Every time a user attempts to access material located on a Web server by entering a domain name address into a Web browser, a request is made to a Domain Name Server, which is a directory of domain names and Ip addresses, to “resolve,” or translate, the domain name address into an Ip address.  That Ip address is then used to locate the Web server from which content is being requested.  A Web site may be accessed by using either its domain name address or its Ip address.

A domain name address typically consists of several parts.  For example, the alphanumeric URL http://www.paed.uscourts.gov/documents/opinions can be broken down into three parts.  The first part is the transfer protocol the computer will use in accessing the content (e.g., “http” for Hypertext Transfer Protocol); next is the name of the host server on which the information is stored (e.g., www.paed.uscourts.gov); and then the name of the particular file or directory on that server (e.g., documentsopinions).  A single Web page may be associated with more than one URL.  For example, the URLs http://www.newyorktimes.com and http://www.nytimes.com will both take the user to the New York Times home page.  The topmost directory in a Web site is often referred to as that Web site’s root directory or root URL.  For example, in http://www.paed.uscourts.gov/documents, the root URL is http://www.paed.uscourts.gov.  There may be hundreds or thousands of pages under a single root URL, or there may be one or only a few.

There are a number of Web hosting companies that maintain Web sites for other businesses and individuals, which can lead to vast amounts of diverse content being located at the same Ip address.  Hosting services are offered either for a fee, or in some cases, for free, allowing any individual with Internet access to create a Web site.  Some hosting services are provided through the process of “Ip-based hosting,” where each domain name is assigned a unique Ip number.  For example, www.baseball.com might map to the Ip address “10.3.5.9” and www.XXX.com might map to the Ip address “10.0.42.5.”  Other hosting services are provided through the process of “name-based hosting,” where multiple domain name addresses are mapped to a single Ip address.  If the hosting company were using this method, both www.baseball.com and www.XXX.com could map to a single Ip address, e.g., “10.3.5.9.”  As a result of the “name-based hosting” process, up to tens of thousands of pages with heterogeneous content may share a single Ip address. 2.  The Indexable Web, the “Deep Web”; Their Size and Rates of Growth and Change