Specifications

Windows Name Resolution with the AVM Access Server
96 AVM Access Server – 5 AVM Access Server Concepts and Functional Principles
NetBIOS names are easier for users to work with than the purely nu-
meric IP addresses. In order for NetBIOS services to be transported
over the network, however, the NetBIOS names must be mapped to IP
addresses. A number of mechanisms serve this purpose.
In a Windows LAN, NetBIOS names are resolved automatically. This
takes place by means of name information which all Windows comput-
ers in the network broadcast to one another. Each computer identifies
itself by its name in a message bearing its IP number as the source ad-
dress. Other computers can then initiate NetBIOS sessions over IP us-
ing that address.
In larger networks, name resolution using broadcasts can consume a
significant proportion of the available bandwidth. Moreover, dial-up
lines, which generally offer very limited bandwidth, would be severely
burdened by such broadcasts, and lines would be constantly busy. For
this reason, broadcasts are generally not routed in IP networks.
This restriction limits automatic Windows name resolution to the local
subnet. If name resolution is required across IP subnetworks, over a
remote-access or LAN-to-LAN connection, for example, then other ap-
propriate name resolution mechanisms can be used.
Windows Name Resolution with the AVM Access Server
Preparation
NetBIOS was originally developed for small LANs, and has certain draw-
backs when used with on-demand WAN connections. Frequent keep-
alive packets can cause a dial-up line to remain continuously connected.
Furthermore, NetBIOS name resolution can pose security risks.
For these reasons the AVM Access Server incorporates a NetBIOS filter
that discards all NetBIOS packets in traffic to remote sites. In order to
use NetBIOS names over remote users’ or remote network connections,
this NetBIOS filter must be deactivated. This setting can be activated or
deactivated in the properties of each user group and remote network.
Because NetBIOS broadcasts can cause undesired ISDN connections,
the filter should only be deactivated if NetBIOS is absolutely neces-
sary. At the same time NetBIOS spoofing should be activated so that
NetBIOS keep-alive packets are answered locally instead of causing
unnecessary ISDN connections.
NetBIOS is not needed for Internet name resolution. The NetBIOS filter
should always be activated for Internet connections.