Authors: Hua Chen, Marc Abrams, Tommy Johnson, Anup Mathur, Ibraz Anwar, and John Stevenson
A two-tier Web caching and replication system, called the INTELSAT Internet Delivery System (IDS) is discussed. Based on a Warehouse-Kiosk paradigm, IDS provides global access and Internet wormholes via a fleet of INTELSAT satellites, the largest commercial satellite communications system in the world. Web content such as cacheable HTTP, FTP and streaming objects are fetched or pushed both actively and reactively into a central repository cache via intelligent Web agents. Fresh objects are constantly sent via IP multicast reliably to registered Kiosk caches. Distributed Web caches in the Kiosks offer content to their local users directly with improved quality of service and less bandwidth cost.
In the IDS architecture, intelligence is added to a conventional Web cache to acquire popular, valuable content into the system in multiple modes and to keep it fresh. These include an adaptive refresh agent, an object discovery crawler and a reactive agent based on the pull functionality in a traditional Web cache. To efficiently store the multicast delivery of Web content both from the Warehouse to Kiosks, and from content providers to the Warehouse, an HTTP PUSH method is proposed as an open protocol for proxies. It follows the message format defined in HTTP 1.1. This method has been integrated into the SQUID Web proxy server to co-exist with other methods like GET. Test results are presented for the performance of this two-way Web cache under various stress tests. Preliminary data collected from the test bed of an upcoming international trial have shown that, as an additional layer complementing existing network resource, IDS is a promising adjunct for the next generation Internet infrastructure to improve network performance.
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