A method of informing a control node (110, 310, 610) in a serving communication network (106, 306) of address information about a session anchor node in the serving communication network (106, 306), wherein the control node (110, 310, 610) is accessible by a terminal (104, 304) via a circuit switched access of the serving communication network (106, 306), and wherein the serving communication network (106, 306) of the terminal (104, 304) is different from an internet protocol based home communication network (102, 302, 402) of the terminal (104, 304), the method being executed by a session anchor node (108, 308, 408, 508) in the home communication network (102, 302, 402), the method comprising: - receiving (120, 320a, 320b, 420a, 420b), from the control node (110, 310, 610) via an intermediate node (112, 312a, 312b) of the serving communication network (106, 306), an update request for the control node (110, 310, 610) being updated of the address information about the session anchor node in the serving communication network (106, 306), wherein the update request is received together with a subscription request for the control node (110, 310, 610) subscribing to being updated of any changes of the address information, - receiving (120, 320a, 320b, 420a, 420b, 114, 214a, 214b, 314, 414) the address information about the session anchor node in the serving communication network (106, 306), - sending (130, 230, 330, 430) the received address information based on the received update request to the control node (110, 310, 610), and - receiving (114, 214a, 214b, 314, 414), via a packet switched access of the serving communication network (106, 306), a packet switched registration request for packet switched registering a subscriber of the terminal (104, 304) in the home communication network (102, 302, 402), wherein the packet switched registration request is received together with the address information about the session anchor node in the serving communication network (106, 306). - receiving (120, 320a, 320b, 420a, 420b), from the control node (110, 310, 610) via an intermediate node (112, 312a, 312b) of the serving communication network (106, 306), an update request for the control node (110, 310, 610) being updated of the address information about the session anchor node in the serving communication network (106, 306), wherein the update request is received together with a subscription request for the control node (110, 310, 610) subscribing to being updated of any changes of the address information, - receiving (120, 320a, 320b, 420a, 420b, 114, 214a, 214b, 314, 414) the address information about the session anchor node in the serving communication network (106, 306), - sending (130, 230, 330, 430) the received address information based on the received update request to the control node (110, 310, 610), and - receiving (114, 214a, 214b, 314, 414), via a packet switched access of the serving communication network (106, 306), a packet switched registration request for packet switched registering a subscriber of the terminal (104, 304) in the home communication network (102, 302, 402), wherein the packet switched registration request is received together with the address information about the session anchor node in the serving communication network (106, 306).