A method of providing an availability of an execution of an Internet Protocol Multimedia Subsystem voice session via a packet switched capable radio access network of an Internet Protocol Multimedia Subsystem based communication network (100, 300) with a terminal (102, 502), wherein the communication network (100, 300) comprises a packet switched domain associated with the packet switched capable radio access network and comprises a circuit switched domain associated with a circuit switched capable radio access network, wherein the communication network (100, 300) supports an Internet Protocol Multimedia Subsystem voice session via the packet switched capable radio access network, the method being executed by a control node (112, 412) of the packet switched domain, the method comprising: - the control node (112, 412) determining that the terminal (102, 502) supports communication with the circuit switched domain of the communication network (100, 300), and determining that the terminal (102, 502) is allowed to communicate via the circuit switched domain by checking a roaming agreement between a serving communication network of the terminal (102, 502) and a home communication network of the terminal (102, 502), and determining that the circuit switched capable radio access network spatially at least covers the packet switched capable radio access network; and - sending, responsive to when said determining steps by the control node (112, 412) are affirmative, instruction information to the terminal (102, 502), wherein the instruction information configures the terminal (102, 502) by setting a parameter to indicate to the terminal the availability of an Internet Protocol Multimedia Subsystem voice session via the packet switched capable radio access network with regard to whether the communication network (100, 300) having indicated support of an emergency session related data transmission via the packet switched capable radio access network and the packet switched domain, wherein the instruction information further instructs the terminal (102, 502), in case of an emergency event, to exclusively initiate a circuit switched emergency voice session via the circuit switched capable radio access network. - the control node (112, 412) determining that the terminal (102, 502) supports communication with the circuit switched domain of the communication network (100, 300), and determining that the terminal (102, 502) is allowed to communicate via the circuit switched domain by checking a roaming agreement between a serving communication network of the terminal (102, 502) and a home communication network of the terminal (102, 502), and determining that the circuit switched capable radio access network spatially at least covers the packet switched capable radio access network; and - sending, responsive to when said determining steps by the control node (112, 412) are affirmative, instruction information to the terminal (102, 502), wherein the instruction information configures the terminal (102, 502) by setting a parameter to indicate to the terminal the availability of an Internet Protocol Multimedia Subsystem voice session via the packet switched capable radio access network with regard to whether the communication network (100, 300) having indicated support of an emergency session related data transmission via the packet switched capable radio access network and the packet switched domain, wherein the instruction information further instructs the terminal (102, 502), in case of an emergency event, to exclusively initiate a circuit switched emergency voice session via the circuit switched capable radio access network.