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Chapter 2
Protocol Attributes
AppleTalk is similar to NetWare because it is a client/server-based tech-
nology. Mac users launch an application called Chooser to locate resources
on the internetwork. Once users launch the Chooser application, they select
an AppleTalk zone and type of resource (file server, printer, and so on).
Chooser then builds a dynamic list of workstation names that offers the
requested service in the selected zone. The user selects one of the names and
then proceeds with their work. The following steps give a more detailed
explanation of the procedure:
1.
The user launches the Chooser application.
2.
The Chooser queries the router for available zones and presents the list
of available zones to the user.
3.
The user selects a zone and the type of resource requested.
4.
The user's Mac issues an NBP request, identifying the requested type
of resource and zone.
5.
The routers ensure that the NBP broadcast is forwarded to all speci-
fied network segments for that zone.
6.
All nodes in the requested zone receive the NBP broadcast, and the
nodes that provide the requested service reply to the requesting work-
station.
7.
Routers forward the responses to the requesting workstation's seg-
ment.
8.
The Chooser builds a list of available services.
9.
The user selects a service and proceeds with their work.
With this arrangement, it's obvious that the proper forwarding of broad-
casts is crucial to locating resources on the internetwork. From the users'
perspective, they can just use the dynamic Chooser to find out which
resources are available on the internetwork. If you get a new laser printer,
you simply plug it in and tell it which zone it's in, and Chooser automatically
lets users looking for that type of printer know that it's available. Figure 2.23
depicts the location of AppleTalk services in relation to the OSI model.
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