Glossary

BPS
(Bits-Per-Second) The speed at which data is transmitted in bits-per-second. A 28.8 modem can move 28,800 bits per second.

Browser
A program that is used to look at various kinds of Internet resources.

Country Codes
In the course of tracing intrusion attempts you will sooner or later encounter a country code. The country code is a two-letter tag at the end of a site URL which identifies the country where the site is located. See the on-line help for a detailed list of country codes.

Domain Name System/Server (DNS)
The Domain Name System simplifies Internet navigation. Computers on the Internet can only be found at their numerical IP address (e.g., 206.216.115.4). An address like "somerspoint.org" makes sense to a human but a DNS server must match it up to its IP address. The DNS server databases are updated regularly as new domain names are registered.

Domain Name
An Internet site's unique name, which can consist of two or more parts separated by dots (sirbranch.com,  jifit.com,  www.somerspoint.org ).

DSL
DSL or Digital Subscriber Line is an increasingly popular method of connecting to the Internet over regular phone lines. DSL offers the advantage of a relatively high speed connection at prices substantially lower than ISDN connections. In theory DSN has a download speed limit of 9 megabits per second and an upload limit of 640 kilobits per second. In reality, and dependent of your provider's equipment as well as your system equipment, you can expect anything from about 1.5 megabit download/128 kilobit upload (Asymmetric DSL) to 384 kilobits in both directions (Symmetric DSL).

E-mail
Electronic Mail, messages sent via the Internet or within a company LAN or WAN. E-mail attachments in the form of EXE (executable) files or VBS (Visual Basic script) files have become increasingly popular as a means of transmitting viruses and Trojans.

Firewall
Hardware and/or software designed to keep unauthorized outsiders from tampering with a computer system. That system may be a standalone computer, a small LAN or a company-wide network or WAN with thousands of users.

HTTP
Hypertext Transfer Protocol moves hypertext (HTML) files on the Internet from the server you are visiting to the browser you are viewing with.

Internet
The Internet consists of a huge number of inter-connected networks that use the TCP/IP protocols for the location and transfer of data. The Internet evolved from a linking of university and college computers (in the late 1960s and early 1970s) funded by the U.S. Department of Defense and called the ARPANET. The Internet today is a global network of almost 100,000 independent networks.

Intranet
A private network, usually inside an organization, that functions very much like the Internet. It has become common practice to permit access to such Intranets from standalone computers used by students or employees off-campus or off-site. Firewalls, login procedures and passwords are designed to provide security.

IP Number
The Internet Protocol Number or IP address is a unique number consisting of four parts separated by dots (e.g. 63.227.89.66). Every computer of the Internet from the largest server to a laptop communicating through a cell phone has a unique IP number. Not every computer has a domain name but every computer uses an IP.

ISP
Internet Service Provider. This is the service you subscribe to in order to connect with the Internet. It may be a small local company with a few thousand subscribers, a regional company (e.g. uswest.net) or a nationwide mega-provider like AOL or AT&T WorldNet. Most ISPs sell a connection, nothing more.

LAN
Local Area Network. Two or more computers that are linked together and able to share programs, data and/or peripherals

Modem
MOdulator/DEModulator. Your modem takes data you are sending and modulates it so that it can be transmitted over an analog voice phone line. Your modem accepts incoming modulated data and demodulates it so that it is usable by your computer. The earliest modems required the user to place the telephone handset into a cradle with padded apertures for the two ends of the handset. Speeds were in the range of 300 to 1,200 BPS. With improvements in error correction, modems today under ideal conditions can transmit data at over 50,000 BPS. over a single phone line. DSL and ISDN connections offer even higher speeds. These days the term modem is frequently used to describe external network connection devices that don't actually perform any modulation or demodulation, such as DSL and Cable modems which are actually digital end-to-end.

NAT (Network Address Translator)
A NAT is logically similar to both a proxy and a gateway. The NAT hides the private addresses of the local network from the public address side attached to the Internet. The NAT takes packets from the private network and re-writes them using one of its public IP addresses and sends it onto the public network (Internet). When the response to the packet comes back the NAT takes this inbound packet and redirects it to the private address that originated the traffic. NATs allow large groups of computers to access the Internet through a very small number of IP addresses. Without NAT technology the supply of IP addresses would have run dry in the late 1990's. The Internet Connection Sharing built into Windows 98SE and later is a NAT.

Network
When you connect two or more computers, you create a network. When you connect two or more networks you create an internet (lower case "i").

Node
A single computer connected to a network. Nodes simply serve as connection points in passing along data.

Non-Routable IP
See 'Private IP Space'

Packet Switching
This is the method used to move data on the Internet. The data you are sending or receiving is broken up into pieces, each piece carrying the IP address of where it is going and where it is coming from. Billions of these pieces are passing through the Internet at any given time and the major node servers are sorting these pieces and routing them at incredible speeds. The E-mail you are reading or the web page you are looking at has been reassembled and delivered to your monitor after traveling across town or around the world and, best of all, you don't have to give it a moments thought.

PING
Packet Internet Groper is a program used to determine whether a specific IP address is accessible. A packet is sent to the specified address and the program waits for a reply. Programs use PING to identify and/or troubleshoot Internet connections. In addition to identifying the target site, these programs also note all of the nodes the data passed through between the two ends of the connection.

Private IP Space
Also known as non-routable IP address space. There are three block of IP addresses which are reserved for private networks. These IP addresses are used only on private networks, and cannot be connected directly to the public Internet. If a non-routable IP address is used on a computer connected to the Internet it must gateway through a NAT. The private IP blocks are:

10.0.0.0 through 10.255.255.255 (Any IP Address starting with 10.)
172.16.0.0 through 172.31.255.255
192.168.0.0 through 192.168.255.255

Proxy Server
Proxies are used as intermediaries in connections to the Internet. They are generally only useful for common application uses such as web browsing. Proxies offer several benefits. They are able to cache page content locally; reducing Internet bound traffic as well as local response time. They offer some security benefits by isolating the local network from direct contact with the Internet. They also offer local ability to restrict access to the Internet in general. Proxies do have many limitations, one of which is that they cannot handle ICMP traffic. For small networks a NAT is a superior solution to a proxy.

Server
A computer or software that provides specific services to software running on other computers. The "mail server" at your ISP is software that handles all of the incoming and outgoing mail for all of your ISP's users. A server on a LAN is hardware that constitutes the primary node on the network. It may also have software which provides specific services, data or other capabilities to all of the client computers attached to it.

TCP/IP
Transmission Control Protocol/Internet Protocol, the protocols that make the Internet possible and that make it possible for your computer to be part of the Internet.

URL
Uniform Resource Locator, the standard format for Internet addresses.

WAN
Wide Area Network, a network of computers that covers an area larger than a single building or campus. In the past WANs have been private networks connecting geographically separated offices of the same organization. WANs are rapidly being replaced by the Internet and the wide use of VPNs.

WWW
The World Wide Web or just "The Web." Many people think of this in terms of what is accessible to their browser but in reality the web now encompasses all of the resources that make up the Internet including such things as FTP sites, USENET, and much more.