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404 Error, diverted to internet glossary
ADSL
(Asymmetric Digital Subscriber Line) A DSL line where the upload speed is
different from the download speed. usually the download speed is much
greater.
Applet
A small Java program that can be embedded in an HTML page. Applets differ from
full-fledged Java applications in that they are not allowed to access certain
resources on the local computer, such as files and serial devices (modems,
printers, etc.), and are prohibited from communicating with most other
computers across a network. The common rule is that an applet can only make an
Internet connection to the computer from which the applet was sent.
Authentication
The process of identifying an individual, usually based on a username and
password. In security systems, authentication is distinct from authorization ,
which is the process of giving individuals access to system objects based on
their identity. Authentication merely ensures that the individual is who he or
she claims to be, but says nothing about the access rights of the
individual.
Backbone
A high-speed line or series of connections that forms a major pathway within a
network. The term is relative as a backbone in a small network will likely be
much smaller than many non-backbone lines in a large network.
Bandwidth
How much stuff you can send through a connection. Usually measured in
bits-per-second. A full page of English text is about 16,000 bits. A fast modem
can move about 57,000 bits in one second. Full-motion full-screen video would
require roughly 10,000,000 bits-per-second, depending on compression.
BGP
Short for Border Gateway Protocol, an Internet protocol that enables groups of
routers (called autonomous systems) to share routing information so that
efficient, loop-free routes can be established. BGP is commonly used within and
between Internet Service Providers (ISPs).
BSD
BSD (originally: Berkeley Software Distribution) refers to the particular
version of the UNIX operating system that was developed at and distributed from
the University of California at Berkeley. "BSD" is customarily
preceded by a number indicating the particular distribution level of the BSD
system (for example, "4.3 BSD"). BSD UNIX has been popular and many
commercial implementations of UNIX systems are based on or include some BSD
code.
CGI
(Common Gateway Interface) A set of rules that describe how a Web Server
communicates with another piece of software on the same machine, and how the
other piece of software (the ?CGI program?) talks to the web server. Any piece
of software can be a CGI program if it handles input and output according to
the CGI standard.
CGI-bin
The most common name of a directory on a web server in which CGIprograms are
stored.
Client
A software program that is used to contact and obtain data from a Server
software program on another computer, often across a great distance. EachClient
program is designed to work with one or more specific kinds of Server programs,
and each Server requires a specific kind of Client. A Web Browser is a specific
kind of Client.
Colocation
Most often used to refer to having a server that belongs to one person or group
physically located on an Internet-connected network that belongs to another
person or group. Usually this is done because the server owner wants their
machine to be on a high-speed Internet connection and/or they do not want the
security risks of having the server on thier own network.
Daemon
Pronounced demon or damon, a process that runs in the background and performs a
specified operation at predefined times or in response to certain events. The
term daemon is a UNIX term, though many other operating systems provide support
for daemons, though they're sometimes called other names. Windows, for example,
refers to daemons and System Agents and services.
Typical daemon processes include print spoolers, e-mail handlers, and other
programs that perform administrative tasks for the operating system. The term
comes from Greek mythology, where daemons were guardian spirits.
DNS
Short for Domain Name System (or Service), 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.
Domain Name
The unique name that identifies an Internet site. Domain Names always have 2 or
more parts, separated by dots. The part on the left is the most specific, and
the part on the right is the most general. A given machine may have more than
one Domain Name but a given Domain Name points to only one machine. For
example, the domain names:
matisse.net
mail.matisse.net
workshop.matisse.net
can all refer to the same machine, but each domain name can refer to no more
than one machine. Usually, all of the machines on a given Network will have the
same thing as the right-hand portion of their Domain Names (matisse.net in the
examples above). It is also possible for a Domain Name to exist but not be
connected to an actual machine. This is often done so that a group or business
can have an Internet e-mail address without having to establish a real Internet
site. In these cases, some real Internet machine must handle the mail on behalf
of the listed Domain Name.
Ethernet
A very common method of networking computers in a LAN. There is more than one
type of Ethernet. By 2001 the standard type was "100-BaseT" which can
handle up to about 100,000,000 bits-per-second and can be used with almost any
kind of computer.
Firewall
A system designed to prevent unauthorized access to or from a private network.
Firewalls can be implemented in both hardware and software, or a combination of
both. Firewalls are frequently used to prevent unauthorized Internet users from
accessing private networks connected to the Internet, especially intranets. All
messages entering or leaving the intranet pass through the firewall, which
examines each message and blocks those that do not meet the specified security
criteria.
FTP
(File Transfer Protocol) A very common method of moving files between two
Internet sites.
Gateway
The technical meaning is a hardware or software set-up that translates between
two dissimilar protocols, for example America Online has a gateway that
translates between its internal, proprietary e-mail format and Internet e-mail
format. Another, sloppier meaning of gateway is to describe any mechanism for
providing access to another system, e.g. AOL might be called a gateway to the
Internet.
GUI
This is an acronym for Graphical User Interface. Examples are Windows and
Apple's Macintosh operating system. The concept originated in the early 1970s
at Xerox's PARC laboratory.
Host
1) A computer system that is accessed by a user working at a remote location.
Typically, the term is used when there are two computer systems connected by
modems and telephone lines. The system that contains the data is called the
host, while the computer at which the user sits is called the remote terminal.
(2) A computer that is connected to a TCP/IP network, including the Internet.
Each host has a unique IP address.
HTTP
(HyperText Transfer Protocol) The protocol for moving hypertextfiles across the
Internet. Requires a HTTP client program on one end, and an HTTP server program
on the other end. HTTP is the most important protocol used in the World Wide
Web (WWW).
Hub
A common connection point for devices in a network. Hubs are commonly used to
connect segments of a LAN. A hub contains multiple ports. When a packet arrives
at one port, it is copied to the other ports so that all segments of the LAN
can see all packets.
IDE
Integrated Drive Electronics. An interface used mainly by hard drives and
CD-ROM drives to connect to the computer.
IDS
An intrusion detection system (IDS) inspects all inbound and outbound network
activity and identifies suspicious patterns that may indicate a network or
system attack from someone attempting to break into or compromise a system.
There are several ways to categorize an IDS:
- misuse detection vs. anomaly detection: in misuse detection, the IDS analyzes
the information it gathers and compares it to large databases of attack
signatures. Essentially, the IDS looks for a specific attack that has already
been documented. Like a virus detection system, misuse detection software is
only as good as the database of attack signatures that it uses to compare
packets against. In anomaly detection, the system administrator defines the
baseline, or normal, state of the network’s traffic load, breakdown,
protocol, and typical packet size. The anomaly detector monitors network
segments to compare their state to the normal baseline and look for anomalies.
- network-based vs. host-based systems: in a network-based system, or NIDS, the
individual packets flowing through a network are analyzed. The NIDS can detect
malicious packets that are designed to be overlooked by a firewall’s
simplistic filtering rules. In a host-based system, the IDS examines at the
activity on each individual computer or host.
- passive system vs. reactive system: in a passive system, the IDS detects a
potential security breach, logs the information and signals an alert. In a
reactive system, the IDS responds to the suspicious activity by logging off a
user or by reprogramming the firewall to block network traffic from the
suspected malicious source.
Though they both relate to network security, an IDS differs from a firewall in
that a firewall looks out for intrusions in order to stop them from happening.
The firewall limits the access between networks in order to prevent intrusion
and does not signal an attack from inside the network. An IDS evaluates a
suspected intrusion once it has taken place and signals an alarm. An IDS also
watches for attacks that originate from within a system.
Internet
A collection of networks linked together using a common protocol. The global
computer network achieved through the interconnection of smaller computer
networks around the world.
IP Address
A digital code that precisely locates a computer connected to the Internet.
ISDN
(Integrated Services Digital Network) Basically a way to move more dataover
existing regular phone lines. ISDN is available to much of the USA and in most
markets it is priced very comparably to standard analog phone circuits. It can
provide speeds of roughly 128,000 bits-per-second over regular phone lines. In
practice, most people will be limited to 56,000or 64,000 bits-per-second.
LAN
(Local Area Network) A computer network limited to the immediate area, usually
the same building or floor of a building.
Linux
Pronounced lee-nucks. A freely-distributable open source implementation of UNIX
that runs on a number of hardware platforms, including Intel and Motorola
microprocessors. It was developed mainly by Linus Torvalds. Because it's free,
and because it runs on many platforms, including PCs, Macintoshes and Amigas,
Linux has become extremely popular over the last couple years.
Log File
A file that lists actions that have occurred. For example, Web servers maintain
log files listing every request made to the server. With log file analysis
tools, it's possible to get a good idea of where visitors are coming from, how
often they return, and how they navigate through a site. Using cookies enables
Webmasters to log even more detailed information about how individual users are
accessing a site.
Mask
mask Last modified: September 1, 1996 A filter that selectively includes or
excludes certain values. For example, when defining a database field, it is
possible to assign a mask that indicates what sort of value the field should
hold. Values that do not conform to the mask cannot be entered.
MIME
(Multipurpose Internet Mail Extensions) Originally a standard for defining the
types of files attached to standard Internet mail messages. The MIME standard
has come to be used in many situations where one cmputer programs needs to
communicate with another program about what kind of file is being sent.
NAT
Short for Network Address Translation, an Internet standard that enables a
local-area network (LAN) to use one set of IP addresses for internal traffic
and a second set of addresses for external traffic. A NAT box located where the
LAN meets the Internet makes all necessary IP address translations.
OC
Short for Optical Carrier, used to specify the speed of fiber optic networks
conforming to the SONET standard. The table shows the speeds for common OC
levels.
OC=Speed
OC-1=51.85 Mbps
OC-3=155.52 Mbps
OC-12=622.08 Mbps
OC-24=1.244 Gbps
OC-48=2.488 Gbps
OC-192=9.952 Gbps
Packet
A piece of a message transmitted over a packet-switching network. See under
packet switching. One of the key features of a packet is that it contains the
destination address in addition to the data. In IP networks, packets are often
called datagrams.
Port
(1) An interface on a computer to which you can connect a device. Personal
computers have various types of ports. Internally, there are several ports for
connecting disk drives, display screens, and keyboards. Externally, personal
computers have ports for connecting modems, printers, mice, and other
peripheral devices.
Almost all personal computers come with a serial RS-232C port or RS-422 port
for connecting a modem or mouse and a parallel port for connecting a printer.
On PCs, the parallel port is a Centronics interface that uses a 25-pin
connector. SCSI (Small Computer System Interface) ports support higher
transmission speeds than do conventional ports and enable you to attach up to
seven devices to the same port.
(2) In TCP/IP and UDP networks, an endpoint to a logical connection. The port
number identifies what type of port it is. For example, port 80 is used for
HTTP traffic.
Postmaster
The person at a host who is responsible for managing the mail system. If you
need information about a user at a particular host, you can usually send e-mail
to the postmaster at postmaster@hostname.
PPP
(Point-to-Point Protocol) A protocol that allows a computer to use the TCP/IP
(Internet) protocols (and become a full-fledged Internet member) with a
standard telephone line and a high-speed modem. PPP is a new standard for this
which replaces SLIP.
Protocol
A set of rules computer programmers apply when writing code for a specific
software. Computers and networks interact according to standard protocols,
which determine the behavior that each side of a network connection expects
from the other side.
Proxy Server
A Proxy Server sits in between a Client and the "real" Server that a
Client is trying to use. Client's are sometimes configured to use a Proxy
Server, usually an HTTP server. The clients makes all of it's requests from the
Proxy Server, which then makes requests from the "real" server and
passes the result back to the Client. Sometimes the Proxy server will store the
results and give a stored result instead of making a new one (to reduce use of
a Network). Proxy servers are commonly established on Local Area Networks
Router
A special-purpose computer (or software package) that handles the connection
between 2 or more Packet-Switched networks. Routers spend all their time
looking at the source and destination addresses of the packets passing through
them and deciding which route to send them on.
SCSI
Acronym for small computer system interface. Pronounced "scuzzy,"
SCSI is a parallel interface standard used by Apple Macintosh computers, PCs,
and many UNIX systems for attaching peripheral devices to computers. Nearly all
Apple Macintosh computers, excluding only the earliest Macs and the recent
iMac, come with a SCSI port for attaching devices such as disk drives and
printers.
SDSL
(Symmetric Digital Subscriber Line) A version of DSL where the upload speeds
and download speeds are the same.
Server
A computer, or a software package, that provides a specific kind of service to
client software running on other computers. The term can refer to a particular
piece of software, such as a WWW server, or to the machine on which the
software is running, e.g. "Our mail server is down today, that's why
e-mail isn't getting out."
A single server machine can (and often does) have several different server
software packages running on it, thus providing many different servers to
clients on the network.
Shell Account
(1) The outermost layer of a program. Shell is another term for user interface.
Operating systems and applications sometimes provide an alternative shell to
make interaction with the program easier. For example, if the application is
usually command driven, the shell might be a menu-driven system that translates
the user's selections into the appropriate commands.
(2) Sometimes called command shell, a shell is the command processor interface.
The command processor is the program that executes operating system commands.
The shell, therefore, is the part of the command processor that accepts
commands. After verifying that the commands are valid, the shell sends them to
another part of the command processor to be executed.
SQL
(Structured Query Language) A specialized language for sending queries to
databases. Most industrial-strength and many smaller database applications can
be addressed using SQL. Each specific application will have its own slightly
different version of SQL implementing features unique to that application, but
all SQL-capable databases support a common subset of SQL.
SMTP
Short for Simple Mail Transfer Protocol, a protocol for sending e-mail messages
between servers. Most e-mail systems that send mail over the Internet use SMTP
to send messages from one server to another; the messages can then be retrieved
with an e-mail client using either POP or IMAP. In addition, SMTP is generally
used to send messages from a mail client to a mail server. This is why you need
to specify both the POP or IMAP server and the SMTP server when you configure
your e-mail application.
Spamming
An inappropriate attempt to use a mailing list, or USENET or other networked
communications facility as if it was a broadcast medium (which it is not) by
sending the same message to a large number of people who didn?t ask for it. The
term probably comes from a famous Monty Python skit which featured the word
spam repeated over and over. The term may also have come from someone?s low
opinion of the food product with the same name, which is generally perceived as
a generic content-free waste of resources. (Spam® is a registered trademark
of Hormel Corporation, for its processed meat product.)
SSL
Short for Secure Sockets Layer, a protocol developed by Netscape for
transmitting private documents via the Internet. SSL works by using a public
key to encrypt data that's transferred over the SSL connection. Both Netscape
Navigator and Internet Explorer support SSL, and many Web sites use the
protocol to obtain confidential user information, such as credit card numbers.
By convention, URLs that require an SSL connection start with https: instead of
http:.
Subnet
A portion of a network that shares a common address component. On TCP/IP
networks, subnets are defined as all devices whose IP addresses have the same
prefix. For example, all devices with IP addresses that start with 100.100.100.
would be part of the same subnet. Dividing a network into subnets is useful for
both security and performance reasons. IP networks are divided using a subnet
mask.
Switch
In networks, a device that filters and forwards packets between LAN segments.
Switches operate at the data link layer (layer 2) and sometimes the network
layer (layer 3) of the OSI Reference Model and therefore support any packet
protocol. LANs that use switches to join segments are called switched LANs or,
in the case of Ethernet networks, switched Ethernet LANs.
T1
A leased-line connection capable of carrying data at 1,544,000 bits-per-second.
At maximum theoretical capacity, a T-1 line could move a megabyte in less than
10 seconds. That is still not fast enough for full-screen, full-motion video,
for which you need at least 10,000,000 bits-per-second. T-1 lines are commonly
used to connect large LANs to theInternet.
T3
A leased-line connection capable of carrying data at 44,736,000
bits-per-second. This is more than enough to do full-screen, full-motionvideo.
TCP/IP
Abbreviation for Transmission Control Protocol/Internet Protocol, the suite of
communications protocols used to connect hosts on the Internet. TCP/IP uses
several protocols, the two main ones being TCP and IP. TCP/IP is built into the
UNIX operating system and is used by the Internet, making it the de facto
standard for transmitting data over networks. Even network operating systems
that have their own protocols, such as Netware, also support TCP/IP.
Telnet
The command and program used to login from one Internet siteto another. The
telnet command/program gets you to the login: prompt of another host.
Unix
Pronounced yoo-niks, a popular multi-user, multitasking operating system
developed at Bell Labs in the early 1970s. Created by just a handful of
programmers, UNIX was designed to be a small, flexible system used exclusively
by programmers. Although it has matured considerably over the years, UNIX still
betrays its origins by its cryptic command names and its general lack of
user-friendliness. This is changing, however, with graphical user interfaces
such as MOTIF.
UNIX was one of the first operating systems to be written in a high-level
programming language, namely C. This meant that it could be installed on
virtually any computer for which a C compiler existed. This natural portability
combined with its low price made it a popular choice among universities. (It
was inexpensive because antitrust regulations prohibited Bell Labs from
marketing it as a full-scale product.)
Bell Labs distributed the operating system in its source language form, so
anyone who obtained a copy could modify and customize it for his own purposes.
By the end of the 1970s, dozens of different versions of UNIX were running at
various sites.
After its breakup in 1982, AT&T began to market UNIX in earnest. It also
began the long and difficult process of defining a standard version of UNIX. To
date, there are two main dialects of UNIX; one produced by AT&T known as
System V and one developed at Berkeley University and known as BSD4.x, x being
a number from 1 to 3.
Due to its portability, flexibility, and power, UNIX has become the leading
operating system for workstations. Historically, it has been less popular in
the personal computer market, but the emergence of a new version called Linux
is revitalizing UNIX across all platforms.
URL
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.
Whois
An Internet utility that returns information about a domain name or IP address.
For example, if you enter a domain name such as microsoft.com, whois will
return the name and address of the domain's owner (in this case, Microsoft
Corporation).
WAN
(Wide Area Network) Any internet or network that covers an area larger than a
single building or campus.
WWW
(World Wide Web) Frequently used (incorrectly) when referring to "The
Internet", WWW has two major meanings - First, loosely used: the whole
constellation of resources that can be accessed using Gopher, FTP, HTTP,telnet,
USENET, WAIS and some other tools. Second, the universe of hypertext servers
(HTTP servers) which are the servers that allow text, graphics, sound files,
etc. to be mixed together.
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