Energy interactions between multicast and content distribution within data communication networks

While commercial data center energy use has shown remarkable progress, other ways to reduce the energy used on behalf of Internet devices within the global telecommunications network have not yet been used to their full benefit; one pertinent example is exploiting the economies of scale that exist due to the remarkable overlap between what individuals are using the Internet to do, creating some definite patterns and commonalities among what individuals watch or download at any given moment, thereby giving a high degree of collective redundancy to Internet transmissions. Redundant transmissions are wasted bits; by some measures, fully capitalizing on this wasted redundancy could reduce the number of transmissions at individual network nodes by as much as two orders of magnitude. Missing from prior analyses is an assessment of the degree to which two current common methods of reducing network activity related to popular content, namely multicast transmissions and a set of mechanisms for wider content distribution such as in-network caching, proxy or edge servers, complement and interfere with one another when the goal is improving the energy efficiency of the ICT as a whole. It can be seen that both categories of methods reduce the number of transmissions in the network; yet dispersing network activity to a wider set of sources also has the unintentional effect of reducing the exploitable redundancy for multicast. This paper defines and characterizes the tradeoff of multicast energy gain for energy gain via shorter transmission paths and the conditions within which overall energy savings occurs.