How much TV is enough? Nowadays, it seems like
we spend most of our time watching it—not sleeping
or working or playing. Of course, that varies
widely. But we’re all TV junkies. And while we
have loads of TV now, we still want more. The affordability
and availability of HDTV has only increased that desire.
We get our TV mainly by cable, but many still watch it
over the air directly from local stations and increasingly by
satellite. Now, Internet Protocol television (IPTV) is being
delivered over high-speed Internet connections. While not
widespread yet, IPTV is becoming available in more places.
Let’s not overlook YouTube downloads and uploads,
which are clogging Internet service providers in many areas.
They’re stealing bandwidth from uers doing more mundane
things like e-mail and searches. All of this activity adds up to
a massive overload of all our wired communications systems,
from the Internet core to high-speed Internet connections
and even to the cabling in our homes.
Though generally invisible to the public, the demand for
ever higher data speeds is impacting the enterprise, especially
in data storage. Many government and industry regulations
mandate how data should be stored and handled, such
as Sarbanes-Oxley and the Health Insurance Portability and
Accountability Act.
Storage and archiving policies are forcing us to use
greater amounts of storage, but that requires faster access
and transmission times. There’s an overwhelming need for
faster serial data networks, which are in the works.
Eternally Ethernet
Ethernet is the most widely used
networking technology on the planet. Over the years, it has
followed a regular upgrade path from 10 Mbits/s to 100
Mbits/s to 1 Gbit/s to today’s 10 Gbits/s. While 10-Gbit
Ethernet (10GE) has been around for a while, it is
just now being gradually adopted. Prices have
dropped, 10GE switches are available,
and there are more options than ever.
Specially enhanced versions of Ethernet
like iWARP and other IETF-approved
(Internet Engineering Task Force) extensions
that use the remote direct memory
access (RDMA) protocol mitigate the CPU
usage and memory bottlenecks usually associated
with TCP transfers. New iWARP network interface cards like
those from NetEffect provide affordable 10GE performance
in servers (see the figure).
As 10GE adoption continues to broaden, work is under
way within the IEEE to extend Ethernet’s speed to the next
order of magnitude. The IEEE’s 802.3 Higher Speed Study
Group is working on a new standard called 802.3ba for 100
Gbits/s, or 100GE. It also will provide for an intermediate
40-Gbit/s version.
Designed as an interim solution, the 40-Gbit/s specification
will take advantage of the technology developed for the
Sonet/SDH OC-768 standard, which runs at 39.812 Gbits/s.
The IEEE is considering a range of options, including 10
parallel 10GE fibers, 10 wavelengths (λ) of 10GE on a dense
wavelength-division multiplexing (DWDM) single fiber, and
four 25-Gbit/s wavelengths on a single fiber. It will be at
least 2009 before such a standard or the hardware is ready.
The main problem with achieving 100 Gbits/s is the chromatic
dispersion of the fiber, which lengthens the pulses
over distance, thereby limiting speed. Considerable work
has already been done in dispersion compensation, but
those efforts must be extended to reach the 100-Gbit/s goal.
Electronic dispersion compensation (EDC) methods
show promise, but higher-level modulation schemes like
differential quadrature phase-shift keying (DQPSK) also are
being considered. Few problems are expected at the usual
Ethernet distance of 100 m, but plans call for 10- and 40-km
versions that will require special compensation measures.
Already, 10GE is affecting other networking technologies.
For example, Fibre Channel (FC), the most widely
used storage-area networking (SAN) technology, appears to
be a fading standard. This fiber-based network has
kept pace with storage transmission speeds
and is currently available in 1-, 2-, and
4-Gbit/s formats. Versions at 8
and 10 Gbits/s are in
the
works, but they
may
never be widely
adopted
because
of
their
high cost.
FC is still the
dominant SAN methodology,
but its popularity for new
installations is giving way to the
Internet Small Computer Systems
Interface or iSCSI (eye scuzzy)
standard,
which uses off-the-shelf and lower-cost Ethernet.
FC is expected to decline further with the widespread adoption
of 10GE and its application to iSCSI.