Connectivity Framework
2 : Connectivity Framework
The data services framework in the distributed data interoperability and management function builds on the syntactic interoperability foundation provided by the connectivity framework to provide the foundation for semantic interoperability required by the dynamic composition and coordination function of the Industrial Internet Reference Architecture ( IIRA ) 1 .
The role and scope of the IIoT connectivity functional layers are summarized in Table 2-1 .
IIoT Connectivity Stack Model
Framework Layer
Correspondence to OSI Model ( ISO / IEC 7498 )
7 . Application
6 . Presentation
5 . Session
Correspondence to Internet Model ( RFC 1122 )
Application Layer
Transport Layer 4 . Transport Transport Layer
Network 3 . Network Internet Layer
Link Physical
2 . Data Link 1 . Physical
Link Layer
Table 2-1 : Role and scope of the Connectivity functional layers .
2.3 KEY ARCHITECTURAL QUALITIES
Correspondence to Levels of Conceptual Interoperability
Syntactic Interoperability : Structured data types shared between endpoints . Introduces a common structure to share data ; i . e ., a common data structure is shared . On this level , a common protocol is used to exchange data ; the structure of the data exchanged is unambiguously defined .
Technical Interoperability : Bits and Bytes shared between endpoints , using an unambiguously defined communication protocol .
Packets shared between endpoints that may not be on the same physical link . Packets are routed between physical links by a “ network router ”.
Digital Frames shared between endpoints on a shared substratum ( link ).
Analog signal modulation between endpoints on a shared substratum .
The connectivity function supports the key architectural qualities of an IIoT system , and they can be used to assess the alternative connectivity choices for concrete architectures . The qualities are described below .
2.3.1 PERFORMANCE
In IIoT systems , high performance connectivity is expected . The spectrum of performance ranges from tight sub-millisecond control loops to supervisory control to analysis at very low frequencies such as daily , weekly or even monthly . The performance characteristic is measured along the following axes .
Latency and jitter . Latency is the time it takes for data to go from source to destination (“ time of flight ”). Jitter is the variation in latency . The data usually has a limited useful lifetime , so low latency is essential . Low jitter is also needed to ensure the application has integrity and system
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See [ IIC-IIRA2015 ] IIC : PUB : G5 : V1.0 : PB : 20170228 - 17 -