So just to give you a contrasting flavor of a different type of network, I'm going to talk about broadband access networks a little bit. These are networks that are used to provide access to homes. So if you're running a home IoT network or some setting where you just a home user, you got to get your cable modem, DSL modem, you're going to use a broadband access network to your conductivity. The way this look is something like this. So you have a bunch of homes and they are distributed around. They all have their individual set-top boxes or cable modems, and they'll have wires going out to them. Those wires connect out to something that goes out to a central box. You may have seen these little tiny green boxes on certain properties or they may be up on telephone lines, those are amplifiers. What those do is they take the signal from the home users, which is going over a wired cable a lot of the time, and which degrades the signal is going to amplify it backups to recover the signal. So it's going to take that information out, and it's this going to send it up to an upstream node. What the node does is it does aggregation. So it takes all of these individual coax connections, coaxial cable, or wire connections, and it's going to turn them into fiber. So a lot of connections come in and very few connections come out. It's going to go up to a hub. So a hub is where signals get mixed in. So what we do is we have all these home users and they're all sending data up, and then you'll see a big building like this. So a lot of these buildings they don't have windows a lot of the time. So these are filled with a bunch of different servers, and terminals, and equipment, they've taken all of these different streams of data and process them in different ways. A lot of times these facilities will have satellite dishes on top, and those are used to receive TV signals. So what we can do is we mix in television signals and disseminate those at two users as well as Internet, and television broadcast, and things like that. So what we're doing here is we're terminating layer two and layer three. Between the hub and the individual home users, we're speaking a protocal like DOCSIS or DSL. So these are different protocols which might use ATM or things like that. So there's different protocols which are used to communicate out to these individual users in layer two, and everything before that is layer one. Then in the hub, we take these signals and we send them up to a head in facility, which is a bigger processing station, which might mix in more signals and do additional sorts of processing. If you have a user and you have the Triple Play Package or whatever, you got your phone, and your Internet, and your TV all coming in, this is where the phone signals might get mixed in. So a long time ago, there was another network which was running parallel with the Internet called the Public Switched Telephone Network. In the old days, when you made a phone call, you would use an entirely separate network. It would be routed over the PSTN. They use different equipment, they use protocols like Signaling System 7 to switch signals, and that would be routed over the PSTN. As in the old days, you'd see different situations where you'd have two signals mixed in like this. You'd have the Internet and the public switch telephone network. Nowadays, you see this too. You see the same structure, but often the PSTN is routed over a public Internet anyway. Because most providers, if you make a cell phone call or a an Internet call, or things like that, that gets quickly moved onto the public Internet anyway because the cost of IP has dropped so much that doesn't make sense to have a separate Signaling System 7 network anymore. So if you have this network, you're going to have a broadband provider. It was going to provide this network-like AT&T or Comcast, and it's actually a huge amount of effort for them to maintain these networks. You see this all the time, you're driving around and you see like a little AT&T track or Comcast truck on the side of the road fiddling with those green boxes, that's because these networks break down all the time. What is most unreliable is not the core, it's not the stuff in the hidden facility, is the stuff near the homes. So as you go out farther and farther, you got a lot more outages. It requires a large number of people to deal with this work, large amount of monetary investment. In the access network, the stuff near the edge is the largest in terms of physical size as well. So for example, Time Warner Cable, one of the reason estimates is that they have only about 1,000 hubs, but they have 95,000 nodes and 1.9 million amps to provide service for 30 million coax users. So you can see this network just mushrooms out exponentially as you get closer to the edge. So the challenges of maintaining these networks increase as well.
