MQTT/AMQP design implications

If you're working with embedded devices or telematics solutions, you might be hearing noise about a fairly new protocol called MQTT. It's a relative newcomer to the network protocol world having been invented in 2009 and first published in the wild in 2010, it is roughly speaking to tcp based binary wire protocols what SPDY is to HTTP.

At the heart of the protocol and why you might use it instead of say..AMQP is its simplicity. There are only 5 operations that must be implemented, it's wire format is minimal, and because of it's simplicity, it is theoretically able to use less power.

A close examination of the differences between AMQP and MQTT show that the low power or low memory devices (think Arduino class) will certainly be more likely to easily speak MQTT rather than AMQP. As an example of how an ideal architecture leveraging the strengths of each protocol might look, take a look at the following diagram:

When looking at this stack, let's talk about the implications of this approach over a SPDY/HTTP implementation from the device perspective.

For devices living in a low power lossy environment (on the right) using MQTT makes a lot of sense. If you periodically transmit 10 bytes and need to know if a device is connected or not...as well as maintain a small footprint for the libraries doing the connection management, MQTT wins hand down versus AMQP or HTTP. On the other hand, once these messages are delivered to an MQTT broker it becomes more important to handle message queuing, reliability, and a host of other things that an embedded device typically won't have the power or inclination to manage. Additionally, in a low memory/power situation, maintaining application message level transaction state for the life of the operation is often rife with error

In short, it seems for many use cases a combination of these protocols is generally going to be the "best" solution, not one or the other by themselves.