Home internet fundamentals
The wifi is bad! Anybody online has felt that. I sure did: my household should’ve had ~400 Mbps, enough to stream 4K videos and play games and video-call, all at the same time. Instead we got 100 Mbps, 10 Mbps, or even 0 Mbps.
Troubleshooting wasn’t easy. None of the usual tricks worked (have you tried turning it off and on again?). I ended up working with several technicians from both the ISP and the building team; I’d never seen something like this.
We found the issue by applying basic principles. With computers, basic doesn’t mean obvious. It means, simple things work together to make a complex thing: high-speed home internet. Running an internet speed test might exercise several parts requiring a closer look.
It’s a tried and true engineering technique: drill down from “it’s broken” to “this specific part(s) is broken”. Isn’t it interesting that a more complex statement is simpler to fix?
In the end it was a faulty cable between my unit and the building’s central networking room. It worked well enough to function at low speeds, but poorly enough that my poor network just stopped trying sometimes.
Several iterations of guessing–ahem–making hypotheses, then experimenting, helped pinpoint the problem. When faced with “my wifi is bad”, I usually assume it’s something wrong with my home setup. Still, you never know: with computers, so many things can go wrong!
This simple question isn’t so simple to answer! Let’s equip ourselves with some networking fundamentals. We need to understand both the home network, and how it connects to the external network. Based on this knowledge, we’ll be able to tackle actual diagnosis in a subsequent article.
Home network
Saying “bad wifi” is a catch-all for several flavors of slow: real-time delays aka lag, buffering interruptions, degraded quality, etc. The “badness” could indeed be the actual wireless, or congested connections, or something else entirely.
Let’s use first principles to explore the problem. Fundamentally, we have a device exchanging data with an app via “the internet”.
Smartphones are increasingly common. These computers use cellular radio to connect to towers, which then join the internet.
Cellular’s big advantage is not requiring a physical connection to a device. It has some drawbacks too: connection quality & bandwidth varies widely, and carriers often charge by data consumption, or reduce speed after relatively little usage. Besides, most consumer devices can’t connect to cellular networks at all. That’s why people get a home network.
To set up a home network, we need (1) networking hardware, and (2) a connection to an internet service provider aka ISP. The ISP is “the internet company”, the provider who provides a connection to the internet. The setup looks like this:
The device in the middle is usually called a router or modem somewhat interchangeably. To be precise several things are happening:
- wireless connects devices to the router
- routers create a private local network, connected to a shared external network also called the wide network (hence the terms LAN and WAN)
- modems connect to another computer over telecommunication infrastructure, converting between digital data (a series of 0s and 1s) and physical transmission (coax electricity, fiber optics, etc).
ISPs often provide “all in one” or “gateway” routers which combine wireless, routing, and modem. Here are the three functions split out:
By the way, it’s possible to connect a computer directly to the modem, meaning directly to the ISP. But it’s usually a Bad Idea™ for various reasons, like security.
Modems are basically interchangeable for our purposes. The main concern is ISP compatibility, typically indicated clearly. If you were online in ye olden age of dialle-uppe, you may recall the song of the modem. Experience it on Youtube. User @fenderpuddy5866 explains the bleeps, bloops, and whirrs in this comment. Today’s modems are fancier but perform the same basic task.
There’s not much reason to buy a modem … except money. Assuming $15/mo rentals, and $200 equipment, buying a modem pays off just after 13 months: $15 * 13 ≈ $195. Then it’s $15 saved per month. Modems usually last years, so it adds up.
Router features vary more widely:
- Wireless: does it have wireless, if yes what kind?
- Ethernet: does it have any wired connections?
- Router features: firewall, family controls, on/off schedules, ease of setup, mobile apps, priority apps, port forwarding, etc.
Routers can get pretty fancy depending on your needs. A standard firewalled router compatible with phones, computers, and gaming or streaming devices is fine for most purposes.
The most common issue with routers is bad wireless connectivity with devices. We’ll talk about this more later. For now, we have an overview of home network components. We’ll assume a 3-in-1 gateway router for simplicity.
External network
The external network is simpler, in a way: there’s not much we can do about problems. There’s a certain zen to it, even if outages don’t spark joy.
Understanding the external network is more about calibrating expectations than actually doing anything about it. Each of the links from home to app and back again can have issues. Sometimes the app itself is overloaded and struggling to meet demand.
From a networking perspective though, if it works, it usually continues to work. The network between ISPs (sometimes called the internet backbone) is quite robust. Other than network congestion, a common cause for “bad wifi” in the external network is the link from the home to the ISP.
The link from the modem to the ISP fundamentally determines how much data flows, how fast, and how reliably. It carries 100% of our traffic to that network–alongside everybody–and everything–sharing it.
The modem bridges the home to the outside. The “outside” for most people’s purposes is the other side of the cable jack on the wall, or maybe an outdoor junction box. Diagnosing issues past the modem requires specialized knowledge & tools, and fixes could involve anything from installing new cables to realigning satellite transmission.
ISPs can typically confirm if they see the modem, as well as the router behind it. They need the router’s MAC address, which uniquely identifies its network hardware. The ISP asks its own hardware if it’s communicating with the router– whether or not that communication was successful in setting up a connection.
The modem to ISP link can take several forms:
Knowing the physical infrastructure can calibrate expectations:
- dsl / dialup: plain-old-phone dial-up lines are limited to 56 kbit/second, whereas fancy-phone DSL can achieve >100 Mbit/s. DSL (or ADSL) was cool beans, until:
- cable: dedicated cable networks are much fancier than the telephone, achieving hundreds of Mbit/s or even 1–2 Gbit/s.
- fiber-optic: modern cables are even fancier, with consumer speeds nearing 10 Gbit/s. Availability is relatively limited, especially in less dense municipalities or rural areas.
- satellite: can achieve 10–100 Mbit/s, but with a half-second delay or more due to the literal trip to space and back. This makes satellite internet less suited to real-time applications, for example video calls are more awkward. Satellite is easier to deploy to remote areas, but sensitive to obstructions like trees, or the weather affecting dish alignment, and also UFOs. 👾 Just kidding, I think.
Based on data from the FCC, here’s a comparison of ISP bandwidth, versus average application usage.
Of course, the advertised link speed doesn’t guarantee actual end-to-end performance between the home network and the application. Many things affect performance in practice:
- service congestion: shared infrastructure means less available bandwidth at peak hours. Too many people going online at the same time can “break the internet” especially when going to the same place. Much like physical transit. This is especially a problem on busy public hotspots.
- bandwidth caps: some providers reduce speed after 5–50–100+ gigabytes. One hour of HD video is ~2–3 gigabytes, so it adds up fast.
- distance: the longer a signal travels, the slower it gets. If a cable jack is “far” from the telecom node, it may degrade speed or quality. This can affect more rural areas, but also simply large buildings.
- infrastructure issues: telecommunication utilities are generally reliable in most of the US. But because computers, any number of things can go wrong. Things just break, disasters happen, and criminals & nation-states alike engage in cyber-attacks. You never know.
My personal ISP setup is a unit in a multi-unit building, all sharing an ISP (Google Fiber). Each unit is connected to a modem in our central telecom room. That modem is wired to a light transmitter on the roof, pointed at a Google Fiber access point. From there, it’s fiber to Google’s backbone.
The transmitter is literally light. Here’s a 2020 article explaining the technology: Your Wi-Fi Could Eventually Arrive Over Light Beams. It’s an innovative workaround when it’s expensive or impractical to run actual fiber from the ISP to a house. But it also means my network can break if a strong enough wind (or something) knocks the receiver out of alignment.
Once we’re on “the internet”, things are usually pretty fast. The “information superhighway” is pretty solid, barring outlier events like world-scale sporting, entertainment, or damage from natural disaster or war. Eventually we get to the app’s ISP, and the app itself.
Sometimes, “bad wifi” is caused by the app and not the network at all. If an app can’t scale to demand, the experience can feel like a slow connection. I’m waving my hands a bit here, as the “app” is typically not a device in the sense a computer or tablet is. Welcome to the cloud!
Conclusion
We’ve covered the fundamentals of home networking, as well as the external network. Using this knowledge, we can draw a map of our home network system. This is key to our work’s next step: diagnosing the problem.
