Specifications

122 AVM Access Server – Glossary
BRI lines and 64 kbit/s for PRI lines. D channel information is used for
ISDN features such as charge information (AOCD) and caller ID (CLIP).
In Germany, the CLIP and AOCD services must be specially requested
on ordering an ISDN line.
DNS (Domain Name System)
DNS is the address resolution service in IP networks such as the Inter-
net, providing other systems with a mapping between human-readable
names and IP addresses. In other words, the DNS converts computers’
domain names into numeric addresses.
Because numeric addresses are difficult for humans to remember and
type, computers and networks are addressed by names in plain text,
such as “www.avm.de”. IP packets are only addressed in numerical
form, however. Thus the computer needs to know the numerical IP ad-
dress that corresponds to a human-readable name such as
“www.avm.de”. The mapping between names and numbers is provid-
ed by name servers, also called DNS servers. A computer in the Inter-
net that only knows a domain name for a server or other destination
can obtain the corresponding IP address from the DNS by sending a
query to the nearest name server.
Domain
In Windows networks, a domain is a logical group of network servers
and other computers that share common security attributes and user
account information. Administrators assign each user a single account
in the domain. Users can then log on to the domain itself rather than to
each server in the domain.
The domain is not necessarily limited to a certain location or type of
network configuration. Rather, computers in a domain can be located
in physical proximity to one another, as in a local-area network (LAN),
or far apart, even across the globe from one another. The computers in
the domain may communicate over any kind of medium, including dial-
up lines, ISDN, ADSL, fiber optic cable, Ethernet, Token Ring, Frame Re-
lay, satellite links and leased lines (see Microsoft Corporation, “Mi-
crosoft Windows NT Server Version 4 – Network”; see also “Further
Reading” on page 115).