USITS 2001 Abstract
PRO-COW: Protocol Compliance on the WebA Longitudinal Study
Balachander Krishnamurthy, AT&T Labs--Research; and Martin Arlitt, Hewlett-Packard Laboratories
With the recent (draft) standardization of the Hypertext Transfer Protocol - HTTP/1.1 protocol on the Web, it is natural to ask what percentage of popular Web sites speak HTTP/1.1 and how compliant are these so-called HTTP/1.1 servers. We attempt to answer these questions through a series of experiments based on the protocol standard. The tests were run on a comprehensive list of popular Web sites to which a good fraction of the Web traffic is directed. Our experiments were conducted on a global extensible testing infrastructure that we built to answer the above questions. The tests were carried out over a period of 16 months and were repeated thrice during the period. Our results show reasons for concern on the state of HTTP/1.1 protocol compliance: some servers do not properly support basic features such as the HEAD method, while many popular servers do not support some of the key features (such as persistent connections) that were added in HTTP/1.1. Perhaps most alarming of all, some servers crashed during testing. As a result we believe that small (but signicant) changes to the
wording of the protocol specication are required.