Vachaspathi P. Kompella

Multicast routing for multimedia communication

The authors present heuristics for multicast tree construction for communication that depends on: bounded end-to-end delay along the paths from source to each destination and minimum cost of the multicast tree, where edge cost and edge delay can be independent metrics. The problem of computing such a constrained multicast tree is NP-complete. It is shown that the heuristics demonstrate good average case behavior in terms of cost, as determined by simulations on a large number of graphs. >

Multicasting for multimedia applications

The authors investigate multicast routing for high-bandwidth delay-sensitive applications in a point-to-point network as an optimization problem. They associate an edge cost and an edge delay with each edge in the network. The problem is to construct a tree spanning the destination nodes, such that it has the least cost, and so that the delay on the path from the source to each destination is bounded. Since the problem is computationally intractable, the authors present an efficient approximation algorithm. Experimental results through simulations show that the performance of the heuristic is near optimal.<<ETX>>

Filter Propagation in Dissemination Trees: Trading Off Bandwidth and Processing in Continuous Media Networks

We describe the concept of the relocatable continuous media filter. The novelty of these filters is how they can propagate over a dissemination tree in a network. We describe the filter propagation protocol to achieve this. Execution of filters inside a network allows the network to be viewed in a novel way, as a “processor” with its “instruction set” being the various types of available filters. Since filters generally modify the data rate of the continuous media stream, usually (but not necessarily) reducing it, filters allow the trading off of bandwidth and processing in a network.

Optimal multicast routing with quality of service constraints

We consider the problem of optimal multicast routing with Quality of Service constraints motivated by the requirements of interactive continuous media communication, e.g., real-time teleconferencing. We concentrate on distributed algorithms for determining a tree over the network topology, rooted at the source and spanning the intended destinations. Quality of Service requirements for interactive continuous media typically impose constraints on some metric over the individual paths from the source to each destination, usually in the form of an upper bound on the delay. Thus, we focus on the problem of minimizing the cost of the tree while at the same time satisfying a common constraint over individual source-destination paths. We have shown that this problem is intractable, but have also devised centralized polynomial time heuristics that perform well. Here we present distributed algorithms to minimize tree cost while satisfying the constraints on the paths from the source to each destination.

Real-time dissemination of continuous media in packet-switched networks

The authors present a model of communication in a packet-switched network called continuous-media (CM) dissemination, which is the distribution of digital audio, video, and other periodic time-correlated data streams, from a source to multiple receivers. This model is similar to that of a cable TV system. The authors discuss an important design principle, the principle of loose coupling between a source and multiple receivers, for supporting this type of communication. The main argument for loose coupling is that there can be an arbitrary number of receivers for a single source of a CM multistream, and that the complexity of keeping track of the states of all receivers would overwhelm the source. Applications of the design principle include group addressing, proactive dynamic control mechanisms, and individualized tailoring of the CM multistream by receivers with limited effect on the source.<<ETX>>