1. A method for transmitting Communication Initiation Request (CIR) messages from a server to a mobile client during a session, the client supporting a plurality of CIR channel bindings, the method comprising: selecting, by a server, a first one of a plurality of CIR channel bindings supported by a mobile client; transmitting, by the server, at least one CIR message via said first CIR channel binding to the mobile client over a unidirectional channel from the server to the mobile client; determining whether the server receives a polling request from the mobile client over a bi-directional data channel between the server and the mobile client, in response to the at least one CIR message; and if the server does not receive the polling request from the mobile client, then: selecting, by the server, a second one of the plurality of CIR channel bindings supported by the mobile client; and subsequently transmitting, by the server, at least one subsequent CIR message via said second CIR channel binding to the mobile client over the unidirectional channel from the server to the mobile client, wherein said at least one CIR message and said at least one subsequent CIR message are transmitted during the same session.