Networks Can Deliver The Universal Database On Waves Of light.

Copper cabling technologies remained the primary interconnect technology for computing components and devices as the past century ended. Today, the predominant communication technology is clearly fiber optics. Fiber optics is the science of transmitting data, voice, and images by the passage of lightwaves through thin, transparent optical fibers. At the basis of the storage networking movement and the Internet explosion is the promise and reality that bandwidth is becoming much more readily available. The bandwidth era and what it means has now risen to the forefront of strategic planning roadmaps for the IT industry and customers alike. With the ability to compute and store information achieving unprecedented levels of price/performance improvement annually, our focus shifts to communication as being the single force that can have more impact than-all the other developments.

The over-arching goal through the evolution of SAN, NAS, Fibre Channel, SCSI, Infiniband, and a variety of wireless and satellite technologies is based on enabling data communications and information movement to become instantaneous, universal, and virtually free. Bandwidth capacity is growing at 300+ % per year, about ten times more on an annual basis than processor power. This delta and how long it might last will be the subject of several future discussions. Currently, bandwidth availability has been outpacing the bandwidth demand. This abundance reminds us of the storage industry that has just completed a decade of more supply than demand, notwithstanding growth rates at over 60% per year. This past year, the price of carrying data fell nearly 25%, while the price of carrying telephony fell about 30%. The auctioning of bandwidth online has already begun and will become more popular to the SSP (Storage Service Provider) model as it unfolds. Though the IT industry debates endlessly about the future of Fibr e Channel, SCSI, xGigE, PCI, ATM, SONET, and, now, Infiniband, the key strategic enabler for any of these is the optical fiber that carries potentially any and all of these protocols.

Optical fiber provides users with higher performance, improved reliability, greater distance, and more flexibility than copper-based systems. Optical fiber is immune to many of the factors that adversely affect copper and many of the factors that become more evident at higher data rates. Since fiber carries light rather than electricity, radio frequency interference signals, and cross talk (signals from conductors that are closely coupled) do not affect fiber optic transmission. The relatively low level of security has now risen to become the primary concern of the Internet community. Since fiber can't be tapped into without interrupting service, any unwanted taps can be fairly easily detected making fiber a more secure transport medium. Fiber is also less expensive to maintain than copper, since it has fewer problems and correspondingly requires less maintenance activity. Measurement data and statistics for fiber usage and deployment are limited, but sources, generally, agree that for every 1% decrease in the price of bandwidth, demand for bandwidth increases 1.5%. The case for fiber rather than copper-based transmission has been made and is obvious.

DWDM Is Key

The current state of the art fiber optic transmission allows 80 wavelengths of light to be placed on a single fiber strand carrying 80 gigabits of data per second. An 864-strand fiber cable can transmit nearly 5.6 million gigabits per second. Fundamental to enabling fiber optic cables to achieve even greater potential is DWDM (Dense Wave Division Multiplexing), which is radically expanding the capability of fiber optic cable. DWDM increases the capacity of existing fiber by assigning optical signals to densely packed wavelengths of light and transmitting them across one fiber strand. At this writing, the ability to carry 6.4 terabits of data per second has been demonstrated using DWDM technology. Each wavelength corresponds to a single DWDM channel and a single fiber optic strand carries multiple wavelengths of light, therefore the name wave division multiplexing. A laser encodes or modulates the data into an optical signal for each wavelength in the system. The process is reversed at the other end where the signals are reassembled.

The higher cost of opto-electronic components is an issue with DWDM, as each wavelength requires an expensive transmitter and receiver at each end. There is no industry standard for DWDM today. The process of converting electrical content into light impulses and conversely light impulses into electrical content is the major remaining performance bottleneck and involves additional costs due to the electronic equipment needed. The ultimate hardware solution is to create an all-optical data path with no software involvement. When an optically transmitted data stream on 10 Gigabit Ethernet meets an electronic switch, the optical signal has to be converted to electronics and, then, transmitted at data streams of 2.5Gbps or less. Light is faster than electricity (silicon) and getting faster every day. This delta will also be the subject of several future articles.

Bandwidth Demand

The overall demand for bandwidth is now based on the projected growth of three components: voice, data, and the Internet. The forecasted bandwidth demand by year-end 2000 is expected to be close to 4Tbps with voice accounting for nearly 20% and the Internet about 25% of the total. By 2004, global bandwidth demand will approach 25Tbps. The total demand for voice is projected to be less than 5%, while the Internet is expected to account for over 50% of the bandwidth consumed. The Internet, as previously noted, accounts for about 8% of all of the KWH generated in the U.S. today and is expected to account for as much as 50% of the KWH by 2010.

According to the research firm Telegeography, all of the 81.8 billion minutes (or 56,805,556 days) of telephone calls that were carried across the worldwide public telephone network (copper) in 1997 could be transmitted across a single fiber cable in 11 days today. The average Internet message packet now takes 17 hops to reach its destination and average delays range between 200ms and 600ms. A public Internet message test by the MidRange Performance Group in Boulder, CO (www.mpginc.com) took 451 hops to successfully reach its destination. This growing "delay syndrome" poses an increasingly serious response time barrier for certain applications. Light wave transfer via fiber optic cable can ease this pain significantly, but performance is still a growing concern for Internet users at long distances as traffic volume increases, even with fiber capability. We will have to deal with congestion through means other than just bandwidth.

The Internet e-commerce explosion is the single biggest factor driving the need for bandwidth, though not the only one. With the supply side of bandwidth not presently a limiting factor, the industry is struggling to determine what the demand levels will be for the next-generation of applications. E-mail, the first killer app for the Internet, clearly stands out, as it is bracing for content consuming voice-mail and video-mail components. Video-mail clips ranging from ten minutes to several hours in duration will change the parameters of the global data transmission industry, as video must be transmitted at a minimum of 4Mbps to deliver a steady image. (Voice and text can survive on 56Kbps). We have created the capability to deliver the universal database, using light waves to transmit all types of content. The basis for delivering a virtually instantaneous communication capability to the world is now within our grasp.