Novell NETWARE 6-DOCUMENTATION Manual page 1879

AppleTalk Filtering
AppleTalk Device Hiding Filters
The AppleTalk protocol supports the following types of filters:
Device hiding filters
Routing information filters
For more information about AppleTalk filtering, refer to
"AppleTalk Device Hiding Filters" on page 19
"AppleTalk Routing Information Filters" on page 20
"AppleTalk Routing Information Filters over AURP" on page 23
AppleTalk device hiding filters restrict the advertisement of services on a
router's internetwork by filtering out packets that advertise those services.
These filters both prevent users from finding the network addresses of services
and provide a level of network security.
In AppleTalk, the Name Binding Protocol (NBP) lets users access services
such as file servers and printers. Specifically, it allows a user or application to
specify search parameters such as the network entity name and service type,
and a zone in which the search should be done. The search is represented in an
NBP lookup request sent to the appropriate zone where the service might be.
Services matching the search parameters reply directly to the requesting user
or application with the AppleTalk address of the service. Once the user or
application has received the NBP reply, the user or application can use the
AppleTalk address to communicate with the service.
When AppleTalk device hiding filters are enabled on a router, the router drops
the NBP replies for specified services. (That is, it does not deliver the replies
to the client machine or application that requested them.) Thus, the services
are hidden from that part of the network.
A common use of NBP is the Macintosh* Chooser application. The user or
application issues an NBP lookup, specifying a zone and service type of
interest. The lookup is sent to the appropriate zone. All devices or services of
the specified type in the zone respond with an NBP reply. The Chooser
displays the list of available devices, based on the NBP replies it receives.
Using the AppleTalk address supplied in each NBP reply, the user or
application can then communicate with the device or service.
19
Understanding