Digital Watermarking
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Data Discovery, Routing and Traffic Patterns
Definition Data conferencing allows participants in a live session to transfer data and to share applications. Information between the users’ applications is transmitted over the network, live and in real-time. Data conferencing is one component of teleconferencing; the others are audio conferencing, and video conferencing. For a teleconferencing system that is ITU-T H.323 [1] compliant, the ITU-T T.120 set of standards [2] are recommended for data conferencing and application sharing, providing real-time communication between two or more entities in a conference. Applications specified as part of the T.120 family include application sharing, electronic whiteboarding, file exchange, and chat. Data conferencing is typically an optional capability in multimedia conferences. The shared data is usually transmitted between the users across the network using a reliable network protocol, such as the TCP (Transmission Control Protocol).
Cross-References ▶ Teleconferencing
References 1.
2.
International Telecommunication Union, Telecommunication Standardization Sector H.323 Recommendation – Packet-based multimedia communications systems, July 2003. International Telecommunication Union, Telecommunication Standardization Sector T.120 Recommendation – Data protocols for multimedia conferencing, July 1996.
Data Discovery in Multimedia
▶ Data Mining for Video Coding and Transcoding
Synonyms ▶ Storage retrieval of dynamic content
Definition Resource discovery and rendezvous mechanisms are necessary to dynamically locate media servers (e.g., the nearest or best servers), data storages, membership servers (for multicast sessions), or peers (e.g., other users) for direct connections. In general, the resource discovery module of CHaMeLeoN can be categorized as either ‘‘locationaware’’ or ‘‘location-free.’’ Location-aware architectures require availability of location information. They typically use geographic or trajectory routing to forward the updates or queries and include geographic rendezvous mechanisms (such as GLS [1], Rendezvous Regions [2], and GHT [3]) and trajectory advertisement schemes (such as TBF [4]). In location-aware networks, geographic-based distributed hash tables [2,3] are utilized to efficiently establish content based routing schemes. In earlier work [2], we designed a geographic rendezvous mechanism based on rendezvous regions. In this architecture, the network is divided into regions, and the resource key space (e.g., file space) is divided into prefixes. Each resource prefixes maps into a region. The mapping can be discovered dynamically using a bootstrap mechanism. We have shown that using regions (instead of locations as in GHT [3]) is robust to mobility and location inaccuracy effects. Furthermore, the performance of the rendezvous architecture depends on the data semantics and access pattern. For example, for media servers, where there is a high lookup-to-insertion ratio (meaning the media is accessed many times per storage), the Rendezvous Regions
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