IMAGIS, a PACS software solution for the National Health System in Cuba

Abstract

Elastic Internet applications have the greatest share in the traffic transported over the Internet today. Web access and e-mail are the most popular applications among most people using the Internet. Although these applications can well adapt to a wide range of bandwidths, their performance is an issue to people using services interactively.In this paper, we use sophisticated application-level evaluations to extract traffic characteristics and performance measures for HTTP, SMTP and POP3 from traffic traces. The process of loading Web pages by real browsers using persistent and parallel connections is studied in detail, revealing statistics about the elements in Web pages as well as the number of parallel connections and the accumulated waiting time during Web page loads.The main results are: (1) High variance distributions are not only found as expected in file sizes, but also in the number of items in a Web page, the number of e-mails transmitted in one connection, the duration of SMTP command exchanges or even the users' viewing times for Web pages. (2) Web browsers utilize more parallel connections than usually expected to simultaneously load items. (3) A large portion of the delay in Web page retrievals or e-mail transfers is due to serial waiting and can therefore not be significantly reduced by increasing bandwidths. Therefore, low latency is as much an issue in access systems as high bandwidth.