CA1230654A - Supervisory control network protocol for communication system - Google Patents
Supervisory control network protocol for communication systemInfo
- Publication number
- CA1230654A CA1230654A CA000480133A CA480133A CA1230654A CA 1230654 A CA1230654 A CA 1230654A CA 000480133 A CA000480133 A CA 000480133A CA 480133 A CA480133 A CA 480133A CA 1230654 A CA1230654 A CA 1230654A
- Authority
- CA
- Canada
- Prior art keywords
- station
- unsolicited
- solicited
- signal
- packet signal
- 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.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/40—Monitoring; Testing of relay systems
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
Abstract
SUPERVISORY CONTROL NETWORK PROTOCOL FOR COMMUNICATION SYSTEM
Abstract of the Disclosure A supervisory control network protocol for transmitting either solicited or unsolicited status messages on a single channel network so that either no overlap between messages occurs, or if it does the message from the upstream station is blocked so that it does not result in a garbled message being communicated downstream. To avoid overlap between solicited and unsolicited messages each transmission of a solicited message signal is preceded by an inhibit signal having a bit length at least equal to that of the unsolicited message signal. Once the inhibit signal is received at a station, it cannot initiate an unsolicited message of its own.
- i -
Abstract of the Disclosure A supervisory control network protocol for transmitting either solicited or unsolicited status messages on a single channel network so that either no overlap between messages occurs, or if it does the message from the upstream station is blocked so that it does not result in a garbled message being communicated downstream. To avoid overlap between solicited and unsolicited messages each transmission of a solicited message signal is preceded by an inhibit signal having a bit length at least equal to that of the unsolicited message signal. Once the inhibit signal is received at a station, it cannot initiate an unsolicited message of its own.
- i -
Description
~L23~D~
SUPERVISORY CONTROL NETWORK PROTOCOL FOR COMMUNICATION SYSTEM
This invention relates to a supervisory control network protocol for a communication system in which both solicited and unsolicited messages can be transmitted along a single path to provide information on the status of the communication system.
Lund of the Invention Multi channel transmission systems which are used to provide communication links generally require a supervisory control network to monitor the status of the various stations along the system. In prior systems, the soliciting of information on the status of each of the communications channels in the transmission system has been done on both a continuous and intermittent basis. It is important that this status information be transmitted with a minimum delay when it is used to signal the need for switching in of a standby channel whenever a fault develops on one of the working channels ox the communication system. One approach to minimizing this delay is to transmit a digital signal in such a way that status information about each of the channels of the system can be updated one bit at a time at each station along the network. This approach results in a delay of about one bit time as the signal passes through each station over and above propagation delay. Systems which modify data on a per character basis will experience a one character delay ( 10 bits) at each station.
However, a disadvantage of polling is that Mach station must wait until a request for status in-formation is made in order that the receiving station can accurately interpret the response ,.
~3~5~
to it. In general, such status information need only be solicited on an occasional basis providing each station can initiate an error (or unsolicited) message should a failure be detected in one of its working channels of the communication system. Thus, it is advantageous to have a single channel network protocol in which both solicited and unsolicited messages can be handled at any station utilizing a relatively simple hardware configuration. One difficulty arising from such a unidirectional protocol is that upstream stations cannot be made immediately aware when a downstream station has initiated an unsolicited message. Consequently, a clash or overlap of two messages may result so that an upstream message is either lost entirely or only partially received as a garbled message, Statement of the Invention The present invention overcomes this problem by providing a protocol for transmitting either solicited or unsolicited status messages over a single channel network so that either an overlap does not occur, or if it does the message from the upstream station is blocked so that it does not result in a garbled message being communicated to the receiver. Hence, only whole solicited or unsolicited messages are communicated to the receiver. The information lost when an upstream unsolicited message is deleted by a downstream message, will eventually be recovered in a solicited message generated by a background poll (auditing activity).
Thus in accordance with the present invention there is provided a method of transmitting supervisory signals along a single path of a supervisory network comprising intermittently transmitting a ~3~65~
solicited message signal of digital bits from a transmitting station through each of a plurality of intermediate stations to a receiving station for soliciting status information from at least one of the intermediate stations, modifying the bits of the solicited message signal at the intermediate station to provide said information for the receiving station, and in response to selected conditions at one of the intermediate stations, transmitting therefrom an unsolicited message signal of digital bits of status information through the downstream intermediate stations to the receiving station.
The method also includes preceding each transmission from the transmitting station of said solicited message signal by an inhibit (hold-off) signal having a bit length at least equal to that of the unsolicited message signal and in response to the inhibit signal, inhibiting the transmission of an unsolicited signal from each of the intermediate stations until after reception of the subsequent solicited message signal, thereby avoiding overlap between a solicited and an unsolicited message signal.
In a particular embodiment, the method includes transmitting an inhibit signal from said one intermediate station for the non-overlapping period of the two signals in response to the reception of an unsolicited message signal from an upstream station overlapping the transmission of the unsolicited message signal -from said one intermediate station, whereby the entire signal from the upstream station is prevented from reaching the receiver and only complete unsolicited message signals reach the receiver.
~3q~
grief Description of the Drawings An example embodiment of the invention will now be described with reference to the accompanying drawings in which:
Figure 1 is a block diagram of a supervisory control network for a communication system, Figure 2 illustrates typical message signals generated at various stations along the network illustrated in Figure 1, and Figures 3, PA, 4B, illustrate flow charts For the various header packets which can be transmitted as part of the message sigrlals by the transmitter and intermediate stations respectively of the network illustrated in Figure 1.
Description of the Preferred Embodiment Referring to Figures 1 and 2, the supervisory control network comprises a transmitter station To connected to a receiver station Rx through a plurality of intermediate stations 11, 12 through In. With the exception of the receiver Rx, each of these stations To, 11, It, through In is connected via status lines to the controlled system which is illustrated as a fiber optics transmission system. Receiver RX9 which is typically co-located with the last station In, is the controlling, decision-making, processor. Stations To, 11...1n are structurally identical but station To uses a slightly modified algorithm. In a typical installation, the fiber optics (or alternately radio transmission system FORTS having d plurality of repeater stations Fit, F1, F2,--Fn, would include both working We, Winnie and standby S channels which would be switched in and out under control of the control information transmitted Jo the respective switch controllers Cut, C1, C2--Cn.
Each of the stations To, If, Inn, Rx of the supervisory control network includes a programmed microcontroller.
The microcontroller in the receiver Rx, in response to status information received from the other stations of the network, transmits switching control information to the controllers Cut, C1, C2 and On via a control line 20 which is utilized to switch in and out the various standby S and working We, Winnie channels of the fiber optics transmission system in a well known manner. Any control message solicits a response which conveys the success or failure of the respective station. In addition, the receiver microcontroller Rx intermittently transmits polling information to the transmitter microcontroller To in response to which the latter transmits a solicited message signal for status information of the stations along the network. This auditing activity is used to recover information lost in deleted unsolicited messages, or in messages lost due to transmission errors. Any of the intermediate stations 11, Inn and the transmitter station To, in response to selected status information such as a failed working channel in the fiber optics transmission system, can immediately initiate an unsolicited message providing a message is not being currently received from an upstream station.
Referring more specifically to Figure 2, the signaling protocol of the network is divided into five-bit packet intervals US which have been numbered for reference purposes only. The output signal waveforms from each of the stations To, 11, 12, and In, are :
I
identified by corresponding reference characters. During the idle state of the network, the transmit station To continuously transmits a null packet of digital bits having a "01110" bit pattern as illustrated in packet interval #1. This pattern is repeated by each of the intermediate stations It, 12, and In with a half-bit delay being introduced at each of these stations by the algorithm together with any propagation delay. This half-bit delay is because the sampling time is delayed from the bit transitions so that the value of the input bit on which the output is to be based, is reliably known.
Sampling occurs at the center of the bit time. However for ease of understanding, neither the half-bit delay nor the propagation delay is shown in Figure 2.
Whenever a failure occurs at a site of the transmission system, an unsolicited message signal is initiated at the corresponding station. In this example, an unsolicited packet header HER having a "01101" bit pattern is initiated at station 12 as shown during interval #2. this is immediately followed by five packets of UNSOLICITED DATA giving channel and status information of the corresponding station F2 in a well known manner. As this data is transferred through intermediate station In to receiver Rx, station In modifies the data with additional information on the status of the channels at station Fun. However, upstream stations such as To and 11 are not aware that station 12 has initiated an unsolicited message signal. A fault therefore could develop which would result in either of these stations To and 11 initiating their own unsolicited message signal. As shown during interval I this has occurred at I
intermediate station 11 which has initiated an unsolicited packet header HER that is followed by its own UNSOLICITED DATA during intervals #6 to #10. In order to avoid a partially garbled signal from station 11 being transferred to the receiver Rx, station 12 blocks the transmission from the upstream station whenever it is transmitting its own UNSOLICITED DATA. In addition, the microcontroller in station 12 which monitors the incoming data from station If has determined that the overlap commenced three packets after initiating its own unsolicited packet header (during interval I and consequently it transmits three INHIBIT packets having a "01010" bit pattern (the same as the HOLD OFF packets) during intervals #8, #9, and ~10 in order to totally block the unsolicited message signal from station Il. As a result, partially garbled signals from upstream stations are inhibited from reaching the receiver Rx.
At any time the receiver Rx can initiate a poll for status request. This poll for status request is transmitted via the control line 20 to the microcontroller in the transmitting station To. This microcontroller then transmits a SOLICITED HOLD-OFF
pattern for at least five consecutive packets as shown during intervals I to ~12. This pattern "01010" is the same as that transmitted from station 12 to provide blocking of the signal from station 11 following the transmission of its unsolicited message signal This HOLD-OFF pattern from the transmitter To insures that none of the intermediate stations If, It or In will initiate transmission of an unsolicited message signal and also provides sufficient time for the network to clear any overlapping unsolicited ~23~
message signals, such as is occurring between output signals from stations To and 11 during intervals #8, I and loo Following the transmission of the five HOLD-OFF packets, the transmitter To then transmits a solicited packet header HER having a "01001" pattern followed immediately thereafter by the solicited data as illustrated during intervals #13 and ~14. As with the unsolicited data, this solicited data may be altered as it is passed through each of the intermediate stations 11, It, and In to provide appropriate status information for the receiver Rx. As the content of this data is not JO of significance to the operation of the present invention, it is only shown in block form and has not been specifically defined.
Referring to the flow charts illustrated in Figures 3 and PA, 4B, there are Four possible five-bit header packets which can be transmitted by the transmitter station To, and by the intermediate stations 11, 12---ln along the network. These header packets are "Oily" null, "Oilily" unsolicited, "Oilily" solicited, and "Oilily"
hold-off. The first two incoming bits of each header with a "O-1"
transition, are always used for bit synchronization. These first two bits are normally not modified by the local station. If the third received bit of each header is a "0" solicited data or a hold-off packet is indicated. Conversely, if bit 3 is a "1" unsolicited or a null packet is indicated. The fourth bit if a "O" advises that a 25-bit message will follow (solicited or unsolicited) and if a "1" it is a hold-off or null packet. Bit 4 is repeated, inverted, in bit 5 to minimize the chance of an error causing a false message start recognition.
I
As shown in Figures PA, 4B, if the local station is in an "inhibit phase" (which is used to block an unsolicited message signal), the last three bits of the header packet are overwritten and a "0, 1, 0" sequence is unconditionally transmitted during bits 3, 4, 5, respectively. However if the local station is to transmit unsolicited data it will modify the incoming unsolicited data, if bits 3, I, 5 of the header are "1, 0, 1" and will transmit its own unsolicited data if these incoming header bits are "1, 1, 0", respectively. Thus, if two stations originate unsolicited messages at the same time (ignoring propagation and half-bit delays) then the downstream station will alter the message of the upstream station.
At each of the intermediate stations (during the transmission of an unsolicited message originated at that station) input data is sampled at bits 4, 9, 14, 19 and 24 (i.e. the Thea bit of every 5-bit packet). If a "0" bit is detected, then the station enters the 'inhibit phase' and 1, 2, 3, 4, or 5 inhibit packets are added at the end of transmission of the unsolicited data (depending upon which of the five packets had the first "0") to inhibit the non-overlapped portion of the up-stream transmission.
In the figures of this illustrated embodiment, there is considerable overlap between the transmission of the various message signals. In practice however, the solicited messages are widely spaced while the unsolicited messages are only transmitted on demand.
Since the failure rate of any contemporary transmission system is generally very low, the likelihood of such an overlap occurring between the various packets is very small. Consequently, when a 3q3~
failure does occur the transmission of an unsolicited packet signal will generally commence immediately so that there is a minimum time loss before the signal reaches the receiver ox which in turn transmits switching control signals back to the stations, thus the total time required to transmit an unsolicited message after a fault is detected will be the sum of: 5 bits/header latency (Max), n x 1/2 bit station delay (where n = number of downstream stations), propagation delay, and 30 bit serialization delay (one 5-bit header packet plus five 5-bit data packets), Solicited messages additionally include at least a 25 bit inhibit signal. Such a protocol minimizes the overall delay in initiating a transfer from a working channel to a standby channel in the fiber optics or other transmission system,
SUPERVISORY CONTROL NETWORK PROTOCOL FOR COMMUNICATION SYSTEM
This invention relates to a supervisory control network protocol for a communication system in which both solicited and unsolicited messages can be transmitted along a single path to provide information on the status of the communication system.
Lund of the Invention Multi channel transmission systems which are used to provide communication links generally require a supervisory control network to monitor the status of the various stations along the system. In prior systems, the soliciting of information on the status of each of the communications channels in the transmission system has been done on both a continuous and intermittent basis. It is important that this status information be transmitted with a minimum delay when it is used to signal the need for switching in of a standby channel whenever a fault develops on one of the working channels ox the communication system. One approach to minimizing this delay is to transmit a digital signal in such a way that status information about each of the channels of the system can be updated one bit at a time at each station along the network. This approach results in a delay of about one bit time as the signal passes through each station over and above propagation delay. Systems which modify data on a per character basis will experience a one character delay ( 10 bits) at each station.
However, a disadvantage of polling is that Mach station must wait until a request for status in-formation is made in order that the receiving station can accurately interpret the response ,.
~3~5~
to it. In general, such status information need only be solicited on an occasional basis providing each station can initiate an error (or unsolicited) message should a failure be detected in one of its working channels of the communication system. Thus, it is advantageous to have a single channel network protocol in which both solicited and unsolicited messages can be handled at any station utilizing a relatively simple hardware configuration. One difficulty arising from such a unidirectional protocol is that upstream stations cannot be made immediately aware when a downstream station has initiated an unsolicited message. Consequently, a clash or overlap of two messages may result so that an upstream message is either lost entirely or only partially received as a garbled message, Statement of the Invention The present invention overcomes this problem by providing a protocol for transmitting either solicited or unsolicited status messages over a single channel network so that either an overlap does not occur, or if it does the message from the upstream station is blocked so that it does not result in a garbled message being communicated to the receiver. Hence, only whole solicited or unsolicited messages are communicated to the receiver. The information lost when an upstream unsolicited message is deleted by a downstream message, will eventually be recovered in a solicited message generated by a background poll (auditing activity).
Thus in accordance with the present invention there is provided a method of transmitting supervisory signals along a single path of a supervisory network comprising intermittently transmitting a ~3~65~
solicited message signal of digital bits from a transmitting station through each of a plurality of intermediate stations to a receiving station for soliciting status information from at least one of the intermediate stations, modifying the bits of the solicited message signal at the intermediate station to provide said information for the receiving station, and in response to selected conditions at one of the intermediate stations, transmitting therefrom an unsolicited message signal of digital bits of status information through the downstream intermediate stations to the receiving station.
The method also includes preceding each transmission from the transmitting station of said solicited message signal by an inhibit (hold-off) signal having a bit length at least equal to that of the unsolicited message signal and in response to the inhibit signal, inhibiting the transmission of an unsolicited signal from each of the intermediate stations until after reception of the subsequent solicited message signal, thereby avoiding overlap between a solicited and an unsolicited message signal.
In a particular embodiment, the method includes transmitting an inhibit signal from said one intermediate station for the non-overlapping period of the two signals in response to the reception of an unsolicited message signal from an upstream station overlapping the transmission of the unsolicited message signal -from said one intermediate station, whereby the entire signal from the upstream station is prevented from reaching the receiver and only complete unsolicited message signals reach the receiver.
~3q~
grief Description of the Drawings An example embodiment of the invention will now be described with reference to the accompanying drawings in which:
Figure 1 is a block diagram of a supervisory control network for a communication system, Figure 2 illustrates typical message signals generated at various stations along the network illustrated in Figure 1, and Figures 3, PA, 4B, illustrate flow charts For the various header packets which can be transmitted as part of the message sigrlals by the transmitter and intermediate stations respectively of the network illustrated in Figure 1.
Description of the Preferred Embodiment Referring to Figures 1 and 2, the supervisory control network comprises a transmitter station To connected to a receiver station Rx through a plurality of intermediate stations 11, 12 through In. With the exception of the receiver Rx, each of these stations To, 11, It, through In is connected via status lines to the controlled system which is illustrated as a fiber optics transmission system. Receiver RX9 which is typically co-located with the last station In, is the controlling, decision-making, processor. Stations To, 11...1n are structurally identical but station To uses a slightly modified algorithm. In a typical installation, the fiber optics (or alternately radio transmission system FORTS having d plurality of repeater stations Fit, F1, F2,--Fn, would include both working We, Winnie and standby S channels which would be switched in and out under control of the control information transmitted Jo the respective switch controllers Cut, C1, C2--Cn.
Each of the stations To, If, Inn, Rx of the supervisory control network includes a programmed microcontroller.
The microcontroller in the receiver Rx, in response to status information received from the other stations of the network, transmits switching control information to the controllers Cut, C1, C2 and On via a control line 20 which is utilized to switch in and out the various standby S and working We, Winnie channels of the fiber optics transmission system in a well known manner. Any control message solicits a response which conveys the success or failure of the respective station. In addition, the receiver microcontroller Rx intermittently transmits polling information to the transmitter microcontroller To in response to which the latter transmits a solicited message signal for status information of the stations along the network. This auditing activity is used to recover information lost in deleted unsolicited messages, or in messages lost due to transmission errors. Any of the intermediate stations 11, Inn and the transmitter station To, in response to selected status information such as a failed working channel in the fiber optics transmission system, can immediately initiate an unsolicited message providing a message is not being currently received from an upstream station.
Referring more specifically to Figure 2, the signaling protocol of the network is divided into five-bit packet intervals US which have been numbered for reference purposes only. The output signal waveforms from each of the stations To, 11, 12, and In, are :
I
identified by corresponding reference characters. During the idle state of the network, the transmit station To continuously transmits a null packet of digital bits having a "01110" bit pattern as illustrated in packet interval #1. This pattern is repeated by each of the intermediate stations It, 12, and In with a half-bit delay being introduced at each of these stations by the algorithm together with any propagation delay. This half-bit delay is because the sampling time is delayed from the bit transitions so that the value of the input bit on which the output is to be based, is reliably known.
Sampling occurs at the center of the bit time. However for ease of understanding, neither the half-bit delay nor the propagation delay is shown in Figure 2.
Whenever a failure occurs at a site of the transmission system, an unsolicited message signal is initiated at the corresponding station. In this example, an unsolicited packet header HER having a "01101" bit pattern is initiated at station 12 as shown during interval #2. this is immediately followed by five packets of UNSOLICITED DATA giving channel and status information of the corresponding station F2 in a well known manner. As this data is transferred through intermediate station In to receiver Rx, station In modifies the data with additional information on the status of the channels at station Fun. However, upstream stations such as To and 11 are not aware that station 12 has initiated an unsolicited message signal. A fault therefore could develop which would result in either of these stations To and 11 initiating their own unsolicited message signal. As shown during interval I this has occurred at I
intermediate station 11 which has initiated an unsolicited packet header HER that is followed by its own UNSOLICITED DATA during intervals #6 to #10. In order to avoid a partially garbled signal from station 11 being transferred to the receiver Rx, station 12 blocks the transmission from the upstream station whenever it is transmitting its own UNSOLICITED DATA. In addition, the microcontroller in station 12 which monitors the incoming data from station If has determined that the overlap commenced three packets after initiating its own unsolicited packet header (during interval I and consequently it transmits three INHIBIT packets having a "01010" bit pattern (the same as the HOLD OFF packets) during intervals #8, #9, and ~10 in order to totally block the unsolicited message signal from station Il. As a result, partially garbled signals from upstream stations are inhibited from reaching the receiver Rx.
At any time the receiver Rx can initiate a poll for status request. This poll for status request is transmitted via the control line 20 to the microcontroller in the transmitting station To. This microcontroller then transmits a SOLICITED HOLD-OFF
pattern for at least five consecutive packets as shown during intervals I to ~12. This pattern "01010" is the same as that transmitted from station 12 to provide blocking of the signal from station 11 following the transmission of its unsolicited message signal This HOLD-OFF pattern from the transmitter To insures that none of the intermediate stations If, It or In will initiate transmission of an unsolicited message signal and also provides sufficient time for the network to clear any overlapping unsolicited ~23~
message signals, such as is occurring between output signals from stations To and 11 during intervals #8, I and loo Following the transmission of the five HOLD-OFF packets, the transmitter To then transmits a solicited packet header HER having a "01001" pattern followed immediately thereafter by the solicited data as illustrated during intervals #13 and ~14. As with the unsolicited data, this solicited data may be altered as it is passed through each of the intermediate stations 11, It, and In to provide appropriate status information for the receiver Rx. As the content of this data is not JO of significance to the operation of the present invention, it is only shown in block form and has not been specifically defined.
Referring to the flow charts illustrated in Figures 3 and PA, 4B, there are Four possible five-bit header packets which can be transmitted by the transmitter station To, and by the intermediate stations 11, 12---ln along the network. These header packets are "Oily" null, "Oilily" unsolicited, "Oilily" solicited, and "Oilily"
hold-off. The first two incoming bits of each header with a "O-1"
transition, are always used for bit synchronization. These first two bits are normally not modified by the local station. If the third received bit of each header is a "0" solicited data or a hold-off packet is indicated. Conversely, if bit 3 is a "1" unsolicited or a null packet is indicated. The fourth bit if a "O" advises that a 25-bit message will follow (solicited or unsolicited) and if a "1" it is a hold-off or null packet. Bit 4 is repeated, inverted, in bit 5 to minimize the chance of an error causing a false message start recognition.
I
As shown in Figures PA, 4B, if the local station is in an "inhibit phase" (which is used to block an unsolicited message signal), the last three bits of the header packet are overwritten and a "0, 1, 0" sequence is unconditionally transmitted during bits 3, 4, 5, respectively. However if the local station is to transmit unsolicited data it will modify the incoming unsolicited data, if bits 3, I, 5 of the header are "1, 0, 1" and will transmit its own unsolicited data if these incoming header bits are "1, 1, 0", respectively. Thus, if two stations originate unsolicited messages at the same time (ignoring propagation and half-bit delays) then the downstream station will alter the message of the upstream station.
At each of the intermediate stations (during the transmission of an unsolicited message originated at that station) input data is sampled at bits 4, 9, 14, 19 and 24 (i.e. the Thea bit of every 5-bit packet). If a "0" bit is detected, then the station enters the 'inhibit phase' and 1, 2, 3, 4, or 5 inhibit packets are added at the end of transmission of the unsolicited data (depending upon which of the five packets had the first "0") to inhibit the non-overlapped portion of the up-stream transmission.
In the figures of this illustrated embodiment, there is considerable overlap between the transmission of the various message signals. In practice however, the solicited messages are widely spaced while the unsolicited messages are only transmitted on demand.
Since the failure rate of any contemporary transmission system is generally very low, the likelihood of such an overlap occurring between the various packets is very small. Consequently, when a 3q3~
failure does occur the transmission of an unsolicited packet signal will generally commence immediately so that there is a minimum time loss before the signal reaches the receiver ox which in turn transmits switching control signals back to the stations, thus the total time required to transmit an unsolicited message after a fault is detected will be the sum of: 5 bits/header latency (Max), n x 1/2 bit station delay (where n = number of downstream stations), propagation delay, and 30 bit serialization delay (one 5-bit header packet plus five 5-bit data packets), Solicited messages additionally include at least a 25 bit inhibit signal. Such a protocol minimizes the overall delay in initiating a transfer from a working channel to a standby channel in the fiber optics or other transmission system,
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of transmitting supervisory signals along a single path of a supervisory network, comprising:
intermittently transmitting a solicited packet signal of digital bits from a transmitting station through each of a plurality of intermediate stations to a receiving station for soliciting status information from the intermediate stations;
modifying the bits of the solicited packet signal at the intermediate stations to provide said information for the receiving station; and in response to selected conditions originating at one of the intermediate stations, transmitting therefrom an unsolicited packet signal of digital bits of status information through the downstream intermediate stations to the receiving station, characterized by:
preceding each transmission from the transmitting station of said solicited packet signal by an inhibit signal having a bit length at least equal to that of the unsolicited packet signal;
and in response to the inhibit signal, inhibiting the transmission of an unsolicited packet signal from each of the intermediate stations until after reception of the subsequent solicited packet signal;
thereby avoiding overlap between a solicited and an unsolicited packet signal.
intermittently transmitting a solicited packet signal of digital bits from a transmitting station through each of a plurality of intermediate stations to a receiving station for soliciting status information from the intermediate stations;
modifying the bits of the solicited packet signal at the intermediate stations to provide said information for the receiving station; and in response to selected conditions originating at one of the intermediate stations, transmitting therefrom an unsolicited packet signal of digital bits of status information through the downstream intermediate stations to the receiving station, characterized by:
preceding each transmission from the transmitting station of said solicited packet signal by an inhibit signal having a bit length at least equal to that of the unsolicited packet signal;
and in response to the inhibit signal, inhibiting the transmission of an unsolicited packet signal from each of the intermediate stations until after reception of the subsequent solicited packet signal;
thereby avoiding overlap between a solicited and an unsolicited packet signal.
2. A method of transmitting supervisory signals as described in claim 1 further characterized by:
in response to the reception of an unsolicited packet signal from an upstream station overlapping the transmission of the unsolicited packet signal from said one intermediate station, transmitting an inhibit signal from said one intermediate station for the non-overlapping period of the two signals, whereby the entire signal from the upstream station is prevented from reaching the receiver and only complete unsolicited packet signals reach the receiver.
in response to the reception of an unsolicited packet signal from an upstream station overlapping the transmission of the unsolicited packet signal from said one intermediate station, transmitting an inhibit signal from said one intermediate station for the non-overlapping period of the two signals, whereby the entire signal from the upstream station is prevented from reaching the receiver and only complete unsolicited packet signals reach the receiver.
3. A method of transmitting supervisory signals as described in claim 2 further characterized by:
continuously transmitting from the transmitting station a null packet signal of digital bits between transmissions of the solicited packet signal having a bit length equal to that of the inhibit signal and a bit length equal to a sub-multiple of that of the solicited and unsolicited packet signals, and commencing transmission of either the solicited packet signal or the unsolicited packet signal coincident with the time of commencement of transmission of the null packet signal from said one intermediate station.
continuously transmitting from the transmitting station a null packet signal of digital bits between transmissions of the solicited packet signal having a bit length equal to that of the inhibit signal and a bit length equal to a sub-multiple of that of the solicited and unsolicited packet signals, and commencing transmission of either the solicited packet signal or the unsolicited packet signal coincident with the time of commencement of transmission of the null packet signal from said one intermediate station.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000480133A CA1230654A (en) | 1985-04-26 | 1985-04-26 | Supervisory control network protocol for communication system |
| KR1019860003149A KR860008659A (en) | 1985-04-26 | 1986-04-24 | Supervisory Control Network Protocol for Communication Systems |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000480133A CA1230654A (en) | 1985-04-26 | 1985-04-26 | Supervisory control network protocol for communication system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1230654A true CA1230654A (en) | 1987-12-22 |
Family
ID=4130367
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000480133A Expired CA1230654A (en) | 1985-04-26 | 1985-04-26 | Supervisory control network protocol for communication system |
Country Status (2)
| Country | Link |
|---|---|
| KR (1) | KR860008659A (en) |
| CA (1) | CA1230654A (en) |
-
1985
- 1985-04-26 CA CA000480133A patent/CA1230654A/en not_active Expired
-
1986
- 1986-04-24 KR KR1019860003149A patent/KR860008659A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| KR860008659A (en) | 1986-11-17 |
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