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The session timer mechanism for the session initiation protocol (SIP) has been proposed to track the states of the communicating sessions for proxy servers. Upon the occurrence of the session failure (e.g., radio link disconnection), the proxy server can quickly release the resources allocated for the failed session by using the SIP session timer. Based on the SIP session timer, we propose a dynamic session refreshing approach to adjust the session timer depending on the radio link conditions for wireless VoIP subscribers. The study indicates that with our dynamic session refreshing approach, the session failure can be efficiently detected without a considerable increase of signaling traffic.