Using Content-Derived Names for Caching and Software Distribution

Abstract

Maintaining replicated data in wide area information services such as the World Wide Web is a difficult problem. Ensuring that the correct versions of libraries and images are installed for application programs presents similar challenges. In this paper, we present a simple scheme to facilitate both of these tasks using content-derived names (CDNs). Content-based naming uses digital signatures to compute a name for an object based only on its content. CDNs can be applied to several common problems of modern computer systems. Caching on the World Wide Web is simplified by allowing references to an object by its content rather than just its location. In a similar fashion, applications can request library objects by their content without having to rely on the presence of a file system hierarchy that the application recognizes. Further, applications that require different versions of an object can coexist peacefully on the same machine. While this idea is still in its early stages, we present experimental evidence from a study of World Wide Web objects that indicates that CDNs could reduce network traffic by allowing requests to be satisfied by differently-named duplicates with the same contents. (Also cross-referenced as UMIACS-TR-96-55)