Improving the WWW: caching or multicast?

We consider two schemes for the distribution of popular Web documents. In t he first scheme the sender repeatedly transmits the Web document into a mul ticast address, and receivers asynchronously join the corresponding multica st tree to receive a copy. In the second scheme, the document is distribute d to the receivers through a hierarchy of Web caches. We develop analytical models for both schemes, and use the models to compare the two schemes in terms of latency and bandwidth usage. We find that except for documents tha t change very frequently, hierarchical caching gives lower latency and uses less bandwidth than multicast. For rapidly changing documents, multicast d istribution reduces latency, saves network bandwidth, and reduces the load on the origin server. Furthermore, if a document is updated randomly rather than periodically, the relative performance of CMP improves. Therefore, th e best overall performance is achieved when the Internet implements both so lutions, hierarchical caching and multicast. (C) 1998 Elsevier Science B.V. All rights reserved.