Panasonic FP2 ET-LAN, Technical Manual

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1.2 Overview of ET-LAN Unit Functions
1.2.1 Function Model
The functions of the ET-LAN unit are shown in the diagram below.
I/O and shared memory are used for the interface to the user program (CPU unit).
A maximum of eight simultaneous connections are possible for each of the computer link, data transfer,
and transparent communication functions.
The layers beneath the transport layer of the ET-LAN unit provide the following communication services.
TCP (Transmission Control Protocol):
TCP is a connection-based communication method which provides the virtual circuit. In the TCP
communication method, since communication services including re-transmission, sequence and flow
control for the communication data are provided, high communication reliability is guaranteed at the
protocol level.
UDP (User Datagram Protocol):
UDP is a connectionless communication method which provides only data communication in IP units. In
the UDP communication method, since no re-transmission, sequence, or flow control for the
communication data is provided, support at the application level is required to guarantee communication
reliability.
IP (Internet Protocol):
IP is used to transmit data in units of datagrams to partner node specified by an IP address. It provides
function such as the dividing and reassembling of communication data and communication services
between networks via a router.
ICMP (Internet Control Message Protocol):
ICMP is used to transmit the error message in the IP. The ET-LAN unit supports the echo replay option
only to the ping command.
ARP (Address Resolution Protocol):
ARP is used to transmit the Ethernet (physical) address, which is essential to Ethernet communications,
by specifying the IP address. When an ET-LAN unit accesses a station with unknown Ethernet address,
you only need to specify its IP address using the broadcast method.
AUI (Attachment Unit Interface
AUI is a transceiver cable that connects the ET-LAN unit with a transceiver.