Components and Architecture - Networking Basics Reference
32 HC900 Hybrid Controller Installation and User Guide Revision 5
9/03
Name/Acronym Name/Definition Comments
Node
Any intelligent device that
includes a hardware address
that can be recognized by
other network devices.
The “node” terminology is sometimes limited to
computing devices such as PC hosts, but can also
include networking devices such as Switches and
Routers.
OPC
Object Linking and
Embedding (OLE) for
Process Control
OPC is an open standard that defines the exchange
of information between cooperating software
applications. OPC is based on the Distributed
Common Object Model (DCOM) defined by
Microsoft Corporation.
OPC server and client software runs in computers
interconnected on a network, and enables
exchanges between process control devices and
PCs configured as HMIs.
OSI Model
Open Systems
Interconnection Reference
Model
The OSI model is established by International
Standards Organization (ISO) to enable computer
communications using disparate media and
protocols. Includes seven “Layers”; refer to "OSI
Reference Model” for more information.
Packet
A bit sequence that is
transmitted as an entity on a
network.
The content of a packet varies with the protocols
that are applied. It includes the data message itself
and various routing and control information such as
source and destination addresses.
In many cases, a packet includes a set of frames for
one protocol embedded (or encapsulated) in a set
of frames for another protocol. (Several levels of
encapsulation could be incorporated in a packet.)
Port
The physical connection on
a networking device.
For 10BaseT networking devices, ports are RJ-45
connectors.
Port Multiplier
A “concentrator” (e.g., a
Hub) is a multi-port device
that enables one device to
be connected to several
others.
The Port Multiplier (a.k.a. Hub) forwards a
message at any of its ports to all of its other ports,
with no isolation between the devices on these
ports. Hence, a Hub constitutes a “collision
domain” for all connected devices.
PPP Point-to-Point Protocol
Provides Router-to-Router and host-to-network
connections over both synchronous and
asynchronous circuits.
Print Server
A PC dedicated to printer
management.
Services print requests from other nodes on the
network.
Protocol
A system of rules for
communicating over a
network.
Remote Access
Access to a network from a
remote computer
Remote access usually uses a telephone line or the
Internet. The remote computer becomes a node on
the accessed network by assuming control of a
node actually on the network.
Repeater
Receives signals on an
incoming cable, reshapes
signal form and restores
timing, then repeats the
signal on an outgoing cable.
A Repeater can extend the distance over which a
message can be transported, but it also expands the
time for transport.
