Specifications

AVM Access Server – Glossary 119
Glossary
ADSL (Asymmetric Digital Subscriber Line)
ADSL is a communication technology that permits Internet access with
high bandwidth over ordinary telephone cables. Data communication
takes place at up to 6 Mbit/s downstream (that is, from the Internet to the
user) and up to 640 kbit/s upstream. Other telecommunication services
and dial-up connections to other subscribers are not possible over ADSL.
ISDN and ADSL can be carried over the same telephone cable using dif-
ferent frequency bands.
AH (Authentication Header)
A data security protocol in the IPsec suite. AH ensures the authenticity
of a packet’s source and the integrity of its contents. AH does not pro-
vide encryption of the data payload, however.
AOCD (Advice of Charge During Call)
AOCD, or Advice of Charge During Call, is an ISDN feature. When this
feature has been activated for the ISDN line, charge information is
transmitted over the D channel as charges are incurred during a con-
nection. For more information about AOCD, consult your ISDN provider.
ARP (Address Resolution Protocol)
The Address Resolution Protocol, or ARP, is part of the TCP/IP protocol
suite. ARP is used dynamically to obtain the Ethernet hardware address
(called the MAC address) of the interface that corresponds to a given IP
address. This takes place automatically, and is normally transparent to
applications and users.
In order for TCP/IP network communication to take place, the transmit-
ting station must obtain the hardware address corresponding to the IP
destination address. To obtain the hardware address, the transmitting
station sends an ARP request packet containing the IP address of the
desired destination. This packet is broadcast to all ARP-capable sta-
tions on the network, and the one with the IP address requested re-
sponds to it with an ARP reply packet. The sender then stores the IP ad-
dress–hardware address association it its ARP cache.