Connectivity Framework Annex E: Assessment Template: CoAP
E. 6.4 Functional Viewpoint E. 6.4.2 Core Transport Layer Functions
Messaging Protocol( Section 5.1.1)
Communication Modes( Section 5.1.2)
Endpoint Addressing( Section 5.1.3)
Connectedness( Section 5.1.4)
Prioritization( Section 5.1.5)
Timing & Synchronization( Section 5.1.6)
Message Security( Section 5.1.7)
Does it require UDP or TCP? What are the salient aspects of the messaging protocol? What are the message size limitations? What are the usage assumptions? Is it optimized for certain message requirements?
The CoAP messaging protocol is a IP based protocol. It supports multiple bindings that are based on IP( i. e., UDP, TCP, SMS, Web Sockets). By default, it works over UDP. CoAP messages size is based on a 32-bit integer but CoAP messages work best without fragmentation, as such implementations tend to keep message sizes less than the underlying network transport layer payload sizes. A CoAP message, appropriately encapsulated, should fit within a single IP packet to packet to avoid IP fragmentation. When necessary CoAP does provide a mechanism to fragment and reassemble larger messages sizes. Which communication modes does it support?
CoAP supports both unicast( default) and multicast( when available by the underlying transport).
Describe the transport endpoints. How are the endpoints addressed? What are the limitations, if any, on the number of endpoints?
A transport endpoint is a server IP address and a port number. There is no inherent limitation on the number of endpoints. Does it require a connected circuit between the endpoints? Summarize the salient aspects. CoAP does not require a connected circuit between a client and server. Does it provide a means to prioritize messages? Summarize the salient aspects.
CoAP itself does not provide a way to prioritize messages. Does it provide the ability to synchronize time? Summarize the salient aspects.
No, CoAP does not provide a way to synchronize time between clients and servers. Does it provide mechanisms for message security? Summarize the salient aspects.
CoAP can use Datagram Transport Layer Security( DTLS) over UDP to provide message security. CoAP ' s default choice of DTLS parameters is equivalent to 3072-bit RSA keys, yet still it runs well on the smallest nodes.
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