001-5006-000_FCC.docx
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2.2.2
Point-to-Multipoint
A Point-to-Multipoint network is a common network type used in SCADA or other polling
systems. The single polling master station communicates with any number of remotes and
controls the network by issuing polls and waiting for remote responses. Individual PLC/RTU
remotes manage addressing and respond when their individual addresses are queried.
PLC/RTU unit addresses are maintained in a scanning list stored in the host program or
master terminal device at the SCADA host site. Communications equipment is transparent
and does not interact with specific remotes; all data is coupled to the host on a single data
line (such a network is commonly used with synchronous radio modems and asynchronous
radio modems).
Figure 2.2 – Point to Multipoint Network
2.2.3
Multiple Point-to-Point
A multiple point-to-point is similar to the point-to-multipoint system except
the SCADA host has multiple serial ports that are directed to different
geographic areas in the SCADA system.
2.2.4
Peer-to-Peer
A Peer-to-Peer network is generally used for device to device communications
among a number of stations. This network requires full addressing capability
on the part of the data equipment (DTE). If the distances involved for any link
or links are too great for a single radio hop, they can be extended by means
of repeaters without affecting the basic network design.
2.2.5
Store and Forward
Store and Forward is a common technique where a data transmission is sent
from one device to a receiving device but first passes through a relaying
device. The device is typically an RTU or PLC used by the message service to
store the received message then it transmits the message to the intended
recipient.
2.2.6
Network Using a T-Base
The Network Using a T-Base configuration has the following characteristics:
Master station may be full duplex (duplexer required), half duplex, or simplex
