Lantronix ETS, Справочное руководство

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Concepts AppleTalk
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2.4 AppleTalk
AppleTalk is a protocol used primarily by Apple Macintoshes to access network resources such as file
servers and printers. AppleTalk is also available for UNIX, NetWare, and other operating systems. The
AppleTalk protocol can be run over Ethernet (EtherTalk), Token Ring (TokenTalk), or LocalTalk, which is
a medium speed network type built into every Macintosh. These various network media can be connected
with AppleTalk routers to allow all nodes to communicate with one another. The AppleTalk protocol
supports features such as file sharing and security in addition to printing.
The ETS supports only the Printer Access Protocol (PAP) and therefore cannot create outgoing AppleTalk
sessions—only incoming print requests are accepted. Any services on the ETS with AppleTalk enabled will
show up as LaserWriters in Macintosh Chooser windows and are associated with an available zone
(explained in Section 2.4.2). Users who select a ETS service as their LaserWriter will have their print jobs
forwarded to the ETS for printing, or for queueing if the print port on the ETS is in use or otherwise
unavailable.
AppleTalk printing is different from printing in other protocols. There are standard Macintosh drivers
provided for specific Apple printer types, such as LaserWriters and ImageWriters, but there are no plain
ASCII line printers by default. ASCII jobs are converted into PostScript (for laser printers) or bitmaps (for
ImageWriters) when printed. Only laser printer devices are supported by the ETS under AppleTalk.
The Macintosh client will need to query the printer about status, so only laser printers that reply to these
interactive PostScript requests can be used. The ETS parallel ports support Bitronics mode, provided the
attached laser printer also implements it.
2.4.1 Addressing
AppleTalk provides for dynamic node addressing, allowing a node to choose its address at boot time. It will
send network packets to the other nodes to avoid choosing a node ID already in use. A node can also
discover its network number by listening for AppleTalk router broadcasts; if none are heard, a default
network number is chosen. The ETS will save zone/network/node ID triplets in permanent memory, which
reduces traffic at reboot time, although the ETS AppleTalk address may change across boots in response to
any network changes.
Network numbers are configured in the routers, so the only AppleTalk configuration supported by the ETS
is the specification of a zone name other than the default. Due to the generally non-configurable nature of
AppleTalk, most AppleTalk devices are truly “plug-and-play”— they can be powered up and used right out
of the box.
2.4.2 Zones
Zones are arbitrary groupings of AppleTalk nodes used to organize resources into groups that are easier for
users to understand. For example, a college may organize zones around departments, like Math
Department and Physics Department. Zones allow users to sift through large numbers of nodes by
choosing those groups they are familiar with regardless of the organization of the network. In general, zones
need not have a correlation to physical or network location, thus any node can declare itself a member of
any single zone.