As is shown in Figure 4, the global control domain can be constructed by the large-scale interconnection of cluster controllers, which take charge of the aggregation switches and local domain controllers within their domain.
Global control domain consisted of a series of distributed cluster controllers which can survive from the danger of single point failure.
As is shown, Figure 7(a) displays the complete network architecture, while Figure 7(b) displays the logical links of data plane in global topology maintained by cluster controllers. And we note that in order to make the diagram more legible there are some unimportant links that have been omitted, such as links between the local controller and the common switch, as the deployment of flow rules and the orchestration of hierarchical controllers in SDN are not our main concern.
We note that each local controller just maintains the detailed routing information within its local scope and cannot obtain the views of other microgrids, while all cluster controllers have consistent global logic views.
The hierarchical propagation of profiles--resulting in a broker maintaining profiles of all attached clients, cluster controllers
maintaining profiles of all brokers within that cluster and so on--ensures that when an event is routed to a unit, there is at least one final destination within that unit.
* The 3276 small cluster controller is built into the same cabinet as a 3278 terminal.
Even if the PC could emulate the 3274 cluster controller, running the software would put a large overhead burden on the microprocessor, possibly more than it can handle.
At the cluster controller coax interface, a processor need deal with only one application, and one or two logical units (end devices like CRT screen or printer).
The remote bridge/routers in turn are linked to Memorex/Telex 1174 cluster controllers
(five of them) at each location.
With it, any ASCII (asynch) or EBCDIC (synch) printer or plotter can be attached to 3270 Type A coas cluster controllers
, connecting to the mainframe.
Each communications station provides one to eight RS-232-C or RS-449 ports for the connection of cluster controllers
or data terminals.