# US 7,609,668 B1 · Distribution of packets to foreign agents using multicast protocols > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,668 B1 - Document ID: US7609668B1 - Status: Granted - Kind: B1 - Application number: 09/752,876 - Filed: 2000-12-28 - Granted: 2009-10-27 - Earliest claimed: 2000-12-28 - Assignees: Cisco Technology, Inc. - Inventors: Malcolm M Smith - Web page: https://patentgrep.com/patent/US7609668B1 ## CPC - H04W 4/06: Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services - H04L 12/18: for broadcast or conference {, e.g. multicast} - H04L 61/5069: for group communication, multicast communication or broadcast communication - H04W 8/02: Processing of mobility data, e.g. registration information at HLR [Home Location Register] or VLR [Visitor Location Register]; Transfer of mobility data, e.g. between HLR, VLR or external networks - H04W 80/04: Network layer protocols, e.g. mobile IP [Internet Protocol] - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A wireless communications system includes a mobile unit having a home network and a home agent in the home network. The system also includes foreign networks with foreign agents that provide wireless services to the mobile unit when the mobile unit travels outside of the service area of the home network. Foreign agents providing or likely to provide services for the mobile unit receive information for communication to the mobile unit by registering for a multicast group associated with the mobile unit. The home agent distributes information for communication to the mobile unit by encapsulating the information in multicast packets and communicating these packets for reception by the foreign agents registered for the multicast group. ## Claims ### Claim 1 A system for distributing packets for communication to a mobile unit comprising: a mobile unit having a device identifier and an internet protocol (IP) address comprising a first subnet identifier, the mobile unit roaming in a foreign network having a second subnet identifier; a mobility manager operable to determine a multicast address for the mobile unit based on the device identifier, to receive multicast address requests that include the device identifier, and to communicate the multicast address responsive to the multicast address requests; a plurality of foreign agents in the foreign network, the foreign agents operable to detect the mobile unit, to determine the device identifier for the mobile unit, to communicate a request including the device identifier to the mobility manager, to receive the multicast address from the mobility manager, and to register for a multicast group identified by the multicast address; and a home agent operable to receive IP packets addressed to the mobile unit, to determine the multicast address associated with the mobile unit, to encapsulate the IP packets as payloads for multicast packets addressed to the multicast address, and to communicate the multicast packets for receipt by said plurality of foreign agents registered for the multicast group using a packet network, wherein the home agent determines the multicast address by communicating a request including the IP address of the mobile unit to the mobility manager and receiving the multicast address from the mobility manager responsive to the request. ### Claim 2 (depends on 1) The system of claim 1, wherein the device identifier is at least one of a mobile identification number (MIN) for the mobile unit and an equipment serial number (ESN) for the mobile unit. ### Claim 3 (depends on 1) The system of claim 1, wherein the foreign agent is further operable to receive the multicast packets from the packet network, to extract the IP packets from the multicast packets, and to communicate the IP packets to the mobile unit. ### Claim 4 (depends on 1) The system of claim 1, wherein the foreign agent is further operable to detect the mobile unit by determining that a signal strength for signals received from the mobile unit have exceeded a threshold. ### Claim 5 A method for registering to receive packets comprising: determining, by a plurality of foreign agents, a device identifier for a mobile unit, the mobile unit having an internet protocol (IP) address comprising a subnet identifier for a remote network; communicating, by the plurality of foreign agents to a mobility manager, a request for a multicast address associated with the mobile unit, the request including the device identifier; receiving, by the plurality of foreign agents from said mobility manager, the multicast address; registering, by the plurality of foreign agents, for a multicast group identified by the multicast address; and receiving, by the plurality of receiving, by the plurality of foreign agents from a home agent, multicast packets addressed to the multicast address, wherein the multicast packets contain information for communication to the mobile unit, wherein the home agent determines the multicast address by communicating a request including the IP address of the mobile unit to the mobility manager and receiving the multicast address from the mobility manager responsive to the request. ### Claim 6 (depends on 5) The method of claim 5, wherein the information in the multicast packets comprises IP packets addressed to the IP address for the mobile unit. ### Claim 7 (depends on 5) The method of claim 5, wherein the information in the multicast packets comprises voice information. ### Claim 8 (depends on 5) The method of claim 5, wherein each of the foreign agents receiving the multicast packets communicates the information from the multicast packets to facilitate handoff of the mobile unit. ### Claim 9 (depends on 5) The method of claim 5, wherein the device identifier is at least one of a mobile identification number (MIN) for the mobile unit and an equipment serial number (ESN) for the mobile unit. ### Claim 10 (depends on 5) The method of claim 5, further comprising determining that signal strength for signals received from the mobile unit have dropped below a threshold and, in response to the determination, withdrawing from the multicast group. ### Claim 11 An apparatus for providing communications services for communications sessions of a mobile unit associated with a foreign network, the apparatus comprising: an interface operable to couple to a communications network; and a processor operable to determine, by a plurality of foreign agents, a device identifier for the mobile unit, the mobile unit having an internet protocol (IP) address comprising a subnet identifier for the remote network, the processor further operable to communicate, by the plurality of foreign agents to a mobility manager, a request for a multicast address associated with the mobile unit, the request including the device identifier using the interface, to receive, by the plurality of foreign agents from said mobility manager, the multicast address using the interface, and to register, by the plurality of foreign agents, for a multicast group identified by the multicast address, wherein the multicast group comprises the plurality of foreign agents, wherein the interface is further operable to receive, by the plurality of foreign agents from a home agent, multicast packets addressed to the multicast address, wherein the multicast packets contain information for communication to the mobile unit, wherein the home agent determines the multicast address by communicating a request including the IP address of the mobile unit to the mobility manager and receiving the multicast address from the mobility manager responsive to the request. ### Claim 12 (depends on 11) The apparatus of claim 11, wherein the information in the multicast packets comprises IP packets addressed to the IP address for the mobile unit. ### Claim 13 (depends on 11) The apparatus of claim 11, wherein the information in the multicast packets comprises voice information. ### Claim 14 (depends on 11) The apparatus of claim 11, wherein each of the foreign agents receiving the multicast packets communicates the information from the multicast packets to facilitate handoff of the mobile unit. ### Claim 15 (depends on 11) The apparatus of claim 11, wherein the device identifier is at least one of a mobile identification number (MIN) for the mobile unit and an equipment serial number (ESN) for the mobile unit. ### Claim 16 (depends on 11) The apparatus of claim 11, wherein the processor is further operable to determine that signal strength for signals received from the mobile unit have dropped below a threshold and, in response to the determination, to withdraw from the muiticast group. ### Claim 17 An apparatus for providing communications services for communications sessions of a mobile unit associated with a foreign network, the apparatus comprising: means for determining, by a plurality of foreign agents, a device identifier for the mobile unit, the mobile unit having an internet protocol (IP) address comprising a subnet identifier for the remote network; means for communicating, by the plurality of foreign agents to a mobility manager, a request for a multicast address associated with the mobile unit, the request including the device identifier; means for receiving, by the plurality of foreign agents from said mobility manager, the multicast address; means for registering, by the plurality of foreign agents, for a multicast group identified by the multicast address, wherein the multicast group comprises the plurality of foreign agents; and means for receiving, by the plurality of foreign agents from a home agent, multicast packets addressed to the multicast address, wherein the multicast packets contain information for communication to the mobile unit, wherein the home agent determines the multicast address by communicating a request including the IP address of the mobile unit to the mobility manager and receiving the multicast address from the mobility manager responsive to the request. ### Claim 18 (depends on 17) The apparatus of claim 17, further comprising means for determining that signal strength for signals received from the mobile unit have dropped below a threshold and means for, in response to the determination, withdrawing from the multicast group. ### Claim 19 A computer program for registering to receive packets, the computer program stored on a computer readable medium and operable to: determine, by a plurality of foreign agents, a device identifier for a mobile unit, the mobile unit having an internet protocol (IP) address comprising a subnet identifier for a remote network; communicate, by the plurality of foreign agents to a mobility manager, a request for a multicast address associated with the mobile unit, the request including the device identifier; receive, by the plurality of foreign agents from said mobility manager, the multicast address; register, by the plurality of foreign agents, for a multicast group identified by the multicast address, wherein the multicast group comprises the plurality of foreign agents; and receive, by the plurality of foreign agents from a home agent, multicast packets addressed to the multicast address, wherein the multicast packets contain information for communication to the mobile unit, wherein the home agent determines the multicast address by communicating a request including the IP address of the mobile unit to the mobility manager and receiving the multicast address from the mobility manager responsive to the request. ### Claim 20 (depends on 19) The computer program of claim 19, wherein the information in the multicast packets comprises IP packets addressed to the IP address for the mobile unit. ### Claim 21 (depends on 19) The computer program of claim 19, wherein the information in the multicast packets comprises voice information. ### Claim 22 (depends on 19) The computer program of claim 19, wherein each of the foreign agents receiving the multicast packets communicates the information from the multicast packets to facilitate handoff of the mobile unit. ### Claim 23 (depends on 19) The computer program of claim 19, wherein the device identifier is at least one of a mobile identification number (MIN) for the mobile unit and an equipment serial number (ESN) for the mobile unit. ### Claim 24 (depends on 19) The computer program of claim 19, further operable to determine that signal strength for signals received from the mobile unit have dropped below a threshold and, in response to the determination, to withdraw from the multicast group.