Graph measures of network content-delivery energy Although much effort has gone into conserving energy in networks at the device level and at the application level, these represent individual-centered metrics of energy conservation. This paper utilizes a large-scale network measure of energy efficiency for competing network architectures, dubbed the content-delivery energy (CDE). This energy-efficiency measure is derived in terms of the total networktraffic typically generated over a time range to satisfy n randomly chosen receivers requesting a single item of interest: all downloads of a new album within the first two weeks after its release, for example. This network-wide measure is intended to assess energy efficiency not only by reflecting the cost of typical single-sink-to-source communication within the scheme, but to capture also how the strategy amortizes costs over multiple receivers. The delivery methods considered include several peer to peerprotocols and several server layouts using unicast delivery.