[From the last episode: We saw reasons for not using the cloudA generic phrase referring to large numbers of computers located somewhere far away and accessed over the internet. For the IoT, computing may be local, done in the same system or building, or in the cloud, with data shipped up to the cloud and then the result shipped back down.; the fogRefers to some way of doing "cloud"-style computing without having to use the cloud. A local server (or router or something else) can act like the cloud; because it's local, it's referred to informally as the fog. gives you another option.]

We know philosophically that the fog can help us keep some data away from the cloud, but what does a fog serverA computer with a dedicated purpose. Older familiar examples are print servers (a computer that controls local printing) and file servers (a computer used for storing files centrally). More modern examples are web servers (the computers that handle your web requests when you use your browser) or application servers (computers dedicated to handling the computing needs of a specific application). Servers are often powerful, expensive machines since they have to handle a heavy load. look like in real life? Is this something we could do at home? Let’s take these one at a time.

Keeping Data Off the Cloud

Let’s start with, conceptually, how you would do this at home or in industry. In general, there will be a gateway that connects your local networkA collection of items like computers, printers, phones, and other electronic items that are connected together by switches and routers. A network allows the connected devices to talk to each other electronically. The internet is an example of an extremely large network. Your home network, if you have one, is an example of a small local network. to the cloud, perhaps over a cable connection. A gateway is basically a network routerAn electronic box that helps steer data on a network. For instance, you may have one in your home connecting your phone and computer and other devices to each other and to the internet. The data itself has information about where it's being sent; the router uses that information to send it in the right direction. At a really basic level, you can think of a router and a switch as being the same thing. If you want to get more technical, a switch creates a local subnetwork, and the router connects multiple subnetworks (or multiple networks)., so it could also connect to a local fog server.

• In your home, your cable modemA piece of network equipment that converts data into a format that can be transmitted. Old modems sent the data on a phone line; modern cable modems send the data across a cable connection. It stands for "modulator/demodulator." or router could act as the gateway; newer ones have room for other softwareIn this context, "software" refers to functions in an IoT device that are implemented by running instructions through some kind of processor. It's distinct from "hardware," where functions are built into a silicon chip or some other component. on them.
• For industrial use, there are purpose-built gatewaysA piece of electronic network equipment that takes a local network and gives it access to the internet. Your cable modem, for instance, might act as a gateway.. Gateway software would decide, for each piece of data it received, whether it should send it to the cloud or to the local fog server.

In the case of something like Amazon’s Alexa, the device can do enough sound processing by itself to figure out if you’re saying, “Alexa” (or whatever the wake wordFor personal assistants like the Amazon Echo, this is a word or phrase that the device listens for. When it hears it, it knows (or thinks) that you're going to give it a command. is). Exactly how much processing it does isn’t precisely clear – and it might vary by equipment and change over time. But the basic point is that some work is done locally, reducing the amount of data that goes to the cloud. (At least for now.) Here the device acts as its own fog server.

The following animation video illustrates the fog. Let’s say we have two chunks of data from two sensorsA device that can measure something about its environment. Examples are movement, light, color, moisture, pressure, and many more. in a piece of equipment.

• One sensor is a thermometerA sensor that measures temperature.; it measures how hot the equipment is. The manufacturer wants to know this so that they can monitor whether or not their equipment has a tendency to overheat.
• The other sensor measures vibration. It analyzes the vibration patterns to learn what “normal” is so that it can detect if that pattern changes. A change could possibly mean that whatever it’s attached to (say, a pump) is about to fail. This could reasonably be sophisticated computing that would be done in the cloud. But let’s say you don’t want to send it all to the cloud either because of confidentiality or because it’s a ton of data. Perhaps only a notification would be sent to the cloud if there were a problem.

Sensor data would be sent to the gateway; gateway software would then decide whether to send the data to the cloud or to the local server – the fog.

Let’s be clear, however: setting up a local server to act as fog is not for the technologically timid. You would need to work with whomever makes your equipment to figure out how to make the gateway decisions and how to get that software onto the gateway. This will also depend on your gateway. If you run a business that needs this, you need to get your IT specialists involved.

It’s very unlikely you would do this at home. At home, any fog capabilities are likely to be built-in so that you won’t have to mess with it yourself. But it’s good for you to understand this so you can be better informed about where you’re data is going.

Avoiding the Cloud Delay

In the prior post, we also say that, for delay reasons, you might not want your phone to send instructions through the cloud. The device maker – say the company building a door lock – would address this by making sure the lock has WiFiA common type of wireless network used to connect computers and phones to each other and the internet. or Bluetooth. They would then create the phone app in a way that lets the app decide which commands go through the cloud and which go direct.

If the lock is connected to the cloud, then it probably already has WiFi. WiFi has to go through an access pointFor wireless network connections like WiFi, this is a router that takes your wireless signal and either connects it to other wireless signals or to a wired signal -- say, for going to the cloud. – which is, more or less, a router for wireless connectionsThis refers to some kind of electrical connection. It might be through a network cable, a cable connection, a wireless connection, or a phone - just to name some options. The connection might be to the internet or to some other local device.. If you have WiFi, then you have an access point. It may be combined with your network router or even your broadband router (like a cable modem). Bottom line: assuming you already use WiFi, you wouldn’t need a new piece of equipment for this.

Bluetooth works a little differently: your phone talks directly to the door lock, without going through some intermediate point. If the door lock used Bluetooth, it would then need to include the circuits and software for doing Bluetooth. It’s unlikely that it would use Bluetooth for getting to the cloud, so either the lock would not connect to the cloud (pretty unlikely), or it would need both WiFi (for getting to the cloud) and Bluetooth (for the direct connection to the phone). That would add to the lock’s cost.

Note, however, that if you were away from home, you could still use your phone to control the lock, but then you’d have to use the cloud – because you’d be out of WiFi or Bluetooth range.

The following animation illustrates the door-lock example. Here we compare local communication using WiFi and Bluetooth, and remote communication using the cellular system.

When You Need Both Private and Fast

There might be times when you have to do some real computing, but you need the fastest possible response. The simple WiFi/Bluetooth solutions don’t help here because they can’t do the computing you need. Here again, you use your own fog server – but it’s important that it be both fast and located nearby. That way it can do the work quickly and then send the results where they need to go with minimal delay. Not a likely DIY project for a home (unless you really know what you’re doing), but a very likely project in an industrial setting.