Port Sharing With Multiple Hosts - GE MDS SD Series Technical Manual

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Port Sharing with Multiple Hosts

The transceiver allows for several external data networks to use the
same RF network without confusing the data streams. In such a system,
multiple host computers at the Master Unit poll their respective RTUs,
which may be alone or co-located at the Remote sites. Figure 8 shows
an example of such a system. In this case, two host computers (Host A
and Host B) are connected to the Master Unit via the applicable data
ports.
At the Remote sites, serial and Ethernet-based RTUs are employed, and
responding to a specific host computer. In the case of the Remote shown
on the lower right side of the drawing, two RTUs are co-located, but
responding to different host computers and handling entirely different
data streams.
The SD eliminates the need for two transceivers to support separate data
collection/control networks. Virtual Radio Channels (VRCs) are used to
separate serial data streams on COM2, COM1, or IP payload ports.
Packet With MAC operation provides Media Access Control. It is the
recommended method of operation for port sharing systems.
An option exists to operate in Packet mode without MAC. In fact, this is
the default mode in both the SS and ES models. However, this Packet
mode option should only be used for systems that use legacy methods of
collision avoidance including Multihost and Listen Before Transmit
(LBT). The mode Packet with MAC provides superior performance and
better network reliability, collision avoidance and better overall
throughput. See corresponding sections of the manual for more informa-
tion on these Packet mode options.
SD Series Technical Manual MDS 05-4846A01, Rev. D