Anticipatory handoffs in networks on mobile platforms

Abstract

A routing device for installation on a mobile platform is connected to a plurality of wireless access devices for wireless interconnection with a wide area network (WAN). The routing device routes traffic to the WAN through an active wireless access device among the wireless access devices. The routing device monitors the connection quality between each wireless access device and the WAN, and in response to a measure of the connection quality of the wireless access device at the active port falling below a threshold, reconfigures the routing device to route data traffic to the WAN through a wireless access device at a target port among the ports that is different from the active port among the ports.

Description

Technical Field

[0001] This involves computer networking, and in particular wirelessly connecting to a network from a physical mobile platform such as a vehicle. Background Art

[0002] Computer networks are often configured in a hierarchical structure: a local area network (LAN) can serve and interconnect devices in a relatively small physical area, and devices called gateways can interface a LAN with other networks (such as other LANs) or wide area networks (such as a private WAN or an internetwork).

[0003] Some LANs may be installed on mobile platforms, such as vehicles. For example, LANs may be installed in cars, trucks, buses, ships, trains and railcars, airplanes, etc. Such LANs may serve devices such as control, telemetry or other operating systems, occupant computing devices, etc.

[0004] In some applications, it may be desirable to interface a LAN on a mobile platform (also referred to herein as a mobile network) with a fixed network such as a cellular network. However, maintaining a connection between a fixed device and a physical mobile device can present challenges.

[0005] For example, wireless access devices such as WiMAX stations, cellular modems, smartphones, etc. often experience bandwidth or connectivity degradation and may switch between base stations when they approach the boundary between the service areas of two base stations. The switching process is called handover or handoff. Unfortunately, the handover process can result in temporary loss of connectivity or data packet loss while the handover is negotiated and completed. Summary of the invention

[0006] An example networking infrastructure for accessing a wide area network (WAN) from a mobile platform includes: a plurality of wireless access devices for wirelessly interconnecting with base stations of the wide area network (WAN), wherein the wireless access devices switch between base stations when the connection deteriorates; a routing device having an interface connected to each corresponding wireless access device and an interface for connecting to a client device, the routing device being configured to route traffic to the WAN via an active wireless access device among the wireless access devices; and a processor at the routing device being configured to: monitor a measure of connection quality between the active wireless access device and the WAN; and in response to the measure of connection quality of the active wireless access device falling below a threshold, reconfigure the routing device to route data traffic to the WAN via a target wireless access device different from the active wireless access device among the wireless access devices.

[0007] A routing device for installation on a mobile platform, comprising: a plurality of ports for connecting to wireless access devices for wireless interconnection with base stations of a wide area network (WAN), wherein when the connection deteriorates, the wireless access devices switch between base stations, and the routing device is configured to route services to the WAN through the wireless access devices at active ports among the ports; an interface for connecting to a client device, the routing device is configured to route services to the WAN through the wireless access devices at active ports among the ports; and a processor configured to: monitor a measure of connection quality between the wireless access devices at the active ports among the ports and the WAN; and in response to the measure of connection quality of the wireless access devices at the active ports dropping below a threshold, reconfigure the routing device to route data services to the WAN through a wireless access device at a target port among the ports that is different from the active port among the ports.

[0008] A method of routing in a computing network, comprising: at a routing device, configuring a data path to direct data traffic toward a wide area network (WAN) through a first wireless access device; monitoring a measure of connection quality between the first wireless access device and the WAN; and in response to the measure of connection quality of the first wireless access falling below a threshold, reconfiguring the data path to route the data traffic to the WAN through a second wireless access device that is different from an active port in the ports. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In the accompanying drawings that illustrate example embodiments:

[0010] Figure 1 is a schematic diagram of the network on a mobile platform;

[0011] Figure 2 yes Figure 1 Schematic diagram of network topology;

[0012] Figure 3 yes Figure 1 A block diagram of a routing device of a network;

[0013] Figure 4 yes Figure 3 A block diagram of a processing unit at a routing device;

[0014] Figure 5 is used to rate the quality of the connection. Figure 3 a representation of a data structure at a routing device;

[0015] Figure 6 Is a description Figure 3 A flowchart of the operating state of the route selector of the routing device;

[0016] Figure 7is described in Figure 3 A flowchart of a networking method executed at a routing device;

[0017] Figure 8A-8C is described in Figure 3 A flowchart of a routing selection method executed at a routing device;

[0018] Fig. 9 is described in Figure 3 A flowchart of a method for switching a wireless network connection executed at a routing device. DETAILED DESCRIPTION

[0019] Figure 1 A network environment 100 is depicted that includes a mobile platform, namely a train 102 .

[0020] A plurality of computing or communication assets are installed on the train 102, and they are interconnected via a LAN 104. The LAN 104 may be referred to herein as a local area network (LAN).

[0021] As will be described in further detail, LAN 104 interconnects another network. The other network may be, for example, a wide area network (WAN) 106, such as the Internet, or a private wide area network (private WAN).

[0022] WAN 106 includes base stations 108-1, 108-2 (individually or collectively referred to as base stations 108). Although two base stations 108 are shown, it should be understood that WAN 106 can include any number of base stations 108. Base stations 108 are fixed and can use any suitable wireless networking technology. For example, in the described embodiment, base stations 108 are WiMAX stations. In other examples, base stations 108 can communicate using cellular technology, such as GSM, GPRS, EDGE, UMTS, LTE, etc.

[0023] Each base station serves a specific physical area, which may be referred to as a cell. Base stations 108 and their respective cells are fixed in space. When train 102 moves, it passes through the cells.

[0024] LAN 104 is a routed Internet Protocol (IP) network that includes devices connected by Ethernet links and wireless technologies such as IEEE 802.11 (Wi-Fi).

[0025] LAN 104 includes a routing device 110, a plurality of client devices such as wired client device 112 and wireless client device 114 (collectively, client devices), and wireless access devices 116-1, 116-2, 116-3 (individually or collectively, wireless access devices 116).

[0026] In the depicted example, the wired client 112 is the control and telemetry system of the train 102. The client 112 may receive operating instructions, etc. from devices on the WAN 106, and may return data, such as telemetry and status data, to devices on the WAN 106. Obviously, such data communications may significantly contribute to the safe and efficient operation of the train 102. In addition, such data communications may be highly time sensitive. For example, data related to hazards, etc. may be received in near real time. Obviously, such real-time communications may require a substantially uninterrupted connection to the devices on the WAN 106.

[0027] LAN 104 may also include one or more wireless clients 114 connected to routing device 110 via a wireless link (e.g., IEEE 802.11 Wi-Fi). Wireless clients 114 may include, for example, vehicle control or telemetry devices, or devices of vehicle occupants. Such clients may include, for example, mobile computing devices such as laptops, smart phones, tablets, etc.

[0028] The routing device 110 is interconnected with the wireless access device 116 for exchanging data with the WAN 106. In the depicted embodiment, the wireless access devices 116-1, 116-2 are WiMAX subscriber stations configured to communicate with corresponding base stations 108-1, 108-2 in the WAN 106. Alternatively or additionally, the wireless access device 116 can be a cellular (e.g., LTE) modem. It will be apparent to a skilled person that other suitable RF networking technologies can be used. The wireless access device 116-3 is a backup device and is connected to a different base station using a different technology than the base stations 116-1, 116-2. For example, as depicted, the wireless access devices 116-1, 116-2 are WiMAX stations and the wireless access device 116-3 is a cellular modem. The wireless access device 116-3 can be interfaced with the WAN 106 indirectly (e.g., on a public WAN (such as the Internet)) via a virtual private network (VPN). Obviously, providing multiple types of wireless access devices 116 for connecting with multiple types of base stations 108 can facilitate robust connectivity with the WAN 106 .

[0029] As described above, as the train 102 moves, it passes through cells served by successive base stations 108. Therefore, the quality of the connection between a given wireless access device 116 and the corresponding base station may vary over time. At the edge of a cell served by a particular base station 108, the wireless access device may need to switch to another (e.g., closer) base station. Typically, the decision to decide when to implement a handoff is handled by the base station 108 or the access device 116. As described in further detail below, the routing device 110 is configured to monitor the quality of the connection and switch to using another wireless access device 116 before a handoff or handoff attempt occurs. In other words, the routing device 110 can avoid a connection interruption by predicting a connection loss at a first access device and switching to a second device before the connection loss occurs.

[0030] Figure 2 Example topologies of networks 104, 106 and devices in those networks are depicted in greater detail.

[0031] In the illustrated embodiment, the routing device 110 has a plurality of routing Ethernet ports 120. Four ports 120 are shown, labeled ports 120-1, 120-2, 120-3, 120-4. However, there may be more or fewer ports. The routing device 110 may also have one or more wireless (e.g., Wi-Fi) interfaces 121.

[0032] Port 120-1 connects wired client 112 to routing device 110. Ports 120-2 and 120-3 connect wireless access devices 116-1 and 116-2 to routing device 110, respectively. Port 120-4 is a backup port for connecting a backup access server, such as an LTE modem. Wireless interface 121 connects wireless client 114 to routing device 110.

[0033] In the described embodiment, the devices of LAN 104 are divided into two logical groups, referred to as subnets.

[0034] The first subnet includes clients 112 and 114 and the routing ports of the routing device 110 to which they are connected.

[0035] The second subnet includes the wireless access devices 116 and the routing ports of the routing device 110 to which they are connected.

[0036] The two subnets may be defined by IP addresses of different devices, such as, for example, IP addresses assigned by routing device 110. Specifically, client devices 112, 114 and their respective ports of routing device 110 may be assigned IP addresses within a first network range, such as, for example, 11.1.1.*. Wireless access device 116 may be assigned an IP address within a second network range, such as, for example, 192.168.*.*. For example, in the depicted embodiment, wired client 112 is assigned IP address 11.1.1.1 / 16, and physical port 120-1 of routing device 110 associated therewith is assigned IP address 11.1.1.2 / 16. Wireless access device 116-1 is assigned IP address 192.168.100.1 / 16, and physical port 120-2 of routing device 110 associated therewith is assigned IP address 192.168.100.2 / 16. Wireless access device 116-2 is assigned IP address 192.168.50.1 / 16, and physical port 120-3 associated therewith of routing device 110 is assigned IP address 192.168.50.2 / 16. In the described embodiment, separate subnets 192.168.*.* and 11.1.1.* are used to separate LAN clients (on subnet 11.1.1.*) and devices involved in the management of access device 116 (subnet 192.168.*.*).

[0037] The routing device 110 provides communication between devices by defining data paths for data packets according to the packet destination. In the depicted embodiment, each client and wireless access device 116 has a unique IP address. The data path is defined by a routing policy, i.e., one or more tables or other structures that identify routing paths for various destination addresses. The routing policy can define a default route, i.e., an IP address to which all data packets will be forwarded unless otherwise specified in the policy. For example, a default route can be applied to packets with all destination addresses outside of the LAN 104.

[0038] As shown, the wireless access devices 116 are connected via RF wireless links to corresponding base stations 108 that form part of the WAN 106. The base stations 108 are also connected to one or more client devices 124.

[0039] The client device 124 may be, for example, a backend computing device used to exchange data, such as control and telemetry data, with devices on the train 102 .

[0040] In the depicted embodiment, WAN 106 is a private WAN. Devices on WAN 106 are assigned addresses in the network range 10.1.1.* / 16.

[0041] The wireless access device 116 forms part of the LAN 104 and part of the WAN 106. That is, the wireless access device 116 is assigned an IP address within the LAN 104 and the WAN 106 and is capable of forwarding data packets from the WAN 106 to the LAN 104 and vice versa. Thus, the wireless access device 116 is capable of interconnecting the client devices 112, 114 with other devices in the WAN 106. As described above, the wired client 112 may be responsible for critical functions, such as control, telemetry, or security functions, which may require a connection with the client device 124. To help maintain the connection, the wireless access device 116 uses a reporting protocol that is continuously or periodically executed by a processor at the wireless access device.

[0042] Figure 3-Figure 4 Components of an example routing device 110 are depicted in greater detail. Figure 3 As shown, routing device 110 includes processor 130, storage device 132, memory 134, wired interface such as Ethernet interface 136, and wireless radio 138 such as LTE radio. Figure 4 are representative examples, and other configurations of routing devices are possible.

[0043] Processor 130 may be a general purpose computer processor, such as an ARM or x86 based processor, and may operate under the control of software stored in storage device 132. Alternatively, processor 130 may include an application specific integrated circuit (ASIC) for performing some or all of the functions described herein.

[0044] Figure 4 An example processing unit 150 is depicted at routing device 110. Processing unit 150 may be a software component that configures processor 130 to perform the functions described herein. Alternatively or additionally, some or all of processing unit 130 may be implemented directly in hardware, for example, by a specialized ASIC.

[0045] The processing unit 150 includes a monitoring engine 152 , a routing selector 154 , and a switching manager 156 .

[0046] The monitoring engine 152 is responsible for obtaining measurements of the quality of the connections between the wireless access devices 116 and their respective base stations 108. In one example, the monitoring engine 152 periodically polls each wireless access device 116 for an indication of the connection status. Each wireless access device is assigned a score based on the connection status. Figure 5 An example data structure 160 defining a scoring system is depicted.

[0047] like Figure 5As shown, each connection is assigned a score based on the modulation scheme used for the connection. The modulation scheme used itself depends on the quality of the connection between the wireless access device 116 and the base station 108. That is, a stronger signal with relatively less noise will support a more efficient or higher rate modulation scheme, while a weaker or noisier signal may require the use of a robust modulation scheme with less data throughput.

[0048] In the depicted example, the connection is scored on a 25-point scale based on the downlink modulation data rate of the wireless access device 116. The highest 25 points are assigned to the connection with the highest data rate. In the described example, the highest data rate modulation is 64QAM 5 / 6, i.e., the highest modulation possible in the IEEE 802.11n standard. However, in other examples, higher rates may be available, for example, via an 802.11ac wireless link. For each modulation, the score is reduced by one point. A score below 10 indicates a disconnected state. If a handover of the wireless access device 116 is in progress or about to begin, the score may be further reduced, for example, by 2 points.

[0049] In some embodiments, the scoring of the connection is done at the routing device 110. In such an embodiment, the monitoring engine 152 can periodically poll the wireless access device 116, which can report parameters indicating the strength or quality of the connection. For example, the device 116 can report the modulation type. The monitoring engine 152 can then assign a score by looking it up in the data structure 160.

[0050] In other embodiments, the scores may be assigned at the devices 116. That is, the monitoring engine 152 may periodically poll the devices 116, which may be configured to determine the scores based on a lookup in a copy of the data structure 160 stored locally at each device 116.

[0051] Thus, the assigned score is a measure of the quality of the connection. In some embodiments, the score may be used for the modulation type. Additionally or alternatively, the score may take into account other factors. Possible factors include, for example, signal-to-noise ratio, signal strength, and bit error rate.

[0052] In the depicted embodiment, scores below 10 are interpreted as indicating a disconnected state. However, in some embodiments, scores below 10 may be used to indicate discrete connection strengths. For example, the scoring system may provide more levels, i.e., from 0-25 instead of 10-25.

[0053] Each wireless access device 116 may be polled individually. That is, a separate processing thread may be responsible for polling each wireless access device 116. Alternatively, all wireless access devices 116 may be polled simultaneously, which may be triggered by a single processing thread.

[0054] The monitoring engine 152 is configured to provide an output message to the router 154 after the polling is completed. The output message contains the reported score and the identifier of the wireless access device to which the score corresponds. For example, the output may include a score pair with a corresponding IP address. If the wireless access devices 116 are polled individually from separate processing threads, individual scores may be provided to the router 154. Alternatively, if the wireless access devices 116 are polled together, a single output message containing multiple scores may be provided.

[0055] The route selector 154 is configured to receive the score output from the monitoring engine 152 and define a data path by selecting a wireless access device 116 to interconnect the LAN 104 with the WAN 106 , referred to as an active wireless access device 116 .

[0056] When the wireless access device is selected as the active wireless access device, the routing selector directs outbound traffic to the WAN 106 through the active wireless access device 116. For example, an IP routing table at the routing device may define a default route to the active wireless access device 116.

[0057] In the depicted embodiment, the route selector 154 is configured as a state machine. That is, the route selector 154 can operate in different states, and depending on the state of the route selector 154, the route selector can apply one of a variety of algorithms to select the wireless access device 116.

[0058] Figure 6 1 is a schematic diagram of the states of the router 154. As shown in the figure, the router has three states 162, 164, 166.

[0059] State 162 is an initialization state in which an active wireless access device is selected based on a physical port at routing device 110. For example, the default active wireless access device may be a device on a particular port 120 of routing device 110.

[0060] State 164 is a state in which one of the wireless access devices 116 is selected as active based on its connection strength score (as provided by monitoring engine 152).

[0061] State 166 is a standby state in which a standby connection to the network is used in the event that no wireless access device 116 provides a sufficiently strong connection (ie, no device 116 has a connection score above a minimum threshold).

[0062] The route selector 154 periodically receives updates to the connection score from the monitoring engine 152. At each update, the route selector 154 compares the received score with the threshold and the value of the currently active wireless access device. Based on these comparisons, the route selector 154 can select a new active wireless access device 116 and can transition to a new state 162, 164, 166. Specifically, the route selector 154 can decide when to select a new active wireless access device 116 depending on an upper threshold and a lower threshold. The lower threshold can be the minimum acceptable connection quality of the currently active wireless access device 116. That is, the route selector 154 can select a new wireless access device 116 in the event that the signal quality of the currently active wireless access device 116 drops below the lower threshold. The upper threshold can be the minimum acceptable connection quality of the new target wireless access device 116. That is, the route selector 154 can only transition to the new wireless access device 116 if the signal quality of the new wireless access device 116 is at least higher than the upper threshold.

[0063] The lower threshold and the upper threshold may be referred to as tuning values ​​because they may be used to tune the performance of routing device 110 .

[0064] In particular, connection quality is generally inversely related to the likelihood that a connection will be dropped or handed off to a new base station. Thus, increasing the lower threshold will tend to increase the frequency of handoffs and reduce the likelihood that a handoff or a drop in connectivity will occur before a handoff is made.

[0065] Similarly, the quality of the connection to the new target wireless access device 116 is generally related to the length of time that the connection is likely to remain of acceptable quality. Thus, increasing the upper threshold may tend to reduce the bouncing of the connection, i.e., making short-lived connection changes, but may reduce the likelihood of a successful transition before the connection is dropped or switched.

[0066] The router 154 is configured to provide an outgoing message to the transition manager 156. The outgoing message includes an identification of the wireless access device 116 that is targeted for use as the active wireless access device 116.

[0067] The switch manager 156 is triggered by an output message from the router 154 .

[0068] The switching manager 156 is configured to establish a connection for the new active wireless access device and switch the route to the new active wireless access device before disconnecting the connection of the previous wireless access device. This may be referred to as a switch-before-break strategy.

[0069] Figure 7 An example routing method 700 performed at a routing device 110 is depicted.

[0070] At block 710, routing device 110 is initialized. As part of the initialization process, routing device 110 is set to initialized state 162 ( Figure 6 ), and based on the port of the routing device 110 to which the wireless access device 116 is attached, the wireless access device 116 is selected as the active wireless access device. In the depicted embodiment, the device 116-1 is selected. For example, by setting the default route set in the routing table of the device 110 that lists the IP address of the device 116-1 as the next hop, the data packets directed to the address outside the LAN 104 are sent to the device 116-1.

[0071] At block 720, the monitoring engine 152 polls the wireless access device 116 for connection status information. The wireless access device 116 determines the connection strength score locally from the data structure 160 and returns the score, or returns data, such as modulation type, based on which the monitoring engine 152 assigns a score. The polling at block 720 may occur periodically, for example, based on a clock at the routing device 110. The score may be recorded in the data structure for comparison with subsequent scores.

[0072] At block 730, the monitoring engine 152 determines whether any received scores are different from previously recorded scores. If not, the process returns to the polling at block 720. If any changes occur, a prompt is provided to the route selector 154 along with the updated score data.

[0073] At block 740, the route selector 154 evaluates the updated connection score and makes a routing decision based on the current one of its three operating states 162, 164, 166 ( Figure 6 ). Fig. 8A , Figure 8B and Figure 8C The processes performed by the router 154 in its initialization state 162, active connection state 164, and standby state 166 are depicted separately. For clarity, operations in the initialization state are indicated as 740-1, 740-2, etc.; operations in the active connection state are indicated as 740'-1, 740'-2, etc.; and operations in the standby state are indicated as 700"-1, 700"-2, etc.

[0074] As described above, following initialization of routing device 110, router 154 is in its initialization state 162.

[0075] refer to Fig. 8A At block 740 - 1 , the routing selector 154 receives a connection score from the monitoring engine 152 .

[0076] At block 740-2, the route selector 154 determines whether any received score is valid. For example, an invalid score may be caused by an error in the monitoring process. If no valid score is received, the selection process terminates at block 740-3 without changing the wireless access device 116 or transferring the route selector 154 from the initialization state.

[0077] At block 740-4, the route selector 154 identifies the highest received connection score. At block 740-5, the route selector 154 determines whether the highest score is above the upper adjustment threshold. If so, at block 740-6, the route selector 154 targets the wireless access device 116 with the highest score. At block 740-7, the route selector 154 transitions to the active connection state 164 ( Figure 6 ).

[0078] Alternatively, if the highest connection score is below the upper adjustment threshold, then at block 740 - 8 , the backup wireless access device 116 - 3 is targeted, and at block 740 - 9 , the route selector 154 transitions to the backup state 166 .

[0079] refer to Figure 8B , in the active connection state, at block 740'-1, the route selector 154 receives the score of the wireless access device 116. At block 740'-2, the route selector 154 identifies the score of the currently active wireless device, and at block 740'-3, the route selector 154 evaluates the score of the currently active wireless device 116 (e.g., device 116-1) and compares it to the lower adjustment threshold (minimum acceptable connection score).

[0080] A score above the lower adjustment threshold indicates that the currently active wireless access device 116 is providing a satisfactory (e.g., fast enough) connection to the WAN 106, and an attempt to switch the currently active wireless access device 116 between base stations may not occur immediately. Therefore, if the score of the current wireless access device is above the minimum threshold, the current access device is maintained. The process terminates at block 740'-4 without targeting a new wireless access device and without transferring the route selector 154 from the active connection state.

[0081] A score below the lower adjustment threshold indicates that the currently active wireless access device 116 is not providing adequate connectivity, or that a handoff or attempted handoff of the active wireless access device 116 may occur soon. Therefore, a transition to another wireless access device 116 may occur to maintain connectivity.

[0082] At block 740'-5, the routing selector 154 identifies the highest received connectivity score, and at block 740'-6, compares the score to an upper adjustment threshold. A score below the upper adjustment threshold indicates that the connection quality is marginal, and switching to the associated wireless access device may result in another switch shortly thereafter. In other words, switching to a wireless access device 116 with a poor connection may result in frequent hopping between devices. Such hopping may impose unnecessary computational overhead on the routing device 110, and may create or increase the risk of lost data packets.

[0083] At block 740'-7, if the highest score is above the upper adjustment threshold, the corresponding device 116 is targeted for transition as the new active device. At block 740'-8, the process ends without transitioning out of the active connection state.

[0084] Conversely, if the highest score is not above the upper adjustment threshold, the route selector 154 returns to the standby access device 116-3. At block 740'-9, the standby device 116-3 is targeted for conversion as the new active device. At block 740'-10, the route selector 154 switches to its standby state 116 ( Figure 6 ).

[0085] refer to Figure 8C , in the standby state 166, at box 740"-1, the routing selector 154 receives the connection score from the monitoring engine 152, and at box 740"-2, the routing selector 154 determines the highest score.

[0086] At box 740"-3, the route selector 154 compares the highest score to a minimum value (i.e., a lower adjustment threshold). If the highest score is below the minimum threshold, then no wireless access device 116 has sufficient connection quality. Therefore, the backup access device 116 continues to be used, and the selection process ends at box 740"-4 without the route selector 154 exiting its backup state 166.

[0087] Alternatively, if the highest connection score is greater than the upper adjustment threshold, then at least one access device 116 has sufficient connection quality. At block 740"-5, the wireless access device 116 with the highest connection score is targeted to become active.

[0088] At block 740"-6, the router 154 transitions to its active connection state 164.

[0089] refer to Figure 7, at block 750, the transition manager 156 determines whether a transition to a new active access device is required. Specifically, if access device 116 or 117 is targeted at block 740, the transition manager 156 determines whether the target device is different from the current active device. If the target device is the same, or if no device is targeted, the process returns to block 720, and the monitoring engine continues periodic polling of access device 116. If the target access device 116 is different from the current active device, then at block 760, the transition manager 156 performs the access device transition.

[0090] Fig. 9 The conversion process performed by the conversion manager 156 at block 760 is depicted.

[0091] At block 760-1, the transition manager 156 assigns the external IP address associated with the LAN 104 to the target wireless access device 116. Figure 2 In the network topology of , the IP address range of WAN 106 is 10.1.*.* and LAN 104 has an external IP address 10.1.1.2, at which devices on WAN 106 can access devices on network 102. To switch to wireless access device 116-2, external IP address 10.1.1.2 is assigned to wireless access device 116-2.

[0092] At block 760-2, neighboring hardware address information (such as an address resolution protocol (ARP) table containing hardware addresses (e.g., MAC addresses) of neighboring network devices) is copied from the currently active wireless access device to the target device. Figure 2 In the topology of FIG. 1 , in order to switch to the wireless access device 116 - 2 , the ARP table is copied from the interface 120 - 2 to the interface 120 - 3 .

[0093] At block 760-3, the routing policy at the routing device 110 is updated. Specifically, the route to the WAN 106 through the currently active wireless access device 116 is edited to instead go through the target wireless access device 116. In some embodiments, the default route of the routing device 110 may be set to define the target wireless access device 116 as the next hop for packets destined for addresses outside the LAN 104. Thus, the update of the routing policy results in traffic being routed to the WAN 106 through the target wireless access device 116.

[0094] At block 760-4, the external IP address assigned at block 760-1 is removed from the previous wireless access device 116. Figure 2In the example of , IP address 10.1.1.2 is removed from wireless access device 116-1. Removing the external IP address from the previous access device ensures that new incoming data packets sent to devices within LAN 104 are routed to network 114 through new target wireless access device 116-2.

[0095] In block 760-5, in order to ensure that the routing of data packets inbound to the LAN 104 is completed correctly, a message is sent to synchronize the hardware address data of the neighboring network devices with the hardware address of the new (target) wireless access device. For example, an ARP message may be sent to synchronize downstream network nodes, switches, etc., with their tables (such as ARP tables, filtering databases, etc.) with the MAC address of the new wireless access device 116-2.

[0096] As described above, the connection between each wireless access device 116 and the base station 118 is substantially continuously monitored through periodic polling. Monitoring of connection quality, rather than simply monitoring connectivity, allows the routing device 110 to preempt a handoff or attempted handoff of an active wireless access device between base stations, limiting or avoiding connectivity loss caused by the handoff or attempted handoff. In other words, the routing device 110 can anticipate an attempt to handoff an active wireless access device and the accompanying loss of connectivity of that access device, and can switch routing to the new access device in order to seamlessly maintain client connectivity.

[0097] Unnecessary computation and network overhead may be limited by the polling interval and the upper and lower thresholds for the connection score. For example, the polling interval may be related to the speed at which the quality of the connection tends to change in a particular application, which may be affected by the speed of the mobile platform in which the access device is installed and the area served by the base stations of the WAN. The lower adjustment threshold affects the tendency of routing devices to switch between access devices. The upper adjustment threshold reduces the likelihood of a transition to an access device, shortly thereafter where the quality of the connection provided by the access device is insufficient and a further transition is required. Therefore, the network overhead associated with making transitions can be limited by raising the upper and lower adjustment thresholds. In one example, polling occurs at intervals of 500 milliseconds, and the upper and lower adjustment thresholds are 13 and 17, respectively.

[0098] The above examples are described with reference to IP addresses in IPv4 format. Obviously, other types of addresses (such as IPv6 addresses) may be substituted.

[0099] As described above, the wireless access device 116 has a unique IP address in the LAN 104, and the selection of the data path is completed by IP routing. In other embodiments, different methods can be used to complete the selection of the data path. For example, the wireless access device 116 can be a modem, such as a WiMAX or cellular modem, and can be connected to the routing device 110 via USB or other suitable interconnection. In such an embodiment, the selection of the path can be completed by activating a specific USB port to access the WAN 106 using the modem connected thereto.

[0100] The above embodiments are intended to be illustrative only and not restrictive. The described embodiments for implementing the invention are susceptible to many modifications in form, arrangement of parts, details and sequence of operations. Other variations are also possible. The invention is defined by the claims.

[0101] When introducing elements of the present invention or embodiments thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements besides the listed elements.

Claims

1. A networking infrastructure for accessing a wide area network (WAN) from a mobile platform, comprising: a plurality of wireless access devices for wirelessly interconnecting with base stations of the wide area network (WAN), wherein the wireless access devices switch between base stations when the connection deteriorates; a routing device having an interface connected to each respective one of the wireless access devices and an interface for connecting to a client device, the routing device being configured to route traffic to the WAN via an active one of the wireless access devices; as well as The processor at the routing device is configured to: monitoring a metric of a connection quality between the active wireless access device and the WAN; as well as In response to the metric of the connection quality of the active wireless access devices falling below a lower threshold and the highest metric of the connection quality of the wireless access devices being above an upper threshold, reconfiguring the routing device to route data traffic to the WAN via a target wireless access device corresponding to the wireless access device having the highest metric of connection quality among the wireless access devices.

2. The networking infrastructure of claim 1, wherein: The processor is configured to monitor a measure of a connection quality between each of the wireless access devices and the WAN.

3. The networking infrastructure of claim 1, wherein: The processor is configured to preempt a handover of the active wireless access device by routing data traffic through the target wireless access device during a handover of the active wireless access device.

4. The networking infrastructure of claim 1, wherein: The routing device includes a routing policy that directs data traffic through the WAN through the active ones of the wireless access devices.

5. The networking infrastructure of claim 4, wherein: The processor is configured to reconfigure the routing device by updating a default route in the routing policy in response to the measure of the connection quality of the active wireless access device falling below a lower threshold.

6. The networking infrastructure of claim 1, wherein: The processor is configured to monitor the wireless access device by periodic polling.

7. The networking infrastructure of claim 1, further comprising a backup wireless access device connected to an interface of the routing device, wherein: The processor is configured to reconfigure the routing device to direct traffic to the WAN through the backup wireless access device in response to the measure of the connection quality of the active wireless access device falling below a lower threshold and the measure of the connection quality of the active wireless access device falling below an upper threshold of all the wireless access devices, wherein the lower threshold is the minimum acceptable connection quality of the current active wireless access device and the upper threshold is the minimum acceptable connection quality of the target wireless access device.

8. The networking infrastructure of claim 1, wherein: The wireless access device is a WiMAX access device.

9. The networking infrastructure of claim 8, wherein: The WAN is a dedicated WAN.

10. A routing device for installation on a mobile platform, comprising: a plurality of ports for connecting to wireless access devices for wireless interconnection with base stations of a wide area network (WAN), wherein the wireless access devices switch between base stations when the connection deteriorates, and the routing device is configured to route traffic to the WAN through the wireless access devices at active ones of the ports; An interface for connecting to a client device; and The processor is configured as: monitoring a metric of a quality of a connection between the wireless access device at the active one of the ports and the WAN; and In response to the metric of the connection quality of the wireless access device at the active port falling below a lower threshold and the highest metric of the wireless access devices at the port being above an upper threshold, reconfiguring the routing device to route data traffic to the WAN through a wireless access device at a target port among the ports corresponding to the wireless access device having the highest metric of connection quality among the wireless access devices.

11. The routing device according to claim 10, wherein: The processor is configured to monitor a measure of connection quality of a wireless access device connected to each of the ports, the measure of connection quality representing a quality of a connection between the corresponding wireless access device and the WAN.

12. The routing device according to claim 10, wherein: The processor is configured to route data traffic through the wireless access device at the target port during a handoff of the wireless access device at the active port.

13. The routing device according to claim 10, wherein: The routing device includes a routing policy that directs data traffic through the WAN via the wireless access device at the active port.

14. The routing device according to claim 13, wherein: The processor is configured to reconfigure the routing device by updating a default route in the routing policy in response to the measure of the connection quality of the wireless access device falling below a lower threshold.

15. The routing device according to claim 10, wherein: The processor is configured to monitor a wireless access device at the port by periodic polling.

16. The routing device according to claim 10, further comprising a spare port for connecting a wireless access device, wherein: The processor is configured to reconfigure the routing device to direct traffic to the WAN through the backup port in response to the measure of the connection quality of the wireless access device falling below a lower threshold and the measure of the connection quality of the active wireless access device at the active port falling below an upper threshold of all the wireless access devices, wherein the lower threshold is the minimum acceptable connection quality of the currently active wireless access device and the upper threshold is the minimum acceptable connection quality of the target wireless access device.

17. A method for routing in a computing network, comprising, at a routing device: configuring a data path to direct data traffic toward a wide area network (WAN) through the first wireless access device; monitoring a metric of a connection quality between the first wireless access device and the WAN; as well as In response to the metric of the connection quality of the first wireless access falling below a lower threshold and the highest metric of the connection quality of the wireless access devices being above an upper threshold, reconfiguring the data path to route data traffic to the WAN via a target wireless access device corresponding to a wireless access device having the highest metric of connection quality among the wireless access devices.

18. The method according to claim 17, wherein: The monitoring includes monitoring a measure of connection quality of each of the wireless access devices, the measure of connection quality representing a quality of a connection between the corresponding wireless access device and the WAN.

19. The method of claim 17, comprising routing data traffic through the target wireless access device during handoff of the first wireless access device between base stations of the WAN.

20. The method according to claim 17, wherein: The configuring data path includes updating a default route in a routing policy.

21. The method of claim 17, comprising sending an address resolution protocol message to the WAN via the target wireless access device.

22. The method according to claim 17, wherein: The monitoring includes periodic polling.

Images