Operation Manual

Filters and Spoofing
NetWAYS/ISDN – 3 Remote Access with NetWAYS/ISDN 27
PC are likewise acknowledged locally by
NetWAYS/ISDN, and not sent over ISDN to the remote
network.
NCP spoofing
NCP (NetWare Core Protocol) spoofing prevents NCP re-
quests such as “Get Directory Path” or “End of Job”
from being sent over ISDN. Such NCP requests are fre-
quently generated by Windows applications opening a
dialog to browse the file system, as when the command
“File / Open” is selected in Microsoft Word for example.
When NCP spoofing is activated, the remote computer
prevents unnecessary NCP request (such as update re-
quests) from being transmitted to all servers on which
the client has mapped a network drive. Instead, the re-
plies to the requests are simulated locally.
ARP spoofing
ARP (Address Resolution Protocol) is used to obtain the
Ethernet hardware address (or “MAC address”) of the
interface that corresponds to a given IP address.
Normally, ARP transmits a message in the IP network
every six minutes to ascertain IP and MAC address map-
ping. The response to a ARP request contains the IP ad-
dress with the corresponding hardware address. When
clients are connected over ISDN, ARP could cause high
connection costs, since the ISDN line would be dialed
up for each ARP request. To prevent this, the AVM
Access Server provides ARP spoofing to supply the re-
quested hardware address locally. ARP spoofing is acti-
vated automatically in NetWAYS/ISDN and in the AVM
Access Server.
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