Connectivity Framework Annex E: Assessment Template: CoAP
E. 6.5 Implementation Viewpoint E. 6.5.1 System Architecture Considerations
Peer-to-Peer vs. Broker:
( Section 4.2.1.1)
Data-Centric vs. Device / App-Centric:( Section 4.2.1.2)
Explicit vs. Implicit Governance:
( Section 4.2.1.3)
E. 6.5.2 Data Considerations
Content-Based Selection( Section 4.2.2.1)
Time-Based Selection( Section 4.2.2.2)
Does the connectivity framework require running a special process or broker? No brokers are required.
E. 6.5.3 Performance Considerations
Real-Time( Section 4.2.3.1)
Latency and Jitter vs. Throughput
( Section 4.2.3.2)
Communication occurs between endpoints acting as clients or servers, and so is peer-topeer oriented.
Does the application code( or business logic) have to be aware of the other endpoints in order to participate in information exchange?
Clients do not have to be aware of the server behavior to participate in a data exchange. Clients need to have mechanisms for finding and operating on resources much as on the web. Servers can dynamically provide their interfaces to the clients.
In practice, depending on the use case, it is feasible to build data-centric( RESTful, dynamic APIs) or device-centric( fixed API) architectures. Is the governance explicit and shareable?
The governance is implicit, embedded in the request and response headers and data exchanged between a client and a server.
Can a content-filter specify the data subset of interest?
No, CoAP does not provide a content filtering mechanism to specify a data subset of interest. However, it does support the concept of“ content negotiation” between a client and a server. A client can express interest in only a subset of the data via the query parameters on a resource. It is left up-to the server to define the results of the content negotiation. Can sub-sampling specify the data subset of interest?
No, CoAP does not provide a sub-sampling mechanism to specify a data subset of interest. A client can express interest in only a subset of the data via the query parameters on a resource being observed. It is left up-to the server to define the results of the content negotiation.
Does the connectivity technology support real-time data distribution? Is the latency deterministic( smaller jitter is better)?
CoAP is not aimed at real-time applications, but rather at resource constrained applications. Similar to TCP / IP connectivity, the exponential back-off and retry algorithm for confirmed reliability is not deterministic. CoAP does not provide mechanisms to ensure timeliness of data; that is left to the connectivity framework. How does the latency and jitter change with throughput? What limits the throughput?
Compared to HTTP, CoAP endpoints should not experience more latency due to the use of CoAP, as it is very constrained and avoids fragmentation at multiple layers. CoAP should have smaller latency and jitter, compared to HTTP when used over UDP.
IIC: PUB: G5: V1.0: PB: 20170228- 109-