Reliable byte stream

Abstract: The usage of multimedia applications on the Internet has seen phenomenal growth in recent years. Transport protocols that provide partially reliable service have been suggested as one approach to better handle the requirements of these applications. A partially reliable service provides applications with the possibility of a flexible tradeoff between reliability and delay/throughput. Appropriately designed coders are, however, required to fully utilize a partially reliable service. In this paper we present a JPEG image coder tailored to suit the behavior of a partially reliable byte stream service. With regular JPEG, data loss typically results in severely distorted images. The robust recoder employs three major modifications to standard JPEG in order to adapt to the partially reliable transport: (1) extended resynchronization markers in order to be able to resynchronize effectively, (2) block interleaving in order to spread out the loss of a packet across the image and (3) error concealment in order to minimize the perceived quality loss. The modifications incorporate both new inventions, such as random window interleaving, as well as variations of previously known techniques.

Abstract: Recently, applications' demands for the network become more multifaceted. Highly functional application-to- application communication services such as bandwidth aggregation, fault tolerant communication, and delay/disruption tolerant networking (DTN) were developed independently in the network layer, the transport layer, and the application layer. As a result, protocol layering has become complicated. This paper proposes Layer-5 (L5) inserted between the application layer and the trans- port layer to separate communication policies and communication mechanisms to make protocol layering clearer. The transport layer (L4) provides end-to-end communication mechanisms such as reliable byte stream while L5 realizes communication policies such as bandwidth aggregation by combining the communication mechanisms in L4. This paper proposes five types of L5-paths as communication policies: (1) the L5 bundled path for bandwidth aggregation or fault tolerant communication, (2) the L5 spatially- spliced path for communication with middleboxes, (3) the L5 temporally-spliced path for DTN, (4) the L5 spliced- bundled path, and (5) the L5 bundled over spatially-spliced path. An application can select and use an appropriate L5- path depending on the network circumstances through a common API. A prototype of L5 is implemented in the Linux user space as a library to make deployment and maintenance easier. The evaluation shows that establishment time of L5- paths is short enough and performance of L5-paths is comparable or superior to existing technologies.