# US 2014/0192773 A1 · Traffic Control Within an IP Multimedia Subsystem > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0192773 A1 - Document ID: US20140192773A1 - Status: Published application - Kind: A1 - Application number: 14/122,281 - Filed: 2011-05-26 - Published: 2014-07-10 - Earliest claimed: 2011-05-26 - Assignees: Telefonaktiebolaget L M Ericsson (publ) - Applicants: Telefonaktiebolaget L M Ericsson (publ) - Inventors: Tobias Austrell; Timo Forsman; Annika Jonsson; Jan Anders Tellinger; Marlene Yared - Web page: https://patentgrep.com/patent/US20140192773A1 ## CPC - H04W 36/22: for handling the traffic - H04L 65/1016: IP multimedia subsystem [IMS] - H04L 65/1073: Registration or de-registration - H04L 65/80: Responding to QoS - H04L 65/1046: Call controllers; Call servers - H04L 67/1001: for accessing one among a plurality of replicated servers - 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 method of handling traffic within an IP Multimedia Subsystem, IMS, network. The method comprises registering an IMS user with a first Serving Call Session Control Function, S-CSCF, of the IMS network. Subsequently, at the first S-CSCF, a decision is made or instruction received to transfer said user to an alternative, second S-CSCF within the IMS network. A notification is sent from said first S-CSCF to a further IMS node, the notification including an explicit instruction to select a second S-CSCF and, upon receipt of said notification at the further IMS node, an S-CSCF reselection initiated for the user in order to select a second S-CSCF. ## Claims ### Claim 1 A method of handling traffic within an IP Multimedia Subsystem (IMS), network, the method comprising: registering an IMS user with a first Serving Call Session Control Function (S-CSCF) of the IMS network; at the first S-CSCF, making a decision or receiving an instruction to transfer said user to an alternative, second S-CSCF within the IMS network; sending a notification from said first S-CSCF to a further IMS node, the notification including an explicit instruction to select a second S-CSCF; and upon receipt of said notification at the further IMS node, initiating an S-CSCF reselection for the user in order to select a second S-CSCF. ### Claim 2 (depends on 1) The method according to claim 1, wherein said further IMS node is a Proxy Call Session Control Function, P-CSCF, to which said IMS user is attached. ### Claim 3 (depends on 2) The method according to claim 2, wherein said notification is a Session Initiation Protocol, SIP, NOTIFY. ### Claim 4 (depends on 3) The method according to claim 3 and comprising, at or following registration of the IMS user with said first S-CSCF, sending a SIP SUBSCRIBE from said P-CSCF to said first S-CSCF in order to subscribe the P-CSCF to event information for said user at the first S-CSCF. ### Claim 5 (depends on 2) The method according to claim 2, wherein said notification is an unsolicited SIP request. ### Claim 6 (depends on 2) The method according to claim 2, wherein said notification includes an identification of said first S-CSCF and said step of performing an S-CSCF reselection for the user involves including said identification in an S-CSCF reselection request sent to an Interrogating Call Session Control Function, I-CSCF, of the IMS network, together with an explicit instruction to select an alternative, second S-CSCF. ### Claim 7 (depends on 1) The method according to claim 1, further comprising comprising, following said step of making a decision to transfer said user to an alternative second S-CSCF, sending a non-register request from said further IMS node, receipt of that request causing said first S-CSCF to send said notification to the further IMS node, the notification being a SIP error message. ### Claim 8 (depends on 7) The method according to claim 7, wherein said SIP error message is a SIP error 504. ### Claim 9 (depends on 1) The method according to claim 1, wherein said step of performing an S-CSCF reselection for the user involves using the IMS Restoration Procedure to install user data into said alternative second S-CSCF. ### Claim 10 (depends on 1) The method according to claim 1, further comprising sending said notification to two or more further IMS nodes. ### Claim 11 (depends on 1) The method according to claim 1, wherein said further IMS node is an IMS Application Server. ### Claim 12 An apparatus configured to operate as a Serving Call Session Control Function within an IP Multimedia Subsystem (IMS) network, the apparatus comprising: a user registration controller for registering users of the IMS network to allow the provision of IMS services to the registered users; a user transfer controller for making a decision or receiving an instruction to transfer a registered user to an alternative S-CSCF within the IMS network; and a transfer notifier, responsive to a decision or instruction to transfer a registered user, for sending a notification to a further IMS node, the notification including an explicit instruction to select an alternative S-CSCF. ### Claim 13 (depends on 12) The apparatus according to claim 12, wherein said transfer notifier is configured to send said notification as a SIP NOTIFY request. ### Claim 14 (depends on 13) The apparatus according to claim 13, wherein said transfer notifier is configured to send event information to said further IMS node following receipt of a SIP SUBSCRIBE for said registered user. ### Claim 15 (depends on 12) The apparatus according to claim 12, wherein said transfer notifier is configured to send said notification as an unsolicited SIP request. ### Claim 16 (depends on 12) The apparatus according to claim 12, wherein said transfer notifier is configured to send said notification in response to receipt of a non-register request from said further IMS node. ### Claim 17 (depends on 12) The apparatus according to claim 12, wherein said transfer notifier is configured to include an identity of the apparatus in the notification. ### Claim 18 An apparatus configured to operate as a Call Session Control Function (CSCF) within an IP Multimedia Subsystem (IMS) network, the apparatus comprising: a receiver for receiving from a first Serving Call Session Control Function (S-CSCF) with which an IMS user is currently registered, a notification including an explicit instruction to select an alternative, second S-CSCF; and a registration initiation entity for sending a registration initiation request to a further IMS node, this request also including an explicit instruction to select an alternative second S-CSCF. ### Claim 19 (depends on 18) The apparatus according to claim 18, wherein said registration initiation entity is configured to include within said registration initiation request, an identification of said first S-CSCF from which said notification is received. ### Claim 20 (depends on 18) The apparatus according to claim 18, wherein the apparatus is configured to operate as one of a Proxy Call Session Control Function, P-CSCF, and an Interrogating Call Session Control Function (F-CSCF). ### Claim 21 An apparatus configured to operate as an Application Server within an IP Multimedia Subsystem (IMS) network, the apparatus comprising: a receiver for receiving from a first Serving Call Session Control Function (S-CSCF) with which an IMS user is currently registered, a notification including an explicit instruction to select an alternative, second S-CSCF; and a response unit for responding to receipt of said explicit instruction by sending a SIP traffic initiation request in respect of said user to an Interrogating Call Session Control Function (I-CSCF).