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Figure 7.6 Power-bandwidth function of active routers
In general, the ECOFEN model consists of three parts:
T
0
∫
ET
()
=
Powertdt
()
•
Energy consumption equation:
. This equation defines the energy
consumption during the time period of
T
to be the accumulation of the power consumption
function
Power
(
t
) all over the period.
•
Router energy consumption model:
E = E
boot
+
E
work
+
E
halt
. This defines the energy con-
sumption of a router to be the accumulation of the energy consumption when the router is
booting, working, and halting.
•
Power-bandwidth function: In
Figure 7.6
, we only show the phased power-bandwidth func-
tion of active routers. This function shows the power variation of the routers along with the
occupied bandwidth of the link. From
Figure 7.6
, it can be seen that with the increment of
occupied bandwidth, the power consumption of the router only incurs a negligible incre-
ment. Until the occupied bandwidth reaches a certain level, the power of the router will incur
a significant increase indicating that the link rate is increased.
According to this energy consumption model, the power-bandwidth function, spe-
cifically the power consumption of active routers, shows a clear steplike pattern with
the link rate. Based on this model, the relationship between link rate and energy con-
sumption of routers can be clearly seen, and the potential possibilities of reducing data
transfer energy consumption by link rate control is clearly revealed.
7.4
Novel cost-effective data transfer strategy LRCDT
Based on the network model and data transfer energy consumption model, in this
section we present details of our novel LRCDT strategy for energy-efficient data
transfer in the Cloud. Under the assumption of the dedicated Cloud network with
bandwidth reservation, our LRCDT schedules the bandwidth for each data transfer
task. By leveraging the phenomenon that the power level of network devices only
changes when the link rate is changed but is insensitive to the utilization of the
bandwidth, LRCDT conducts data transfer in a link rate controlled fashion. This
means that the link rate of network devices is limited to the minimum level while
as much available bandwidth as possible (within the link rate) is scheduled for data
transfer tasks. In LRCDT, data transfer tasks are divided into two types according to
the data transfer speed requirement. These are “eager” data transfer and “lazy” data
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