The method of claim 1 wherein the at least one device includes a receiver responsive to the to the first signal for acknowledging receipt thereof to the remote controller.
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/026,353 US20030120966A1 (en) | 2001-12-21 | 2001-12-21 | Method for encoding/decoding a binary signal state in a fault tolerant environment |
TW091134652A TW200301419A (en) | 2001-12-21 | 2002-11-28 | Method for encoding/decoding a binary signal state in a fault tolerant environment |
GB0228197A GB2384408B (en) | 2001-12-21 | 2002-12-03 | Method for encoding/decoding a binary signal state in a fault tolerant environmnet |
JP2002364523A JP2003248633A (en) | 2001-12-21 | 2002-12-17 | Method of encoding/decoding binary signal state in fault tolerant environment |
KR1020020081742A KR20030053430A (en) | 2001-12-21 | 2002-12-20 | Method for encoding/decoding a binary signal state in a fault tolerant environment |
US11/142,562 US7480821B2 (en) | 2001-12-21 | 2005-05-31 | Method for encoding/decoding a binary signal state in a fault tolerant environment |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/026,353 US20030120966A1 (en) | 2001-12-21 | 2001-12-21 | Method for encoding/decoding a binary signal state in a fault tolerant environment |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/142,562 Continuation US7480821B2 (en) | 2001-12-21 | 2005-05-31 | Method for encoding/decoding a binary signal state in a fault tolerant environment |
Publications (1)
Publication Number | Publication Date |
---|---|
US20030120966A1 true US20030120966A1 (en) | 2003-06-26 |
Family
ID=21831327
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/026,353 Abandoned US20030120966A1 (en) | 2001-12-21 | 2001-12-21 | Method for encoding/decoding a binary signal state in a fault tolerant environment |
US11/142,562 Expired - Fee Related US7480821B2 (en) | 2001-12-21 | 2005-05-31 | Method for encoding/decoding a binary signal state in a fault tolerant environment |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/142,562 Expired - Fee Related US7480821B2 (en) | 2001-12-21 | 2005-05-31 | Method for encoding/decoding a binary signal state in a fault tolerant environment |
Country Status (5)
Country | Link |
---|---|
US (2) | US20030120966A1 (en) |
JP (1) | JP2003248633A (en) |
KR (1) | KR20030053430A (en) |
GB (1) | GB2384408B (en) |
TW (1) | TW200301419A (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB0418123D0 (en) | 2004-08-13 | 2004-09-15 | Asahi Chemical Ind | Polymers useful as medical materials |
CN101027927A (en) * | 2004-12-21 | 2007-08-29 | 中兴通讯股份有限公司 | Exchange based baseband processing module N+M back up method and device |
KR20080087909A (en) * | 2006-01-19 | 2008-10-01 | 엘지전자 주식회사 | Method and apparatus for decoding a signal |
RU177174U1 (en) * | 2017-11-07 | 2018-02-12 | федеральное государственное бюджетное образовательное учреждение высшего образования "Волгоградский государственный аграрный университет" (ФГБОУ ВО Волгоградский ГАУ) | DEVICE FOR CODING AND DECODING BINARY DATA CODES |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3920975A (en) * | 1974-11-14 | 1975-11-18 | Rockwell International Corp | Data communications network remote test and control system |
US5893162A (en) * | 1997-02-05 | 1999-04-06 | Transwitch Corp. | Method and apparatus for allocation and management of shared memory with data in memory stored as multiple linked lists |
US6035416A (en) * | 1997-10-15 | 2000-03-07 | International Business Machines Corp. | Method and apparatus for interface dual modular redundancy |
US6215998B1 (en) * | 1997-12-11 | 2001-04-10 | Nortel Networks Limited | Local component-specific console |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6650803B1 (en) * | 1999-11-02 | 2003-11-18 | Xros, Inc. | Method and apparatus for optical to electrical to optical conversion in an optical cross-connect switch |
US6792174B1 (en) * | 1999-11-02 | 2004-09-14 | Nortel Networks Limited | Method and apparatus for signaling between an optical cross-connect switch and attached network equipment |
US6882765B1 (en) * | 1999-11-02 | 2005-04-19 | Xros, Inc. | Connection protection between clients and optical cross-connect switches |
US6862380B2 (en) * | 2000-02-04 | 2005-03-01 | At&T Corp. | Transparent optical switch |
EP1298868B1 (en) * | 2001-09-27 | 2015-04-22 | Alcatel Lucent | System and method for selection of redundant control path links in a multi-shelf network element |
US6836353B1 (en) * | 2001-11-20 | 2004-12-28 | Nayna Networks, Inc. | Redundant switch fabric methods and system for switching of telecommunication signals |
-
2001
- 2001-12-21 US US10/026,353 patent/US20030120966A1/en not_active Abandoned
-
2002
- 2002-11-28 TW TW091134652A patent/TW200301419A/en unknown
- 2002-12-03 GB GB0228197A patent/GB2384408B/en not_active Expired - Fee Related
- 2002-12-17 JP JP2002364523A patent/JP2003248633A/en active Pending
- 2002-12-20 KR KR1020020081742A patent/KR20030053430A/en not_active Application Discontinuation
-
2005
- 2005-05-31 US US11/142,562 patent/US7480821B2/en not_active Expired - Fee Related
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3920975A (en) * | 1974-11-14 | 1975-11-18 | Rockwell International Corp | Data communications network remote test and control system |
US5893162A (en) * | 1997-02-05 | 1999-04-06 | Transwitch Corp. | Method and apparatus for allocation and management of shared memory with data in memory stored as multiple linked lists |
US6035416A (en) * | 1997-10-15 | 2000-03-07 | International Business Machines Corp. | Method and apparatus for interface dual modular redundancy |
US6215998B1 (en) * | 1997-12-11 | 2001-04-10 | Nortel Networks Limited | Local component-specific console |
Also Published As
Publication number | Publication date |
---|---|
GB2384408B (en) | 2005-02-23 |
GB0228197D0 (en) | 2003-01-08 |
US7480821B2 (en) | 2009-01-20 |
KR20030053430A (en) | 2003-06-28 |
JP2003248633A (en) | 2003-09-05 |
TW200301419A (en) | 2003-07-01 |
US20050223276A1 (en) | 2005-10-06 |
GB2384408A (en) | 2003-07-23 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US4745597A (en) | Reconfigurable local area network | |
US5218465A (en) | Intelligent interconnects for broadband optical networking | |
US5387902A (en) | Data networks | |
US4270715A (en) | Railway control signal interlocking systems | |
US7480821B2 (en) | Method for encoding/decoding a binary signal state in a fault tolerant environment | |
US7836208B2 (en) | Dedicated redundant links in a communicaton system | |
JP2983319B2 (en) | Communication device | |
JP3221259B2 (en) | Bus type duplex transmission equipment | |
JPH095125A (en) | Monitoring apparatus of on-off sensor | |
JPH0546735B2 (en) | ||
KR100265888B1 (en) | Method for controlling taxi link duplication of data communication system | |
JP2555975B2 (en) | Communication line test method | |
KR20220144693A (en) | Controller and communication system comprising the same | |
KR200403626Y1 (en) | Duplex control device of communication system | |
JPS6124348A (en) | Remote supervisory and controlling equipment | |
JPH05250195A (en) | Health check control system of information processing system | |
JPH07202923A (en) | Fault position detecting system for loop-shaped transmission line | |
JPH0319451A (en) | Fault detecting system | |
JPH0231535B2 (en) | ||
JP2001325117A (en) | Stand-by duplex system information processor and its system state checking method | |
JPH07107021A (en) | Remote equipment control system | |
JPH01303598A (en) | Disaster preventive monitoring device | |
JPH0389739A (en) | Reception part duplex circuit | |
JPH04315239A (en) | Bus line testing system | |
JPH0918388A (en) | Transmission line switching system |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: AGERE SYSTEMS GUARDIAN CORP., FLORIDA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MOLLER, HANAN Z.;SONNIER, DAVID P.;REEL/FRAME:012733/0236 Effective date: 20020201 |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |
|
AS | Assignment |
Owner name: INTEL CORPORATION, CALIFORNIA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LSI CORPORATION;REEL/FRAME:035090/0477 Effective date: 20141114 |