Partial order and partial reliability transport service innovations in a multimedia application context.

摘要

This dissertation investigates an innovation in computer communications called Partially Ordered and Partially Reliable ( PO/PR) Transport Service. PO/PR service bridges the gap between two traditional forms of transport service: Ordered/Reliable (O/R) service, such as the Internet's Transmission Control Protocol (TCP), and Unordered/Unreliable (U/U) service, such as the Internet's User Datagram Protocol (UDP). Some applications—in particular, multimedia applications—require services that lie in between these two extremes. U/U service is insufficient for these applications, yet O/R service is too restrictive and may cause the application to pay a performance penalty.; Previous investigations of PO/PR transport service used analytic and service called Partial Order Connection. We build on this work by first describing several innovations in PO/PR transport service developed by the dissertation author, including a new approach to coarse-grained multimedia synchronization based on extending the Object-Composition Petri Net (OCPN) of Little and Ghafoor. We then provide empirical evidence that an implementation of Partially Ordered/Reliable (PO/R) transport service called Partial Order Connection version 2 (POCv2) can provide better Quality of Service (QoS) tradeoffs to applications by providing a transport service better matched to an application's needs. In particular, we show that for multimedia document retrieval, PO/R service provides performance benefits over O/R transport service when the network loses packets.; Our experiments compare O/R service to PO/R service for a variety of documents, bit rates, window sizes, and propagation delays, with packet loss rates ranging from 0% to 30%. The results show that between 5% and 20% loss, user-perceivable improvements in progressive display are observed for bit rates between 2.4kbps to 512kbps. These results suggest that transport services providing reliable delivery over independent streams (such as the emerging Internet protocol SCTP) can provide important performance benefits over lossy networks (including wireless nets or combat net radios).; We also describe two systems developed by the dissertation author for experimenting with transport services: (1) the Universal Transport Library (UTL), a framework for implementation and testing of transport services, and (2) a Remote Multimedia Document Retrieval System (ReMDoR) that uses UTL transport services.