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Welcome to the preview of DPS for IoT

Note: DPS is currently released as a technical preview for evaluation. It is very much as work in progress and is not intended for commercial deployment at this time.

Background

Distributed Publish Subscribe for the Internet of Things, which we will refer to as DPS in this document, is a new protocol that implements the pub/sub (publish/subscribe) communication pattern. The pub/sub pattern for device to device communication is simple and powerful. There are several existing pub/sub protocols seeing heavy use in IoT applications, perhaps most notably MQTT and DDS but there are numerous other. Two characteristics of pub/sub that make it attractive for IoT uses cases are support for loose-coupling between publishers and subscribers, and inherent support for point-to-multipoint messaging. There are generally two implementation approaches: brokered (e.g. MQTT), or multicast (e.g. DDS). In brokered pub/sub systems publishers and subscribers connect to a centralized server that routes publications to matching subscribers. In a multicast pub/sub system subscribers receive messages from all publishers and selectively forward matching publications up to the application. The disadvantage of a brokered approach is that the broker is single point of failure, must be 100% available, and scales linearly with bandwidth and processing capability of the broker. Also all messages do a round-trip through the broker which puts a lower bound on communication latency. Multicast pub/sub systems are hard to scale beyond a single subnet and work much better over wired than wireless networks.

Distributed Publish Subscribe as the name implies is a fully-distributed pub/sub framework. There is no broker, devices or applications (we will just call them nodes) running the DPS protocol form a dynamic multiply-connected mesh where each node functions as a message router. The DPS framework supports a topic string syntax that will be very familiar to MQTT users and also supports MQTT-like retained messages. The mesh is boot-strapped using IP multicast, a directory service, or by explicit URL. The DPS protocol is light-weight and amenable to implementation on very small devices such as sensors that primarily publish data. The DPS architecture is well suited for applications that leverage edge computing in combination with cloud-based analytics.