Abstract: Described is a communication mechanism that provides push-to-talk functionality for mobile and desktop computing environments. Mobile and desktop computers are configured as client computers in a client/server architecture. Some of the client computers are configured to handle multiple push-to-talk sessions simultaneously. If multiple streams from different sessions are active at the same time, the client computer may determine which of these overlapped streams to record and then record them for later playback. A server handles the registration of the client computers, manages the multiple sessions for each of the client computers, and performs a floor control process so that each push-to-talk session operates in a half-duplex mode.

Abstract: Transmission optimization for application-level multicast is described. For each member of a video conference, a multicast tree is generated that represents a data communication configuration of a data source and the other members of a video conference which are data recipients that receive video and audio data from the data source. An end-to-end transmission delay from each data source to each of the respective data recipients is determined, and the available bandwidth between each data source and the respective data recipients is determined. One or more of the multicast trees, each corresponding to a data source, are refined according to the end-to-end transmission delay and available bandwidth for a particular data source to optimize the data communication configuration of the data source in the video conference.

Abstract: The techniques and mechanisms described herein are directed to controlling communication paths between conference members in a decentralized multi-party conference that supports a full mesh architecture. Several check points are tested in order to handle concurrency issues and to ensure quality of service. First, a check is made to determine whether any pending communication paths exist between the two systems. Second, a check is made to determine whether one of the systems is in the process of leaving the multi-party conference. Third, a check is made to determine whether a maximum number of conference members already exist in the conference. Upon failing any of these checks, the communication path between the two systems fails. Upon success, the new system initiates the joining process with each of the other members in the conference in order to maintain the full mesh architecture.