| 摘要 |
An IP telephony gateway and a voice mail resource enable a voice mail subscriber to place an outgoing call to a destination party from a voice mail session according to the voice over IP (H.323) protocol, and resume the voice mail session upon completion of the outgoing call with the destination party. The IP telephony gateway establishes a voice mail session for the voice mail subscriber with the voice mail resource across a first Real Time Protocol (RTP) data stream. The voice mail resource initiates a second RTP data stream to a destination party in response to reception of a prescribed command from the voice mail subscriber. Although an RTP bridge connecting the first and second RTP data streams can be maintained by the voice mail resource, the voice mail resource may also use the Empty Capability Set feature in the H.323 standard to cause the IP telephony gateway to close the first and second RTP data streams to the voice mail resource. The voice mail resource then issues Non-Empty Capability Set messages to the IP telephony gateway for the first and second RTP data streams, causing the IP telephony gateway to internally bridge the first and second RTP data streams. The voice mail resource monitors connections between the voice mail subscriber and the destination party, and upon detecting a disconnect by the destination party causes the IP telephony gateway to resume the voice mail session, by repeating the sequence of sending Empty Capability Set and Non-Empty Capability Set messages to the IP telephony gateway to break down the bridge and re-establish the connection between the voice mail subscriber and the voice mail resource.
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