Low carbon economy considerations in designing and operating content delivery networks for VoD services

The advances in information, computer technology and broadband connectivity have eased the way to reach desired content. This is especially true for the Internet TV (IPTV) services such as Video-on-Demand (VoD). This has brought forth many technical challenges regarding the distribution of electronic content, such as how to send large video files, how to deal with the stream load from large numbers of users, and how to transmit the video stream to a global network over a long distance. To address this, Content Delivery Networks (CDN) have been brought into the overall VoD system design. CDNs are based on a system of data centers containing servers and massive storage that places copies from the content library closer to the end user. However, this trend brings some unfavorable conditions in terms of energy usage; worldwide, data centers account for a significant percentage of the total energy consumed by ICT industry. Better energy efficiency of data centers would significantly cut the CO ₂ emission from ICT operations. As a CDN is an assembly of mutually interconnected data centers the overall efficiency has to factor for efficiency of each CDN geographical node/data center. The aggregate energy efficiency could not be simple multiplication of individual data centers/servers involved but has to introduce corrective factors to account for energy efficiency tradeoffs brought about by specific geographcal CDN topology and how effectively the additional resources deployed and energy consumed by them helps improve content access performance of a given CDN design. In this article, we aim to shed additional light onto the technical challenges and recommend possible improvements as related to the energy consumption within a given CDN topology.