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The IPSec sender can encrypt packets before transmitting them across a network.

The IPSec receiver can validate packets sent by the IPSec sender to ensure that the data has

not been altered during transmission.

The IPSec receiver can verify the source of IPSec packets. This service depends on the data integrity service.

This is a period during the late spring, summer and early fall when many countries set their clocks

ahead of normal local time by one hour to give more daylight time in the evenings.

Data Communications Equipment is typically a modem or other type of communication device.

The DCE sits between the DTE (data terminal equipment) and a transmission circuit such as a phone line.

The act of restoring an encrypted file to its original state.

Act of preventing customers, users, clients or other computers from accessing data on a computer.

This is usually accomplished by interrupting or overwhelming the computer with bad or excessive information requests.

Data Encryption Standard is a widely-used method of data encryption that uses a private (secret) key.

DES applies a 56-bit key to each 64-bit block of data.

Device filter rules are filter rules that treat a packet as a byte stream as opposed to an IP or IPX packet.

You specify the portion of the packet to check with the Offset (from 0) and the Length fields, both in bytes.

Device Filters decide whether or not to allow passage of a data packet and/or to make a call. Device

filters act on raw data from/to LAN and WAN and serve as a limited firewall to your device.

Diffie-Hellman is a public-key cryptography protocol that allows two parties to establish a shared secret over

an unsecured communications channel. Diffie-Hellman is used within IKE SA setup to establish session keys.

Dynamic Host Configuration Protocol automatically assigns IP addresses to clients when they log on.

DHCP centralizes IP address management on central computers that run the DHCP server program.

DHCP leases addresses, for a period of time, which means that past addresses are "recycled" and made

available for future reassignment to other systems.

Dynamic Host Configuration Protocol Relay is a function that allows DHCP data to be forwarded

between the computer that requests the IP address and the DHCP server.

This is a device that uses DHCP (see DHCP) to assign addresses to nodes on a LAN.

Dial backup is an auxiliary WAN connection that you can use if your primary WAN link goes down.

This is the process of setting up a connection through a switched network. It also describes a type

of Internet service where you have to connect (like a call) to your ISP for each session.

The use of a binary code to represent information, such as 0/1, or on/off.

A digital certificate is an electronic ID card that proves the sender's identity. A digital certificate

is issued by a certificate authority.

Digital code that authenticates whomever signed the document or software.

A DLCI specifies the channel and destination that frame relay traffic will use.

A DMZ is a network that makes public servers visible to the outside world and physically

separates them from the LAN, thus making the LAN more secure.

Domain Name System links names to IP addresses. When you access Web sites on the Internet

you can type the IP address of the site or the DNS name.

The unique name that identifies an Internet site. Domain Names always have two or more parts

that are separated by dots. The part on the left is the most specific and the part on the right is the most general.

This is the writing out of a decimal number (base-10) using periods (dots or decimals) to separate

it into parts. This is commonly used for IP addresses, such as 192.168.1.1. Also referred to as

dotted-decimal notation.

This is the writing out of a decimal number (base-10) using periods (dots or decimals) to

separate it into parts. This is commonly used for IP addresses, such as 192.168.1.1. Also

referred to as dot-decimal format.

This port connects to the uplink port of another device when the devices are cascaded.

Also known as a subtending port.

Dynamic RAM stores information in capacitors that must be refreshed periodically.

Digital Subscriber Line technologies enhance the data capacity of the existing twisted pair

wire that runs between the local telephone company switching offices and most homes and offices.

There are actually several types of DSL service, ranging in speeds from 16 Kbits/sec to 52 Mbits/sec.

The services are either symmetrical (traffic flows at the same speed in both directions) or asymmetrical

(the downstream capacity is higher than the upstream capacity). DSL connections are point-to-point

dedicated circuits, meaning that they are always connected. There is no dial-up. There is also no switching,

which means that the line is a direct connection into the carrier's frame relay, ATM (Asynchronous Transfer

Mode) or Internet-connect system.

A Digital Subscriber Line Access Multiplexor (DSLAM) is a network device, usually at a

telephone company central office, that receives signals from multiple customer Digital Subscriber Line

connections and puts the signals on a high-speed backbone line using multiplexing techniques.

Depending on the product, DSLAM multiplexers connect DSL lines with some combination of

asynchronous transfer mode ATM, frame relay or IP networks.

Originally, DTE meant Dumb Terminal Equipment. But today it is a computer, bridge or router

that interconnects local area networks (LANs) in increasingly more intelligent ways.

Devices with a "dual firmware block structure" have one "main block" and another "backup block"

You can save the current firmware into the backup block before you upload new firmware.

If the firmware in the main block gets corrupted, the device tries to boot from the backup block

automatically so the service is not interrupted.

With Dynamic DNS support, you can have a static hostname alias for a dynamic IP address,

allowing the host to be more easily accessible from various locations on the Internet. You must

register for this service with a Dynamic DNS service provider to use this service.

The IEEE802.3ad standard describes Link Aggregate Control Protocol (LACP), which is a

protocol that dynamically creates and manages trunk groups. When you enable LACP link aggregation

on a port, the port can automatically negotiate with the ports at the remote end of a link to establish trunk

groups. LACP also allows port redundancy, that is, if an operational port fails, then one of the "standby"