System, apparatus and method for reducing failover time through redundancy using virtual access points

According to one embodiment of the disclosure, a non-transitory computer readable medium is described for an network device, where the medium comprising instructions which, when executed by one or more hardware processors, cause performance of a number of operations. These operations include configuring a first network device to provide network access to a client device using a first Basic Service Set Identification (BSSID) and determining that the first network device is not responsive. Based on determining that the first network device is not responsive, the one or more hardware processors further configure a second network device to provide the network access to the client device using the same first BSSID that was previously used by the first network device without the client device disassociating with the first BSSID.

FIELD

Embodiments of the disclosure relate to the field of wireless digital networks. More specifically, one embodiment of the disclosure relates to the reduction of failover times based on redundancy through virtual access points (VAPs).

GENERAL BACKGROUND

Wireless local area networks (WLANs) are becoming ubiquitous. Particularly in locations such as school and businesses, there may be a number of wireless access points (APs), each operating as a gateway for wireless connectivity to a wired network. In this type of complex networking system, there is a need to provide a redundancy mechanism with a short failover time in order to at least maintain client(s) connectivity.

Currently, conventional wireless systems are adapted to handle failover conditions based on redundancy at the controller. For instance, three primary controller-based redundancy mechanisms include backup-LMS (Local Area Network “LAN” Management Solution), Virtual Router Redundancy Protocol (VRRP), and High Availability (HA)-Lite. For backup-LMS, the AP system profile is configured with a primary and a backup LMS address. APs initially connect to the Primary LMS. When an AP loses connectivity with the primary controller, it fails over to the backup controller. As part of failover, it re-establishes the tunnel with the backup-LMS, downloads the configuration and then becomes operational. In accordance with VRRP, two controllers are configured to form a VRRP pair. The VRRP IP address is configured as the LMS in the AP system profile.

All these mechanisms provide controller-based redundancy. However, it is contemplated that redundancy provided at the edge of the network may enable compliance with more stringent failover requirements.

DETAILED DESCRIPTION

Embodiments of the disclosure relate to a system and framework for reducing failover time by providing redundancy for services at an edge device (e.g. an access point “AP”). In particular, a redundancy scheme may be implemented at the edge device in order to ensure that none of the Basic Service Sets (BSSes) experiences a complete disruption of service upon failure of the edge device. Hence, failure at the edge device (e.g. AP failover) is transparent to associated client devices.

In a wireless distributed system, a single edge device (e.g. an access point “AP”, a base station, etc.) together with all associated client devices (STAs) is referred to as a “Basic Service Set” or “BSS”. An example of a particular types of wireless distributed system includes a first type of wireless (WiFi™) network operating in accordance with the IEEE 802.11-2012 standard. It is contemplated that the invention may be applicable to other network types such as a second type of wireless (WiMax™) network (representative of an IEEE 802.16-based network), and/or a Bluetooth™ network.

Herein, the BSS is uniquely identified by a BSS Identification (BSSID), which also correlates to a Service Set Identifier (SSID) being the informal name of the BSS. For a BSS operating in infrastructure mode, the BSSID is the Media Access Control (MAC) address of a Virtual Access Point (VAP). By placement of BSSID redundancy at the edge devices, in lieu of controller-based redundancy, faster failover may be achieved.

In general, according to one embodiment of the invention, redundant edge devices are chosen from the same radio frequency (RF) neighborhood, such as the same clique set that features two or more edge devices operating within the same RF neighborhood. Herein, at least two neighboring edge devices being part of the same clique set, also referred to as a “redundant grouping,” include BSSIDs stored in redundancy for each other. For instance, a first network (edge) device is adapted with both a first storage portion that stores a first plurality of available BSSIDs associated with BSSes primarily handled by the first network device (referred to as “primary BSSIDs”) and a second storage portion. The second storage portion is configured to store a second plurality of BSSIDs (referred to as “backup BSSIDs”) that are associated with BSSes primarily supported by the second network (edge) device of the redundant grouping.

According to one embodiment of the disclosure, two types of messages may be used to trigger a failover event. A first type of message, which is referred to as an “AP heartbeat,” is a message transmitted between a network (edge) device and a controller on a wired link. A second type of message, which is referred to as a “virtual AP heartbeat,” is a message between network (edge) devices in the same redundant grouping. Herein, a second edge device listens to messages associated within BSSes including the first edge device. In response to no heartbeat messages being detected during prescribed transmission times (e.g. heartbeat messages are missed “B” times consecutively or in total, where “B” may be set to any integer value and/or for a prescribed time (e.g. 3 beacons or 300 milliseconds), a heartbeat miss event is considered to have occurred. Upon detecting the heartbeat miss event that constitutes a failover triggering event, the second edge device (or one of the redundant edge devices) activates the backup BSSes available with it.

In order to achieve transparent failover, both edge devices need to synchronize information for the BSS(es) currently active on each other. Examples of information to be synchronized may include two or more of the following: (1) Timing Synchronization Function (TSF); (2) associated Client MAC addresses; (3) client information (e.g. association identifier, power-save state, capabilities, rates, etc.); and/or (4) encryption key(s).

In summary, one embodiment of the disclosure describes a non-transitory computer readable medium comprising instructions which, when executed by one or more hardware processors, causes performance of operations including, subsequent to a client device associating with a first Basic Service Set Identification (BSSID), configuring a first edge device to provide services to the client device by the first edge device using the first BSSID to communicate with the client device. Examples of such services may include, but are not limited or restricted to network connectivity. Upon determining that the first edge device is not responsive, a second edge device is configured to provide the services to the client device by the second edge device using the first BSSID to communicate with the client device without the client device disassociating with the first BSSID.

Herein, certain terminology is used to describe features within embodiments of the invention. For example, the term “network device” generally refers to electronic equipment configured to communicate over a wired and/or wireless network and process information related to such communications. Hence, the network device may be adapted with circuitry to support wireless connectivity with other network devices being part of a wireless network. Different types of network devices may include, but are not limited to (1) a client device being any consumer electronics with connectivity to multiple networks that are based on different technologies such as cellular, wireless (e.g., WiFi™ or WiMax™), Bluetooth™ or the like; (2) an edge device; and/or (3) a data control device.

Herein, an “edge device” may include a wireless access point, a wireless base station, a Bluetooth® receiver/transceiver, or any device configured as a hot spot or gateway for providing services such as network connectivity, which may include any type of mobile network device. A “client device” may be a stationary network device (e.g., desktop computer, television, set-top box, video gaming console, etc.) or a mobile network device capable of connecting to one or more networks. Illustrative examples of mobile network devices may include a tablet, laptop, netbook, bar-code scanner, a digital camera, and/or a mobile handset such as a smartphone, personal digital assistant “PDA”, or the like. Likewise, illustrative examples of a data control device may include, but are not limited or restricted to a network switch, a controller, a router, a brouter, or the like.

It is contemplated that a network device includes hardware logic such as one or more of the following: (i) processing circuitry; (ii) one or more communication interfaces such as a radio (e.g., component that handles the wireless data transmission and/or reception) and/or a physical connector to support wired connectivity; and/or (iii) memory in the form of a non-transitory computer readable storage medium (e.g., a programmable circuit; a semiconductor memory such as a volatile memory such as random access memory “RAM,” or non-volatile memory such as read-only memory, power-backed RAM, flash memory, phase-change memory or the like; a hard disk drive; an optical disc drive; etc.); or any connector for receiving a portable memory device such as a Universal Serial Bus “USB” flash drive, portable hard disk drive, or the like.

Herein, the term “logic” is generally defined as hardware and/or software. For example, as hardware, logic may include processing circuitry (e.g., a microcontroller, any type of processor, a programmable gate array, an application specific integrated circuit, etc.), semiconductor memory, combinatorial logic, or the like. As software, logic may be one or more software modules, such as executable code in the form of an executable application, an application programming interface (API), a subroutine, a function, a procedure, an object method/implementation, an applet, a servlet, a routine, a source code, an object code, a shared library/dynamic load library, or one or more instructions. These software modules may be stored in any type of a suitable non-transitory computer readable medium (described above) or transitory computer readable transmission media (e.g., electrical, optical, acoustical or other form of propagated signals such as carrier waves, infrared signals, digital signals).

The term “link” is a physical or logical communication path between two or more network devices. Examples of links supporting wireless communications may include certain radio frequency (RF) channels and/or bands, as well as the logic associated therewith.

The terms “connected” and “connection” generally relate to an established communication path between two network devices that enables one network device to transfer data targeted specifically for receipt by the other network device.

The term “message” generally refers to information transmitted as information in a prescribed format, where each message may be in the form of a packet, a frame, an Asynchronous Transfer Mode (ATM) cell, or any other series of bits having the prescribed format.

As this invention is susceptible to embodiments of many different forms, it is intended that the present disclosure is to be considered as an example of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described.

III. General Architecture

Referring toFIG. 1A, an exemplary embodiment of a wireless distributed system with BSSID redundancy located at one or more edge devices is shown. Herein, according to one embodiment of the disclosure, each of the one or more (N) edge devices1001-100Noperates as a gateway to provide communicative coupling to a wired network110which provides access to a common, public network140such as the Internet. Such communicative coupling may be via a centralized network device120(e.g. controller) or may be conducted directly by the various edge devices. These edge devices1001-100Nmay include one or more access points (APs) that control connectivity over a first wireless (WiFi™) network, and/or one or more wireless base stations that control connectivity to a second wireless (WiMAX™) network. Each of these edge devices1001-100Nenables one or more client devices130, such as a mobile network device for example, to access public network140.

As shown, edge devices1001-100N(M≧2) are within the same RF neighborhood150as, at least, wireless signaling from edge device1001is detected by edge device1002and wireless signaling from edge device1002is detected by edge device1001. However, edge device100M+1may be within a different RF neighborhood160as signaling from edge devices1001-100Mare not detected by edge device100M+1and vice versa. Hence, edge device100M+1is outside the coverage areas of edge devices1001-100M. The selection of redundant groupings within the RF neighborhood150may be accomplished through the formation of clique sets as described in U.S. patent application Ser. No. 13/959,603 entitled “Task Processing and Resource Sharing In a Distributed Wireless System,” the entire contents of which are incorporated by reference.

In particular, according to one embodiment of the disclosure, centralized network device120may be configured with neighborhood identification logic125, namely software including routines for identifying a plurality of network devices. In some embodiments, the neighborhood identification logic125can be a set of instructions executable by the processor (not shown) within the network device120that provide the functionality described below for identifying a clique for selection of redundant network device(s).

In particular, the neighborhood identification logic125determines a list of available network devices in a wireless distributed system, and identifies a plurality of network devices from the list of available network devices, where each identified network device in the plurality of network devices has a radio frequency (RF) neighborhood that includes the other network devices. For an identified network device in the plurality of network devices, a RF neighborhood of the identified network device includes the other network devices, and the other network devices are capable of hearing messages, such as beacons for example, from the network device. In other words, each identified network device in the plurality of network devices is in an RF neighborhood with other network devices that are each capable of hearing each other's messages.

Herein, as an illustrative embodiment shown inFIG. 1A, network devices1001-1003are RF neighboring network devices. The network devices1001-1003are “RF neighbors” as these devices have a similar view of a communication network. For example, network devices1001-1003are located in close geographical proximity to each other so that they are neighbors and operate in the same radio frequency environment. In some embodiments, network devices1001-1003are “RF neighbors” if client device130is able to connect to network devices1001-1003. In some embodiments, network devices1001-1003are RF neighbors if a task (e.g., a channel scanning task or a load balancing task) which can be processed by one network device1001can also be processed by the other network device1002and1003. For example, three network devices1001-1003are “RF neighbors” if the same result is produced for the same task being performed on either network device. In some embodiments, network devices1001-1003are “RF neighbors” if their radio frequency spectrums are substantially overlapped with each other.

In some embodiments, any network device in the identified plurality of network devices is an RF neighbor if it is associated with a RF spectrum that is substantially overlapped with RF spectrums of the other network devices. For example, a spectrum associated with one network device is at least 70% overlapped with a spectrum associated with the other network device constitutes an RF neighbor. In some embodiments, the plurality of network devices1001-100Mcan be identified manually. In some other embodiments, the plurality of network devices can be identified automatically.

In some embodiments of the disclosure, first network device1001generates and sends a particular message to a second network device1002that is in the RF neighborhood of the second network device1002, and the second network device1002is also in the RF neighborhood of the first network device1001. The particular messages are used to establish one or more redundancy groupings170(e.g. clique set) from the plurality of network devices1001-100Mof the RF neighborhood, where the redundancy grouping is automatically conducted under control by network device120or manually controlled.

As an exemplary embodiment, this grouping logic127can be software including routines for identifying one or more redundancy groupings (e.g. clique sets). In some embodiments, the grouping logic127can be a set of instructions executable by the processor (not shown) to provide the functionality described below for identifying one or more redundancy groupings. In some other embodiments, the grouping logic127can be stored in the memory of the network device130and can be accessible and executable by the processor (not shown). The grouping logic127may be adapted for cooperation and communication with the processor and other components of the network device120.

A “redundancy grouping” and “clique set” are generally defined as a set of network devices with any two or more network devices in the grouping (or set) being RF neighbors. In some embodiments, the redundancy grouping is a subset of RF neighbors such that each of the device is RF neighbor of each other. For instance, device A, B and C may be in an RF neighborhood such that A is in neighborhood of B and not in RF neighborhood of C (e.g. 3 APs placed in a straight line). In such case, RF neighborhood of B has both A and C but it's redundancy group can have either A or C.

In some embodiments, as shown inFIG. 1B, an undirected graph G(V, E)180is used to represent network devices available in a distributed wireless system, where the set “V” (V=5) includes all the vertices in the graph with each vertex representing one network device, and the set “E” (E=4) represents all the connection in the graph. If three network devices1001,1002and1003are RF neighbors, three vertices190,192and194representing the three network devices1001,1002and1003are connected by an undirected connections in the graph while vertices196and198represent network devices1004and1005(M=3; N=5). The redundancy grouping170(represented by a symbol “S”) is a subset of the set “V” (e.g., S is a subset of V), where any two vertices in the redundancy grouping “S” are connected (e.g., the network devices in the redundancy grouping are pair wise connected to each other). The size of the redundancy grouping “S” is the number of vertices included in the set “S.” An exemplary graph and redundancy grouping is illustrated inFIG. 1B.

According to one embodiment of the disclosure, one or more edge devices (e.g. edge devices1001-1002) from the same redundancy grouping170may be selected as for redundancy. For instance, second edge device1002may be selected to operate as a redundant edge device for first edge device1001, as thus, second edge device1002includes backup BSSes for edge device1001. Similarly, first edge device1001operates to include backup BSSes for second edge device1002as shown inFIG. 2.

Referring to bothFIGS. 1A and 2, first edge device1001is communicatively coupled to network device120which operates as a controller. Similarly, second edge device1002is communicatively coupled to network device120. According to this illustrative embodiment, both first edge device1001and second edge device1002constitute access points (APs) within the same redundancy grouping. More specifically, AP11001operates as part of a redundant grouping200with AP21002.

As further shown inFIG. 2, AP11001is configured to handle “S” identifiers210, and AP1002is also configured to handle “S” identifiers230. For illustrative purposes, the number of identifiers (S) is set as sixteen and the type of identifiers may include BSSIDs. According to one embodiment of the disclosure, AP11001is configured to support a first group of BSSIDs220(referred to as “primary BSSIDs”) along with a second group of BSSIDs225(referred to as “backup BSSIDs”). As shown, the number of primary BSSIDs220may be equal in number (eight) to the number of backup BSSIDs225, although it is contemplated that the number of primary BSSIDs220may exceed the number of backup BSSIDs225or the number of backup BSSIDs225may exceed the number of primary BSSIDs220.

Herein, AP11001has a base address “X” and AP21002has a base address “Y”. Hence, first group of BSSIDs220(starting with base BSSID “X”) is equivalent to the backup BSSIDs245within AP21002. Similarly, second group of BSSIDs225(starting with base BSSID “Y”) constitutes backup BSSIDs that are equivalent to the primary BSSIDs240within AP21002. Hence, in response to a primary BSSID221(e.g. BSSID “X”) experiencing a failover triggering event, under control by the network device120or operating independently, AP21002is now configured to support BSSID “X” previously supported by AP11001.

It is noted thatFIG. 2illustrates a redundant scheme [1:1] in which redundancy is provided by a counterpart edge device and the number of backup BSSes supported are equal in number to the number of primary BSSes supported. However, it is contemplated that multiple edge devices may provide redundancy for a corresponding AP (e.g. a first set of backup BSSes is supported by one “redundant” edge device while another set of backup BSSes is supported by another redundant edge device). Assigned with a unique identifier (e.g. MAC address or derivation thereof) normally at configuration, each edge device advertises this unique identifier in a Vendor Information Element (IE) in a broadcast message (e.g. beacon). Selection of redundant edge device is as simple as the edge device having the lowest ID operating at any point of time. For example if primary edge device has ID X and two redundant edge devices have IDs Y and Y+Z, when edge device X fails, edge device having ID Y will take over. Since all APs are hearing each other Y as well as Y+Z know the presence/absence of each other.

For instance, AP21002may be selected as a part of a redundant grouping with AP11001based on AP21002having the greater signal strength measurement for access points detected by AP11001. Alternatively, AP21002and AP31003may be selected as a part of a redundant grouping with AP11001, where both AP21002and AP31003include backup BSSIDs for primary BSSIDs associated with AP11001. As a result, in response to detecting of a failover triggering event at AP11001, the AP21002and AP31003operate as redundant APs for client devices associated with AP11001. Similarly, AP11002and AP21003include backup BSSIDs for primary BSSIDs associated with AP31002, and AP11001and AP31003include backup BSSIDs for primary BSSIDs associated with AP21002.

V. Synchronization for Transparent Failover

Referring now toFIG. 3, an exemplary embodiment of signaling in order to synchronize edge devices for transparent failover is described. Herein, a first edge device1001and the second edge device1002are communicatively coupled and operate as a redundant grouping300. As the operating states for each of the edge devices1001and1002forming the redundant grouping300frequently vary, certain state information310from edge device1001needs to be continuously shared with edge devices1002. Similarly, certain state information320from edge device1002needs to be continuously shared with edge devices1001. Such state information310and320may include, but it is not limited or restricted to two or more of the following: (1) Timing Synchronization Function (TSF) information; (2) associated Client MAC addresses; (3) client information (e.g. association identifier, power-save state, capabilities, rates, etc.); and/or (4) encryption key(s)

Herein, the TSF information is configured to maintain synchronization between the timers associated with the network devices, namely at least edge devices1001and1002. The Client MAC addresses are the MAC addresses for the client devices associated with the other edge device. For instance, edge device1001supplies to second edge device1002MAC address for the client devices associated with edge device1001. This client MAC address listing is modified continuously as associations by the client devices may vary, especially for mobile client devices.

Besides TSF information and the Client MAC addresses, edge device1001supplies client information to second edge device1002, where the client information may include one or more association identifiers (AIDs), power-saving state information associated with each client device, transmission rates associated with each client device and other client capabilities. Encryption keys need to be synchronized to enable edge device1002to decrypt information from a client device currently associated with edge device1001if the VAP associated with edge device1001fails.

Referring now toFIG. 4, an exemplary block diagram of logic associated with the edge (network) device1001is illustrated. Edge device1001comprises one or more processors400that are coupled to communication interface logic410via a first link420. Communication interface logic410enables wireless and/or wired communications with other network devices such as edge device1002, centralized network device120, or the like. According to one embodiment of the disclosure, communication interface logic410may be implemented as a physical interface including one or more ports for wired connectors. Additionally, or in the alternative, communication interface logic410may be implemented with one or more radio units for supporting wireless communications with other network devices.

Processor400is further coupled to a memory device430via a second link425. According to one embodiment of the disclosure, the memory device430, such as persistent storage for example, may include neighborhood identification logic125, grouping logic127, device-specific synchronization information310, neighboring device synchronization information320, and failover control logic450.

As described above, neighborhood identification logic125and grouping logic127are adapted to identify and establish one or more RF neighborhoods and one or more redundant groupings (e.g. cliques) associates with the RF neighborhood(s). The device-specific synchronization information310includes information associated with the first edge device1001that is continuously monitored, updated (when applicable) and provided to its corresponding redundant edge device(s) (e.g., edge device1102). The neighboring device synchronization information320associated with the second edge device1002and continuously provided therefrom.

Failover control logic450responds to a failure by another edge device that is part of the redundant grouping, normally through detection of a prolonged interruption of heartbeat messages exchanged between the edge device and other network devices. A “heartbeat message” is a periodic signal generated by hardware and/or software to indicate normal operations or synchronize different logic within a network device. For instance, according to one embodiment of the disclosure, a plurality of heartbeat messages may be used to trigger a failover event. One type of heartbeat message may be referred to as an “AP heartbeat,” which is periodic signaling between edge device1101and centralized network device120ofFIG. 2over a wired link. Another type of heartbeat message may be referred to as a “virtual AP heartbeat,” which is periodic signaling between edge device1101and its redundant grouping device (e.g. edge device1102).

For a particular BSS identified by BSSID (e.g. BSSID “Y”), if failover control logic450fails to detect the presence of an AP heartbeat and/or a virtual AP heartbeat from network device1002for “T” consecutive times intervals (e.g. “T” beacons, where T≧3), the failover control logic450determines that a heartbeat miss event has occurred, which constitutes a failover triggering event. In response to an occurrence of the failover triggering event, edge device1001activates the backup BSS identified by BSSID “Y” that is primarily handled by edge device1002. Hence, edge device1001operates as a backup AP by providing services to those client devices that were previously provided services by edge device1002without requiring client devices associated with a particular BSS (BSSID “Y”) to be disassociated from that particular BSS. Hence, by activation of the backup BSS, at least the BSS remains in service despite an operating failure by edge device1002.

Upon determining that the edge device1002has resumed being responsive and in an active status, which may be determined by repeated detection of the above-identified heartbeat messages, the primary BSS identified by BSSID “Y” is re-activated and the backup BSS (BSSID Y) maintained by edge device1001is deactivated without client devices disassociating from the BSSID “Y”.

Referring toFIG. 5, an exemplary flowchart of the enhanced VAP redundancy is shown. Initially, a redundant grouping is created in which two or more edge (network) devices operate as redundant VAPs for each other (block500). Herein, the redundant grouping includes at least a first edge device and a second edge device.

In response to a failover triggering event associated with a BSS managed by the second edge device (identified by “BSSID-Y”), the first edge device now supports BSSID-Y, namely a BSS having a backup BSSID corresponding to the failed BSSID-Y (blocks510and520). Thereafter, as an optional feature, when the backup BSS becomes active, the backup tunnels to the centralized network device (e.g., controller) also are activated as prior tunnels associated with the primary BSS are inactive (block530).

Although not shown, in response to the second edge device returning to an active status and being able to again support the backup BSS (BSSID-Y), it is contemplated that the second edge device actively supports services pertaining to BSSID-Y while the first edge device halts providing further services pertaining to BSSID-Y. Hence, the second edge device now is responsible for services requested by the associated client device(s). Of course, alternatively, first edge device may continue to actively support services pertaining to BSSID-Y until a load or capacity factor is reached by the first edge device, after which, the second edge device would regain its support of BSSID-Y and providing services to its associated client device(s).