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CHAPTER 5: Protocol Overview
The EPS provides two major methods of printing via TCP/IP. Berkeley
Remote LPR is supported, as is the RTEL software. Both methods provide
queueing of jobs on the host if the host is busy with another job. The remote
LPR software allows the EPS to look like another host that can spool and print
files, and hosts wishing to print to the EPS simply send the print data and
assume the EPS will handle it properly. The RTEL software, which you must
install and configure on the host, provides more functionality than remote-
LPR. It allows the host’s lp or lpr printing system to transparently use the
EPS’s print devices, and also allows you to create tty devices on the host that
map to the EPS.
The EPS’s IP address must be set before you can use any of the TCP/IP
functionality. You can set the address by hand or via BOOTP or RARP—
see Chapter 3 for more details. In general, you must tell the EPS’s address
to any host wishing to access the EPS. You can usually configure this via a file
(/etc/hosts) containing all the local IP addresses, or a nameserver on the
network. Specifying a gateway IP address on the EPS allows the server to reply
correctly to non-local network connections.
TCP/IP print services are entirely host driven—the EPS does nothing until
a host connects to it and requests a print job. The service does not check to
see if the EPS and the print resource exists on the host until you queue a
print job. The only time the EPS will initiate a connection is to tell a host
to start a previously queued job.
5.3 AppleTalk
AppleTalk includes a variety of network media types. LocalTalk is frequently
used to refer to AppleTalk running over 230 kbps serial lines. All Macintosh
computers provide LocalTalk support, but the EPS does not. The other two
types, EtherTalk and TokenTalk, provide AppleTalk over Ethernet and Token
Ring, respectively. The EPS supports only EtherTalk, so most Macintosh
computers will need either an Ethernet card or a LocalTalk-to-EtherTalk
router to connect to the EPS’s services. TokenTalk users wishing to use the
EPS print services have to have an Ethernet-Token Ring bridge or router to
connect the two networks. In the following discussions, AppleTalk refers only
to EtherTalk.
The EPS provides only enough of the AppleTalk protocol stack to provide
printing. You can only access the EPS as a LaserWriter from an AppleTalk
client (Chooser menu, etc.) The device name that shows up in the Chooser
menu is the name of the service defined on the EPS. If the EPS service name
is “LAB_SERIAL,” that’s what will show up in the client Macintosh computer’s
Chooser menus.