CATP: a context-aware transportation protocol for HTTP

Abstract

The rendering mechanism used in Web browsers have a significant impact on the user behavior and delay tolerance of retrieval. The head-of-line blocking phenomena prevents the browser to render partial results within the HTTP document. This phenomena stems from two factors: TCP's in-order data uploading to the browsers and HTML tag matching constraint. We propose a context-aware transportation protocol (CATP) to run on top of UDP. This protocol does not transmit HTML pages in-order Instead, it reorganizes the pages and transmit HTML tags first before transporting their enclosed data. Conforming browsers receive the page structures and fill them in with subsequent data packets in whatever sequence they arrive. As a result, lost and delayed packets do not hinder rendering of those that are logically behind but have already arrived at the client sides. Thus the retransmission of the lost frames can be concealed and overall user perceived performance improved. The user-perceivable performance is quantified in terms of silent time during which no activity is observed at the browser display. The protocol also facilitates partial content caching, non-interactive applications of Web services. We validated this protocol through prototype implementation and compared the performance with TCP and in-order delivery UDP schemes. Our protocol provides better user-perceivable performance under various loss loss rates and document sizes.