Data Communications Networking Devices - 4th Ed.pdf

222 __________________________________________________________ WIDE AREA NETWORKSTable 2.5 Internet top-level domain namesDomain name AssignmentExisting.COM.EDU.GOV.MIL.NET.ORGPending.®rm.store.web.arts.rec.info.nomCommercial organizationEducational organizationGovernment agencyDepartment of DefenseNetworking organizationNot-for-pro®t organizationBusiness/commercial ®rmsGoods for purchaseWorld Wide Web related activitiesCulture/entertainment organizationsRecreation/entertainment organizationsInformation/servicesIndividual/personal nomenclatureInformation Center InterNIC) at the time this book was prepared. These toplevel domains are listed in Table 2.5.Under each top level domain the InterNIC will register subdomains which areassigned an IP network address. An organization receiving an IP network addresscan further subdivide their domain into two or more subdomains. In addition,instead of using dotted decimal notation to describe the location of each host, theycan assign names to hosts as long as they follow certain rules and install a nameserver which provides IP address translation between named hosts and their IPaddresses.To illustrate the operation of a name server consider the network domainillustrated in Figure 2.32. In this example we will assume that a well-knowngovernment agency has a local area network with several computers that will beconnected to the Internet. Each host address will contain the speci®c name of thehost plus the names of all of the subdomains and domains to which it belongs.Thus, the computer `WARRANTS' would have the of®cial address:warrants:telnet:fbi:govSimilarly, the computer `COPS' would have the addresscops:ftp:fbi:govIn examining the domain naming structure illustrated in Figure 2.32 note thatcomputers were placed in subdomains using common Internet application names,such as telnet and ftp. This is a common technique organizations use to make iteasier for network users both within and outside the organization to remembermnemonics that represent speci®c hosts on their network.