A service provision method in an Internet Protocol Multimedia Subsystem (IMS) network is provided. A service request message is transmitted from a first user terminal to a second user terminal for requesting a service. The service request message includes global identifiers (IDs) allocated to the first user terminal and the second user terminal. A service response message is transmitted from the second user terminal to the first user terminal. A service session is established between the first user terminal and the second user terminal, when the service response message is received by the first user terminal.