FEATURE: GREEN NETWORKING
savings that can be achieved across
the estate. Newer, more advanced
switches contain smart power
control. Kicked off initially with the
IEEE802.3az Green Ethernet standard,
and now often referred to as EEE
(energy efficient Ethernet), these
devices switch off the transmitters in
the PHY (physical interface) when not
needed, detect when far-end devices
like PCs are inactive and instigate
sleep-mode. They even measure
the length of the link when active –
turning down their transmit power
(and hence power draw) to match.
Most importantly, the operating
systems of these switches have the
facility to completely de-activate
the PHYs of individual ports so that
they consume no power at all. So
take the trouble to do this and you’ll
immediately save kilowatts of 24*7
power consumption. (And disconnect
patch cords on unused ports to avoid
confusion, increase airflow and re-use
instead of buying more.)
Even though switch ports individually
use only a watt or two, by the time
you’ve multiplied that by 10,000
or so around the estate and each
burning power 8,860 hours per year
you will understand why – as far back
as 2005 is was estimated that the
combined pool of switch ports in the
USA devoured 5.3Terawatt hours
(Tw) of energy a year. Imagine what
that figure would be were it not for
technology like EEE?
Make space for air
10Gigabit/s cabling is required by
the data centre standards and is
now being installed in an increasing
proportion of large enterprise projects.
But some standard UTP Category 6A
cables are bulky, difficult to work with
and seriously impede both in-rack and
under-floor airflow. The consequence
of this is that cooling fans have to work
harder and draw a lot more power.
Shielded Cat6A cables are smaller
in diameter whilst some specifically
designed for the data center like
Brand-Rex zone cable is as thin as
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INTELLIGENTCIO
Cat5e cable freeing up the airflow
and allowing fans to slow down and
use less power.
Fibre or copper
It seems this debate will rage on for
as long as we need to transport bits
from A to B. The truth is there is no
one-solution-fits-all answer.
If 10Gbit/s is the highest speed your
network will ever need then copper is
probably the answer. You can lay in
Cat6A cables well in advance of need,
but fit only EEE Gigabit switches. In
fact you can save more power by
doing this and then delaying the roll
out of more power hungry 10Gb/s
switches until they are absolutely
needed. And then only upgrading
enough switches to match the real
need and not a blanket upgrade.
If fibre is an option for tour
application then consider the power
consumption for single-mode versus
multi-mode versus copper and factor
this into your business case. Bear in
mind that one pair of single mode
fibres will handle 1Gb/s, through
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