Implicit Quality Channels (IQC): Distributed Quality Management for Multi-Party Real-Time Applications
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Multi-party, interactive multimedia (MIM) applications pose challenges for resource management due to their simultaneous use of multiple media and their heterogeneous, distributed, and potentially large numbers of participants. Two main difficulties are the support of (1) quality of service (QoS) and (2) scalable group or multi-peer communication, where QoS management is complicated by relationships between different media streams and by the sizes and dynamics of groups. That is, QoS management must capture not only the identities of group participants, but also their run-time behavior. This paper describes a novel operating system construct, termed Implicit Quality Channels (IQC), which extends standard Berkeley Sockets to support resource management of multi-peer applications like teleconferencing and CSCW. Specifically, when a participant joins an MIM, its inclusion in the MIM's quality management infrastructure is triggered transparently. Such inclusion is implemented in three steps. First, when creating a listening socket, the MIM associates appropriate quality management information with that socket. Second, when another participant connects to this socket, the operating system kernels involved implicitly create a kernel-level event channel that will carry this QoS as well as adaptation information. Third, the resource managers on the participating hosts transparently subscribe to this event channel, thereby dynamically creating appropriate groupings of collaborating resource managers and ensuring that all participants are managed properly.Management includes the monitoring of participant behavior, the submission and receipt of adaptation events, and the dealing with requests for re-negotiation of the initial QoS. In effect, any MIM participant establishing a connection to an MIM-provided socket implicitly accepts the MIM's QoS management.