Abstract: The invention relates to a method of changing allocation of Serving-Call Session Control Functions (S-CSCFs) to a user of an IMS network. The user is being provided with services via a first S-CSCF allocated to the user. The method includes implementing a re-allocation instruction at the first S-CSCF. The reallocation instruction includes criteria for de-allocation of the user from the first S-CSCF. The S-CSCF determines if the criteria are met; and if the criteria are met, de-allocates the user.

Abstract: In one aspect, the invention provides a method, and associated apparatus for re-registering a contact address of a user of an IP Multimedia Subsystem, IMS, network. A request for re-registration of the contact address is received at a Serving-Call Session Control Function, S-CSCF, node serving the user. After a determination that the S-CSCF has no stored information relating to the contact address, a request is sent to a Home Subscriber Server, HSS, of the user to register the contact address information. The HSS detects if the contact address information relating to the user has already been backed-up by the HSS, and notifies the node serving the user of registered contact address information backed-up by the HSS. Another aspect provides a method and associated apparatus for de-registering a registered contact address of a user of an IP Multimedia Subsystem, IMS, network.

Abstract: A method and apparatus for establishing a communication session in an IMS Centralized Services communication network. A Service Centralization and Continuity Application Server (SCC AS) receives a request from an originating device to establish a session with a target device. The request includes a plurality of codec identifiers that could be used by the originating device. The SCC AS sends a second request to establish the session to the target device. The SCC AS subsequently receives, from an intermediate node between the SCC AS and the target device, an invite message. The invite message includes an indication that a codec identifier has been selected from the plurality of codec identifiers. The SCC AS then sends a message to the intermediate node instructing the intermediate node to establish the session.

Abstract: A method and apparatus for processing a floor request in a push to talk type service in which a floor is required for a first terminal to distribute media to a second terminal. The first terminal sends a floor request message to a PoC Server. The message relates to at least two different types of media content and indicates how and to what extent the granting or denial of the different media types interrelate. The message may indicate, for example, that if a first media type is denied, the others should be denied; or that the granting or denial of the first media type should not affect the other media types. The message may also indicate other conditions and relationships. The PoC Server processes the request based on the indicated interrelationships and/or conditions, and grants or denies each media type.

Abstract: The invention relates to a method of notifying an Application Function, AF, in a communications network of resource restrictions relating to a communications session. The network includes a Policy and Charging Rules Function, PCRF, for authorising and controlling flows of data in the session. In the method the AF sends an authorisation request to the PCRF for establishing the communication session. The authorisation request includes an indication that the AF is to be notified of resource restrictions for the data flows in the session. The PCRF notifies the AF of the resource restrictions.

Abstract: A method is provided for facilitating recovery from the failure of a P-CSCF within an IP multimedia Subsystem network. A gateway, such as a GGSN, monitors signals arriving at the gateway from the P-CSCF and provides an indication if the monitored signals become unacceptable, for example because of an interruption in the signals. The gateway responds by signalling the unavailability of the P-CSCF to user equipment, which was associated with the P-CSCF during a previous registration with the IMS network. In response, for example, the user equipment affected by the failure may request re-registration with the IMS network using a different available P-CSCF.

Abstract: Apparatus for generating policy and charging rules to control IP flows across a packet switched network. The apparatus comprises a first interface for coupling to an application function and a second interface for coupling to a policy and charging enforcement function implemented at a node through which said IP flows pass. A processor or processors is/are configured to receive service information at said first interface, and, via said second interface to trigger the removal of one or more pre-existing policy and charging rules at the policy and charging enforcement function following a predefined delay.

Abstract: A method and communications network node for allocating a priority level to an Internet Protocol (IP) packet containing all or part of a Session Initiation Protocol (SIP) message. One or more characteristics of the SIP message are determined, and the characteristics are mapped to a Differentiated Services Code Point (DSCP) value. The DSCP value is then applied to the IP packet header.

Abstract: A generic method is described for storing data in the HSS (2) by the S-CSCF (1) of an IMS. When a SIP message containing new information relating to an IMPI/IMPU pair is received by the S-CSCF (1), a data package is created for storage at the HSS (2), containing the new information. An SAR command is sent to the HSS (2) containing an AVP including an instruction to the HSS (2) and the new data package. In one aspect a unique data package is controlled by the S-CSCF (1). When new information relating to the IMPI/IMPU is received in a SIP message, this is added to any previously sent data package to create a new data package. In another aspect the HSS (2) controls a unique data package, returning the data package to the S-CSCF (1) to be amended if necessary. In another aspect separate data packages are used.

Abstract: The present invention is aimed to provide means and methods for recovery of the IMS where an S-CSCF has suffered a restart after a failure, software upgrade or other reasons. To this end, the present invention provides for a first method to be applied in a HSS holding subscriber data for subscribers of the IMS and a second method to be applied in a S-CSCF selected for serving a given subscriber, upon restart of a S-CSCF assigned for serving a given subscriber. Both first and second methods cooperating to submit from the S-CSCF towards the HSS contact data required by the S-CSCF to contact the given subscriber, or to contact a proxy server where the subscriber is accessible through; storing the contact data at the HSS; and providing from the HSS towards an IMS entity, which may be the previously assigned S-CSCF or a new S-CSCF, contact information elements selectable from the contact data.

Abstract: The invention relates to a method of establishing a session between client user terminals accessing IP Multimedia Subsystem, IMS, networks. At least one of the IMS networks implements the use of Quality of Service, QoS, preconditions, and at least one of the client user terminals does not use QoS preconditions. The method includes receiving, at an inter-working function, IWF located in one of the IMS networks, an IMS session initiation request originated by an originating client, the request indicating a terminating client for the session. A decision is made, based on the session initiation request, that one of the originating client and the terminating client is not using QoS preconditions. A set of QoS preconditions is inserted into a procedure for establishing the IMS session on behalf of the client that is not using QoS preconditions. Session establishment is completed only after QoS resources complying with the set of QoS preconditions have been established.

Abstract: A method is disclosed for use by an Interrogating Call/Session Control Function (I-CSCF) of an IP Multimedia Subsystem (IMS). In the method, a Session Initiation Protocol (SIP) message is received by the I-CSCF, which the I-CSCF attempts to forward to a Serving Call/Session Control Function (S-CSCF) of the IMS assigned to provide services to a user. If the attempt is determined to have failed, the I-CSCF sends a message to a Home Subscriber Server (HSS) of the IMS to request capabilities information for selecting a S-CSCF, the request message also providing first information relating to the status of the assigned S-CSCF. On receipt of the capabilities information at the I-CSCF from the HSS, the I-CSCF selects a replacement S-CSCF to provide services to the user. Related methods are also disclosed for use by the HSS and S-CSCF.

Abstract: A method of operating an Internet Protocol Multimedia Subsystem (IMS) network having a plurality of user interfaces. A terminal agent is interposed between a plurality of Session Initiation Protocol (SIP) User Agents and a Serving Call/Session Control Function (S-CSCF) of the IMS network. The terminal agent registers its contact address with the S-CSCF on behalf of the plurality of SIP User Agents and emulates a single SIP User Agent to the S-CSCF.

Abstract: The invention relates to a method of enabling use equipment to establish a communication session over an IMS network. The communication session is enabled by one or more call/session control functions in the network in accordance with media characteristics that define the network resources to be utilised for the session. The method comprises: receiving with the IMS network a subscriber registration request originating from the user equipment and, in response thereto, sending to the user equipment an identification of allowable media characteristics.

Abstract: The invention relates to a method of notifying an Application Function (AF) in a communications network of resource restrictions relating to a communication session. The network includes a Policy and Charging Rules Function (PCRF) for authorising and controlling flows of data in the session. In the method the AF sends an authorisation request to the PCRF for establishing the communication session. The authorisation request includes an indication that the AF is to be notified of resource restrictions for the data flows in the session. The PCRF notifies the AF of the resource restrictions.

Abstract: A method of handling SIP requests received by an IP Multimedia Subsystem network. The method comprises determining whether or not the SIP destination identity is within a range of identities owned by an operator of the network but is currently unallocated to a subscriber or service of the network and, if yes, routing the message to one or more SIP application servers within the network and implementing service logic at the application server(s) specific to a network owned but unallocated SIP identity.

Abstract: A method of distributing application server addresses in an IP Multimedia Subsystem. Upon allocation of an application server to a subscriber, the allocated or another application server sends at least one application server address to a Home Subscriber Server (HSS). The HSS stores the address(es) in association with the subscriber identity and sends the address(es) to a Serving Call/Session State Control Function (S-CSCF) allocated to the subscriber. The S-CSCF caches the address(es) in association with the subscriber identity and uses the address(es) to send subscriber-related messages to the allocated application server.

Abstract: A method of evaluating Initial Filter Criteria (IFC) at a terminating Serving Call Session Control Function (S-CSCF) in an IP Multimedia Subsystem network. Upon receiving a Session Initiation Protocol (SIP) message containing a destination Uniform Resource Identifier (URI), the S-CSCF applies an Initial Filter Criterion to the message, sends the message to an Application Server (AS), and suspends further IFC evaluation. When a return message is received from the AS, the S-CSCF determines whether the AS changed the URI. If so, the S-CSCF makes a determination of whether to resume IFC evaluation. If the AS did not change the URI, the S-CSCF resumes IFC evaluation.

Abstract: A method of registering or deregistering a user to or from an IP Multimedia Subsystem (IMS) network. A SIP Application Server (SIP-AS) performs a registration or deregistration with the IMS network on a user's behalf. The registration or deregistration is performed over one of the following interfaces: a Service Control Interface (ISC) with a Serving Call State Control Function (S-CSCF), a Gm interface with a Proxy CSCF (P-CSCF), or an Ma interface with an Interrogating CSCF (I-CSCF).

Abstract: A method of controlling access to services of an IP Multimedia Subsystem (IMS) by a user based upon the user's location. In response to a user requesting access to a service, information identifying the user's location is provided to the IMS. Within the IMS, the provided information is compared with authorization information stored in a database. The authorization information includes information identifying prohibited and/or allowed access locations. Dependent upon the result of the comparison, access to the IMS services is allowed or denied.