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 -