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Information Security Gateway
Peer-to-peer (P2P) is where computing devices link directly to each other and can directly initiate
communication with each other; they do not need an intermediary. A device can be both the client and the
server.
Packet Filter
A filter that scans packets and decides whether to let them through or not.
Port
An Internet port refers to a number that is part of a URL, appearing after a colon (:), directly following the
domain name. Every service on an Internet server listens on a particular port number on that server. Most
services have standard port numbers, for example, Web servers normally listen on port 80.
Protocol
A "language" for communicating on a network. Protocols are sets of standards or rules used to define,
format and transmit data across a network. There are many different protocols used on networks. For
example, most web pages are transmitted using the HTTP protocol.
Router
A device that connects two networks together. Routers monitor, direct and filter information that passes
between these networks.
RS-232
RS-232 is an EIA standard which is the most common way of linking data devices together.
Server
A computer, or a software package, that provides a specific kind of service to client software running on
other computers.
SSL (Secured Socket Layer)
Technology that allows you to send information that only the server can read. SSL allows servers and
browsers to encrypt data as they communicate with each other. This makes it very difficult for third parties
to understand the communications.
Subnet Mask
The subnet mask specifies the network number portion of an IP address. Your device will compute the
subnet mask automatically based on the IP Address that you entered. You do not need to change the
computer subnet mask unless you are instructed to do so.
Switch
A layer-2 network device that selects a path or circuit to send a data packet through.
TCP (Transmission Control Protocol)
TCP is a connection-oriented transport service that ensures the reliability of message delivery. It verifies
that messages and data were received.
Telnet
Telnet is the login and terminal emulation protocol common on the Internet and in UNIX environments. It
operates over TCP/IP networks. Its primary function is to allow users to log into remote host systems.
Terminal
A device that allows you to send commands to a computer somewhere else. At a minimum, this usually
means a keyboard, display screen and some simple circuitry.
TFTP (Trivial File Transfer Protocol)
TFTP is an Internet file transfer protocol similar to FTP (File Transfer Protocol), but it is scaled back in
functionality so that it requires fewer resources to run. TFTP uses the UDP (User Datagram Protocol)
rather than TCP (Transmission Control Protocol).
Transparent Firewall
A transparent firewall, also known as a bridge firewall, is a device that can act as a bridge and also filter/
inspect packets. You do not have to change other network settings when you add a transparent firewall to
the network.
URL (Uniform Resource Locator)
Appendix B: Glossary -- 119
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