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- backbone
- The top level in a hierarchical network. Stub and
transit networks that connect to the same backbone are guaranteed to be
interconnected.
- browser
- A program that lets you display a file containing hypertext and graphic images. The browser also lets
you navigate from one hypertext file to another via links using URLs.
- cache
- Memory holding recently accessed data, designed to speed up subsequent access to the same data. The term
cache is often applied to processor-memory access but can also be used to indicate a local copy of data
Internet accessible within a network.
- client
- A computer system or process that requests a service of another computer system or process (referred to
as a server). For example, a workstation requesting the contents of a file from a file server is a client
of the file server.
- cookie
- A handle, transaction ID or other token of agreement between cooperating programs.
An HTTP cookie is data sent by an HTTP server to a browser and then sent back by the browser
each time it accesses that server. Cookies can contain any arbitrary information the server chooses
and are used to maintain a state (i.e., a computer's configuration, attributes, condition or information
content) between stateless HTTP transactions.
Typically an HTTP cookie is used to authenticate or identify a registered user of a web
site without requiring an additional sign-in every time that site is accessed. Cookies are also used to
maintain a "shopping basket" of goods selected for purchase during a session at a site, to personalize a site
(i.e., presenting different pages to different users), and to track a particular user's access to a site.
- DAHA
- See Dynamically Assigned Host Address (DAHA).
- datagram
- A packet format with Internet headers defined by the Internet Protocol (IP). Datagrams are self-contained,
independent entities carrying sufficient information to be routed from the source to the destination computer
without relying on earlier exchanges between this source and destination computer and the transporting network.
Datagrams are small and of a fixed size. See also data packet.
- data packet
- The basic unit of information exchange between computers engaged in data communications.
- de facto standard
- A widespread consensus on a particular product or protocol that has not been ratified by any official
standards body, such as the International Organization for Standardization (ISO), but which nevertheless has a
large market share. The ISO is a voluntary, nontreaty organization founded in 1946 that is responsible for
creating international standards in many areas, including computers and communications.
- DNS
- See Domain Name System (DNS).
- domain
- Refers to a group of computers whose hostnames share a common suffix, the domain name. Some
important domains are .com (commercial), .edu (educational, mostly U.S.), .net (network
operations), .gov (U.S. government) and .mil (U.S. military). Most countries also have a domain, for
example, .us (United States), .uk (United Kingdom) and .au (Australia). See also DNS.
- Domain Name System (DNS)
- A general-purpose distributed, replicated, data query service chiefly used on the Internet for translating hostnames into Internet addresses. Also, the style of hostname used on the Internet (though
such a name is properly called a fully qualified domain name). DNS can be configured to use a sequence of name
servers, based on the domains in the name being looked for, until a match is found.
The Domain Name System refers to both the way of naming hosts and the servers and clients that administer that
information across the Internet.
- Dynamically Assigned Host Address (DAHA)
- An AOL proprietary method of assigning IP addresses when a member signs on. An IP tunnel server
assigns the address and allows the member access to the Internet.
- handle
- A number or token that lets a program access a resource. Programs often
receive a handle in response to a request for a resouce, and then they use
the handle when they need to access the resource. When the program uses
the handle, the value of the handle tells the system which resource, from
the pool of resources maintained by the system, to use.
- hostname
- The unique name by which a computer is known on a network. The hostname is used to identify the computer in
electronic mail, Usenet news, or other forms of electronic information exchange.
On the Internet, the hostname is an ASCII string, e.g., schnauz.office.aol.com, that consists of a local
part (schnauz.office) and a domain name (aol.com). The hostname is translated into
an Internet address either via the /etc/hosts file or an application like Domain Name System
(DNS). It is possible for one computer to have several hostnames (aliases) though one is designated as its standard
or primary name.
- HTML
- See HyperText Markup Language (HTML).
- HTTP
- See HyperText Transfer Protocol (HTTP).
- hypermedia
- An extension of hypertext that includes graphics, sound, video and other kinds of data.
- hypertext
- A collection of documents (or nodes) containing cross-references or links which, with the aid of an interactive browser
program, let the reader move easily from one document to another. See also hypermedia.
- HyperText Markup Language (HTML)
- The markup language with which World Wide Web (WWW) documents are written. HTML lets you create hypertext links, fill-in
forms and clickable images (i.e., images that you click to access another area).
- HyperText Transfer Protocol (HTTP)
- An application-level protocol for distributed, hypermedia information systems. HTTP/1.0 is the version presently used.
HTTP/1.1 is in pre-release stage.
- Internet protocol (IP)
- A protocol that enables packets of data to be transmitted throughout the
Internet using the transmission control protocol (TCP).
A data entity is broken into individual packets. Each packet is wrapped
with header information that indicates where the packet came from, where
it is going, and what part of a whole entity it belongs to. Once the packets
arrive at their destination, they are reassembled into their original order
by TCP.
- IP address
- Internet protocol (IP) address. A unique 32-bit number specified as four 8-bit numbers (represented as integers)
called octets. The four octets are connected by periods. The numbers must be in the range 0-255. A sample IP
address is 255.32.3.10.
This address is often assigned by a government agency called the DDN Network Information Center (NIC).
- lossy
- Refers to a data compression algorithm that actually reduces the amount of information in the data, rather than just the number
of bits used to represent that information. The lost information is usually removed because it is subjectively less important
to the quality of the data (usually an image or sound) or because it can be recovered reasonably by interpolation from the
remaining data.
- origin server
- A server on which a given resource resides or was created.
- protocol
- A set of formal rules describing how to transmit data, especially across
a network. Low-level protocols define the electrical and physical standards
to be observed, bit- and byte-ordering and the transmission and error detection
and correction of the bit stream. High-level protocols deal with the data
formatting, including the syntax of messages, the terminal-to-computer dialog,
character sets, and sequencing of messages.
- proxy
- An intermediary program that acts as both a server and a client for the purpose of making requests on behalf of other
clients. Proxies are often used as client-side portals (i.e., a trusted agent that can access the Internet on the client's
behalf) through the network firewall and as helper applications for handling requests via protocols
not implemented by the user agent.
- server
- An application program that accepts connections in order to service requests by sending back responses.
- stub network
- A network that only carries packets to and from local hosts. Even if it has paths to more than one other network, it
does not carry traffic for other networks. See also backbone and transit network.
- transit network
- A network that passes traffic between other networks in addition to carrying
traffic for its own hosts. It must have paths to at least two other networks.
See also backbone and stub
network.
- Transmission Control Protocol/Internet Protocol (TCP/IP)
- The de facto standard Ethernet protocols
incorporated into 4.2BSD UNIX and developed by the Department of Defense
(DOD) for communications between computers. The DOD's Defense Advanced
Research Project Agency (DARPA) developed TCP/IP for internetworking,
encompassing both network-layer and transport-layer protocols. While TCP and
IP specify two protocols at specific layers, TCP/IP is often used to refer
to the entire DOD protocol suite.
- uniform resource locator (URL)
- A text string of a standard format that describes the address of a networked
resource. There are two basic types of URL formats that are prefixed: http://www
and aol:// (Internet and America Online type). The America Online
URL (aol://) can define an internal (within the host) address (for
example, aol://4400:2164) or an external (Internet) address (for
example, aol://home:kodak).
- URL
- See uniform resource locator.
- user agent
- The client that initiates a request. User agents are
often browsers, editors, spiders (web-traversing applications) or other
end-user tools.
- web site
- Any computer on the Internet running a World Wide Web server process.
A particular web site is identified by the hostname
part of an URL. Multiple hostnames may actually map to
the same computer, in which case they are known as virtual servers.
- wrapper
- An envelope placed around a data packet, which
typically provides new header information including destination and source
address information. Wrappers are often used to transport one type of packet
through a different network protocol.
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