A network service system for a telecommunications network and for initiating a communication session between a first terminal for a first user and a second terminal for a second user, the network service system comprising a plurality of network modules associated with the first user, wherein the network service system is configured to: receive a session setup message originating from the first terminal and addressed to the second terminal, wherein the session setup message comprises a request to initiate the communication session between the first terminal and the second terminal; and route the received session setup message through an originating leg in the network service system of a routing of the session setup message between the first terminal and the second terminal and send the session setup message to a terminating leg of the routing of the session setup message between the first terminal and the second terminal, wherein the originating leg comprises routing of the session setup session message via a plurality of network modules associated with the first user and the terminating leg comprises routing of the session setup message via a plurality of network modules associated with the second user; wherein, the originating leg of the routing of the session setup message includes a network service module associated with the first user and configured to generate, in response to receiving the session setup message in the originating leg, a connection request message addressed to the second terminal and for initiating connection of the second terminal to a telecommunications network serving the second terminal; and wherein the network service system is further configured to send the connection request message to the terminating leg before sending the session setup message to the terminating leg. receive a session setup message originating from the first terminal and addressed to the second terminal, wherein the session setup message comprises a request to initiate the communication session between the first terminal and the second terminal; and route the received session setup message through an originating leg in the network service system of a routing of the session setup message between the first terminal and the second terminal and send the session setup message to a terminating leg of the routing of the session setup message between the first terminal and the second terminal, wherein the originating leg comprises routing of the session setup session message via a plurality of network modules associated with the first user and the terminating leg comprises routing of the session setup message via a plurality of network modules associated with the second user; wherein, the originating leg of the routing of the session setup message includes a network service module associated with the first user and configured to generate, in response to receiving the session setup message in the originating leg, a connection request message addressed to the second terminal and for initiating connection of the second terminal to a telecommunications network serving the second terminal; and wherein the network service system is further configured to send the connection request message to the terminating leg before sending the session setup message to the terminating leg.