NETWORK CONTROLLER FAILOVER REQUEST TO REDUCE NETWORK OUTAGES

[0001] The present disclosure relates to the quick transition between master and standby controllers to reduce the duration of network outages for an access point following a failure of the master network controller. In particular, the standby network controller may transmit a failover request to the access point upon detecting that the master controller has failed and without waiting for the access point to determine that the master network controller has failed.

[0002] Over the last decade, there has been a substantial increase in the use and deployment of wireless client devices, from dual-mode smartphones to tablets capable of operating in accordance with a particular Institute of Electrical and Electronics Engineers (IEEE) standard. With “wireless” becoming the de-facto medium for connectivity among users, it has become increasingly important for network systems to intelligently manage connections.

[0003] For example, access points may wirelessly associate with one or more client devices. These access points may establish tunnel connections via corresponding network controllers to provide network access to the one or more client devices. Accordingly, these access points and associated client devices rely on the network controllers to be active and operating correctly such that network access may be maintained for each access point and client device while in tunnel mode.

[0004] The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.

[0010] In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding. One or more embodiments may be practiced without these specific details. Features described in one embodiment may be combined with features described in a different embodiment. In some examples, well-known structures and devices are described with reference to a block diagram form in order to avoid unnecessarily obscuring the present invention.

[0011] Herein, certain terminology is used to describe features for embodiments of the disclosure. For example, the term “digital device” generally refers to any hardware device that includes processing circuitry running at least one process adapted to control the flow of traffic into the device. Examples of digital devices include a computer, a tablet, a laptop, a desktop, a netbook, a server, a web server, an authentication server, an authentication-authorization-accounting (AAA) server, a Domain Name System (DNS) server, a Dynamic Host Configuration Protocol (DHCP) server, an Internet Protocol (IP) server, a Virtual Private Network (VPN) server, a network policy server, a mainframe, a television, a content receiver, a set-top box, a video gaming console, a television peripheral, a printer, a mobile handset, a smartphone, a personal digital assistant “PDA”, a wireless receiver and/or transmitter, an access point, a base station, a communication management device, a router, a switch, and/or a controller.

[0012] It is contemplated that a digital device may include 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/reception) and/or a physical connector to support wired connectivity; and/or (iii) a non-transitory computer-readable storage medium (e.g., a programmable circuit; a semiconductor memory such as a volatile memory and/or 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.

[0013] Herein, the terms “logic” (or “logic unit”) are generally defined as hardware and/or software. For example, as hardware, logic may include a processor (e.g., a microcontroller, a microprocessor, a CPU core, 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, source code, 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 storage medium, or transitory computer-readable transmission medium (e.g., electrical, optical, acoustical or other form of propagated signals such as carrier waves, infrared signals, or digital signals).

[0014] Lastly, the terms “or” and “and/or” as used herein are to be interpreted as inclusive or meaning any one or any combination. Therefore, “A, B or C” or “A, B and/or C” mean “any of the following: A; B; C; A and B; A and C; B and C; A, B and C.” An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive.

[0015] Network System

[0016] FIG. 1 shows a block diagram example of a network system 100 in accordance with one or more embodiments. The network system 100, as illustrated in FIG. 1, is a digital system that may include a plurality of digital devices such as one or more access points 101₁-101_N, one or more network controllers 103₁-103_M, and one or more client devices 105₁-105_P. The access points 101₁-101_N and the network controllers 103₁-103_M may be connected through the switching fabric 107 via wired and/or wireless connections. The client devices 105₁-105_P may be connected or otherwise associated with the access points 101₁-101_N through corresponding wireless connections.

[0017] The network system 100 may be installed/distributed in any region or area. For example, the access points 101₁-101_N may be installed in an office building or another similar structure. In some embodiments, the network controllers 103₁-103_M may provide tunneling mode capabilities for the client devices 105₁-105_P. In this tunnel mode, data transmitted to/from the client devices 105₁-105_P and the access points 101₁-101_N may be encapsulated while transmitted over another network. These tunnel encapsulated data segments may be managed by the network controllers 103₁-103_M prior to forwarding to/from the client devices 105₁-105_P and the access points 101₁-101_N. Accordingly, network access for the client devices 105₁-105_P and/or the access points 101₁-101_N may rely on corresponding network controllers 103₁-103_M being active and responsive.

[0018] In some embodiments, a master network controller 103₁-103_M may be assigned to an access point 101₁-101_N along with one or more standby network controllers 103₁-103_M. The master network controller 103₁-103_M may be utilized by the access point 101₁-101_N until the master network controller 103₁-103_M fails or otherwise becomes unresponsive. Upon detecting the failure of the master network controller 103₁-103_M, the network system 100 may cause one of the standby network controllers 103₁-103_M to transition to the role of master controller. As will be described in greater detail below, the network system 100 may ensure a quick transition between a master network controller 103₁-103_M and a standby network controller 103₁-103_M when the master network controller 103₁-103_M fails such that minimal network interruption is experienced by the access point 101₁-101_N and client devices 105₁-105_P associated with the access point 101₁-101_N.

[0019] Each element of the network system 100 will now be described below by way of example. In one or more embodiments, the network system 100 may include more or less devices than the devices illustrated in FIG. 1, which may be connected to other devices within the network system 100 via wired and/or wireless mediums.

[0020] The access points 101₁-101_N may be any device that can associate with the client devices 105₁-105_P to transmit and receive data over wireless channels. Each of the access points 101₁-101_N may operate on various wireless channels (i.e., frequency segments). In one embodiment, the access points 101₁-101_N may correspond to a network device such as a wireless access point, a switch, a router, or any combination thereof. FIG. 2 shows a component diagram of the access point 101₁ according to one embodiment. In other embodiments, the access points 101₂-101_N may include similar or identical components to those shown and described in relation to the access point 101₁.

[0021] As shown in FIG. 2, the access point 101₁ may comprise one or more of: a hardware processor 201, data storage 203, an input/output (I/O) interface 205, and device configuration logic 207. Each of these components of the access point 101₁ will be described in further detail below.

[0022] The data storage 203 of the access point 101₁ may include a fast read-write memory for storing programs and data during performance of operations/tasks and a hierarchy of persistent memory, such as Read Only Memory (ROM), Erasable Programmable Read Only Memory (EPROM) and/or Flash memory for example, for storing instructions and data needed for the startup and/or operation of the access point 101₁. In one embodiment, the data storage 203 is a distributed set of data storage components. The data storage 203 may store data that is to be transmitted from the access point 101₁ or data that is received by the access point 101₁. For example, the data storage 203 of the access point 101₁ may store data to be forwarded to the client devices 105₁-105_P or to one or more of the network controllers 103₁-103_M.

[0023] In one embodiment, the I/O interface 205 corresponds to one or more components used for communicating with other devices (e.g., the client devices 105₁-105_P, the network controllers 103₁-103_M, and/or other access points 101₂-101_N) via wired or wireless signals. The I/O interface 205 may include a wired network interface such as an IEEE 802.3 Ethernet interface and/or a wireless interface such as an IEEE 802.11 WiFi interface. The I/O interface 205 may communicate with the client devices 105₁-105_P and the network controllers 103₁-103_M over corresponding wireless channels in the system 100.

[0024] In one embodiment, the I/O interface 205 facilitates communications between the access point 101₁ and one or more of the network controllers 103₁-103_M through the switching fabric 107. In one embodiment, the switching fabric 107 includes a set of network components that facilitate communications between multiple devices. For example, the switching fabric 107 may be composed of one or more switches, routers, hubs, etc. These network components that comprise the switching fabric 107 may operate using both wired and wireless mediums.

[0025] In some embodiments, the I/O interface 205 may include one or more antennas 209 for communicating with the client devices 105₁-105_P, the network controllers 103₁-103_M, and/or other wireless devices in the network system 100. For example, multiple antennas 209 may be used for forming transmission beams to one or more of the client devices 105₁-105_P or the network controllers 103₁-103_M through adjustment of gain and phase values for corresponding antenna 209 transmissions. The generated beams may avoid objects and create an unobstructed path to the client devices 105₁-105_P and/or the network controllers 103₁-103_M.

[0026] In one embodiment, the hardware processor 201 is coupled to the data storage 203 and the I/O interface 205. The hardware processor 201 may be any processing device including, but not limited to a Microprocessor with Interlocked Pipeline Stages (MIPS)/ARM-class processor, a microprocessor, a digital signal processor, an application specific integrated circuit, a microcontroller, a state machine, a field-programmable gate array (FPGA), or any type of similar type of programmable logic array.

[0027] In one embodiment, the device configuration logic 207 includes one or more functional units implemented using firmware, hardware, software, or a combination thereof for configuring parameters associated with the access point 101₁. In one embodiment, the device configuration logic 207 may be configured to establish tunnels with one or more of the network controllers 103₁-103_M and/or transmit Virtual Router Redundancy Protocol (VRRP) advertisements (e.g., “Hello” messages) to one or more of the network controllers 103₁-103_M.

[0028] As described above, the other access points 101₂-101_N may be similarly configured and designed as described above in relation to the access point 101₁. For example, the access points 101₂-101_N may each comprise a hardware processor 201, data storage 203, an input/output (I/O) interface 205, and device configuration logic 207 in a similar fashion as described above in relation to the access point 101₁.

[0029] In one embodiment, the client devices 105₁-105_P may be any wireless or wired electronic devices capable of receiving and transmitting data over wired and/or wireless mediums. For example, the client devices 105₁-105_P may be one or more of personal computers, laptop computers, netbook computers, wireless music players, portable telephone communication devices, smart phones, set-top boxes, tablet computers, and digital televisions. In one embodiment, the client devices 105₁-105_P are digital devices that include a hardware processor, memory hierarchy, and inputloutput (I/O) interfaces including a wired and/or wireless interface such as an IEEE 802.3 interface. In one embodiment, the configuration and design of the components within the client devices 105₁-105_P may be similar to those discussed above in relation to the access point 101₁. In other embodiments, the client devices 105₁-105_P may include more or less components than those shown in FIG. 2 in relation to the access point 101₁.

[0030] In one embodiment, the network controllers 103₁-103_M are digital devices that include a hardware processor, memory hierarchy, and input/output (I/O) interfaces including a wired and/or wireless interface such as an IEEE 802.3 interface.

[0031] In one embodiment, the configuration and design of the components within the network controllers 103₁-103_M may be similar to those discussed above in relation to the access point 101₁. In other embodiments, the network controllers 103₁-103_M may include more or less components than those shown in FIG. 2 in relation to the access point 101₁.

[0032] In one embodiment, the network controllers 103₁-103_M may be any set of devices that assist the access points 101₁-101_N in performing network tasks and operations. For example, the network controllers 103₁-103_M may assist the access points 101₁-101_N in providing tunneling services to the client devices 105₁-105_P. In some embodiments, the network controllers 103₁-103_M may provide redundancy to ensure that network access to the access points 101₁-101_N and the client devices 105₁-105_P is not severely impacted (e.g., network access is not lost/interrupted for an extended period of time) due to a network controller 103₁-103_M failure.

[0033] For example, as briefly described above, in some embodiments, master and standby network controllers 103₁-103_M may be assigned to a single access point 101₁-101_N or a single set of access points 101₁-101_N and corresponding client devices 105₁-105_P. For instance, as shown in FIG. 3, the network controller 103₁ may be assigned as the master network controller and the network controller 103₂ may be assigned as the standby network controller for the access point 101₁ and the client devices 105₁-105₃, which are associated with the access point 101₁. In this example, when the master network controller 103₁ fails or is otherwise unresponsive, the standby network controller 103₂ may assume the role and responsibilities of the master network controller 103₁. These responsibilities may include, but are not limited to, providing tunneling services to the access point 101₁ and the client devices 105₁-105₃ associated with the access point 101₁.

[0034] In one embodiment, this determination that the master network controller 103₁ has failed may be facilitated using the VRRP. In this embodiment, a communication path may be established between the master network controller 103₁ and the standby network controller 103₂ as shown in FIG. 3. On this communication path, the master network controller 103₁ and the standby network controller 103₂ may share a common Internet Protocol (IP) address. This common IP address may be known as the VRRP_IP. Once VRRP is enabled on the master network controller 103₁ and/or the standby network controller 103₂, the master network controller 103₁ may send a VRRP advertisement (e.g., a “hello” message) to the standby network controller 103₂, which indicates that the master network controller 103₁ owns the VRRP_IP. This ownership of the VRRP_IP will ensure that the standby network controller 103₁ does not flip state from standby to master since the VRRP_IP can be owned by only one network controller 103. In one embodiment, this VRRP advertisement may be transmitted by the master network controller 103₁ to the standby network controller 103₂ every second (i.e., the VRRP Advertisement Interval set at default of one second).

[0035] VRRP 301 operating on the standby network controller 103₂ may be used for determining the state of the master network controller 103₁ based on these VRRP advertisements. For example, upon failing to receive VRRP advertisements from the master network controller 103₁ for three consecutive seconds, VRRP 301 operating on the standby network controller 103₂ may determine that the master network controller 103₁ has failed or is otherwise unresponsive. VRRP 301 operating on the network controller 103₂ may thereafter (1) begin sending VRRP advertisements to the network controller 103₁ indicating that the network controller 103₂ owns the VRRP_IP and consequently is the new master and (2) report this status to a service access point manager (SAPM) 303 running within a station management (STM) process 305 of the standby network controller 103₂.

[0036] In one embodiment, a high availability manager 307 (i.e., HA_mgr) may be running on both the master network controller 103₁ and the standby network controller 103₂. In this embodiment, upon the access point 101₁ connecting to the master network controller 103₁ and setting up a set of corresponding tunnels, the high availability manager 307 running on the master network controller 103₁ may pass the address (e.g., the Internet Protocol (IP) address) of the standby network controller 103₂ to the access point 101₁. The access point 101₁ may use the address of the standby network controller 103₂ provided by the master controller 103₁ to establish tunnels between the access point 101₁ and the standby network controller 103₂. These tunnels between the access point 101₁ and the standby network controller 103₂ may remain inactive until the master network controller 103₁ is determined to have failed based on communications using VRRP 301 as described above and heartbeats from the access point 101₁.

[0037] For example, after VRRP 301 operating on the standby network controller 103₂ reports a failure of the master network controller 103₁ to the SAPM 303, the network controller 103₂ may change role from standby controller to master controller (i.e., the network controller 103₂ may take on the master role from the failed network controller 103₁) as described above by taking ownership of the VRRP_IP. However, the new master network controller 103₂ may not immediately activate tunnels between the network controller 103₂ and the access point 101₁. Instead, the activation of the tunnels between the network controller 103₂ and the access point 101₁ may await a failover request from the access point 101₁ before this activation change is made.

[0038] In particular, the access point 101₁ may transmit a series of heartbeat messages to each of the network controllers 103₁ and 103₂ using separate respective heartbeat tunnels. The heartbeats may be transmitted at one second intervals to each of the network controllers 103₁ and 103₂. Upon the access point 101₁ failing to receive an acknowledgement in response to a predefined number of consecutively transmitted heartbeats, the access point 101₁ may conclude that the non-responding controller 103₁ has failed. For example, in one embodiment, the threshold may be set to eight heartbeats. In this example embodiment, upon failing to receive acknowledgments to eight consecutive heartbeats transmitted to the network controller 103₁, the access point 101₁ may conclude that the network controller 103₁ has failed and in response may transmit a failover request to the network controller 103₂.

[0039] Upon receiving the failover request, the network controller 103₂, which previously determined that the network controller 103₁ had failed using VRRP advertisements and switched roles by taking ownership of the VRRP_IP, may activate previously established tunnels between the access point 101₁ and the network controller 103₂. Accordingly, the network controller 103₂ may now be fully activated as the master network controller for the access point 101₁ and associated client devices 105₁-105₃ following (1) the determination that the network controller 103₁ has failed based on the lack of VRRP advertisements transmitted between the network controller 103₁ and the network controller 103₂ and (2) the determination that the network controller 103₁ has failed using heartbeats from the access point 101₁.

[0040] In this embodiment, the access point 101₁ may experience longer than necessary network outages caused by the failed controller 103₁ as a result of the requirement that both the access point 101₁ and the network controller 103₂ must jointly determine that the network controller 103₁ has failed before transitioning to the network controller 103₂. In particular, as shown above, the access point 101₁ may only determine that the network controller 103₁ has failed after the network controller 103₁ fails to acknowledge eight heartbeats from the access point 101₁. Since heartbeats from the access point 101₁ are transmitted at one second intervals, the access point 101₁ requires at least eight seconds to determine that the network controller 103₁ has failed. In contrast, using VRRP advertisements between the network controllers 103₁ and 103₂, the network controller 103₂ may determine that the network controller 103₁ has failed after three seconds (i.e., failing to receive three VRRP advertisements from the network controller 103₁). Thus, in this embodiment, the access point 101₁ and associated client devices 105₁-105₃ may not have network access in tunnel mode for five additional seconds following the network controller 103₂ determining that the network controller 103₁ has failed. Different techniques and processes are discussed below for overcoming/mitigating these inefficiencies to reduce network outages for access points 101₁-101_N.

[0041] Network Controller Failover Request

[0042] FIG. 4 shows a method 400 according to one embodiment for intelligently and efficiently transitioning between a failed master network controller 103₁-103_M and a standby network controller 103₁-103_M to reduce network access downtime for one or more access points 101₁-101_N and associated client devices 105₁-105_P. The method 400 may be performed by one or more devices in the network system 100. For example, the method 400 may be performed by one or more of the network controllers 103₁-103_M in conjunction with one or more of the access points 101₁-101_N. In one embodiment, one of the network controllers 103₁-103_M may be designated as a master network controller for a particular access point 101₁-101_N and another network controller 103₁-103_M may be designated as a standby network controller. In this embodiment, each of the operations of the method 400 may be performed by the standby network controller 103₁-103_M.

[0043] Although each of the operations in the method 400 is shown and described in a particular order, in other embodiments, the operations of the method 400 may be performed in a different order. For example, although the operations of the method 400 are shown as being performed sequentially, in other embodiments the operations of the method 400 may be performed concurrently or during partially overlapping time periods.

[0044] The method 400 will be described in relation to the network controllers 103₁ and 103₂, which provide network access to the access point 101₁ and the client devices 105₁-105₃. However, in other embodiments, the method 400 may be performed for any combination and of network controllers 103₁-103_M that operate in a master-standby relationship to provide network access to access points 101₁-101_N and client devices 105₁-105_P.

[0045] In one embodiment, the method 400 may commence at operation 401 with a Virtual Router Redundancy Protocol (VRRP) communication path being established between a first network controller 103₁ and a second network controller 103₂. The VRRP communication path allows the transmission of VRRP advertisements (e.g., hello messages) between the first network controller 103₁ and the second network controller 103₂ such that the first and second network controllers 103₁/103₂ may determine the status of the other respective device (e.g., alive/responsive or failed/unresponsive). In one embodiment, the VRRP 301 on each of the network controllers 103₁ and 103₂ may communicate VRRP advertisements and establish/determine the status of the other device.

[0046] At operation 403 the access point 101₁ may establish a connection with the first network controller 103₁. In one embodiment, the network controller 103₁ and the access point 101₁ may establish one or more tunnels during this connection at operation 403. The tunnels may facilitate the transfer of data, including heartbeats and keep-alive messages, between the first network controller 103₁ and the access point 101₁. In one embodiment, the number of tunnels established at operation 403 may correspond to the number of virtual access points (VAPs) and/or radios operating on the access point 101₁.

[0047] Following the establishment of a connection between the first network controller 103₁ and the access point 101₁, the network controller 103₁ may transmit the address of a second network controller 103₂ to the access point 101₁ at operation 405. In this embodiment, the first network controller 103₁ may be initially used by the access point 101₁ as a master network controller while the second network controller 103₂ may be assigned as a standby network controller. As will be described in greater detail below, upon the first network controller 103₁ failing (i.e., not responding to messages transmitted from other network devices in the network system 100), the method 400 may assign the second network controller 103₂ to the role of master. In one embodiment, the address transmitted between the first network controller 103₁ and the access point 101₁ at operation 403 may be an Internet Protocol (IP) address that is transmitted through a tunnel established at operation 403.

[0048] At operation 407, the access point 101₁ may establish a set of tunnels with the second network controller 103₂ based on the address received from the first network controller 103₁ at operation 405. Similar to the tunnels established between the access point 101₁ and the first network controller 103₁ at operation 403, the tunnels established at operation 407 may facilitate the transfer of data, including heartbeats and keep-alive messages, between the second network controller 103₂ and the access point 101₁. Further, the number of tunnels established at operation 407 may correspond to the number of virtual access points (VAPs) and/or radios operating on the access point 101₁. In one embodiment, the tunnels between the second network controller 103₂ and the access point 101₁ may be set to be inactive while the tunnels between the access point 101₁ and the first network controller 103₁ may be set to be active. Accordingly, the access point 101₁ may initially utilize the first network controller 103₁ to communicate in tunnel mode; however, as will be described in greater detail below, upon failure of the first network controller 103₁, the tunnels established with the second network controller 103₂ may be utilized for network access.

[0049] At operation 409, the second network controller 103₂ may attempt to receive VRRP advertisements from the first network controller 103₁. In particular, while properly operating, the first network controller 103₁ may continually transmit VRRP advertisements to the network controller 103₂ over the VRRP communication path established at operation 401 using VRRP 301. The messages transmitted from the first network controller 103₁ to the second network controller 103₂ may indicate that the first network controller 103₁ is taking ownership of a shared VRRP_IP address and consequently is the master. Further, VRRP advertisements indicate that the transmitting network controller 103₁ is operating properly. The VRRP advertisements may be transmitted at any interval, including one second intervals, two second intervals, etc. Accordingly, the second network controller 103₂ may expect to receive VRRP advertisements at an established interval at operation 409.

[0050] At operation 411, the second network controller 103₂ may determine if VRRP advertisements have been received from the first network controller 103₁ during a threshold time period using VRRP 301. For instance, in some embodiments, the threshold time period may be three seconds. In one embodiment in which VRRP advertisements are transmitted at one second intervals, during a three second threshold time period, the second network controller 103₂ could receive up to three VRRP advertisements from the first network controller 103₁. Upon failing to receive any VRRP advertisements from the first network controller 103₁ at operation 409 during the threshold time period, operation 411 may determine that the first network controller 103₁ has failed or is otherwise unresponsive (i.e., is no longer able to transmit data). In this failed state, the network controller 103₁ may not properly operate as a master controller for the access point 101₁ and/or the client devices 105₁-105₃. In particular, the failed network controller 103₁ may be unable to transfer data in tunnel mode for the access point 101₁ and/or the client devices 105₁-105₃.

[0051] In response to receiving one or more VRRP advertisements during the threshold time period, the method 400 may return to operation 409. At operation 409, the network controller 103₂ may continue to attempt to receive VRRP advertisements such that operation 411 may continue to determine the status of the network controller 103₁.

[0052] Conversely, in response to not receiving VRRP advertisements during the predefined threshold time period and consequently determining that the first network controller 103₁ has failed, VRRP 301 of the second network controller 103₂ may switch the status of the second network controller 103₂ from standby to master at operation 413. In one embodiment, this switch of status may be performed by the second network controller 103₂ transmitting VRRP advertisements over the VRRP communication path established at operation 401. These VRRP advertisements indicate that the second network controller 103₂ (1) is taking ownership of the VRRP_IP address and thus is now the master and (2) is operating properly. Accordingly, after the first network controller 103₁ has failed, the second network controller 103₂ may takeover master status for the access point 101₁ and/or the client devices 105₁-105₃ at operation 413 using VRRP 301. Immediately after or concurrent with the change of status at operation 413, the second network controller 103₂ may transmit a failover request to the access point 101₁ at operation 415. The failover request transmitted from the second network controller 103₂ informs the access point 101₁ that the second network controller 103₂ will now be operating as the master controller.

[0053] In response to the failover request, the access point 101₁ may transmit an acknowledgment (ACK) message to the second network controller 103₂ at operation 417. In some embodiments, the second network controller 103₂ may retransmit the failover request to the access point 101₁ upon failing to receive an acknowledgment message. Upon receipt of the acknowledgment message from the access point 101₁, the second network controller 103₂ may activate the tunnels between the access point 101₁ and the second network controller 103₂, which were established at operation 407, using the high availability manager 307. Accordingly, with the transfer of status at operation 413 and the activation of the tunnels at operation 417 the second network controller 103₂ may now entirely operate as the master network controller for the access point 101₁ and/or the client devices 105₁-105₃. In particular, the new master network controller 103₂ may facilitate tunnel operations for the access point 101₁ and/or the client devices 105₁-105₃ just as the network controller 103₁ previously did.

[0054] By transmitting a failover request message from the second network controller 103₂ to the access point 101₁ upon the detection by the second network controller 103₂ that the first network controller 103₁ has failed, the method 400 reduces network access downtime for the access point 101₁ and/or the client devices 105₁-105₃. In particular, although the access point 101₁ may transmit heartbeat messages to the network controller 103₁ to determine the status of this device (i.e., determine whether the network controller 103₁ has failed or is otherwise non-responsive), the method 400 does not wait or rely on this determination before initiating a role transfer between the first network controller 103₁ and the second network controller 103₂ (i.e., transfer of master role). Since the status determination made by the access point 101₁ may take longer than the status determination made by the controller 103₂, by not relying on this longer determination the method 400 reduces the time before a role transfer may be initiated. For example, the access point 101₁ may require eight consecutive unacknowledged heartbeats that are each separated by one second before indicating a network controller 103₁ failure while the network controller 103₂ may only require failure to receive three VRRP advertisements each separated by a second from the network controller 103₂ before indicating a network controller 103₁ failure. By reducing the time period before triggering a role transition between the failed first network controller 103₁ and the operating second network controller 103₂, the method 400 reduces network access down time for the access point 101₁ and/or the associated client devices 105₁-105₃ while operating in a tunnel mode.

[0055] Although described in relation to a single access point 101₁ associated with the first and second network controllers 103₁ and 103₂, which respectively function as master and standby controllers, in other embodiments the method 400 may operate in relation to multiple access point 101₁-101_N. In particular, the first and second network controllers 103₁ and 103₂ may simultaneously operate as master and standby for two or more of the access points 101₁-101_N. In this embodiment, the failover request transmitted at operation 415 may be sent from the second network controller 103₁ to each of the access points 101₁-101_N connected to the failed first network controller 103₁. In this fashion, the method 400 may efficiently operate to transition between a failed master network controller 103₁-103_M and a standby network controller 103₁-103_M to reduce network access downtime for multiple more access points 101₁-101_N and associated client devices 105₁-105_P.

[0056] An embodiment of the invention may be an article of manufacture in which a machine-readable medium (such as microelectronic memory) has stored thereon instructions which program one or more data processing components (generically referred to here as a “processor”) to perform the operations described above. In other embodiments, some of these operations might be performed by specific hardware components that contain hardwired logic (e.g., dedicated digital filter blocks and state machines). Those operations might alternatively be performed by any combination of programmed data processing components and fixed hardwired circuit components. Also, although the discussion focuses on uplink medium control with respect to frame aggregation, it is contemplated that control of other types of messages are applicable.

[0057] Any combination of the above features and functionalities may be used in accordance with one or more embodiments. In the foregoing specification, embodiments have been described with reference to numerous specific details that may vary from implementation to implementation. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indicator of the scope of the invention, and what is intended by the applicants to be the scope of the invention, is the literal and equivalent scope of the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction.