Understanding Bidirectional Communication Nodes
Types of Communications
If a link between two nodes can be selected for communication in both directions (but alternatively), the link is bidirectional. If it is set in one direction and under the terms of a node, it will be one-way (incoming or outgoing).
- If a user node wants to communicate with another user and it also belongs to the node, the switching system has to make the connection of both. This communication is called local communication.
- If the user wishes to establish communication with another user that does not belong to the node, the switching system is to make the connection between the user and one of any of the free outgoing links, which would be responsible for routing the communication to the node where the end user is connected, either directly or through other intermediate nodes. This communication is called outgoing communication.
- If a user that does not belong to the node wants to communicate with a user of the node, the switching system has to make the connection between the arrival of the link which shows the switching node and the user to communicate. It is worth noting that in this last situation, the submission is presented by a bond of arrival, instead of a user line. This communication is called incoming communication or communication of arrival.
- It may be a communication between two users outside of the node. In this case, the communication link is presented by the arrival mission and the switching system is to make the connection between said arrival link and one of any of the free departure links to route the communication to the node where the called user is connected, either directly or through other intermediate nodes. The communication issued by the destination node without source is called communication in transit.
Switching System
This system is composed of several functional areas that will allow the entire process. Since not all users can simultaneously attempt to establish communication, allowing successive process steps to be performed, the devices can be reduced. This area is called concentration.
In the next phase, the number of inputs and outputs are similar. Some go to the next phase of the node, other modules communicate with the output links, heading for another node. Finally, the arrival link module also defines which entries are directed toward the outlet within the stage. This process is called distribution.
The final stage is expansion, in which from 200 entries we completed in 4000 outputs.
SPC Control System
- Centralized SPC control: If a given processor has direct access to all resources of the node and performs all system functions. They usually mean that the node has a single central computer (doubled for security).
- SPC distributed control: If a processor is in a given state, but that does not have access to some of the resources and/or is not able to run only some of the functions of the system. In practice, this leads to a digital system with a high number of microprocessors that perform, as a whole, the control node.