language: en

Real-Time Reliable Multicast Using Proactive Forward Error Correction

Dan Rubenstein, Jim Kurose, and Don Towsley
Computer Science Department University of Massachusetts
Amherst, MA 01003
fdrubenst, kurose, towsleyg@cs.umass.edu Technical Report 98-19
Department of Computer Science
March 1998

Abstract Real-Time reliable multicast over a best-effort service network remains a challenging research problem. Most protocols for reliable multicast use repair techniques that result in significant and variable delay, which can lead to missed deadlines in real-time scenarios. This paper presents a repair technique that combines forward error correction (FEC) with automatic repeat request (ARQ). The novel aspect of the technique is its ability to reduce delay in reliable multicast delivery by sending repairs proactively (i.e., before they are required). The technique requires minimal state at senders and receivers, and no additional active router functionality beyond what is required by the current multicast service model. Furthermore, the technique uses only end-to-end mechanisms, where all data and repairs are transmitted by the data-originating source, leaving receivers free from any burden of sending repairs. We simulate a simple round-based version of a protocol embodying this technique to show its effectiveness in preventing repair request implosion, reducing the expected time of reliable delivery of data, and keeping bandwidth usage for repairs low. We show how a protocol using the technique can be adapted to provide delivery that is reliable before a real-time deadline with probabilities extremely close to one. Finally, we develop several variations of the protocol that use the technique in various fashions for high rate data streaming applications, and present results from additional simulations that examine performance in a variety of Internet-like heterogeneous networks.

1 Introduction