Encyclopedia of Computer Science and Technology

neural interfaces 335The growing appetite for data-rich applications such ashigh-fidelity audio and video (see streaming and multimedia)tends to put a strain on the capacity of most networks.In response, institutional users look to optical fiber andother high capacity connections (see bandwidth), whilehome users are rapidly switch in from dial-up service onregular phone lines (see modem) to DSL phone lines andcable.While existing network architectures have workedremarkably well, they were designed for only a small fractionof today’s traffic. There have been a number of initiativesand proposals for higher capacity networks andfor integrating new features (such as security and e-mailsender verification). For a review of these developments, seeInternet architecture and governance.Further ReadingDerfler, Frank J., Jr., and Les Freed. How Networks Work. 7th ed.Indianapolis: Que, 2004.Donahue, Gary. Network Warrior. Sebastapol, Calif.: O’ReillyMedia, 2007.Komar, Brian. Sams Teach Yourself TCP/IP Networking in 21 Days.2nd ed. Indianapolis: Sams, 2002.Kozierok, Charles. “The TCP/IP Guide.” Available online. URL:http://www.tcpipguide.com/free/index.htm. Accessed August16, 2007.Tanenbaum, Andrew S. Computer Networks. 4th ed. Upper SaddleRiver, N.J.: Prentice Hall, 2002.networked storageWith huge databases, e-commerce and other Web servers,and even home media centers, more data needs to be servedover networks than ever before. There are two commonways to provide storage for databases and other resourceson a network.A network attached storage (NAS) unit can be thought ofas a dedicated data storage unit that is available to all usersof a network. Unlike a traditional dedicated file storage unit(see file server), a NAS unit typically has an operatingsystem and software designed specifically (and only) forproviding data storage services. The actual storage is usuallyprovided by an array of hard drives (see raid). Fileson the NAS are accessed through protocols such as SMB(server message block), common on Windows networks,and NFS (network file system), used on many UNIX andsome Linux networks. In recent years smaller, lower-costNAS devices have become available for smaller networks,including home networks, where they can store music,video, and other files (see also media center PC).Storage Area Network (SAN)Although it sounds similar, a storage area network (SAN)does not function as its own file server. Rather, it attachesstorage modules such as hard drives or tape libraries to anexisting server so that it appears to the server’s operatingsystem as though it were locally attached. Typically theprotocol used to attach the storage is SCSI (see SCSI), butthe physical connection is fiber or high-speed Ethernet. Theemphasis for SAN applications is the need for fast access todata, such as in large online databases, e-mail servers, andhigh-volume file servers. SANs offer great flexibility, sincestorage can be expanded without changing the networkstructure, and a replacement server can quickly be attachedto the storage in case of hardware failure.Further ReadingBird, David. “Storage Basics: Storage Area Networks.” Availableonline. URL: http://www.enterprisestorageforum.com/sans/features/article.php/981191. Accessed October 5, 2007.NAS. Network World. Available online. URL: http://www.networkworld.com/topics/nas.html. Accessed October 5,2007.Network Attached Storage Reviews and Price Comparisons. PCMagazine. Available online. URL: http://www.pcmag.com/category2/0,1738,677853,00.asp. Accessed October 5, 2007.Poelker, Christopher, and Alex Nikitin. Storage Area Networks forDummies. New York: Wiley, 2003.Preston, W. Curtis. Using SANs and NAS. Sebastapol, Calif.:O’Reilly, 2002.Tate, Jon, Fabiano Lucchese, and Richard Moore. Introductionto Storage Area Networks. 4th ed. IBM Redbooks. Availableonline. URL: http://www.redbooks.ibm.com/redbooks/pdfs/sg245470.pdf. Accessed October 5, 2007.neural interfacesIn the kind of science fiction sometimes called “cyberpunk,”people are able to “jack in” or connect their brains directly tocomputer networks. Because of this direct input into the brain(or perhaps the optic and other sensory nerves), a personwho is jacked in experiences the virtual world as fully real,and can (depending on the world’s rules) manipulate it withhis or her mind. This kind of all-immersive virtual reality isstill science fiction, but today people are beginning to controlcomputers and artificial limbs directly with their minds.NeuroprostheticsNeuroprosthetics is the creation of artificial limbs or sensoryorgans that are directly connected to the nervous system.The first (and most widely used) example is the cochlearimplant, which can restore hearing by taking sound signalsfrom a microphone and converting them to electricalimpulses that directly stimulate auditory nerves within thecochlea, a part of the inner ear. Similarly, experimental retinalimplants that stimulate optic nerves are beginning tooffer crude but useful vision to certain blind patients.Research in connecting the brain to artificial arms orlegs is still in its early stages, but scientists using microelectrodearrays have been able to record signals from thebrain’s neurons and correlate them to different types ofmotor movements. In a series of experiments at Duke University,researchers first trained a monkey to operate a joystickto move a shape in a video game. They then recordedand analyzed the signals produced by the monkey’s brainwhile playing the game, and correlated them with themotor movements in the joystick. Next, they replicatedthese movements with a robotic arm as the monkey movedthe joystick. Finally, they were able to train the monkey tomove the robotic arm without using the joystick at all, simplyby “thinking” about the movements.