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ETHERNET PRINT SERVER
An AppleTalk zone name is configurable, in case there are multiple zones
on the LAN to which the EPS is connected. If you are using the default zone
or only one zone, you do not need to configure any information on the EPS.
Only AppleTalk routers provide zones, so if you have no router on your
network, you will not need a zone configuration.
Many third-party packages are available that provide AppleTalk support on
UNIX or other operating systems. You can use these to print to the EPS via
AppleTalk, but it is typically more efficient and easier to configure printing
via the native UNIX or TCP/IP print utilities (lp or lpr).
Like TCP/IP, AppleTalk is passive regarding printing jobs. When a client
wishes to print, it will send out a broadcast asking what print resources are
available. The EPS will answer, and the client will request a print job to the
EPS. If the print resource is available, the print job will complete normally.
If the print resource is busy, however, the EPS will enter a prolonged
“arbitration” phase to keep track of which print client has been waiting for
the resource the longest. In this phase, multiple clients may be sending
packets to the EPS once every 2-5 seconds until the resource is available
and their jobs are serviced.
The parallel port service does not have AppleTalk enabled. AppleTalk
printing typically requires a bi-directional data path, so the printing node
must be able to receive data from the printer port as well as send to it. Since
the parallel port on the EPS is not bi-directional, AppleTalk clients will not
be able to print to it. This is not a PostScript or printer limitation, but an
AppleTalk limitation. You can use any PostScript printer with the parallel
port if the host does not need information returned from the printer.
5.4 LAT
Like AppleTalk, LAT was designed to let nodes on a LAN quickly and easily
access other nodes’ resources. There is, however, little support for raw data
streams, file services, or other operating-system related items. LAT is more
intended for host connections to limited-function nodes (printers, terminal
servers, etc.). Central to LAT is the concept of “services,” or resources that
another LAT node can use. Services on the EPS can be associated with one
or both physical ports, and each port can be associated with multiple services.
LAT nodes typically send out announcements (“multicasts”) telling what
resources they provide. Other LAT nodes listen to these periodic
announcements, and will connect to the node to use these services whenever
requested.