Standard Update 25GBASE-T Joins the Party!

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Standard Update 25GBASE-T Joins the
Party!-Mark Mullins
www.flukenetworks.com 2006-2017 Fluke
Corporation
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Standard Update 25GBASE-T Joins the Party!
Since the development of 40GBASE-T (IEEE
802.3bq) began a few years ago, most of us
believed that the next Ethernet data center speed
for twisted-pair copper cabling beyond 10 Gb/s
would be 40 Gb/s. But in November 2014, IEEE
802.3 put out a call for interest on 25GBASE-T,
driven by the likes of Cisco, Microsoft and Intel
who recognized 25 Gb/s as a more efficient,
cost-effective option for switch-to-server speeds
in cloud-based data centers. Hence the 25GBASE-T
IEEE study group was formed. Within just four
months following the formation of the study
group, the objectives for 25GBASE-T were
determined and approved, and the development of
the 40GBASE-T standard was expanded to include
this new application. In other words, 25GBASE-T
has officially joined the party!
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Standard Update 25GBASE-T Joins the Party!
Not Exactly a Newcomer
If it seems as though the objectives for
25GBASE-T were established very quickly, thats
because they build upon much of the work that was
already completed by IEEE in the development of
40GBASE-T. For example, both applications are
slated to use the same Category 8 shielded
cabling in a two-connector, 30 meter channel.
Objectives also include support for full duplex
operation only, a bit error rate better than or
equal to 10-12, auto negotiation, Energy
Efficient Ethernet and point-to-point links over
structured cabling topologies, including directly
connected link segments. In other words, while
25GBASE-T is joining the party, its objectives
mirror that of 40GBASE-T and dont exactly
include any newfangled complexities.
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Standard Update 25GBASE-T Joins the Party!
A Welcomed Guest
With representatives from 25 companies
overwhelmingly pledging support for the formation
of the 25GBASE-T study group, the likes of
Microsoft, Cisco and Intel driving the party bus,
and a demonstrated broad market potential,
25GBASE-T is definitely a welcomed
partygoer. Why is 25GBASE-T considered a more
cost-effective step in the migration to
40GBASE-T? Not only does it support the backwards
compatibility of BASE-T technology and enable
equipment vendors to limit the power per port to
under 3W, it can also leverage existing
transceiver technology to establish a fixed
migration path to 40GBASE-T over the same
30-meter channel.  Furthermore, 25GBASE-T offers
something more than 25 Gb/s direct attach copper
(DAC) cables using the SFP form factordistance.
Limited to about 5 to 7 meters, passive 25 Gb/s
DAC cables are primarily targeted to top-of-rack
(ToR) topologies where switches connect directly
to servers in the same cabinet. At 30 meters,
25GBASE-T will support a broader range of
topologies, including end-of-row (EoR) and
middle-of-row (MoR) topologies that many large
cloud-based data centers see as an advantage over
managing switches in hundreds of racks.
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Standard Update 25GBASE-T Joins the Party!
A Welcomed Guest
And then there is the familiarity factor. Its
always easier to welcome a guest that everyone is
comfortable with. While category 8 twisted-pair
cabling that will be used for both 25GBASE-T and
40GBASE-T will be a fully shielded solution, it
is expected to use the popular RJ45 style
connector that has been in place for multiple
BASE-T generations.
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Standard Update 25GBASE-T Joins the Party!
The Party is in Full Swing
While 25GBASE-T just joined the 40BASE-T party,
development of PHYs to support both applications
have been in full swing for a while. It is
expected that 25GBASE-T equipment will be
available as early as this year, with the
standard planned for ratification in 2016. And
with cabling, equipment and standards in place
comes the need for testing. Since 25GBASE-T will
use the upcoming category 8 cabling that is well
into its development, the testing parameters are
already fairly well known. While the testing
standards for test accuracies and reporting
requirements have yet to be defined, you can rest
assured that Fluke Networks is hard at work on
the accuracy requirements and test equipment to
support this latest addition to the party.
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