Encyclopedia of Computer Science and Technology

DNS 155Remote Method Invocation (Java/RMI). While these implementationsare quite different in details, they provide mostof the elements and facilities summarized above.ApplicationsDistributed computing is particularly suited to applicationsthat require extensive computing resources and thatmay need to be scaled (smoothly enlarged) to accommodateincreasing needs (see grid computing). Examplesmight include large databases, intensive scientific computing,and cryptography. A particularly interesting exampleis SETI@home, which invites computer users to install aspecial screen saver that runs a distributed process duringthe computer’s idle time. The process analyzes radiotelescope data for correlations that might indicate receipt ofsignals from an extraterrestrial intelligence (see cooperativeprocessing).Besides being able to marshal very large amounts ofcomputing power, distributed systems offer improved faulttolerance. Because the system is decentralized, if a particularcomputer fails, its processes can be replaced byones running on other machines. Replication (copying) ofdata across a widely dispersed network can also provideimproved data recovery in the event of a disaster.Further ReadingFarley, Jim, and Mike Loukides. Java Distributed Computing. Sebastopol,Calif.: O’Reilly, 1998.Garg, Vijay K. Concurrent and Distributed Computing in Java. NewYork: Wiley, 2004.———. Elements of Distributed Computing. New York: Wiley,2002.Goff, Max K. Network Distributed Computing: Fitscapes and Fallacies.Upper Saddle River, N.J.: Prentice Hall, 2003.MacDonald, Matthew. Microsoft .NET Distributed Applications:Integrating XML Web Services and .NET Remoting. Redmond,Wash.: Microsoft Press, 2003.Obasanjo, Dare, and Sanjay Bhatia. “An Introduction to DistributedObject Technologies.” Available online. URL:http://www.25hoursaday.com/_IntroductionToDistributedComputing.html. Accessed February 1, 2008.Shan, Yen-Ping, Ralph H. Earle, and Marie A. Lenzi. EnterpriseComputing with Objects: from Client-Server Environments to theInternet. Reading, Mass.: Addison-Wesley, 1997.SETI@Home. Available online. URL: http://setiathome.ssl.berkeley.edu/. Accessed August 14, 2007.DNS (domain name system)The operation of the Internet requires that each participatingcomputer have a unique address to which data packetscan be routed (see Internet and tcp/ip). The DomainName System (DNS) provides alphabetical equivalents tothe numeric IP addresses, giving the now familiar-lookingWeb addresses (URLs), e-mail addresses, and so on.The system uses a set of “top-level” domains to categorizethese names. One set of domains is based on thenature of the sites involved, including: .com (commercial,corporate), .edu (educational institutions), .gov (government),.mil (military), .org (nonprofit organizations), .int(international organizations), .net (network service providers,and so on).The other set of top-level domains is based on the geographicallocation of the site. For example, .au (Australia),.fr (France), and .ca (Canada). (While the United States hasthe .us domain, it is generally omitted in practice, becausethe Internet was developed in the United States).ADAEAFAGAIALAMANAOAQARASATAUAWAZBABBBDBEBFBGBHBIBJBMBNBOBRBSBTBVBWBYBZCACCCFCGCHCICKCLCMCNCOCRINTERNET COUNTRY CODES(partial list)AndorraUnited Arab EmiratesAfghanistanAntigua and BarbudaAnguillaAlbaniaArmeniaNetherlands AntillesAngolaAntarcticaArgentinaAmerican SamoaAustriaAustraliaArubaAzerbaijanBosnia and HerzegovinaBarbadosBangladeshBelgiumBurkina FasoBulgariaBahrainBurundiBeninBermudaBrunei DarussalamBoliviaBrazilBahamasBhutanBouvet IslandBotswanaBelarusBelizeCanadaCocos (Keeling) IslandsCentral African RepublicCongoSwitzerlandCôte d’Ivoire (Ivory Coast)Cook IslandsChileCameroonChinaColombiaCosta Rica