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Glossary
A
Access Point.
A device that transports data between a wireless network and a wired network. With the help
of the system, a wireless base station is an example of an access point that acts between a wireless node
and with other wired PCs and peripherals.
D
Default Gateway.
A device that is placed between network segments (or “subnets”) to ensure that traffic is
properly routed between different subnets. To communicate with a device on another network, users need
to know the default gateway’s IP address.
DHCP (Dynamic Host Configuration Protocol).
A TCP/IP protocol that allows servers to assign IP
addresses dynamically to PCs and workstations. The PC or workstation “borrows” the IP address for a
period of time, then the IP address returns to the DHCP server for reassignment.
DMZ (Demilitarized Zone).
A computer or small subnetwork that sits between a trusted internal network
(such as a LAN), and an untrusted external network (such as the Internet). Typically, the DMZ contains
devices accessible to Internet traffic, such as Web (HTTP) servers, FTP servers, SMTP (e-mail) servers and
DNS servers.
DNS (Domain Name System).
The DNS is the way that Internet domain names (such as www.2wire.com)
are located and translated into IP addresses.
DSLAM (Digital Subscriber Line Access Multiplexer).
A device found in telephone company central offices
that takes a number of DSL subscriber lines and concentrates them onto a single ATM line.
E
Ethernet.
A type of local area network that operates over twisted wire and cable at speeds of up to 10
Mbps.
I
ICMP (Internet Control Message Protocol).
ICMP supports packets containing error, control, and
informational messages. For example, the PING command uses ICMP to test an Internet connection.
Although ICMP is generally harmless, there are some message types that should be dropped. Redirect (5),
Alternate Host Address (6), and Router Advertisement (9) can be used to redirect traffic from your site.
Echo (8), Timestamp (13), and Address Mask Request (17) can be used to obtain information on whether
the host is up, the local time, and the address mask used on your network, respectively. ICMP messages
are also sometimes used as part of DOS attacks (such as flood ping or ping of death).
Invalid TCP flags.
Combination of TCP flags (such as SYN/FIN) that signal a malicious attempt to get past
the firewall.
IP (Internet Protocol).
The standard signaling method used for all communication over the Internet.
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