To provide a call tracing mechanism in an SIP environment.

A method of performing a call trace comprises steps of: (A) receiving a second message; (B) applying a second filter reference to the second message; thereby performing a predetermined process to the second message and creating the second filter reference in consequence of previously analyzing a characteristic of a first message received before the second message and of determining to apply the predetermined process to the first message, (C) determining that the second message is suitable to the second filter reference; and (D) processing the second message by the predetermined process.