Here is an oversimplified view of the networking protocol stack. There is much more going on here than we will cover in this chapter, but to help in understanding the discussion, it is useful to reduce it to a simple diagram:

Network communications operates in layers with the bottom layers not needing to know about the layers above it. It can get confusing talking about all the options available at each layer of the stack. The diagram shows the key layers that we are concerned with for IoT analytics, but know that there is more to the story.

The diagram is based on the simplified OSI model, which divides communication into five fundamental layers. There is a Physical layer at bottom that has more to do with device electrical engineering. We will leave that out to simplify things since we are focusing on analytics.

Connectivity will refer to options primarily in the Link layer of the stack. Data communication or messaging will be referring mainly to the Application layer. The Network layer is (usually) the Internet Protocol (IP) that we all know and love. It is a great consolidator that enables so much flexibility in the networking stack for internet communications.

Transport is either TCP or UDP for most networking schemes that transmit data over long distances. TCP has more delivery guarantees but more overhead; UDP has less overhead but less guarantees on delivery.

There is a wide variety of networking protocols for both connectivity from the internet to the IoT device and for the communication of the data the device generates. They solve two main problems:

• How do I establish communication, so I can send data packets?
  • Let's use snail mail as an analogy. If you have limited funds, you prefer sending brief postcards even it takes longer to arrive to the recipient. It costs less, and it does not take much effort to write. If money is not a problem, you would hire some professional authors and send prose approaching poetry. You would use airmail so it arrives quickly. In this analogy, battery power is like money and CPU/memory is like writing effort.
• How are the data packets delivered so that my needs are met?
  • Do you and I agree to get each other's address and send letters direct? Or do you always give them to Tom, in the cubicle down the hall, and he sends it out to whoever needs it? Do you send it certified mail because you have to be certain it was delivered? Or do you send it third-class post because it is much cheaper and not the end of the world if it gets lost?

The network protocol used depends on the type of device and the environment in which it is located. It can also depend on the business priorities for which the data will be used.

For example, in the case of monitoring aircraft engines in flight, it is more important to get the most recent data than to get all of the data. You need problems identified as soon as possible more than you need a complete recording of all in flight data, which is mostly the same. So if you have to make a choice between waiting but getting everything or never waiting but losing some data packets from time to time, you choose the latter.

This is different from the logistics provider that has a sensor, which detects tractor trailers entering and leaving a distribution hub. In this case, you want a complete record of traffic, and you would be willing to wait a minute or two to have it.

Another important component to understand for IoT is that of a gateway. A gateway is a network node that connects two separate networks that use different protocols. The gateway handles the translation between them. A gateway is common in many IoT networks of constrained devices. It translates from the protocol optimized for the constrained devices to (usually) the protocol used by the wider internet (IP).

There are multiple standards spread across several organizations such as the Industrial Internet Consortium, the IPSO Alliance, and the IEEE P2413. It is continuously evolving with many companies and alliances aligned along different connectivity protocols. It may be another five to 10 ten years before the options coalesce into a smaller group of consistently used standards.

We will review the top ones you are likely to run across with an eye on the problems they are trying to solve.