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F o u r
Cha p te r

Substation

Substation

Substation
Key: Node
Gateway

FIGURE 4.18 Multiple-ring digital communication network—AbNET.

would also include power distribution substations and power
controlling units. In addition to serving data acquisition and control
functions, each node would act as a repeater, passing on messages to
the next node.
Network topology is arbitrary, governed by the power system.
The token ring protocols used in single-ring digital communication
networks are not adequate. The multiple-ring communication net-
work would operate on the new AbNET protocol, which has already
been developed, and would feature fiber optics for this more compli-
cated network.
Initially, a message inserted anywhere in the network would
pass from node to node throughout the network, eventually reach-
ing all connected nodes. On the first reception of a message, each
node would record an identifying number and transmit the message
to the next node. On second reception of the message, each node
would recognize the identifying number and refrain from retrans-
mitting the message. This would prevent the endless repetition and
recirculating of messages. This aspect of the protocol resembles the
behavior of cells in the immune system, which learn to recognize
invading organisms on first exposure and kill them with antibodies
when they encounter the organisms again. For this reason, the proto-
col is called AbNET after the microbiologists’ abbreviation Ab for
antibodies. The AbNET protocols include features designed to maxi-
mize the efficiency and fault-tolerant nature of the approach. Multi-
ple service territories can be accommodated, interconnected by gate-
way nodes (Fig. 4.18).
The AbNET protocol is expected to enable a network to operate
as economically as a single ring that includes an active monitor node to