Globally Distributed Content Delivery

Akamai's distributed content delivery system fights service bottlenecks and shutdowns by delivering content from the Internet's edge. A s Web sites become popular, they're increasingly vulnerable to the flash crowd problem, in which request load overwhelms some aspect of the site's infrastructure, such as the front-end Web server, network equipment, or bandwidth, or (in more advanced sites) the back-end transaction-processing infrastructure. The resulting overload can crash a site or cause unusually high response times — both of which can translate into lost revenue or negative customer attitudes toward a product or brand. Our company, Akamai Technologies, evolved out of an MIT research effort aimed at solving the flash crowd problem Our approach is based on the observation that serving Web content from a single location can present serious problems for site scalability, reliability, and performance. We thus devised a system to serve requests from a variable number of surrogate origin servers at the network edge. 1 By caching content at the Internet's edge, we reduce demand on the site's infrastructure and provide faster service for users, whose content comes from nearby servers. When we launched the Akamai system in early 1999, it initially delivered only Web objects (images and documents). It has since evolved to distribute dynamically generated pages and even applications to the network's edge, providing customers with on-demand bandwidth and computing capacity. This reduces content providers' infrastructure requirements , and lets them deploy or expand services more quickly and easily. Our current system has more than 12,000 servers in over 1,000 networks. Operating servers in many locations poses many technical challenges, including how to direct user requests to appropriate servers, how to handle failures, how to monitor and control the servers, and how to update software across the system. Here, we describe our system and how we've managed these challenges. Researchers have explored several approaches to delivering content in a scalable and reliable way. Local clustering can improve fault-tolerance and scalability. If the data center or the ISP providing connectivity fails, however, the entire cluster is inaccessible to users. To solve this problem, sites can offer mirroring (deploying clusters in a few locations) and multihoming (using multiple ISPs to connect to the Internet). Clustering, mirroring, and multihoming are common approaches for sites with stringent reliability and scalability needs. These methods do not solve all connectivity problems , however, and they do introduce new ones: I It is difficult …