ZyXEL Communications Prestige 1600 - Manual (Page 154)

Prestige 1600 Universal Access Concentrator
Glossary J
are divided into incoming and outgoing filters, depending on the direction of the packet relative
to a port. Data filtering can be applied on either the WAN side or the LAN side.
DCE 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.
Device Filter Rules For Device rules, the Prestige treats 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.
DHCP 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 addresses are
made available to assign to other systems.
DLCI For Frame Relay connections, DLCI (Data Link Connection Identifier) is a path number of a
portion of the PVC (the DLCI changes for each hop through the network). It is a logical identifier
with local significance only and is not the address of the destination.
DNS 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. When you type a domain
name in a Web browser, a query is sent to the primary DNS server defined in your Web
browser’s configuration dialog box. The DNS server converts the name you specified to an IP
address and returns this address to your system. From then on, the IP address is used in all
subsequent communications.
Domain Name The unique name that identifies an Internet site. Domain Names always have two 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.
DRAM Dynamic RAM that stores information in capacitors that must be refreshed periodically.
DSL Digital Subscriber Line technologies enhances 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 seven 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.
DSLAM A Digital Subscriber Line Access Multiplexer (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.
DTE Originally, the DTE (data terminal equipment) was a dumb terminal or printer, but today it is a
computer, or a bridge or router that interconnects local area networks.
Dual Firmware Block
Structure The Prestige 1600 employs a “dual firmware block structure” where one block is called the “main
block” and the other block is called the “backup block”. You can save the current firmware into
the backup block before you try to upload new firmware. If the firmware in the main block gets
corrupted, the Prestige will try to boot from the backup block automatically so the service will not
get interrupted.
E1 European basic multiplex rate which packs thirty voice channels into a 256 bit frame and
transmitted at 2.048 Mbps.
EIR (Excess
Information Rate) This is the burst capability of the connection, i.e., the maximum allowable data transfer rate.
EMI ElectroMagnetic Interference. The interference by electromagnetic signals that can cause
reduced data integrity and increased error rates on transmission channels.
Ethernet A very common method of networking computers in a LAN. There are a number of adaptations
to the IEEE 802.3 Ethernet standard, including adaptations with data rates of 10 Mbits/sec and
100 Mbits/sec over coaxial cable, twisted-pair cable and fiber-optic cable. The latest version of
Ethernet, Gigabit Ethernet, has a data rate of 1 Gbit/sec.
FAQ (Frequently Asked Questions) -- FAQs are documents that list and answer the most common
questions on a particular subject.