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Abstract-Internet protocol (IP) based media delivery enables applications such as Voice over IP or, most recently, stereoscopic HD-TV. Suchlike transport of typically time-constrained media between two end-points has a number of important characteristics, both on the transport and content side. We focus on live streams of audio-visual data that are assumed as time-constrained and loss-tolerant. We aim at optimizing IP transport over heterogeneous networks by hybrid and loss domain separated error correction with residual error. Hybrid error correction (HEC) approaches the channel capacity dynamically and achieves predictable reliability and predictable delay (PRPD) when residual loss is tolerable, while loss domain separation applies optimally chosen HEC parameters to individual network segments. In this paper, we apply an atomic HEC coding unit to individual segments of network links between source and sink, and show by analysis and example how redundancy is distributed optimally.

Overlay architectures [1] are the information theoretical playgrounds of the Internet. They provide significant gains in throughput by shifting complexity into the network nodes. A consequence is the requirement for smart routers between adjacent network segments. Since meanwhile audiovisual media allocate the major part of the Internet traffic, protocols as well as overlay structures have to serve Predictable Reliability under Predictable Delay (PRPD). The link-level operation mode of the AHEC architecture [6] is an approach to fit individual channel coding parameters to inhomogeneous network segments. All link segments of a chosen network route share an overall time and reliability budget determined by the respective constraints of the application. Whereas some structures require support by all intermediate nodes, just the contribution from a limited number of routers is reasonable in the AHEC overlay: The budget distribution hits a saturation point above which configurations are suboptimal. This paper derives the saturation point with respect to the distribution of the delay constraint of audiovisual applications in the link-level operation mode of the AHEC. The result has major impact on the complexity of coding as well as the protocol parametrization.