A method of operating a single registrar component of an Internet Protocol, IP, Multimedia Subsystem, IMS, network, comprising: receiving a first request to register a first client device associated with a given user to an IMS service; registering the first client device to the IMS service with a first set of device-specific routing identifiers; transmitting, from the single registrar component to the first client device, a first acknowledgment to the first request that indicates that the first client device is registered to the IMS service with the first set of device-specific routing identifiers; receiving a second request to register a second client device associated with the given user to the IMS service; registering the second client device to the IMS service with a second set of device-specific routing identifiers; transmitting, from the single registrar component to the second client device, a second acknowledgment to the second request that indicates that the second client device is registered to the IMS service with the second set of device-specific routing identifiers, wherein the second acknowledgment further includes an indication of the first set of device-specific routing identifiers registered to the first client device; transmitting, in response to the second request, a message to the first client device that is configured to prompt the first client device to perform another registration procedure; receiving a third request, from the first client device in response to having received the message to register the first client device associated with the given user to the IMS service; and transmitting, from the single registrar component to the first client device, a third acknowledgment to the third request that indicates the second set of device-specific routing identifiers for the second client device. receiving a first request to register a first client device associated with a given user to an IMS service; registering the first client device to the IMS service with a first set of device-specific routing identifiers; transmitting, from the single registrar component to the first client device, a first acknowledgment to the first request that indicates that the first client device is registered to the IMS service with the first set of device-specific routing identifiers; receiving a second request to register a second client device associated with the given user to the IMS service; registering the second client device to the IMS service with a second set of device-specific routing identifiers; transmitting, from the single registrar component to the second client device, a second acknowledgment to the second request that indicates that the second client device is registered to the IMS service with the second set of device-specific routing identifiers, wherein the second acknowledgment further includes an indication of the first set of device-specific routing identifiers registered to the first client device; transmitting, in response to the second request, a message to the first client device that is configured to prompt the first client device to perform another registration procedure; receiving a third request, from the first client device in response to having received the message to register the first client device associated with the given user to the IMS service; and transmitting, from the single registrar component to the first client device, a third acknowledgment to the third request that indicates the second set of device-specific routing identifiers for the second client device.