Correlation of Sessions in Case of Session Transfer in IMS Domain

A method implemented by a control node for supporting session control in an IP Multimedia Subsystem (IMS) domain of a communications network, wherein the control node is configured to control centralized services and service continuity in the IMS domain, and wherein the method comprises:

• storing a session information item for each of a plurality of ongoing communication sessions, the session information item stored for any given session comprising a user identity identifying a user of a user device involved in the session and a first device identifier identifying that user device in a Circuit Switched (CS) domain of the communications network, wherein the user identity is associated with multiple user devices of said user and wherein the first device identifier comprises at least one of a Mobile Subscriber ISDN Number (MSISDN), an International Mobile Subscriber Identity (IMSI), and a Globally Routable Unique User (GRUU) identifier;
• receiving a session transfer request that has been transparently forwarded by a call control node in the IMS domain to the control node, the session transfer request requesting transfer of a session associated with a second device identifier included in the request, the second device identifier identifying a user device in the CS domain and comprising at least one of an MSISDN, an IMSI, and a GRUU identifier;
• comparing the received second device identifier, or a third device identifier determined based on the second device identifier, with the stored plurality of first device identifiers;
• and
• identifying, based on the comparison, a particular ongoing session to which the received session transfer request relates.

A computer program product stored on a computer readable medium and comprising program code portions that, when executed on one or more computing devices associated with a control node configured to control centralized services and service continuity in an IP Multimedia Subsystem (IMS) domain of a communications network, cause the control node to support session control in the IMS domain, the program code portions causing the control node to:

• store a session information item for each of a plurality of ongoing communication sessions, the session information item stored for any given session comprising a user identity identifying a user of a user device involved in the session and a first device identifier identifying that user device in a Circuit Switched (CS) domain of the communications network, wherein the user identity is associated with multiple user devices of said user and wherein the first device identifier comprises at least one of a Mobile Subscriber ISDN Number (MSISDN), an International Mobile Subscriber Identity (IMSI), and a Globally Routable Unique User (GRUU) identifier;
• receive a session transfer request that has been transparently forwarded by a call control node in the IMS domain to the control node, the session transfer request requesting transfer of a session associated with a second device identifier included in the request, the second device identifier identifying a user device in the CS domain and comprising at least one of an MSISDN, an IMSI, and a GRUU identifier;
• compare the received second device identifier, or a third device identifier determined based on the second device identifier, with the stored plurality of first device identifiers;
• and
• identify, based on the comparison, a particular ongoing session to which the received session transfer request relates.

A control node for controlling centralized services and service continuity in an IP Multimedia Subsystem (IMS) domain of a communications network, the control node configured to support session control in the IMS domain and comprising:

• a memory configured to store a session information item for each of a plurality of ongoing communication sessions, the session information item stored for any given session comprising a user identity identifying a user of a user device involved in the session and a first device identifier identifying that user device in a Circuit Switched (CS) domain of the communications network, wherein the user identity is associated with multiple user devices of said user and wherein the first device identifier comprises at least one of a Mobile Subscriber ISDN Number (MSISDN), an International Mobile Subscriber Identity (IMSI), and a Globally Routable Unique User (GRUU) identifier;
• a session transfer request processor configured to receive a session transfer request that has been transparently forwarded by a call control node in the IMS domain to the control node, the session transfer request requesting transfer of a session associated with a second device identifier included in the request, the second device identifier identifying a user device in the CS domain and comprising at least one of an MSISDN, an IMSI, and a GRUU identifier;
• a comparator configured to compare the received second device identifier, or a third device identifier determined based on the second device identifier, with the stored plurality of first device identifiers;
• and
• an identification circuit configured to identify, based on the comparison, a particular ongoing session to which the received session transfer request relates.