Directionality

Scope

This page describes the different "directionality" types which can be use in a topology.

The property "directionality" supports different values depending on the object class.

Topology and Edge

The object classes "Topology" and "Edge" share the same definition and values of the property "directionality".

directionality : =

• bidirectional
  
  • A bidirectional "Topology" contains unidirectional and/or bidirectional nodes and edges
  • A bidirectional "Edge" serves in a telecommunication context can support traffic in both directions.
• unidirectional
  • A unidirectional "Topology" contains  only unidirectional nodes and edge
  • A unidirectional "Edge" serves in a telecommunication context supports traffic in one direction only.

Node

Also nodes can be divided into "unidirectional" and "bidirectional" nodes. However, for unidirectional nodes it is important to know whether the nodes is the source or the sink of the related "Edge". 

directionality : =

• bidirectional
  
  • A bidirectional "Node" can act as "sink" and/or as "source"
• sink
  • A unidirectional "Node" with directionality "sink" is in context of telecommunication the receiver of a signal. Sometimes also the label "out" is applied. 
• source 
  • .A unidirectional "Node" with directionality "sink" is in context of telecommunication the transmitter of a signal. Sometimes also the label "out" is applied. 

Combination of Nodes and Edges with certain directionalities

This chapter discusses the different combinations of Nodes and Edges depending on their directionality.

Creating a protected unidirectional server for a TV signal

The following example is already and extreme  case. An abstract topology model may not support it by default and needs to add rules for simplification purposes. 

However, such cases should be possible with "small" extensions. 

Explanations

Analog signal protection are often often comes with the concept of "broadcast and select". The transmitter sends the same signal towards different paths. On the receiver side both could be processed but often just one is selected. In case no signal is detected the receiver switches to the other input signal. (This here is just an example, to explain the potential need of a directionality also per edges. There are several more clever technical solution at the receiver).