Digital Equipment RapidPrint 500, Reference Manual

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B -2
flash ROM See ROM .
gateway A TCP/IP host that can access two or more different Ethernet networks.
As such, it can forward messages across networks that other hosts would
not be able to access. The host generally has multiple IP addresses, one
for each network. For example, a gateway might “live” at addresses
192.0.1.8 and 193.0.1.8. Hosts wishing to forward messages may address
the messages to the gateway which will then pass them on to the other
network. The RapidPrint 500 supports this with the
Set/Define Server
Gateway command. The IP address of the gateway host on this server’s
network is specified, and messages for hosts not on the local network will
be forwarded. For example, if a RapidPrint 500 at address 192.0.1.33
wished to talk to a host at address 196.0.1.58, he would have to go
through a gateway machine on his network. The gateway would forward
messages between networks 192.0.1 and 196.0.1. See the
subnet mask
entry for information on how these networks work.
hardware address See Network Address.
host Host is generally used in this manual to mean a node on a network that
can be used interactively, or logged into. This generally refers to interac-
tive computers. In the RapidPrint 500’s command set, host is used to refer
to a TCP/IP node, rather than TCP/IP and LAT nodes. For example, the
Show Hosts command displays only the known TCP/IP nodes.
ICMP ICMP stands for the Internet Control Message Protocol. ICMP messages
are sent by TCP/IP
nodes in response to errors in TCP/IP messages or
queries from other nodes. They are sent, for example, when a node sends
a packet to an incorrect gateway host, or when a network packet expires.
ICMP messages may also be sent as broadcasts, not just sent to a specific
host. The RapidPrint 500 counters for ICMP messages may be helpful for
detecting network problems.
IP address See network address .
LAT Local Area Transport. LAT is a Digital Equipment Corporation propri-
etary network communication
protocol . The protocol is based on the idea
of a relatively small, known number of hosts on a local network sending
small network packets at regular intervals. LAT will not work on a wide
area network scale as
TCP/IP does, as it cannot distinguish large numbers
of nodes . For local networks, however, LAT is usually faster and less
prone to pauses than TCP/IP.
LAT also allows remote connections to services and other network
devices, about which TCP/IP has no understanding. The fact that the
RapidPrint 500 supports both LAT and TCP/IP protocols transparently
means that you are not bound by the limitations of either protocol.
login service If the RapidPrint 500 is configured to allow users to log in from the net-
work (as opposed to logging in from the serial ports), it creates what is
called a login
service . The RapidPrint 500 advertises a new service with
the same name as the server. LAT users who connect to the “service” will
not be connected to a physical port or device; they will be given a “virtual
port” on the RapidPrint 500 instead. Although they obtain a “Local>”
prompt and can issue commands as if they were physically connected to
the RapidPrint 500. When they log off the RapidPrint 500, their “port”
disappears.