Automatic Deployment of Transcoding Components for Ubiquitous, Network- Aware Access to Internet Services

摘要

Advances in wireless communication together with the growing number of mobile end devices hold the potential of ubiquitous access to sophisticated internet services; however, such access must cope with an inherent mismatch between the low-bandwidth, limited-resource characteristics of mobile devices and the high-bandwidth expectations of many content-rich services. One promising way of bridging this gap is by deploying application-specific components on the path between the device and service, which perform operations such as protocol conversion and content transcoding. Although several researchers have proposed infrastructures allowing such deployment, most rely on static, hand-tuned deployment strategies restricting their applicability in dynamic situations. In this paper, we present an automatic approach for the dynamic deployment of such transcoding components, which can additionally be dynamically reconfigured as required. Our approach relies on three components: (a) a high-level integrated type-based specification of components and network resources, essential for 'late binding' components to paths; (b) an automatic path creation strategy that selects and maps components so as to optimize a global metric; and (c) system support for low-overhead path reconfiguration, consisting of both restrictions on component interfaces and protocols satisfying application semantic continuity requirements. We comprehensively evaluate the effectiveness of our approach over a range of network and end- device characteristics using both a web-access scenario where client performance is for reduced access time, and a streaming scenario where client preference is for increased throughput. Our results verify that (1) automatic path creation and reconfiguration is achievable and does in fact yield substantial performance benefits; and (2) that despite their flexibility, both path creation and reconfiguration can be supported with low run-time overhead.