Cooperative Architectures and Algorithms for Discovery and Transcoding of Multi-version Contents

A clear trend of the Web is that a variety of new consumer deviceswith diverse computing powers, display capabilities, andwired/wireless network connections is gaining access to the Internet.Tailoring Web content to match the device characteristicsrequires functionalities for content transformation, namelytranscoding, that are typically carried out by the content Webserver or by an edge proxy server. In this paper, we explorehow to improve the user response time by considering systemsof cooperative edge servers which collaborate in discovering,transcoding, and delivering multiple versions of Web objects.The transcoding functionality opens an entirely new space ofinvestigation in the research area of distributed cache cooperation,because it transforms the proxy servers from contentrepositories along the client-server path into pro-active networkelements providing computation and adaptive delivery.We propose and investigate different algorithms for cooperativediscovery, delivery, and transcoding in the context of edgeservers organized in hierarchical and flat peer-to-peer topologies.We compare the performance of the proposed schemesthrough ColTrES (Collaborative Transcoder Edge Services),a flexible prototype testbed that implements all consideredmechanisms.