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.
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