Fault-Tolerant Real-Time Streaming with FEC thanks to Capillary Multi-Path Routing

Erasure resilient FEC codes in off-line packetized streaming rely on time diversity. This requires unrestricted buffering time at the receiver. In real-time streaming the playback buffering time must be very short. Path diversity is an orthogonal strategy. However, the large number of long paths increases the number of underlying links and consecutively the overall link failure rate. This may increase the overall requirement in redundant FEC packets for combating the link failures. We introduce the Redundancy Overall Requirement (ROR) metric, a routing coefficient specifying the total number of FEC packets required for compensation of all underlying link failures. We present a capillary routing algorithm for constructing layer by layer steadily diversifying multi-path routing patterns. By measuring the ROR coefficients of a dozen of routing layers on hundreds of network samples, we show that the number of required FEC packets decreases substantially when the path diversity is increased by the capillary routing construction algorithm

Fault-Tolerant Streaming with FEC through Capillary Multi-Path Routing

Abstract – Erasure resilient FEC codes in off-line packetized streaming rely on time diversity, which in its turn relies on unrestricted buffering time at the receiver. In real-time streaming the playback buffering time must be very short. Path diversity is an orthogonal strategy, but its drawback is that large number of long paths increases the number of underlying links and consecutively the overall link failure rate. It may result in increase of the overall requirement in redundant FEC packets combating the link failures. We introduce Redundancy Overall Requirement (ROR), a routing coefficient of the total number of FEC packets required for compensation of all underlying link failures. We present capillary routing algorithm constructing layer by layer steadily diversifying multi-path routing patterns. By measuring ROR coefficients of a dozen of routing layers on hundreds of network samples, we show that the number of required FEC packets decreases substantially when the path diversity is achieved by capillary routing algorithm. I

SFIO, Parallel File Striping for MPI-I/O

SFIO, Parallel File Striping for MPI-I/O Emin Gabrielyan EPFL, Computer Science Dept. Peripheral Systems Lab. [email protected] Abstract This paper presents the design and evaluation of a Striped File I/O (SFIO) library for parallel I/O in an MPI environment. We present techniques for optimizing communications and disk accesses for small striping factors. Using MPI derived datatype capabilities, we transmit fragmented data over the network by single MPI transfers. We present first results regarding the I/O performance of the SFIO library on DEC Alpha clusters, both for the Fast Ethernet and for the TNet Communication networks

Rating of Routing by Redundancy Overall Need

Thanks to the large buffering time of off-line streaming applications, erasure resilient Forward Error Correction (FEC) codes can improve the reliability of communication particularly well. However real-time streaming puts hard restrictions on the buffer size making FEC inefficient for combating long link failures on single path routes. Path diversity is orthogonal to buffering and permits real-time streaming to also benefit from application of FEC. We introduce a capillary routing algorithm offering layer by layer a wide range of multi-path routing topologies starting from a simple solution and evolving toward reliable routing patterns with highly developed path diversity. The friendliness of a multi-path routing pattern is rated by the overall amount of FEC redundancy required for combating the non-simultaneous failures of all links of the communication footprint. We rated the friendliness of a dozen of capillary routing layers, built on several hundreds of network samples obtained from a random walk Mobile Ad-Hoc Network (MANET). The overall requirement in redundant FEC codes decreases substantially as the spreading of the routing grows

Reliable Multi-Path Routing Schemes for Real-Time Streaming

In off-line streaming, packet level erasure resilient Forward Error Correction (FEC) codes rely on the unrestricted buffering time at the receiver. In real-time streaming, the extremely short playback buffering time makes FEC inefficient for protecting a single path communication against long link failures. It has been shown that one alternative path added to a single path route makes packet level FEC applicable even when the buffering time is limited. Further path diversity, however, increases the number of underlying links increasing the total link failure rate, requiring from the sender possibly more FEC packets. We introduce a scalar coefficient for rating a multi-path routing topology of any complexity. It is called Redundancy Overall Requirement (ROR) and is proportional to the total number of adaptive FEC packets required for protection of the communication. With the capillary routing algorithm, introduced in this paper we build thousands of multi-path routing patterns. By computing their ROR coefficients, we show that contrary to the expectations the overall requirement in FEC codes is reduced when the further diversity of dual-path routing is achieved by the capillary routing algorithm.Comment: Emin Gabrielyan, "Reliable Multi-Path Routing Schemes for Voice over Packet Networks", ICDT'06, International Conference on Digital Telecommunications, Cote d'Azur, France, 29-31 August 2006, pp. 65-7