System, methods, and computer program products are provided for configuring a computing system that processes messages according to the Session Initiation Protocol (SIP). The method includes defining, by a scripting-type computer processing language, one or more variables, where each variable is configured to store state data based on at least a portion of a SIP message and is associated with the SIP message flow. Once configuration is complete, a series of SIP messages belonging to the SIP message flow is received by the computer system. As each SIP message in the series is received, each SIP message is processed where the message processing includes modifying the state data stored in at least one of the variables based on data included in the respective SIP message.