# US 2014/0153473 A1 · Managing Router Advertisement Messages To Support Roaming Of Wireless Mobile Client Devices > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0153473 A1 - Document ID: US20140153473A1 - Status: Published application - Kind: A1 - Application number: 14/172,440 - Filed: 2014-02-04 - Published: 2014-06-05 - Earliest claimed: 2009-11-04 - Assignees: Cisco Technology, Inc. - Applicants: Cisco Technology, Inc. - Inventors: Srinath Gundavelli; Abhijit Choudhury; Rohit Suri; Venkatesh Kanagasabapathy; Bhavannarayana Nelakanti; Sudhir Jain - Web page: https://patentgrep.com/patent/US20140153473A1 ## CPC - H04L 12/189: {in combination with wireless systems (selective distribution or broadcast in wireless communication networks H04W4/06)} - H04L 12/18: for broadcast or conference {, e.g. multicast} - H04L 12/4641: {Virtual LANs, VLANs, e.g. virtual private networks [VPN] (LAN interconnection over a bridge based backbone H04L12/462; encapsulation techniques H04L12/4633; routing of packets H04L45/00; packet switches H04L49/00; virtual private networks for security H04L63/0272)} - H04L 45/16: Multipoint routing - H04W 28/0226: {based on location or mobility (handoff or reselection H04W36/00; mobile application services making use of the location of users or terminals H04W4/02)} - H04W 40/023: {Limited or focused flooding to selected areas of a network} - H04W 40/24: Connectivity information management, e.g. connectivity discovery or connectivity update - H04W 40/248: {Connectivity information update} - H04W 40/30: for proactive routing - H04W 84/12: WLAN [Wireless Local Area Networks] - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract Techniques are provided to manage how router advertisement messages are forwarded for ultimate wireless transmission in a wireless network. In one embodiment, a multicast router advertisement message intended for a virtual local area network is converted into individual unicast router advertisement messages directed to specific wireless mobile client devices that are part of that virtual local area network. In another embodiment, router advertisement messages are routed between controllers according to the current location of a wireless mobile client device. In still other embodiments, techniques are provided to minimize the volume of the router advertisement messages sent over a wireless network, and to proactively send a unicast router advertisement message to a mobile client device that has performed a handoff, without waiting for a router solicitation message. ## Claims ### Claim 1 A method comprising: at a controller configured to control one or more wireless access point devices that serve wireless mobile client devices that are part of a first virtual local area network, storing information identifying any other controllers that control other wireless access point devices to which at least one wireless mobile client device that is part of the first virtual local area network has roamed; at the controller, receiving a router advertisement message sent by a network router device; determining whether the router advertisement message is a multicast message and if so determining for which virtual local area network the router advertisement message is intended; generating a unicast router advertisement message by changing a header field of the router advertisement message to replace a multicast destination address in the router advertisement message with a media access control address for a wireless mobile client device that is part of the first virtual local area network for which the router advertisement message was intended; sending the unicast router advertisement message to one or more wireless access point devices for wireless transmission to a wireless mobile client device that is part of the first virtual local area network that is connected to one of the wireless access point devices when it is determined that the router advertisement message is intended for the first virtual local area network; and forwarding a copy of the multicast router advertisement message to the other controllers that control wireless access point devices to which at least one wireless mobile client device that is part of the first virtual local area network has roamed. ### Claim 2 (depends on 1) The method of claim 1, wherein determining which virtual local area network the router advertisement message is intended for comprises either examining a field of the router advertisement message or determining a configuration associated with the router advertisement message. ### Claim 3 (depends on 1) The method of claim 1, wherein determining comprises determining that the router advertisement message is sent to a unicast destination address corresponding to a particular wireless mobile client device, and if so, forwarding it for wireless transmission to the particular wireless mobile client device as part of normal wired to wireless bridging operations. ### Claim 4 (depends on 1) The method of claim 1, further comprising suppressing a router advertisement message received from the network router device so as not to forward it to any one or more of a plurality of wireless access point devices associated with the controller based on a stored router advertisement frequency parameter. ### Claim 5 A method comprising: at a controller configured to control one or more wireless access point devices that serve wireless mobile client devices that are part of a first virtual local area network, receiving a router advertisement message from a network router; determining for which of a plurality of virtual local area networks the router advertisement message is intended; storing the router advertisement message together with information identifying the virtual local area network to which the router advertisement message is intended; receiving from a wireless access point device a router solicitation message sent by a particular wireless mobile client device that is part of the first virtual local area network; determining to which of the plurality of virtual local area networks the particular wireless mobile client device belongs; determining whether there is a router advertisement message stored for the virtual local area network to which the particular wireless mobile client device belongs; and when there is a router advertisement message stored for the virtual local area network to which the particular wireless mobile client device belongs, retrieving the stored router advertisement message and sending it as a unicast message to the one or more wireless access point devices configured to serve wireless mobile client devices that are part of the first virtual local area network if the wireless mobile client device is attached to a wireless access point device controlled by the controller or to another controller that is configured to control at least one wireless access point device to which the wireless mobile client device has roamed. ### Claim 6 (depends on 5) The method of claim 5, when it is determined that there is no router advertisement message stored for the virtual local area network to which the particular wireless mobile client device belongs, forwarding the router solicitation message to the network router. ### Claim 7 (depends on 5) The method of claim 5, wherein determining which of the plurality of virtual local area networks for which the router advertisement message is intended comprises examining a field of the router advertisement message or determining a configuration associated with the router advertisement message. ### Claim 8 (depends on 5) The method of claim 5, and further comprising, at the other controller that controls a wireless access point device to which the particular wireless mobile client device has roamed, storing the router advertisement message, and wherein sending comprises sending the stored router advertisement message to the particular wireless mobile client device from the controller to which the particular wireless mobile client device has roamed. ### Claim 9 (depends on 5) The method of claim 5, and further comprising at the controller, storing a list of one or more wireless mobile client devices from which router solicitation messages have been received, and wherein upon receiving a router advertisement message intended for a virtual local area network to which a particular wireless mobile client device in the stored list is associated, generating a unicast router advertisement message addressed to the particular wireless mobile client device and sending the unicast router advertisement message to the particular wireless mobile client device without waiting for a next permitted router advertisement message according to the stored router advertisement frequency parameter. ### Claim 10 (depends on 5) The method of claim 5, further comprising forwarding the unicast router advertisement message to another controller without waiting for a router solicitation message from the particular wireless mobile client device. ### Claim 11 (depends on 10) The method of claim 10, and further comprising receiving a notification of a handoff event associated with the particular wireless mobile client device from a wireless access point device under control of the controller to a wireless access point device under control of another controller. ### Claim 12 (depends on 5) The method of claim 5, further comprising suppressing a router advertisement message received from the network router device so as not to forward it to any one or more of a plurality of wireless access point devices associated with the controller based on a stored router advertisement frequency parameter. ### Claim 13 An apparatus comprising: a network interface unit configured to send and receive messages over a wired network on behalf of a controller configured to control one or more wireless access point devices that serve wireless mobile client devices that are part of a first virtual local area network; a processor coupled to the network interface unit and configured to: receive a router advertisement message from a network router; determine for which of a plurality of virtual local area networks the router advertisement message is intended; store the router advertisement message together with information identifying the virtual local area network to which the router advertisement message is intended; receive from a wireless access point device a router solicitation message sent by a particular wireless mobile client device that is part of the first virtual local area network; determine to which of the plurality of virtual local area networks the particular wireless mobile client device belongs; determine whether there is a router advertisement message stored for the virtual local area network to which the particular wireless mobile client device belongs; and when there is a router advertisement message stored for the virtual local area network to which the particular wireless mobile client device belongs, retrieve the stored router advertisement message and cause it to be sent as a unicast message to the one or more wireless access point devices configured to serve wireless mobile client devices that are part of the first virtual local area network if the wireless mobile client device is attached to a wireless access point device controlled by the controller or to another controller that is configured to control at least one wireless access point device to which the wireless mobile client device has roamed. ### Claim 14 (depends on 13) The apparatus of claim 13, wherein the processor is configured to forward the router solicitation message to the network router when it is determined that there is no router advertisement message stored for the virtual local area network to which the particular wireless mobile client device belongs. ### Claim 15 (depends on 13) The apparatus of claim 13, wherein the processor is configured to suppress a router advertisement message received from the network router so as not to forward it to any one or more of a plurality of wireless access point devices associated with the controller based on a stored router advertisement frequency parameter. ### Claim 16 (depends on 15) The apparatus of claim 15, wherein the processor is configured to store a list of one or more wireless mobile client devices from which router solicitation messages have been received, and upon receiving a router advertisement message intended for a virtual local area network to which a particular wireless mobile client device in the stored list is associated, generate a unicast router advertisement message addressed to the particular wireless mobile client device and cause the unicast router advertisement message to be sent to the particular wireless mobile client device without waiting for a next permitted router advertisement message according to the stored router advertisement frequency parameter. ### Claim 17 (depends on 13) The apparatus of claim 13, wherein the processor is configured to determine which of the plurality of virtual local area networks for which the router advertisement message is intended by examining a field of the router advertisement message or determining a configuration associated with the router advertisement message. ### Claim 18 (depends on 13) The apparatus of claim 13, wherein the processor is configured to determine whether a router advertisement message is due to be forwarded based on the stored router advertisement frequency parameter that specifies a frequency at which the controller forwards router advertisement messages independent of a frequency at which the network router sends router advertisement messages to the controller, and forwarding the router advertisement message. ### Claim 19 (depends on 18) The apparatus of claim 18, wherein the processor is configured to store a list of one or more wireless mobile client devices from which router solicitation messages have been received, and wherein upon receiving a router advertisement message intended for a virtual local area network to which a particular wireless mobile client device in the stored list is associated, generate a unicast router advertisement message addressed to the particular wireless mobile client device and send the unicast router advertisement message to the particular wireless mobile client device without waiting for a next permitted router advertisement message according to the stored router advertisement frequency parameter. ### Claim 20 (depends on 13) The apparatus of claim 13, wherein the processor is configured to receive, via the network interface unit, a notification of a handoff event associated with the particular wireless mobile client device from a wireless access point device under control of the controller to a wireless access point device under control of another controller.