A
name that identifies one or more IP addresses. For
example, the domain name microsoft.com represents about a
dozen IP addresses. Domain names are used in
URLs
to identify particular Web pages. For example, in the URL
http://www.pcwebopedia.com/index.html, the domain name is
pcwebopedia.com.
Every domain name has a suffix
that indicates which top level domain (TLD) it belongs to. There
are only a limited number of such domains. For example:
Short for Domain Name
System (or Service or Server),
an Internet service that translates
domain
names into IP addresses. Because domain names are
alphabetic, they're easier to remember. The Internet however, is
really based on IP addresses. Every time you
use a domain name, therefore, a DNS service must translate the
name into the corresponding IP address. For example, the domain
name www.example.com might translate to 198.105.232.4.
The DNS system is, in fact, its
own network. If one DNS server doesn't know how to translate a
particular domain name, it asks another one, and so on, until
the correct IP address is returned.
An identifier for a computer or
device on a TCP/IP network. Networks using the TCP/IP protocol
route messages based on the IP address of the destination. The
format of an IP address is a 32-bit numeric address written as
four numbers separated by periods. Each number can be zero to
255. For example, 1.160.10.240 could be an IP address.
Within an isolated network, you
can assign IP addresses at random as long as each one is unique.
However, connecting a private network to the Internet requires
using registered IP addresses (called Internet addresses) to
avoid duplicates.
The four numbers in an IP address
are used in different ways to identify a particular network and
a host on that network. Four regional Internet registries --
ARIN, RIPE NCC, LACNIC and APNIC -- assign Internet addresses
from the following three classes.
The number of unassigned Internet
addresses is running out, so a new classless scheme called CIDR
is gradually replacing the system based on classes A, B, and C
and is tied to adoption of IPv6.
Because the Internet is based on
IP addresses, not domain names, every Web server requires a
Domain Name System (DNS) server to translate
domain names into IP addresses.
A program that searches documents
for specified keywords and returns a list of the documents where
the keywords were found. Although search engine is really
a general class of programs, the term is often used to
specifically describe systems like Alta Vista and Excite that
enable users to search for documents on the World Wide Web and
USENET newsgroups.
Typically, a search engine works
by sending out a spider to fetch as
many documents as possible. Another program, called an
indexer, then reads these documents and creates an index
based on the words contained in each document. Each search
engine uses a proprietary algorithm to create its indices such
that, ideally, only meaningful results are returned for each
query.
A program that automatically fetches
Web pages. Spiders are used to feed pages to
search engines. It's called a spider
because it crawls over the Web. Another term for these
programs is webcrawler.
Because most Web pages contain
links to other pages, a spider can start almost anywhere. As
soon as it sees a link to another page, it goes off and fetches
it. Large search engines, like Alta Vista, have many spiders
working in parallel.
Abbreviation of Uniform
Resource Locator, the global address
of documents and other resources on the World Wide Web.
The first part of the
address indicates what protocol to use, and the second
part specifies the IP address or the domain name where
the resource is located.
For example, the two URLs
below point to two different files at the domain
pcwebopedia.com. The first specifies an executable
file that should be fetched using the FTP protocol; the
second specifies a Web page that should be fetched using
the HTTP protocol:
Quik-Info
