Patent ID: 7623529

Claim:
A system, comprising: at least one first network and at least one second network providing application services over the first network, the first network allocating an IP address of a user equipment based on a communication channel activated by the user equipment in the first network, the IP address being conveyed to the second network during an application level registration at the second network by the user equipment; a first network unit configured to receive a message associated with said IP address from the second network, configured to detect that there is no active communication channel for said IP address, and configured to send an indication that the user equipment is not reachable through said IP address to the second network; and a second network unit configured to receive said indication, wherein the second network unit, upon receiving the user equipment not reachable indication, is configured to initiate a de-registration of the user equipment in the second network, and wherein the second network unit, for initiating the de-registration, is configured to send a message with an indication to perform de-registration to a serving network node in the second network, said message being sent to inform at least one other network element that said IP address can no longer be used to reach said user equipment.