Wellink Corporation W202ER-4 Manual Do Utilizador

Página de 151
VisionNet 202ER-4 ADSL Ethernet Router User’s Guide 
146 
from a shared pool of IP addresses; after a specified time limit, 
DHCP returns the address to the pool. 
DHCP relay 
Dynamic Host Configuration Protocol relay 
A DHCP relay is a computer that forwards DHCP data between 
computers that request IP addresses and the DHCP server that 
assigns the addresses. Each of the VisionNet 202ER-4's 
interfaces can be configured as a DHCP relay. See DHCP. 
DHCP server 
Dynamic Host Configuration Protocol server 
A DHCP server is a computer that is responsible for assigning IP 
addresses to the computers on a LAN. See DHCP. 
digital 
Of data, having a form based on discrete values expressed as 
binary numbers (0's and 1's). The data component in DSL is a 
digital signal. See also analog
DNS 
Domain Name System  
The DNS maps domain names into IP addresses. DNS 
information is distributed hierarchically throughout the Internet 
among computers called DNS servers. When you start to access 
a web site, a DNS server looks up the requested domain name 
to find its corresponding IP address. If the DNS server cannot 
find the IP address, it communicates with higher-level DNS 
servers to determine the IP address. See also domain name. 
domain name 
A domain name is a user-friendly name used in place of its 
associated IP address. For example, www.globespan.net is the 
domain name associated with IP address 209.191.4.240. 
Domain names must be unique; their assignment is controlled by 
the Internet Corporation for Assigned Names and Numbers 
(ICANN). Domain names are a key element of URLs, which 
identify a specific file at a web site, e.g., 
http://www.globespan.net/index.html. See also DNS. 
download 
To transfer data in the downstream direction, i.e., from the 
Internet to the user. 
DSL 
Digital Subscriber Line 
A technology that allows both digital data and analog voice 
signals to travel over existing copper telephone lines.  
Ethernet 
The most commonly installed computer network technology, 
usually using twisted pair wiring. Ethernet data rates are 10 
Mbps and 100 Mbps. See also 10BASE-T, 100BASE-T, twisted 
pair
. 
filtering 
To screen out selected types of data, based on filtering rules. 
Filtering can be applied in one direction (upstream or 
downstream), or in both directions. 
filtering rule 
A rule that specifies what kinds of data the a routing device will 
accept and/or reject. Filtering rules are defined to operate on an 
interface (or multiple interfaces) and in a particular direction 
(upstream, downstream, or both). 
firewall 
Any method of protecting a computer or LAN connected to the 
Internet from intrusion or attack from the outside. Some firewall 
protection can be provided by packet filtering and Network 
Address Translation services.