Identifying next protocols to work

[egekorkan]

This is a placeholder for grouping previously (2 years ago) discussed protocols and similar mechanisms in the context of GitHub issues. I will close the following issues and group them here:

• 41

• 1

Following protocols were of interest in #1 and #41 and #42 :

• Events using WebSocket protocol
• Events using EventSource
• OCF flavor of CoAP
• LWM2M flavor of CoAP
• Proxy Bindings for Interconnected Servient use case
• Echonet
• Webhook/web callback-based notification
• OPC-UA

Additionally, the following protocols were briefly discussed in the call of 31.01.2020:

• Modbus
• Bacnet
• ROS
• WebThing API by Mozilla

[mjkoster]

Cases where a protocol binding doesn't need to be able to map all WoT defined ops:

• special cases where TDs don't use all ops, like exposing sensor data
• where a combination of protocols is used e.g. HTTP for writeProperty, readProperty and MQTT for observeProperty, invokeAction, and subscribeEvent

It is a tradeoff: unconditional interoperability vs. good vertical domain coverage. Unconditional interoperability is good within a given vertical domain; for that we have Zigbee. I see the mission of WoT as crossing the vertical domains and needing a lot of protocol options, including "natural" pub/sub.

[mjkoster]

There is also the web-device interaction pattern, with the following communication primitives:

• Enroll/discover: upload metadata from device to service
• Bulk state update: upload state from device to service
• Notifications and incremental state: send incremental updates from device to service
• Commands and configuration updates: from service to device

I would like to be able to use WoT Thing Descriptions in this protocol environment, since the actions, events, and properties, all look the same to the end user apps and automations.

This maps naturally to Pub/Sub systems but requires a proxy at the application layer to cache data for program reads, etc.

Another use case for this interaction model is for (what I am calling) IoT-Fieldbus where we use IoT protocols and mechanisms to build agile and efficient systems for industrial controls.

[mmccool]

I think 0MQ would also be very interesting; it is used in a lot of high-efficiency microservices, including Intel's Edge Insight platform. It supports both request/response and publish/subscribe patterns.

[mmccool]

DDS would also be interesting... if we do it right, it might give us ROS2 as well.

[egekorkan]

OPC-UA, NETCONF and Modbus examples of node-wot will be used for the vocabulary and clearly indicate that they are prototypes. @relu91 for the Modbus and @lukesmolo for OPC-UA and Netconf