located in Herndon, Virginia. InterNIC controls all Internet addresses and naming conventions. Each website is identified by an address indicator known as a Uniform Resource Locator (URL). The URL is a unique alphanumeric code that allows you to quickly locate and access a specific website. A typical URL  might  read:  http://www.weather.edu.  The  first part of the URL indicates the type of Internet protocol your computer must use. In this case, http:// (hypertext transfer protocol), is used. The second part of the URL represents the name of the web server (www) followed by the website’s domain (weather.edu). Most URLs end with an extension identifier that is used to access a particular  network  domain,  such  as  .edu  (educational institutions), .com (commercial websites), and .mil (military  websites). Websites   can   be   easily   accessed   by   using commercial software known as a web browser. As soon as you type in the URL of the website you wish to access, your browser goes to the web server that holds the page and retrieves it. If a specific website address is unknown, there are Internet search engines that can be used to rapidly locate websites pertaining to a particular area of interest. For example, a keyword such as "aircraft," or a more specific term, such as "F-14 Tomcat," may be used to easily locate information concerning  that  topic. A  wealth  of  information  is  available  via  the Internet. But keep in mind that since any individual or organization can develop their own website, not all the information is accurate or reliable. Also, keep in mind that the Internet is not a secure telecommunications network. Military Networks The U.S. military operates its own environment on the  Internet  that  provides  more  security  than commercial methods. This environment, known as the Defense Information Systems Network (DISN), is managed by the Defense Information Services Agency (DISA).  It  consists  of  two  primary  networks,  the NIPRNET  (Nonsecure  Internet  Protocol  Routing Network) and the SIPRNET (Secure Internet Protocol Routing Network). These networks require special dedicated circuits as directed by higher authority. Most Navy  and  Marine  Corps  METOC  activities  have NIPRNET access, and many also have SIPRNET access. In addition, almost all METOC activities, including most ships, maintain their own website (or homepage).  Each  of  these  websites  may  contain information on command history and mission, as well as provide access to various environmental products. Figure  1-6  is  an  example  of  the  Naval  Training Meteorology and Oceanography Facility (NTMOF), Pensacola,  Internet  homepage. A   tremendous   amount   of   environmental information can be downloaded from various METOC activities.  The  NIPRNET  and  SIPRNET  can  be  used  to access  environmental  data  from  the  website  at  the  Fleet Numerical  Meteorology  and  Oceanography  Center (FNMOC), Monterey, California, including Navy Oceanographic  Data  Distribution  System  (NODDS) products and products from the Joint METOC Viewer (JMV). User manuals for NODDS, JMV, and other software programs can also be downloaded via the FNMOC  website.  In  addition,  there  are  several nonmilitary and nongovernment websites that contain valuable  environmental  information,  which  include looped   satellite   images,   current   weather   maps, climatological data, and so forth. Many METOC websites  include  links  to  other  sites  with  related information. Table 1-2 contains a listing of some of the most frequently accessed METOC-related websites. Bulletin Board Systems There  are  still  a  few  environmental  software programs that are available via bulletin board systems. Bulletin board services are acquired by dialing a telephone number for access to government computer networks. All government bulletin board services, including NODDS, require user identification codes and passwords. These are provided along with detailed operating instructions for all registered system users. All user identification codes and passwords must be protected and should never be disclosed to unauthorized users.  Once  user  identification  and  passwords  have been entered, your computer will be connected to the bulletin board system. Electronic Mail Electronic   mail   or   e-mail   is   the   electronic transmission  of  messages,  letters,  documents,  and  other materials via a communications network, such as the Internet. It allows computer-based messages to be electronically edited, replied to, or pasted into another electronic document. Most e-mail allows messages to be sent to multiple recipients. E-mail may even contain graphics,  sound,  and  video  attachments.  Messages  or files are sent to "accounts" or electronic mail addresses. An e-mail address is a unique identifier that is used to 1-9