Digital Equipment RapidPrint 500, Справочное руководство

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PostScript Notes Concepts
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2.7.1 Networking
Each NetWare node uses its hardware address as its node ID; no additional address configuration
is necessary. In addition, the RapidPrint 500 gets all the networking information it needs from
periodic broadcasts sent by NetWare routers on the network. It will learn its own network number
as well as routes to non-local file servers. No further configuration is needed.
The NetWare protocol can use all four Ethernet frame formats. It will listen for all frame formats,
and then use the correct one for the connection. The different frame types are treated as different
networks, and thus each frame type has a different network number. If there is only one frame for-
mat in use on the LAN, the RapidPrint 500 will use the network number for that frame type. If
there are multiple frame types, limitations to the NetWare protocol require that the RapidPrint 500
use a different network number for each frame type on which it wants to advertise itself.
The RapidPrint 500 can use multiple frame types by creating a new, unique “internal network
number” and advertising itself as a router to the internal network. Any nodes or fileservers that
need to communicate with the RapidPrint 500 use this new network number, and treat the Rapid-
Print 500 as a router to that network. If this behavior is not desired, the RapidPrint 500 can be
forced to use only one frame type (and thus not need an internal network number).
2.7.2 Access Lists
Since NetWare networks can be quite large, with hundreds of file servers, a method for restricting
the RapidPrint 500 print polling is needed. If polling is left unrestricted, the time needed to poll
each server would make printing incredibly slow and inefficient. By using access lists (created
with the
Set/Define Protocols NetWare Access command) you can control which file servers the
RapidPrint 500 will and won’t poll for print jobs. Note that the file servers have no control over the
RapidPrint 500 access lists, so they will never know if a misconfiguration of the access list prevents
them from spooling print jobs to the RapidPrint 500.
2.8 PostScript Notes
Many printers (including all LaserWriters and other AppleTalk compatible laser printers) use a
printing language called PostScript. Unlike other printer protocols, which typically accept ASCII
characters and print them verbatim, PostScript is also a programming language. Shapes and fonts
can be defined as routines and re-used on successive pages, multiple fonts and copies can be
printed, and text and diagrams can be rotated and shifted on pages.
PostScript is also an interactive language, where the printing host can query the printer for its
knowledge about fonts and software versions. If the host expects to receive data from the printer
(as is the case for all AppleTalk printing), the printer must be connected to a bidirectional port
such as the RapidPrint 500 port. Note that the attached printer must also support the Bitronics
mode. PostScript printing from UNIX, LAT, and NetWare hosts, where bidirectional data flow is
not a requirement, can generally use any parallel port.
Due to the interactive nature of PostScript, it is possible for the printer and host to get out of synch
in their communication. Since the printer “interprets” the entire PostScript job and then prints the
pages, it is possible for the RapidPrint 500 to complete the transfer and accept a new job while the
printer is still digesting the last job. For this reason, an end-of-job character (ASCII 0x4, or Ctrl-D)
is used to end all PostScript jobs. Typically the host will send one at the end of the job and the
printer will reply with one when it is done processing.