# Patent

## Title
Methods for providing a status to devices in a distributed system

## Abstract

A method for providing a status of a device to a plurality of devices in a distributed system includes receiving a status data packet from the device, the status data packet including the status of the device. The method also includes saving the status of the device to a memory and obtaining a list of the plurality of devices in the distributed system. The list is associated with a sequence for circulating the status data packet between the plurality of devices. The method further includes sending the status data packet including the status of the device to a next device in the sequence.

## Background
BACKGROUND OF THE INVENTION
The present invention relates generally to methods for providing a status to devices in a distributed system. Merely by way of example, embodiments of the present invention provide a method for providing a meeting status to conference bridges in a distributed Voice over-Internet Protocol (VoIP) system. The scope of embodiments of the present invention is broader than this particular application, however, and can be applied to other applications and distributed systems.
VoIP systems route voice conversations and other communications over the Internet or other packet switched networks. A distributed VoIP system typically includes a distributed set of devices, such as switches, servers, and conference bridges, that provide applications enabled by the integration of computer systems with telephony services.
A distributed system increases system performance and reliability by eliminating single points of failure. If a device in the system fails, other devices can backup the failed device by providing the services and functions of the failed device. However, this redundancy requires that extra resources be available within the system. For example, if a switch supporting 10 IP phones fails, the remaining switches in the system must have the capacity to support the 10 IP phones that were being supported by the failed switch. To provide the extra resources, a system may be designed to have extra capacity to support the failure of any device in the system.
Additionally, to be able to backup other devices, each device must know or have access to the necessary configuration of the other devices within the system. Continuing the example above, the switches that backup the failed switch need to know the configuration of the failed switch (e.g. time zone, language preference, dialing prefix, local area code). This also requires extra resources because the configuration of each device must be known or available to the other devices in the system (e.g. stored in memory or stored in a central location).
The devices also need to know the status of other devices in the system. For example, each conference bridge within a VoIP system needs to know which meetings are being hosted by other conference bridges as well as the participants associated with each meeting. In the event a conference bridge fails, the other conference bridges in the system can backup the failed device and host the meetings that were in progress. Knowing the status of the other devices also enables resources to be shared and managed to improve the performance of the system. For example, if the resources of a particular conference bridge are being utilized near capacity, and a new meeting request is received by the conference bridge, the request may be routed to another conference bridge in the system that is better suited to host the new meeting. This also requires extra resources because the status of each device must be known or available to the other devices in the system. Additionally, the status must be kept current through periodic updates.
Conventional methods for providing a status to devices in a distributed system include a broadcast method and a central server method. The broadcast method involves periodic status updates that are broadcast from each device to all of the other devices in the system. This method, however, leads to a significant increase in network traffic. For example, if each device in a system sends a status message to every other device in the system, N*(N−1) status messages are sent for each status update (where N is the number of devices in the system). As the number of devices in the system increases, the number of status messages required for each update increases geometrically.
The central server method involves periodic status updates that are sent from each device to a central server, and periodic system status updates that are sent from the central server to each device. However, this method reduces the reliability of the system because the central server is a single point of failure. This method also increases network traffic. For example, if each device sends a status message to a central server, and the central server sends a system status message to each device in the system, 2*N status messages are sent for each status update (where N is the number of devices in the system).
Thus, there is a general need in the art for improved methods of providing a status to devices in a distributed system.
SUMMARY OF THE INVENTION
The present invention provides improved methods for providing a status to devices in a distributed system. Merely by way of example, an embodiment of the present invention provides a method for providing a meeting status to conference bridges in a distributed VoIP system. The scope of embodiments of the present invention is broader than this particular application, however, and can be applied to other applications and distributed systems.
According to an embodiment of the present invention, a method for providing a status of a device to a plurality of devices in a distributed system is provided. The method includes receiving a status data packet from the device, the status data packet including the status of the device. The method also includes saving the status of the device to a memory and obtaining a list of the plurality of devices in the distributed system. The list is associated with a sequence for circulating the status data packet between the plurality of devices. The method further includes sending the status data packet including the status of the device to a next device in the sequence.
According to another embodiment of the present invention, a method for providing a status to a plurality of devices in a distributed VoIP system is provided. The distributed VoIP system includes a first device, a second device, and a third device. The method includes, at the second device, receiving a first status data packet from the first device, the first status data packet including a first status of the first device. The method also includes, at the second device, saving the first status of the first device to a memory and updating the first status data packet including the first status of the first device with a second status of the second device. The method also includes, at the second device, obtaining a list of the plurality of devices in the distributed VoIP system. The list is associated with a sequence for providing the status to the plurality of devices in the distributed VoIP system. The method further includes, at the second device, sending the first status data packet including the first status of the first device and the second status of the second device to the third device. The third device is after the second device in the sequence.
Numerous benefits are achieved using the present invention over conventional techniques. For example, some embodiments according to the present invention provide methods for providing a status to devices in a distributed system with minimal impact on network traffic. In one embodiment, as few as N status messages may be sent for each system status update (where N is the number of devices in the system). In another embodiment, less than N status messages may be sent for each system status update. Additionally, other embodiments according to the present invention provide methods for providing a status to devices in a distributed system with increased performance and reliability. In one embodiment, a status message is circulated between the devices in the system thus eliminating single points of failure. In another embodiment, if a device fails or a status message is lost, a new status message is generated and circulated between the active devices in the system.
Depending upon the embodiment, one or more of these benefits may exist. These and other benefits are described throughout the present specification and more particularly below.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified schematic diagram of a distributed VoIP system according to an embodiment of the present invention;
FIG. 2 is a simplified schematic diagram of conference bridges in a distributed VoIP system according to an embodiment of the present invention;
FIG. 3 is a simplified schematic diagram of conference bridges in a distributed VoIP system according to another embodiment of the present invention;
FIG. 4 is a simplified flowchart illustrating a method for providing a status to devices in a distributed system according to an embodiment of the present invention;
FIG. 5 is a table illustrating an exemplary header structure of a status data packet; and
FIG. 6 is a table illustrating an exemplary device status structure of a status data packet.



DETAILED DESCRIPTION OF THE INVENTION
In accordance with embodiments of the present invention, improved methods for providing a status to devices in a distributed system are provided. Some embodiments reduce network traffic by minimizing the number of status messages required to provide a status update to each device in the system. Other embodiments improve system performance and reliability by circulating status messages between devices thus eliminating single points of failure. These and other embodiments of the invention, as well as other features and advantages, are described in more detail below.
FIG. 1 is a simplified schematic diagram of a distributed VoIP system according to an embodiment of the present invention. The system illustrated in FIG. 1 includes three groupings of devices labeled as first site 102, second site 134, and third site 152. As used herein, a site may represent a grouping of devices or resources that is physically distinct from other groupings of devices. Alternatively, a site may represent a topology-related grouping of devices that are not in physically distinct locations. Also, while the system illustrated in FIG. 1 shows three sites that each include similar groupings of devices, embodiments of the present invention are not so limited. For example, the present invention may apply to systems with more or fewer sites as well as sites with different devices and configurations compared to other sites in the system. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.
As shown in FIG. 1, first site 102, second site 134, and third site 152 are communicatively coupled via network 120. The network 120 may be the Internet or another packet switched network over which the distributed VoIP system operates.
In the example illustrated in FIG. 1, first site 102 includes several devices including server 110, conference bridge 112, and switch 114. First site 102 also includes communication devices such as IP phone 104 and soft phone 106. Also included within first site 102 is a data storage device labeled as data storage 108. Each of these components within first site 102 may communicate with each other via network 120 or via a local network.
Switch 114 may communicate with IP phone 104 and soft phone 106 to establish communications channels that are used to make and receive calls. Switch 114 manages call setup and resource allocation by provisioning an extension for IP phone 104 and soft phone 106. In the example illustrated in FIG. 1, switch 114 is also coupled to PSTN 116. Switch 114 and PSTN 116 may be coupled via an analog or digital trunk line (e.g. a T1 or E1 interface). In the illustrated configuration, switch 114 provides an interface between the VoIP system and the PSTN 116.
Switch 114 typically includes familiar software and hardware components. For example, switch 114 may include an operating system, processor, local memory for storage, I/O devices, and a system bus interconnecting the hardware components. RAM and disk drives are examples of local memory for storage of data and computer programs. Other types of local memory include magnetic storage media, optical storage media, flash memory, networked storage devices, and the like.
Other communication devices that are used to make or receive phone calls, messages, or other communications may also be included within the VoIP system. For example, although not shown in the example illustrated in FIG. 1, a VoIP system may include analog or digital phones, button boxes, “virtual phones” (e.g. extensions that are not assigned to a specific device), IP trunks (e.g. endpoints that can make inbound and outbound calls to the PSTN and to other telephony systems), and other communication devices.
Server 110 may be configured to implement the applications of the VoIP system. For example, server 110 may be configured to provide voicemail features to IP phone 104 and soft phone 106. Server 110 may store data in local memory or in data storage 108. Server 110 typically includes familiar software and hardware components. For example, server 110 may include an operating system, processor, local memory for storage, I/O devices, and a system bus interconnecting the hardware components. RAM and disk drives are examples of local memory for storage of data and computer programs. Other types of local memory include magnetic storage media, optical storage media, flash memory, networked storage devices, and the like. In some embodiments, server 110 may include more than one server (e.g. server cluster).
In an embodiment, server 110 may be linked directly to data storage 108 as shown in FIG. 1. In another embodiment, data storage 108 may be linked to server 110 via the network 120 or a local network. Data storage 108 is configured to store and maintain data. For example, data storage 108 may be configured to store and maintain voicemail messages, voicemail data, site configuration data, and other information. Data storage 108 may be any conventional database such as those powered by My SQL, Oracle, Sybase, and the like, or other data sources such as an LDAP server.
Conference bridge 112 may be configured to provide conferencing applications to participants in conference meetings. The participants may include users outside the VoIP system, such as a user connected to a meeting through external phone 118 or external phone 136, and users within the VoIP system, such as a user connected to a meeting through IP phone 104 or IP phone 132. Conferencing applications provided by conference bridge 112 may include audio conferencing, web conferencing, document sharing, application sharing, instant messaging, integrated audio and visual recording, and other applications.
Conference bridge 112 typically includes familiar software and hardware components. For example, conference bridge 112 may include an operating system, processor, local memory for storage, I/O devices, and a system bus interconnecting the hardware components. RAM and disk drives are examples of local memory for storage of data and computer programs. Other types of local memory include magnetic storage media, optical storage media, flash memory, networked storage devices, and the like.
In the VoIP system illustrated in FIG. 1, second site 134 includes several devices including server 126, conference bridge 124, and switch 122. Second site 134 also includes communication devices such as IP phone 132 and soft phone 130. Also included within second site 134 is a data storage device labeled as data storage 128. Similar to the components within first site 102, each of these components within second site 134 may communicate with each other via network 120 or via a local network. Each of the components within second site 134 may be configured in a manner similar to the components within first site 102 described above.
In the VoIP system illustrated in FIG. 1, third site 152 includes several devices including server 144, conference bridge 142, and switch 140. Switch 140 is coupled to PSTN 138. PSTN 138 may be coupled with various communication devices, including external phone 136. Switch 140 and PSTN 138 may be coupled via an analog or digital trunk line (e.g. a T1 or E1 interface). In the illustrated configuration, switch 140 provides an interface between the VoIP system and the PSTN 138. Third site 152 also includes communication devices such as IP phone 150 and soft phone 148. Also included within third site 152 is a data storage device labeled as data storage 146. Similar to the components within the other sites, each of the components within third site 152 may communicate with each other via network 120 or via a local network. Each of the components within third site 152 may be configured in a manner similar to the components within first site 102 described above.
It is to be understood that FIG. 1 is presented merely as an exemplary embodiment to illustrate some of the features and functionality of the present invention. Not all distributed VoIP systems include the components shown in FIG. 1. Likewise, some distributed VoIP systems include additional components that are not included in the VoIP system of FIG. 1. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. For example, in some configurations the components shown in FIG. 1 may be combined or provide functionality that is different from that described herein. Thus, the present invention can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
In accordance with embodiments of the present invention, methods for providing a status to devices in a distributed system, such as the distributed VoIP system illustrated in FIG. 1, are provided. For example, in accordance with an embodiment, a method for providing a status to conference bridge 112, conference bridge 124, and conference bridge 142 is provided. The status may include the meetings that are being hosted by each conference bridge and the participants associated with each meeting. In accordance with another embodiment, a method for providing a status to server 110, server 126, and server 144 is provided. Here, the status may include voicemail messages or other data that may be used to backup a failed server or to manage system resources. Similarly, in accordance with yet another embodiment, a method for providing a status to switch 114, switch 122, and switch 140 is provided. Here, the status may include the number of calls the switch is supporting and the communication devices associated with each call. The scope of embodiments of the present invention is broader than these particular applications, however, and can be applied to other applications and distributed systems. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.
FIG. 2 is a simplified schematic diagram of the conference bridges in a distributed VoIP system according to an embodiment of the present invention. VoIP system 220 includes conference bridge 202, conference bridge 204, conference bridge 206, and conference bridge 208. Although not shown in FIG. 2, each of the conference bridges may be part of the same or different sites within VoIP system 220. Also, although conference bridges are used in the example illustrated in FIG. 2, it is to be understood that the method may be used to provide a status between other devices in a distributed system.
Each of the conference bridges illustrated in FIG. 2 are communicatively coupled to network 210. For example, conference bridge 202 is coupled to network 210 via link 212, conference bridge 204 is coupled to network 210 via link 214, conference bridge 206 is coupled to network 210 via link 216, and conference bridge 208 is coupled to network 210 via link 218.
In accordance with an embodiment of the present invention, a status is provided between the conference bridges illustrated in FIG. 2. For example, in one embodiment a status data packet is generated by conference bridge 202 that includes the status of conference bridge 202. The status may include the meetings that are being hosted by conference bridge 202 and the participants associated with each meeting. The data packet is sent from conference bridge 202 to conference bridge 204. Conference bridge 204 receives the data packet and saves the status of conference bridge 202 to memory. For example, the status of conference bridge 202 may be saved in local memory or stored in external data storage. Conference bridge 204 sends the data packet to conference bridge 206. Conference bridge 206 receives the data packet and saves the status of conference bridge 202 to memory. Conference bridge 206 sends the data packet to conference bridge 208. Conference bridge 208 receives the data packet and saves the status of conference bridge 202 to memory. Thus, N−1 status messages are required to provide the status of conference bridge 202 to each conference bridge in the system (where N is the number of devices in the system). In one embodiment, conference bridge 208 sends the data packet to conference bridge 202. Conference bridge 202 receives the data packet and determines if its status has changed. If the status of conference bridge 202 has changed, conference bridge 202 updates its status and sends the data packet with the updated status to conference bridge 204, and the process of receiving the data packet, storing the status, and sending the data packet to the next conference bridge repeats. If the status of conference bridge 202 has not changed, conference bridge 202 may send the data packet without updating the status to conference bridge 204, or conference bridge 202 may wait until its status has changed and then update its status and send the data packet with the updated status to conference bridge 204.
In accordance with another embodiment of the present invention, the status data packet includes a status of each device in the distributed system. For example, in one embodiment a data packet is generated by conference bridge 202 that includes the status of conference bridge 202. The data packet is sent from conference bridge 202 to conference bridge 204. Conference bridge 204 receives the data packet and saves the status of conference bridge 202 to memory. Conference bridge 204 updates the data packet with its status. Conference bridge 204 sends the updated data packet to conference bridge 206. Conference bridge 206 receives the data packet and saves the status of conference bridges 202, 204 to memory. Conference bridge 206 updates the data packet with its status. Conference bridge 206 sends the updated data packet to conference bridge 208. Conference bridge 208 receives the data packet and saves the status of conference bridges 202, 204, 206 to memory. Conference bridge 208 updates the data packet with its status. Conference bridge 208 sends the updated data packet to conference bridge 202. Conference bridge 202 receives the data packet and saves the status of conference bridges 204, 206, 208 to memory. In one embodiment, conference bridge 202 determines if its status has changed. If the status of conference bridge 202 has changed, conference bridge 202 updates the data packet with its status and sends the updated data packet to conference bridge 204. Conference bridge 204 receives the data packet and saves the status of conference bridges 202, 206, 208 to memory, and the process of receiving the data packet, storing the status of each conference bridge, updating the status, and sending the status updated data packet to the next conference bridge repeats. If the status of conference bridge 202 has not changed, conference bridge 202 may send the data packet without updating its status to conference bridge 204. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.
As illustrated in the above examples, methods according to the present invention provide a status to devices in a distributed system with minimal impact on network traffic. For example, providing a status to each device in the system requires only N or fewer status messages (where N is the number of devices in the system). Furthermore, such methods are scalable in that one additional status message is required for each additional device added to the system.
In accordance with an embodiment of the present invention, a circulation counter is associated with the status data packet. The circulation counter is incremented as the status data packet is circulated between the devices in the system. For example, the circulation counter may be incremented by each device that receives the status data packet, or it may be incremented by only one device in the system each time the status data packet is received by that device. In one embodiment, the device that updates the circulation counter is determined according to a device identification. Using the conference bridges in FIG. 2 as an example, conference bridge 202 may update the circulation counter because it has the lowest device identification number in the system (or conference bridge 208 because it has the highest device identification number in the system). If conference bridge 202 is offline, the conference bridge with the next lowest device identification number may update the circulation counter. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. Further, the circulation counter may be stored by only one device in the system or at only a single location, or it may be included as part of the data carried by the data packet.
In accordance with another embodiment, each device in the system is arranged in a sequence or order and the status data packet is sent between devices according to the sequence. Using VoIP system 220 in FIG. 2 as an example, the conference bridges may be ordered by device identification number, with conference bridge 1 (202) being first, conference bridge 2 (204) being second, conference bridge 3 (206) being third, and conference bridge 4 (208) being fourth in the sequence. The first device in the sequence follows the last device. For example, conference bridge 4 (208) may send the status data packet to conference bridge 1 (202) to continue the sequence.
Furthermore, the sequence may be pre-defined at a system level or it may be dynamic and updated periodically. For example, the sequence may be determined at the time the status data packet is generated and included as a list in the data packet. In this case, each conference bridge determines the next conference bridge in the sequence according to the list. Also, the list may be updated on a periodic basis. For example, the list may be obtained by query from a particular database in the system and updated at set time intervals or based on the circulation counter. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.
In accordance with another embodiment, each device that receives a status data packet sends an acknowledgement of receipt to the device that sent the data packet. Accordingly, each device listens for an acknowledgement of receipt after sending a status data packet. If an acknowledgement of receipt is not received, the device assumes that the status data packet was not received. In this scenario, the status data packet may be re-sent to the device that failed to send an acknowledgement of receipt, or it may be sent to the following device in the sequence.
Using the system illustrated in FIG. 3 as an example, a status data packet is sent by conference bridge 304 to conference bridge 306. As illustrated in FIG. 3, however, conference bridge 306 is not coupled to network 310. Such a scenario may arise when a network connection is lost or a device in the system is offline. Because conference bridge 306 is not coupled to network 310, the status data packet is not received and an acknowledgement of receipt is not sent to conference bridge 304. After waiting a period of time, conference bridge 304 may send the status data packet to the following device in the sequence, which is conference bridge 308 in this example. The period of time may be a set time or it may be dependent on network traffic or resource utilization. As illustrated in FIG. 3, conference bridge 308 is coupled to network 310. After receiving the status data packet, conference bridge 308 sends an acknowledgement of receipt to conference bridge 304. Conference bridge 308 then circulates the status data packet as described above, sending it to conference bridge 302. Conference bridge 302 sends an acknowledgement of receipt to conference bridge 308 and sends the status data packet to conference bridge 304. Conference bridge 304 sends an acknowledgement of receipt to conference bridge 302. Since conference bridge 304 did not receive an acknowledgement of receipt from conference bridge 306 during the previous circulation of the data packet, conference bridge 304 may attempt to send the status data packet to conference bridge 306 once again. Alternatively, conference bridge 304 may send the status data packet to conference bridge 308 and only attempt to send the status data packet to conference bridge 306 after a predetermined number of circulations of the status data packet. For example, conference bridge 304 may send the status data packet to conference bridge 306 every other circulation or every third circulation of the status data packet. As illustrated in the above example, embodiments of the present invention can improve performance and reliability by eliminating single points of failure in a distributed system.
In accordance with another embodiment, a status data packet may be sent to the next device in the sequence as soon as it is processed. Alternatively, a status data packet may be sent to the next device in the sequence after waiting a period of time. This may be used to balance network traffic with the requirements of a particular system. For example, if a status data packet can be circulated to each device in a system in one second, and according to system requirements status updates are required at least once every five seconds, each device may wait a period of time before sending the device to reduce network traffic. The period of time may be predetermined, or it may be determined depending on the number of devices in the system, system utilization, network traffic, and the like. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.
In accordance with another embodiment, each status data packet is associated with a unique identifier and includes a time the data packet was generated. When a device receives a status data packet, it compares the identifier and time with the previous status data packet it received. If the status data packet has a different identifier than the previous data packet and a more recent time, it may process the data packet and send it to the next device as explained above. If the status data packet has a different identifier than the previous data packet and an older time, it may discard the data packet. Alternatively, the data packet with the more recent time may be discarded and the data packet with the older time may be processed and sent to the next device.
A discarded data packet is not sent to the next device thus stopping the circulation of that data packet. This is to ensure that only one status data packet is circulated at a time. For example, if a status data packet is delayed and a device starts a new status data packet into circulation, one of the data packets will be discarded so that only one status data packet is circulated. As another example, the devices in a system may get separated into more than one group with each group circulating a status data packet between the devices in that group. When the groups are merged, one of the status data packets will be discarded. A scenario where more than one group of devices exists may arise, for example, when a group of devices that are offline are brought online at approximately the same time and one or more of the devices start a new status data packet into circulation. As explained above with regard to FIG. 3, a device that is online may attempt to send a status data packet to a device that is offline after a predetermined number of circulations of the status data packet. In this scenario, after the predetermined number of circulations the status data packet will be sent to one of the devices that had previously been offline, and the groups of devices will be merged into a single group and one of the status data packets will be discarded.
In accordance with another embodiment of the present invention, each device in the system expects to receive periodic status updates via the status data packets. For example, each device may maintain a time associated with the last status update it received and have an expectation of receiving another status update within a certain period of time. If a device does not receive another status update within the period of time, the device may generate a new status data packet and send it to the next device in the sequence. Here, the period of time may be a set time, or it may be determined based on network traffic, resource utilization, or the number of devices in the system. The new status data packet may include only the status of the device generating the status data packet, or it may include the last known status of each device in the system. Such a method may also be used to start a status data packet into circulation upon bringing a system on-line or adding a new device to the system.
In accordance with another embodiment of the present invention, the status of each device includes a time stamp. The time stamp is the time at which the status was last updated. A time stamp can serve several functions. For example, a time stamp allows a device to determine how long it takes for the status data packet to circulate between the devices in the system. A time stamp also provides information on how current the status is from each of the other devices in the system. Continuing with the example illustrated in FIG. 3, the status of conference bridge 306 will not be updated while it is offline. This will be reflected in the time stamp associated with the status of conference bridge 306. This can provide information on the health of the devices in the system. For example, this can be used as an indicator that a device is offline. This information can be used in implementing backup procedures and allocating resources.
In accordance with another embodiment, the number of times a device receives and sends a status data packet can be used as a health indicator. For example, a device that has received and sent more than a predetermined number of status data packets may be considered “connected” to the system, whereas a device that did not receive or send the last status data packet may be considered “disconnected” from the system. Further, a device may be considered in an “evaluation” mode if it received and sent the last data packet but has not received and sent more than the predetermined number of status data packets required to be “connected” to the system. Health indicators may be used, for example, for resource allocation.
In accordance with another embodiment, a device may compare the status of each device as indicated in the data packet with the status of each device as stored in memory. If the status of the devices has not changed and its status has not changed, it may update its time stamp and send the data packet to the next device without saving the status of each device to memory. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.
In accordance with another embodiment, a device within the system may resolve status conflicts. Such conflicts may exist, for example, when more than one conference bridge in a system indicates that it is hosting a particular meeting. In some embodiments, the conflict may be resolved using device and resource identifiers. For example, the device with the lowest (or highest) device identification number may resolve status conflicts using the identifiers of the devices involved and/or the identifier of the resource involved. As an example, if more than one conference bridge in a system indicates that it is hosting a particular meeting, the device with the lowest device identification number recognizes the conflict and uses the identifiers of the devices involved in the conflict and the identifier of the particular meeting to determine which device will host the meeting. The status of the devices involved in the conflict is updated and the conflict is resolved. In other embodiments, the IP addresses of the devices involved in the conflict may be used to resolve the conflict. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.
FIG. 4 is a simplified flowchart illustrating a method of providing a status to devices in a distributed system according to an embodiment of the present invention. In step 402, a status data packet is received from a device in the distributed system. For example, a conference bridge may receive a status from another conference bridge in a distributed VoIP system. The status data packet includes the status of the device. As explained above, if the status data packet has a different identifier than a previous data packet received by the device, the status data packet may be processed or discarded. If the status data packet is processed, in step 404 the status of the device is saved to a memory. In step 406, a list of the plurality of devices in the distributed system is obtained. For example, the list may be included in the status data packet, or it may be obtained from a particular server or database in the system. The list is associated with a sequence for circulating the status data packet between the plurality of devices in the system. In step 408, the status data packet including the status of the device is sent to a next device in the sequence.
It should be appreciated that the specific steps illustrated in FIG. 4 provide a particular method of providing a status to a plurality of devices in a distributed system according to an embodiment of the present invention. Other sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments of the present invention may perform the steps outlined above in a different order. Moreover, the individual steps illustrated in FIG. 4 may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. Furthermore, additional steps may be added or removed depending on the particular applications. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.
FIG. 5 is a table illustrating an exemplary header structure of a status data packet. In this example, the status data packet includes the header structure illustrated in FIG. 5 and the device status structure illustrated in FIG. 6. The header illustrated in FIG. 5 includes a packet ID, a generation time, a circulation counter, a list of devices in the system, as well as other fields. As explained above, in some embodiments each status data packet is associated with a unique identifier referred to here as the packet ID. The identifier may be determined when the data packet is generated, and the time may include the time the data packet was generated. As explained above, the packet ID and time may be used to determine if a particular data packet is to be processed or discarded. In this example the circulation counter is also included in the data packet. As explained above, the circulation counter is incremented as the status data packet is circulated between the devices in the system. In this example the list of devices in the system is also included in the status data packet. As explained above, the list of devices may be used to determine the sequence or order the status data packet is sent between devices in the system.
FIG. 6 is a table illustrating an exemplary device status structure of a status data packet. In this example, the device status includes the device ID, the number of meetings hosted by the device and the number of users associated with the meetings, the time of the last status update, and other fields. As explained above, each device may be associated with a device identification referred to here as the device ID. The device ID may be used to determine which device updates the circulation counter. In some embodiments, the device ID may be used to determine the order of the devices in the list. In this example, the device is a conference bridge and the device status includes the number of meetings hosted by the conference bridge and the number of users associated with the meetings. This information is specific to the particular device type, and may include information used for backup and resource management. As explained above, the status of each device may include a time stamp referred to here as the time of the last status update. This may be used by other devices to determine if the status is up to date. In one embodiment where the status update is provided between conference bridges, updating the status data packet includes updating the number of meetings hosted, the number of users attached to the meetings, and the time of the last status update.
Note that in FIGS. 1-3 the links between the various components are shown using arrows. These links are not limited to physical connections, but may also represent logical connections between the components. Where the links represent physical connections, they may represent wired or wireless connections. For example, FIG. 1 shows switch 114 linked with IP phone 104 and soft phone 106. These links may be wired, wireless, or a combination of wired and wireless technologies.
While the present invention has been described in terms of specific embodiments, it should be apparent to those skilled in the art that the scope of the present invention is not limited to the embodiments described herein. For example, it is to be understood that the features of one or more embodiments of the invention may be combined with one or more features of other embodiments of the invention without departing from the scope of the invention. The examples and embodiments described herein are for illustrative purposes only and various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.

## Claims

1. A method for providing a status to a plurality of conference bridges in a distributed system, the status comprising a list of meetings hosted by one or more of the plurality of conference bridges, the method comprising:
at a second conference bridge:
receiving a status data packet at the second conference bridge, the status data packet sent from a first conference bridge to the second conference bridge and including a status of the first conference bridge, an ID of the first conference bridge, and a list of the plurality of conference bridges in the distributed system, the list being associated with a sequence for circulating the status data packet between the plurality of conference bridges;
saving the status of the first conference bridge to a memory of the second conference bridge;
updating the status data packet with a status of the second conference bridge and a time associated with receiving the status data packet at the second conference bridge;
sending the updated status data packet including the status of the first conference bridge and the status of the second conference bridge from the second conference bridge to a next conference bridge in the sequence;
waiting a period of time;
determining that an acknowledgement of receipt of the updated status data packet is not received from the next conference bridge during the period of time; and
sending the updated status data packet to a following conference bridge in the sequence, the following conference bridge being after the next conference bridge in the sequence.

2. The method of claim 1 further comprising sending an acknowledgement of receipt of the status data packet from the second conference bridge to the first conference bridge.

3. The method of claim 1 further comprising receiving an acknowledgement of receipt of the updated status data packet from the following conference bridge in the sequence.

4. The method of claim 1 wherein the distributed system is a distributed VoIP system.

5. The method of claim 1 wherein the following conference bridge is a last conference bridge in the sequence, and the last conference bridge sends the updated status data packet to the first conference bridge, the first conference bridge being a first conference bridge in the sequence.

6. The method of claim 1 further comprising incrementing a circulation counter after receiving the status data packet.

7. The method of claim 1 wherein the period of time is determined based at least in part on a time duration required for the next conference bridge to receive the status data packet and send an acknowledgement of receipt of the status data packet.

8. The method of claim 1 further comprising:
at the second conference bridge:
waiting a period of time after receiving the status data packet and before sending the updated status data packet to the next conference bridge, wherein the period of time is greater than a time duration required to save the status of the first conference bridge to the memory.

9. The method of claim 8 wherein the period of time is based at least in part on a number of conference bridges in the plurality of conference bridges.

10. A method for providing a status to a plurality of devices in a distributed VoIP system, the plurality of devices comprising a first device, a second device, a third device, and a fourth device, the method comprising:
at the second device:
receiving a first status data packet from the first device, the first status data packet sent from the first device to the second device, the first status data packet including a first status of the first device, an ID of the first device, and a list of the plurality of devices in the distributed VoIP system, the list being associated with a sequence for providing the status to the plurality of devices in the distributed VoIP system; thereafter
saving the first status of the first device to a memory;
updating the first status data packet including the first status of the first device with a second status of the second device and a time associated with receiving the first status data packet at the second device;
sending the first updated status data packet including the first status of the first device and the second status of the second device from the second device to the third device, the third device being after the second device in the sequence;
waiting a period of time;
determining that an acknowledgement of receipt of the first updated status data packet is not received from the third device during the period of time; and
sending the first updated status data packet to the fourth device in the sequence, the fourth device being after the third device in the sequence.

11. The method of claim 10 further comprising:
at the second device:
receiving a second status data packet from the first device, the second status data packet sent from the first device to the second device;
determining a second time associated with the second status data packet;
determining that the second time associated with the second status data packet is later in time than the time associated with receiving the first status data packet; and
sending the second status data packet from the second device to the third device.

12. The method of claim 10 further comprising:
at the second device:
receiving a second status data packet from the first device, the second status data packet sent from the first device to the second device;
determining a second time associated with the second status data packet;
determining that the second time associated with the second status data packet is earlier in time than the first time associated with the first status data packet; and
discarding the second status data packet.

13. The method of claim 10 further comprising:
at the second device:
adding a time stamp to the first status data packet, the time stamp being associated with a time the first status data packet is processed by the second device.

14. The method of claim 10 wherein the plurality of devices are conference bridges.

15. The method of claim 10 wherein the second device resolves a status conflict between the first device and the third device using device identifiers.

16. The method of claim 10 wherein the second device is one of a first plurality of devices circulating the first status data packet, and the fourth device is one of a second plurality of devices circulating a second status data packet, and wherein sending the first updated status data packet from the second device to the fourth device merges the first plurality of devices and the second plurality of devices into the plurality of devices.

17. The method of claim 16 wherein the second status data packet is discarded after the first plurality of devices and the second plurality of devices are merged into the plurality of devices.

18. The method of claim 10 the fourth device and the first device are the same device.

19. A non-transitory computer readable medium including computer program code for providing a status to a plurality of conference bridges in a distributed system, the status comprising a list of meetings hosted by one or more of the plurality of conference bridges, the computer readable medium comprising:
code for receiving a status data packet at a second conference bridge, the status data packet sent from a first conference bridge to the second conference bridge, the status data packet including the status of the first conference bridge, an ID of the first conference bridge, and a list of the plurality of conference bridges in the distributed system, the list being associated with a sequence for circulating the status data packet between the plurality of conference bridges;
code for saving the status of the first conference bridge to a memory of the second conference bridge;
code for updating the status data packet with a status of the second conference bridge and a time associated with receiving the status data packet at the second conference bridge;
code for sending the updated status data packet including the status of the first conference bridge and the status of the second conference bridge from the second conference bridge to a next conference bridge in the sequence;
code for waiting a period of time;
code for determining that an acknowledgement of receipt of the updated status data packet is not received from the next conference bridge during the period of time; and
code for sending the status data packet to a following conference bridge in the sequence, the following conference bridge being after the next conference bridge in the sequence.

20. The non-transitory computer readable medium of claim 19 further comprising code for sending an acknowledgement of receipt of the status data packet from the second conference bridge to the first conference bridge.

21. The non-transitory computer readable medium of claim 19 further comprising code for receiving an acknowledgement of receipt of the updated status data packet from the next conference bridge.

22. The non-transitory computer readable medium of claim 19 further comprising code for incrementing a circulation counter after receiving the status data packet.

23. The non-transitory computer readable medium of claim 19 wherein the following conference bridge is a last conference bridge in the sequence, and the last conference bridge sends the updated status data packet to the first conference bridge, the first conference bridge being a first conference bridge in the sequence.

24. The non-transitory computer readable medium of claim 19 wherein the period of time is determined based at least in part on a time duration required for the next conference bridge to receive the status data packet and send an acknowledgement of receipt of the status data packet.

25. The non-transitory computer readable medium of claim 19 further comprising:
code for waiting a period of time after receiving the status data packet and before sending the updated status data packet to the next conference bridge, wherein the period of time is greater than a time duration required to save the status of the first conference bridge to the memory.

26. The non-transitory computer readable medium of claim 25 wherein the period of time is based at least in part on a number of conference bridges in the plurality of conference bridges.