• Domain Names and IP Addresses
  • The Domain Name System (DNS) and Your Domain

    Download 100.46 Kb.
    Hajmi100.46 Kb.
    1   2   3   4   5   6   7

    The Domain Name System (DNS) and Your Domain

    The Domain Name System, or DNS, is a remarkable distributed database that provides a mechanism for naming hosts on the Internet. It’s called the Domain Name System because it divides the global Internet into a number of administrative domains, each of which can be sub-divided according to the desires of its administrators.

    At the top of the hierarchy are, appropriately enough, a series of “top-level” domains many of which will be familiar to you:

    Each of these top-level domains has its own meaning which dates back to the beginning of the Internet:
    .com Commercial entity, typically a corporation or small business.

    .net Traditionally, an Internet service provider. Today, anyone who wishes to register a .net domain is able to do so, regardless of whether they represent a computer network of any sort.

    .org Non-profit organization.

    .gov Governmental entity.

    .edu Institution of higher education.

    .us Any entity associated with a geographic or political subdivision of the United States. In particular, a .us subdomain exists for every state in the nation; thus mi.us is the subdomain for Michigan.
    The state hierarchy within the .us domain is well-suited to domains assigned to municipalities, counties, and school districts.
    This naming system is oriented towards the United States due to the historical fact that the Internet was born in the United States. Two-character country codes analogous to .us exist for every country on Earth. For example, .uk is the United Kingdom; .ca is Canada; .ch is Switzerland. (Note, however, that many .org, .net, and .com registrations apply to non-U.S. organizations.)
    You may already have a domain assigned to your organization, which you may decide to use to house your new community information site. In this case you do not need to register a new domain. Instead, you need merely ask your domain administrator to assign you a new host name if necessary. You may want to read further about domains and host names to understand this process better.

    In many cases, a new CI project will want to establish its own new domain. How you proceed depends on the domain you wish to use. For instance, you may want to register your CI site in the .org, .com, or .net domains. In this case, you will need to contact a registrar for these “top-level” domains, either directly or through the services of your ISP.
    Note that domain names are not case-sensitive. For marketing purposes, you may publish your domain with capital letters; smallville.org and Smallville.org refer to the same site.
    As this book goes to press, the handling of these top-level domains is undergoing a major change, as the process moves from a monopoly to a new shared scheme. From 1993 until 1999, all registration in these domains was handled by the registration “InterNIC,” a service of Network Solutions, Inc. As of this writing, Network Solutions remains a service provider in this arena, but a number of new companies will be added to the mix, each offering registration on a competitive basis.
    If you wish to register a new domain in .org, .net, or .com, your options are:

    • Register using the services of Network Solutions. Visit www.networksolutions.com.

    • Use one of the new competitive registration services. For a list, visit www.icann.org.

    • Work with your ISP to register the domain. You can use the services of your existing ISP, or you can use the services of one of a large number of “host content” services to register a domain on your behalf. Many ISPs offer free “domain parking” which allows you to register a new domain without any special fee for the creation of the domain. (In all cases, you must pay a fee to the actual registrar, whether it is Network Solutions or one of the new registrars. The current rate as of this writing is $70 per two years per domain.)

    If you want a domain outside of .org, .net, and .com, such as a domain in the mi.us hierarchy, you must pursue this with the administrator of the domain in question. The handling of the .us domain is documented here:

    A convention that’s commonly applied calls for “ci” to be in the domain name of a community information site. For instance, the domain ci.east-lansing.mi.us might be used for a CI project for East Lansing, Michigan.
    The DNS works on a distributed basis. The existence of your domain (for instance, smallville.org) is recorded in a root server. Every domain must run its own DNS server – in fact, a primary server and a backup are required. In turn, each domain is able to add hosts within its domain. Thus, if you wish to have a server called www.smallville.org, it’s up to your domain administrator to add an entry into your domain server. The DNS allows any user anywhere on the global Internet to discover www.smallville.org through a simple process: first the user’s computer discovers where the DNS server for smallville.org resides; then, the user’s computer interrogates that server to find the specific address of www.smallville.org.

    For obvious reasons, it is important that your DNS server remain operational as much as possible. If it’s down, your users won’t be able to locate your server. (In fact, you’re expected to have a primary and a backup DNS server in order to assure reliable participation in the Domain Name System.) Often your ISP will be willing to provide DNS services on your behalf as part of the cost of providing you with a dedicated Internet connection.

    Domain Names and IP Addresses

    Every host computer – server or otherwise – on the Internet is assigned an IP address. IP addresses are four-part, all-numeric “handles” that are easily used by networks. For instance, the Community Information site for East Lansing, Michigan has a host name of www.ci.east-lansing.mi.us; it has a corresponding IP address of

    In general, each computer on the Internet has its own host name and its own IP address. However, it’s possible for a single computer to have more than one host name. For instance, you may want to register both ci.smallville.mi.us and www.ci.smallville.mi.us as host names for your Web server. This allows users who guess your host name to find the computer either way. In this case, your server administrator simply creates an “alias” in your DNS tables so that both host names correspond to the same IP address.

    In this example, the Web server for the Jet Propulsion Laboratory, jpl.nasa.gov, has been assigned the IP address Normally the only people who have to worry about IP addresses are the administrators of servers or networks. If an organization handles its own IP address administration, it will be assigned a pool of IP addresses to use when new computers are installed. If IP administration is handled by an organization’s ISP, new addresses will be assigned by the ISP’s domain administrator, and given to the administrator of each new server as it is installed.
    It’s also possible for a single physical computer to have more than one IP address associated with it. This may be done to support virtual hosts, or it may be done if the server has more than one LAN (Ethernet) adapter installed for performance reasons. In the most common case, you will only have one IP address per server (or other computer) you install.
    Generally speaking, you never want to publish the IP address of your Web server – or any other server. Let the DNS map the friendly host names to IP addresses for you and your users. Users should see friendly, domain-style host names, not IP addresses, in the URLs your publish and in the “Location” box on their Web browsers.

    Download 100.46 Kb.
    1   2   3   4   5   6   7

    Download 100.46 Kb.

    Bosh sahifa

        Bosh sahifa

    The Domain Name System (DNS) and Your Domain

    Download 100.46 Kb.