Connectivity Framework
2 : Connectivity Framework
The layers above the network layer have evolved rapidly in the last decade and are not as widely recognized or understood . Therefore , the focus of this document is on the layers above the network layer , namely the transport and framework layers , as shown in Figure 2-2 .
2.2 ARCHITECTURAL ROLE
The connectivity function in the IIRA supports exchange of data among endpoints in a system of interest . The information , for example , can be sensor updates , telemetry data , control commands , alarms , events , logs , status changes or configuration updates . Fundamentally , connectivity ’ s role is to provide interoperable communications among endpoints to facilitate component integration .
Interoperability in communication can be achieved at various levels of abstraction , from custom integration to plug-and-play interfaces based on open standards . One common classification of interoperability is as follows ( see Tolk , Wikipedia 1 ):
Technical interoperability is the ability to exchange information as bits and bytes ( e . g . pencil scribbles ), assuming that the information exchange infrastructure ( e . g . pencil and paper ) is established and the underlying networks and protocols are unambiguously defined .
Syntactic interoperability is the ability to exchange information in a common data structure ( e . g . using words from a language ), assuming that a common protocol to structure the data is used ( e . g . the language ’ s alphabet and rules of grammar ) and the structure of the information exchange is unambiguously defined ( e . g . whitespace , punctuation ). Syntactic interoperability requires that technical interoperability be established .
Semantic interoperability is the ability to interpret the meaning of the exchanged data unambiguously as information in the appropriate context . However , the goal of the connectivity function is limited to provide syntactic interoperability between participating endpoints .
For IIoT systems , connectivity comprises two functional layers :
The connectivity transport layer provides the means of carrying data between endpoints . It provides technical interoperability between endpoints participating in a data exchange . This function maps to layer 4 ( transport ) of the OSI model or the transport layer of the Internet model ( see Table 2-1 ).
The connectivity framework layer facilitates how data is unambiguously structured and parsed by the endpoints . It provides the mechanisms to realize syntactic interoperability between endpoints . In this context , “ common data structure ” refers to the structure or schema of the data being exchanged . Familiar examples include data structures in programming languages and schemas for databases . The connectivity framework function spans layers 5 ( session ) through 7 ( application ) of the OSI model or the application layer of the Internet Model ( see Table 2-1 ).
1
See [ Tolk-2007 ], for overview [ WKPD-CI ]
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