FIELD OF THE INVENTION

[001] The present invention generally relates to a system and method for identifying a BacNet Broadcast Management Device (BBMD) failure and replacing the failed BBMD in the BACNet IP (BIP) devices in the BACNet IP network, but not exclusively, to the BACNet manger which automatically identifies and replaces the failed BBMD in the BACNet IP network.

BACKGROUND OF THE INVENTION

[002] BACnet is an open standard data communications protocol for building automation and control networks, such as for HVAC (heating, ventilation and air conditioning) applications. It was developed under the auspices of ASHRAE (American Society of Heating, Refrigeration and Air-conditioning Engineers). It may be often necessary to set up multiple networks to communicate with each other. This may be required because different network types with different characteristics are being used. For multiple networks to communicate, there needs to be a common language or protocol used by the devices on those networks.

[003] A protocol may define the format of the message packets exchanged between devices. It may also define the format of the message frame, the surrounding envelope that determines what destination address should be used, and what protocol the frame is using. Some protocols, such as BACnet, may define the entire frame and packet together. Other protocols, such as IP (Internet protocol), may state within the frame that a different protocol is to be used to decode the packet within. A BACnet I/P Network is a collection of one or more IP sub networks (IP domains) that are assigned a single BACnet network number. All BacNet IP (BIP) devices are connected to BACnet IP network via hub and switches etc. BACnet I/P network also consist of the gateways and routers.

[004] Figure 1 illustrates a block diagram of a typical BACnet IP network system. The BACnet IP network system includes one or more IP subnets 102A-B. Each of the one or more subnets 102A-B includes one or more BIP devices 104A-B, a BACnet/IP Broadcast Management Device (BBMD) 106A-B and an internet router 108A-B. Each BBMD includes a table called a Broadcast Distribution Table (BDT) which shall be the same in every BBMD in the BacNet IP network. If the BBMD has also been designated to register foreign device and it shall also includes a Foreign Device Table (FDT). To establish and operate the typical BacNet IP network 100 the following steps has to be taken

1. In current BACnet Communication if active BBMD fail then user has to indentify failed BBMD and has to search new device on the network that can act as the BBMD. After that user is starting the BBMD configuration. The typical method is time consuming and user can loss the data and control over process during failure and configuration time. There is some method to configure redundant BBMD over subnet but this method is not explaining about foreign device registration in case of failure of BBMD.

2. If one of the device is not supporting the segmentation then the BACnet device will not transmit the complete message to other device. There is always loss of the data. Currently this issue can be handling by requesting the read only property for single property of single object. Suppose BACnet client want to read the 5 properties of 100 object that create 500 request if segmentation not supported and cause of that there is always chance of slow down the network.

3. In case failure of the alarm and trendlog recipient there is no automatic management to assign the recipient or to store the data in to in the event of failure. So there will be loss of data on BACnet IP Network

[005] Accordingly there is a need in the art to provide a solution to one or more of above said problems. The present invention solves one or more of these problems in a unique and economical manner.

SUMMARY OF THE INVENTION

[006] It is a feature of the present invention to provide a system which substantially overcomes the one or more of the above mentioned disadvantages.

[007] The objective of the present invention provides the following solutions for the above mentioned problem:

[008] Automatic Registration of a BBMD Foreign device in case of failure of Active BBMD: BACnet Manger is able to communicate other subnet when user will register the BBMD as Foreign devices at specific subscription interval. In case failure of the registered BMMD BACnet Manger has ability select the another BBMD for registration from Broadcast Distribution Table.

[009] Automatic Detection of a BBMD Capable Device and Configuration in case of failure: In case of the failure of the Active BBMD, the BACnet manger is able to transfer the Broadcast Distribution table to another BBMD capable device by replacing the IP address fail BBMD address with new BBMD capable device.

[0010] Segmentation issue: Segmentation issue can be taken care by in built FTP server. If message size is greater than size specified then message will be proceed by FTP server internally to another device and can written to BACnet Stack of another device in fragment that reduces the network traffics.

[0011] Alarm Trend Log Data Handling: In case of failure of alarm Trend log recipient failure data can store in to local buffer of the controller via FTP For detail please check the section.

[0012] In one aspect, a method for identifying and replacing a BBMD failure in a BacNet IP Network is provided. The BacNet IP Network includes one or more subnets and each of the one or more subnets includes one or more BIP device. The one or more BIP device includes the BBMD and at least one BBMD capable device. The method includes (i) sending, from a BacNet manager, a request to read a Broadcast Distribution Table (BDT) to the BBMD in each of the one or more subnets, (ii) receiving an acknowledgement from the BBMD in each of the one or more subnets, (iii) identifying an error message in the acknowledgement received from at least one the BBMD of the one or more subnets, (iv) selecting the at least one BBMD capable device in the subnet associated to the error message identified, (v) modifying the BDT by replacing an IP address of the BBMD capable device, and (vi) transferring a modified BDT to the BBMD capable device and the BBMD in the one or more subnets. To perform the above methods a redundancy option should be enabled in the BacNet manager.

[0013] In another aspect, a method for registering a BBMD as a foreign device in a BacNet IP network is provided. The method includes (i) selecting, by a BacNet manger, a first BBMD in a first subnet, (ii) setting, at the BacNet manager, an UDP port and a re-registration interval, (iii) sending a foreign registration request to the first BBMD selected by the BacNet manager at the re-registration interval, (iv) receiving a response
from the first BBMD at each of the re-registration interval, and (v) selecting, by the BacNet manager, a second BBMD in a second subnet when the response is not received from the first BBMD.

BRIEF DISCRIPTION OF THE ACCOMPANYING DRAWINGS

[0014] The advantages and features of the invention will become more clearly apparent from the following description which refers to the accompanying drawings given as non-restrictive examples only and in which:

[0015] Figure 1 illustrates a block diagram of a typical BACnet IP network system;

[0016] Figure 2A illustrates a BacNet management system (BMS) in accordance to the preferred embodiment herein;

[0017] Figure 2B illustrates a BACNet architecture in accordance to the preferred embodiment herein;

[0018] Figure 3 illustrates a BacNet IP network which includes a foreign device in accordance to the preferred embodiment herein;

[0019] Figure 4 is a flow diagram which illustrates the method for automatic registration of the BBMD as the foreign device in accordance to the preferred embodiment herein;

[0020] Figure 5 is a flow diagram which illustrates a method for detecting and replacing the BBMD capable device, when the active BBMD fails in accordance to the preferred embodiment herein; and

[0021] Figures 6A and 6B illustrates a BacNet alarm services and trendlog in accordance to the preferred embodiment herein.

DETAILED DISCRIPTION OF THE INVENTION

[0022] The present invention will be described herein below with reference to the accompanying drawings. A system and method for identifying a BacNet Broadcast Management Device (BBMD) fault and replacing the failed BBMD in the BACNet IP (BIP) devices in the BACNet IP network is described.

[0023] The following description is of exemplary embodiment of the invention only, and is not limit the scope, applicability or configuration of the invention. Rather, the following description is intended to provide a convenient illustration for implementing various embodiments of the invention. As will become apparent, various changes may be made in the function and arrangement of the structural/operational features described in these embodiments without departing from the scope of the invention as set forth herein. It should be appreciated that the description herein may be adapted to be employed with alternatively configured devices having different shaped, components, and the like and still fall within the scope of the present invention. Thus the detailed description herein is presented for purposes of illustration only and not of limitation.

[0024] The present embodiments provides system and method for identifying a BacNet Broadcast Management Device (BBMD) fault and replacing the failed BBMD in the BACNet IP (BIP) devices in the BACNet IP network, and more particularly, but not exclusively, the embodiment relates to the to the BACNet manger which automatically identifies and replaces the failed BBMD in the BACNet IP network.

[0025] Figure 2A illustrates a BacNet management system (BMS) 200 in accordance to the preferred embodiment herein. The BMS 200 includes one or more subnets such as campus A BacNet network, campus B BacNet network and campus C BacNet network and a BacNet manager. A BACnet/IP network is a collection of one or more IP sub networks (IP domains) that are assigned a single BACnet network number. All BIP devices are connected to BACnet IP network via hub, switches etc. BACnet I/P network also includes the gateways and routers. In order to gain remote access to or from the Internet, BMS can be connected to Wireless Area Network (WAN). For network security reason network IP router may be used with firewall protection. The Operator Work Station (OWS) mainly used for controlling and monitoring the BMS system. The BACnet manger is managing the automatic network configuration for BIP devices. BACnet Manger has in built FTP server and Web server.FTP server is used for exchanging the configuration file via FTP while web server is used serving HMI pages to BACnet Client. BACnet Manger will also responsible for transferring the data to SQL server via FTP. A storage area network (SAN) is a dedicated network that provides access to consolidated, large data storage. A SAN typically has its own network of storage device.

[0026] Figure 2B illustrates BACNet architecture in accordance to the preferred embodiment herein. The BACNet architecture includes one or more IP subnets such as building A network, building B network, building C network and building D network
and the BacNet manager. Each of the one or more subnets includes one or more BIP devices and a BBMD and they are connected to the BacNet manager via a network switch. The BBMD is configured to enable communication over different subnet. The BIP device include in-built FTP server which includes a configuration file. The configuration file includes a properties and capability information related to each of the BIP device. A few of the BIP devices in each of the one or more subnets is capable of acting as the BBMD which are named as BBMD capable in the figures.

[0027] The BacNet manager includes in built FTP server and Web server. The FTP server is used for exchanging the configuration file via FTP. The web server is used serving HMI pages to a BACnet Client. The BACnet manager is responsible for performing the automatic network configuration of the one or more BIP devices in the BacNet system. The BACnet manager reads the network capabilities from every BIP devices via FTP and based upon that BACnet Manager would modify the configuration files for every BIP devices. The modified configuration file is transferred to respective BACnet devices based upon the IP address via FTP. FTP will transfer configuration files to individual BIP devices internally.

[0028] Figure 3 illustrates a BacNet IP network which includes a foreign BacNet IP device in accordance to the preferred embodiment herein. The BacNet IP network includes one or more subnets such as IP subnets 1-3 which are connected through internet. Each of the one or more IP subnets includes internet router, a BBMD and one or more BIP devices. The IP subnet 3 includes a foreign device. The foreign device is a BACnet device that has an IP subnet address different from those comprising the BACnet/IP network that the device seeks to join in the BacNet IP system. The foreign device may be a full-time node on the foreign subnet or may be a part-time participant. In order for a foreign device to fully participate in the activities of the BacNet IP network, the foreign device must register itself with a BBMD serving one of the IP subnets
comprising that network. "Full participation" implies the ability to send and receive both directed and broadcast messages. The BACnet manager of the BacNet system needs to register at least one of the BBMD in the one or more subnets as foreign device to communicate with all subnet. In the present BACnet solution user has to specify the BBMD address with registration interval in the BacNet manger. If the registered foreign device is failed then the communication between all subnets is interrupted. In the present invention provides the automatic registration of the foreign device in case of failed foreign device in the BacNet IP network.

[0029] The auto registration consists of sending a BACnet virtual link layer (BVLL) Register-Foreign-Device message to an appropriate BBMD and receiving a BACnet virtual link control(BVLC)-Result message containing a result code of X'0000' indicating the successful completion of the registration. Ascertaining the IP address of such a BBMD is a local matter but could involve the use of a domain name server or the distribution of a numeric IP address to authorized users. The UDP port X'BACO' shall be considered the default, but the use of other port values is permitted if required by the local network architecture, e.g., where two B/IP networks share the same physical LAN. From the figure 5, the "foreign" BACnet device on Subnet 3 is registered to receive broadcasts from devices on subnets 1 and 2 by sending a BVLL Register-Foreign-Device message to the BBMD that supports foreign device registration.

[0030] BACnet Manager will register the one of the BBMD as foreign device to forward the BACnet message to other subnet. BACnet manger will subscribe this BBMD after every subscription interval mention in the settings of BacNet manager.

[0031] Each device that registers as a foreign device shall be placed in an entry in the BBMD's Foreign Device Table (FDT). Each entry shall consist of the 6-octet B/IP address of the registrant; the 2-octet Time-to-Live value supplied at the time of
registration; and a 2-octet value representing the number of seconds remaining before the BBMD will purge the registrant's FDT entry if no re-registration occurs. This value will be initialized to the 2-octet Time-to-Live value supplied at the time of Registration.

[0032] BVLL Message Format for Foreign Device Registration

The Register-Foreign-Device message consists of four fields:

BVLC Type: 1-octet X'81' BVLL for BACnet/IP

BVLC Function: 1-octet X'05' Register-Foreign-Device

BVLC Length: 2-octets X'0006' Length, in octets, of the BVLL message

Time-to-Live 2-octets T Time-to-Live T, in seconds

[0033] Upon receipt of a BVLL Register-Foreign-Device message, a BBMD which is capable of providing foreign device support and having available table entries, shall add an entry to its FDT and reply with a BVLC-Result message containing a result code of X'0000' indicating the successful completion of the registration. A BBMD incapable of providing foreign device support shall return a BVLC-Result message containing a result code of X'0030' indicating that the registration has failed.

[0034] Figure 4 is a flow diagram which illustrates the method for automatic registration of BBMD as a foreign device in accordance to the preferred embodiment herein. In step 402, the BacNet manager selects the BBMD from at least one of the one or more subnets to register a foreign device. In step 404, the BacNet manager sets an UDP port and the re-registration interval. In step 406, the BacNet manager sends the register foreign device message to the selected BBMD in the step 402. In step 408 and 410, the BacNet manager checks whether the response received from the BBMD after every registration intervals is X'000 or X'0040. If yes then the selected BBMD is successfully registered as the foreign device. If no, the BacNet manager selects another BBMD in other subnet in the step 412 for resuming the auto registration process again.

[0035] Typically, the BACnet/ IP packets have a maximum length of 1500 bytes, if the BACnet IP message that is longer than 1500 bytes then it has to segmented and send in multiple segments. If the BIP device (source) has a large number of objects and a message is sent to read the object list then it is possible that the response won't fit in a single packet. If both the BIP device i.e. source and destination support segmentation then there is no problem. If either side doesn't support segmentation then there will be a loss of data during the transmission. In one scenario, if both BacNet devices i.e. source and destination are supporting segmentation. If the BacNet message is greater 1500 byte then transmitting device will segment the BacNet message and send to the receiving device in the segment. So there is no data loss while transferring the message. In another scenario, the receiving BacNet device is not supporting segmentation. If the BacNet message is greater 1500 byte then transmitting device will segment the BacNet message and send to the receiving device in the segment. But the receiving device will not accept the second segment as it is not supporting segmentation. So there will be a loss of data. In yet another scenario, the transmitting BacNet device is not supporting segmentation. If the BacNet message is greater 1500 byte then transmitting device will not segment the BacNet message. It will just send the first 1500 byte to receiving device. So loss of data will occur. In current BacNet system 200 you can configure the services so that you use read-property for a single property - avoiding read-property for all properties. If you have to use read-property-multiple then limit the list of properties to be read and avoid reading all using this service. This approach is increase network traffic and degrades the performance of BacNet network. Further, the segmentation issue can be taken care by in built FTP server in every BIP device. If message size is greater than size specified and BacNet IP Device is not supporting the segmentation then transmitting device will decode message in text format and copied to it's own FTP server internally .After
copying on the in-built FTP of the receiving BIP device will receive the text format message and then the message will decoded by receiving device for understanding to BacNet stack that reduces the network traffics.

[0036] For encoding and decoding, an application Layer Protocol Data Units (APDUs) is used in BACnet IP network to convey the information contained in the application service and parameters. Within the Open Systems Interconnection model, the encoding rules to be used are chosen by the presentation layer through a process of negotiation. This negotiation is used by cooperating systems to determine not only the basic encoding rules, of which Because BACnet's collapsed OSI architecture does not incorporate any presentation layer functionality, APDU encoding must be defined and agreed to by communicating devices in advance. BACnet's encoding rules have been designed to take into account the requirements of building automation and control systems for simplicity and compactness. Each APDU consist of the fixed part and variable part. Fixed part consist of the PCI (protocol control information "Protocol control information" (PCI) comprises data required for the operation of the application layer protocol, including the type of APDU, information to match service requests and service responses, and information to carry out the reassembly of segmented messages. This information is contained in the "header," or fixed part, of the APDU. "User data" comprises information specific to individual service requests or responses. This portion of the APDU will be referred to as the 'variable part' of the APDU.

[0037] The fixed part of BacNet message format includes the following fields:

(i) PDU Type: The portion of message indicates the type of PDU out of eight PDU Following table III shows the BACnet PDU is available in the BACnet.

Table III

(ii) Segmented-message: This parameter indicates whether or not the confirmed service response is entirely, or only partially, contained in the present PDU. If the response is present in its entirety, the 'segmented-message' parameter shall be FALSE. If the present PDU contains only a segment of the response, this parameter shall be TRUE.

(iii) more-follows: This parameter is only meaningful if the 'segmented-message' parameter is TRUE. If 'segmented-message' is TRUE, then the 'more-follows' parameter shall be TRUE for all segments comprising the confirmed service response except for the last and shall be FALSE for the final segment. If 'segmented-message' is FALSE, then 'more-follows' shall be set FALSE by the encoder and shall be ignored by the decoder.

(iv) original-invokelD: This parameter shall be the 'invokelD' contained in the confirmed service request being acknowledged. The same 'originalinvokelD' shall be used for all segments of a segmented acknowledgment.

(v) sequence-number: This optional parameter is only present if the 'segmented-message' parameter is TRUE. In this case, the 'sequence-number' shall be a sequentially incremented unsigned integer, modulo 256, which identifies each segment of a segmented response. The value of the received 'sequence-number' is used by the original requester to acknowledge the receipt of one or more segments of a segmented response.

The sequence-number of the first segment of a segmented response shall be zero.

(vi) proposed-window-size: This optional parameter is only present if the 'segmented-message' parameter is TRUE. In this case, the 'proposed-window-size' parameter shall specify as an unsigned binary integer the maximum number of message segments containing 'original-invokelD' the sender is able or willing to send before waiting for a segment acknowledgment PDU. The value of the 'proposed-window-size' shall be in the range 1-127.

(vii) service-ACK-choice: This parameter shall contain the value of the BACnet Confirmed Service Choice corresponding to the service contained in the previous BACnet-Confirmed-Service-Request that has resulted in this acknowledgment. 20.1.5.7 service-AC. This parameter shall contain the parameters of the specific service acknowledgment that is being encoded.

[0038] The variable part of the BacNet message format includes the following fields a tag class and value information of data.

[0039] Figure 5 is a flow diagram which illustrates a method for detecting and replacing the BBMD capable device, when the active BBMD fails in accordance to the preferred embodiment herein. In case of failure of BBMD in at least one of the subnet, BACnet manager will automatically select the BBMD capable device in the corresponding subnet and configures as BBMD. In step 502, the BacNet manager sends the "Read BDT message" to all BBMD in the BacNet system 200. In step 504, The BacNet manager receives the acknowledgement from all BBMDs in the BacNet system 200 and checks whether any of the acknowledgements includes the error message i.e. X'0020'. In step 506, the BacNet manager identifies the corresponding BBMD and its subnet which is failed based on the error message received in the acknowledgement. In step 508, the BacNet manager selects the BBMD capable from the identified subnet. In step 510, the BacNet manager modifies the BDT by replacing the IP address of the failed BBMD with the address of newly selected BBMD capable. In step 512, the BacNet manager transfers the modified BDT to all BBMDs in the BacNet system 200 by "Write BDT message".

[0040] Figures 6A and 6B illustrates a BacNet alarm services and trendlog in accordance to the preferred embodiment herein. BIP devices are supporting the BACnet alarm functionality. The BACnet Notification object is a BACnet Object which is present in all the BIP devices. The BACnet Notification object is used to send event notifications within a BACnet System, when an object has a problem or a fault, such as the present value of a property rise above a predetermined level, a notification object would be created to inform the rest of the BACnet system that there is something wrong. There are several way of sending this type of message to other devices with different priorities and different destination. Notification class can route alarms to different places depending on the time of day.

[0041] Form the figure 6A, the chilled beam controller (one of the BacNet device in the BacNet system) generates the alarm when chilled water temperature goes beyond the chilled water temp high alarm limit (12.5 Deg c).Once the alarm is generated the alarm is notified to alarm recipient (BACnet Manager). The BACnet manager then sends this alarm to respective work stations.

[0042] The BIP devices collect the trend log sample in its memory, upon certain sample count (Notification Threshold), BIP device will send the collected information to the recipient specified in the notification object. There are some important parameters for the configuration of BACnet trend log. In figure 6B, the chilled beam controller is collecting the chilled water Trend log sample. After collecting 180 samples (Notification Threshold), controller will send this to Trend log recipient (BACnet Network Manger). BACnet network manger will forward the Trend log to OWS via web server. An important calculation is a slack time. This is the amount of time that the recipient operator workstation can be offline before the oldest samples in the Trend log are deleted. If slack time is exceeded, gaps in trend log data appear hence the trend log data is not accurate.

[0043] The table IV below shows the typical structure of BacNet Notification object in the BIP device

[0044] In one scenario, in typical system the BacNet device is configured to send the alarm to recipient-1 and recipient-2. Recipient-1 will receive the alarm on Sunday to Tuesday. Recipient-2 will receive the alarm on Wednesday to Saturday. For example if BacNet device is lost communication on Sunday with BacNet recipient-1 then there is no way to route the alarm to other BacNet recipient in the event of failure. This can accomplish by modifying the structure of Notification object and Device. Monitoring the communication watchdog timer between the recipient and BacNet Device If first recipient is failed then another recipient will be active for the controller.

[0045] The table V below shows the structure of BacNet Notification object used in the present invention BIP device

Table V

[0046] In new proposed architecture, the BacNet Notification object includes "redundant recipient list" option to configure redundant recipient. In above table recipient no 20 has redundant recipient 70, recipient number 25 has recipient number 50. If redundant recipient is also not available on the network then internal FTP server of BACnet Device will act as the recipient. That will store the information related with alarm and Trendlog.

[0047] The systems and methods disclosed herein may be embodied in various forms including, for example, a data processor, such as a computer. Moreover, the above-noted features and other aspects and principles of the present invention may be implemented in various environments. Such environments and related applications may be specially constructed for performing the various processes and operations according to the invention or they may include a general-purpose computer or computing platform selectively activated or reconfigured by code to provide the necessary functionality. The processes disclosed herein are not inherently related to any particular computer or other apparatus, and may be implemented by a suitable combination of hardware, software, and/or firmware. For example, various general-purpose machines may be used with programs written in accordance with teachings of the invention, or it may be more convenient to construct a specialized apparatus or system to perform the required methods and techniques.

[0048]

[0049] Several exemplary embodiments have thus been described. Modifications and alterations may occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiments be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

We claim:

1. A method for identifying and replacing a Broadcast Management device (BBMD)
failure in a BacNet IP Network, said BacNet IP Network comprises a plurality of subnets
and each of said plurality of subnet comprises a plurality of BIP devices, wherein said
plurality of BIP devices comprises said BBMD and at least one BBMD capable device,
said method comprising the steps of:

sending (502), from a BacNet manager, a request to read a Broadcast Distribution Table (BDT) to said BBMD in each of said plurality of subnets;

receiving, at said BacNet manger, an acknowledgement from said BBMD device in each of said plurality of subnets; and

identifying (504 and 506) an error message in said acknowledgement received from at least one said BBMD of said plurality of subnets.

2. The method as claimed in claim 1, comprising:

selecting (508) said at least one BBMD capable device in said subnet associated to said error message identified;

modifying (510) said BDT by replacing an IP address of said BBMD capable device; and
transferring (512) a modified BDT to said BBMD capable device and said BBMD device in said plurality of subnets.

3. The method as claimed in claim 1, wherein a redundancy option is enabled in said
BacNet manager.

4. A method for registering a BBMD as a foreign device in a BacNet IP network
comprising the steps of:

selecting (402), by a BacNet manger, a first BBMD in a first subnet;

setting (404), at said BacNet manager, an User Datagram Protocol (UDP) port and a re-registration interval;

sending (406) a foreign registration request to said first BBMD selected by said BacNet manager at said re-registration interval;

receiving (408 and 410) a response from said first BBMD at each of said re-registration interval; and

selecting (412), by said BacNet manager, a second BBMD in a second subnet when said response is not received from said first BBMD.