Method and apparatus of communications over a network

A communications system includes a packet-based data network to which are coupled various network elements. At least some of the network elements are capable of participating in real-time interactive communications sessions over the data network. Protocols that provide for such communications sessions include Session Initiation Protocol (SIP) and the H.323 Recommendation. The data network includes subscriber systems that are capable of receiving advertising information in one or more messages communicated from a service provider system over the data network. The service provider system identifies the types of advertising information that may be of interest to one or more users at the subscriber systems. The service provider system is able to receive the advertising information from a data warehouse source, which may collect transaction information, such as retail transaction information, from retail sources. The advertising information provided by the service provider system may include locator information (which may be in the form of an address or uniform resource locator) that a subscriber system may use to establish a real-time interactive communication session with the source of the advertising information.