MCU Hardware

Networking Concepts
Quick Reference

A practical, opinionated reference for engineering co-op students getting started with home and farm networking, IoT, and the protocols that wire it all together. 70+ terms covering the foundational concepts: TCP/IP, DHCP, DNS, subnets, NAT, VLAN, mesh, gateways — and the rest of the vocabulary your colleagues use without explaining. Companion to the Networking Protocols Quick Reference (Wi-Fi, LoRaWAN, Zigbee, Matter, MQTT, Modbus, NMEA 2000, …) — same search engine, same look, cross-linked.

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70
Glossary terms
23
Letter sections
5
Learning path
6
Quick tables

1. How to use this document

You will not read this end-to-end. Use it like a dictionary with a learning path on top.

  1. Day 1 of your co-op: skim sections 2–4 (Prerequisites, Suggested Path, the Practical 20 list at the end of section 5). That alone puts you ahead of most interns.
  2. When you hit an unfamiliar term in code or a meeting: Cmd-F the term in section 5. Each entry is self-contained.
  3. When you want depth on a topic: follow the 📚 links at the bottom of the section. Those are the canonical, freely available resources — not random blog posts.
  4. When you're about to wire a part on your bench: jump to the sister Hardware Quick Reference (link in the navbar) and look up the exact part — it cross-links back to the concepts here.

2. Prerequisites

You don't need an EE degree, but the following mental model is assumed throughout this document. If you don't have it, the Practical 20 in section 4 will catch you up over a week.

Math (intuition, not proofs):

  • Algebra: solve for an unknown. Why: every circuit calculation is solving V = IR for one of the three.
  • Trig: sine, cosine, frequency, phase. Why: AC analysis, audio, filters, control loops.
  • Logarithms. Why: decibels, RC time constants, RC filter cutoff math.

Programming (one of these is enough):

  • Python — the default for MicroPython on the Pico and ESP32-S3. You should be comfortable with classes, decorators, async, and type hints.
  • C / C++ — for ESP-IDF, Arduino, or any low-level work. Pointers, structs, volatile, static, bit manipulation.
  • Shell — cd, ls, grep, |, >, python -m venv, esptool.py.

Tools to install (do this on day 1):

# Thonny (the friendliest MicroPython IDE — recommended for first month)
sudo apt install thonny   # or download from thonny.org

# mpremote — the official MicroPython command-line tool
pip install mpremote

# esptool — for flashing ESP32 / ESP32-S3 boards over USB
pip install esptool

# Arduino IDE 2.x — for Arduino C/C++ projects
# Download from arduino.cc

3. Suggested learning path (5 steps)

Do these in order. Each step is one evening on the bench (or on the laptop). By the end you will have a home or small-farm network that you actually understand.

Step 1 — Map your current network

Find your router’s IP (usually 192.168.1.1 or 192.168.0.1). From a laptop, run ip route to see the default gateway, ip a to see your own IP, and ping 8.8.8.8 to confirm you reach the internet. List every device on your network (router admin page, or an app like Fing). Goal: you can name every IP and what it does.

Step 2 — Configure DNS and DHCP

Set up Pi-hole or AdGuard Home on a Raspberry Pi. Point your router’s DHCP to hand out the Pi-hole as the network DNS. Verify that ads are blocked network-wide (visit a known ad-heavy site, check the Pi-hole dashboard). Goal: you have a single local service that every device on the network uses, and you can read its logs.

Step 3 — Segment the network (VLANs)

On a managed switch and a router that supports VLANs (UniFi, MikroTik, pfSense, OPNsense), create three VLANs: VLAN 10 = trusted devices (laptops, phones), VLAN 20 = IoT (smart bulbs, cameras, voice assistants), VLAN 30 = guest. Set up firewall rules so VLAN 20 and 30 can reach the internet but not each other or VLAN 10. Goal: a compromised smart bulb can’t reach your laptop.

Step 4 — Add a sensor network

Pick one wireless technology from section 5 that fits your use case: MQTT over Wi-Fi for a few indoor sensors, Zigbee or Thread for a home-automation mesh, LoRaWAN for a farm sensor a few hundred metres from the house. Buy a starter kit (a coordinator + 2–3 sensor modules), set up Home Assistant on a Pi or NAS, and make the data visible on a dashboard. Goal: a real network with real data flowing.

Step 5 — Add a remote-access story

Set up Tailscale (or ZeroTier) on the Pi, your laptop, and your phone. Verify you can reach the Pi-hole admin and the Home Assistant dashboard from a coffee shop over your phone’s cellular. If you want to do it without Tailscale: get a VPS, run WireGuard on it, and connect back to your home network through that. Goal: you can troubleshoot your network from anywhere with internet, without exposing any service to the public internet.

Optional but recommended: set up a local MQTT broker (Mosquitto) so devices can talk to each other without the cloud; explore IPv6 (ask your ISP for a prefix, enable SLAAC on your router) to future-proof against CGNAT.

4. The Practical 20 — read these first

If you only read 20 entries in this glossary, read these. They cover ~90% of what you'll see in your first month on a microcontroller project.

🔥CIDR (Classless Inter-Domain Routing)🔥DHCP (Dynamic Host Configuration Protocol)🔥DNS (Domain Name System)🔥IP Address (IPv4)🔥MAC Address🔥MQTT (Message Queuing Telemetry Transport)🔥NAT (Network Address Translation)🔥OSI Model (7 Layers)🔥Port Number🔥Router🔥SSID (Service Set Identifier)🔥Subnet / Subnetting🔥Wi-Fi (802.11)

Each entry: a one-line definition, then a practical note in italics that says what it means on the bench. Entries marked 🔥 are the practical-20.

Letter

A

2 terms

Access Point (AP)

#
A device that bridges wireless clients to a wired network. The Wi-Fi router in your house is a combination of AP + router + switch + firewall in one box. Practical: In a multi-AP home (Unifi, TP-Link Omada, mesh), every AP is a separate “cell” on the same SSID; the controller hands off clients between them as you walk around. Watch for: cheap “router/AP combos” can be set to AP-only mode by disabling DHCP — do that when adding a second box to an existing network, or you'll get two DHCP servers fighting. See also: SSID (Service Set Identifier), Router, Mesh Network, VLAN (Virtual LAN).

ARP (Address Resolution Protocol)

#
The protocol that maps an IP address to a MAC address on a local network. When your laptop wants to talk to 192.168.1.50, it broadcasts “who has 192.168.1.50? tell me your MAC” and the right device replies. Practical: Every IPv4 LAN depends on ARP. arp -a on Linux/macOS shows the table. ARP cache poisoning is a classic attack vector — switches with ARP inspection (most managed switches) defend against it. See also: MAC Address, IP Address (IPv4), Subnet / Subnetting.
Letter

B

6 terms

Bandwidth (Network)

#
The maximum data rate a link can carry, measured in bits per second (Mbps, Gbps). Distinct from latency (how long a single packet takes) and throughput (what you actually get). Practical: Three numbers worth knowing: (1) Wi-Fi 5 (802.11ac) = up to ~1.3 Gbps PHY, ~600 Mbps real-world. (2) Wi-Fi 6 (802.11ax) = up to ~9.6 Gbps PHY, ~1.5 Gbps real-world. (3) 1 Gbps Ethernet = 940 Mbps real-world (after protocol overhead). See also: Throughput, Latency, Wi-Fi (802.11).

Band Steering

#
A Wi-Fi controller feature that pushes dual-band clients (2.4 + 5 GHz) to the less-crowded band. The AP delays 5 GHz probe responses slightly, or simply puts 2.4 GHz on a lower-power channel. Practical: Enable it on your home Wi-Fi if you have a controller. Old 2.4 GHz-only IoT devices (Zigbee-like, some smart plugs) must stay on 2.4 — band steering doesn't affect them. See also: Wi-Fi (802.11), Access Point (AP), SSID (Service Set Identifier).

Bandwidth-Delay Product

#
Bandwidth × round-trip latency = the number of bits in flight on a link. Matters for TCP tuning (how big the receive window needs to be to fill the pipe). Practical: 1 Gbps × 50 ms RTT (typical continental US) = 6.25 MB. Default Linux TCP window is 4 MB, so a single bulk transfer is slightly sub-optimal. Real-world: only matters for >100 ms RTT (intercontinental) or >1 Gbps links. See also: TCP (Transmission Control Protocol), Bandwidth (Network), Latency.

Bridge (Network)

#
A device that connects two network segments at Layer 2, forwarding Ethernet frames by MAC address. A Wi-Fi AP is essentially a wireless-to-Ethernet bridge. Practical: In a home network, your router's “LAN” ports form a single bridge; in a managed network, you might have multiple VLANs each bridged independently. Watch for: a “bridge mode” on a router disables its routing/NAT/firewall — used when you have a separate router and want the device to be a dumb AP. See also: Router, VLAN (Virtual LAN), MAC Address.

Broker (MQTT)

#
The central server in an MQTT pub/sub system. Clients connect to it; the broker routes messages between publishers and subscribers. Practical: For a home or farm, run Mosquitto on a Raspberry Pi, on the same box as Home Assistant, or as a Docker container on a NAS. Configure it to require authentication (username/password) — the default is open. See also: MQTT (Message Queuing Telemetry Transport), Home Assistant (HASS).

Bluetooth (BLE / Classic)

#
Short-range radio (2.4 GHz) for low-power peripherals. BLE (Bluetooth Low Energy, 4.0+) is the modern one. Practical: Used for: phone-as-remote (lightbulbs, locks), beacons (Apple AirTag, indoor positioning), headphones (though not as low-power as you'd hope), sensors (heart rate, temperature). For IoT, BLE is best for one-to-one, low-data-rate, short-range. Watch for: BLE range is 10–30 m typical; mesh (Bluetooth Mesh) extends it but adds complexity. See also: Zigbee, Wi-Fi (802.11).
Letter

C

3 terms

CIDR (Classless Inter-Domain Routing)

#
The notation for IP subnets: 192.168.1.0/24 means the first 24 bits are the network, the last 8 are host addresses. Practical: Three ranges to memorize for home/LAN: /24 = 254 usable hosts (most home networks), /16 = 65 534 hosts (large campus), /30 = 2 hosts (point-to-point link). IPv6 uses the same notation: fd00::/8 is the Unique Local Address range (like 192.168.0.0/16 in IPv4). See also: Subnet / Subnetting, IP Address (IPv4), IP Address (IPv6).

CPE (Customer Premises Equipment)

#
The equipment at the customer's site: the cable modem, ONT (fiber), or 5G home router. Practical: On a farm, your CPE might be a directional 5G/LTE antenna pointed at the nearest tower, or a Starlink dish. Watch for: many ISPs lock the CPE to their network — you can buy your own but you have to register its MAC. See also: ISP (Internet Service Provider), Router.

CGNAT (Carrier-Grade NAT)

#
When your ISP doesn't give you a real public IP — it puts you behind their own NAT, sharing one IP with many customers. Practical: Symptom: traceroute from the internet to your home shows an intermediate hop owned by your ISP, not your router. You can't port-forward or host a server. Workarounds: (1) call your ISP and ask for a public IP (often free on business plans, pay on residential), (2) use a VPN with a static endpoint (Tailscale, ZeroTier, Wireguard to a VPS), (3) IPv6, which avoids NAT entirely. See also: NAT (Network Address Translation), DDNS (Dynamic DNS), VPN (Virtual Private Network).
Letter

D

5 terms

DHCP (Dynamic Host Configuration Protocol)

#
The protocol that hands out IP addresses automatically. Your router runs a DHCP server; every device on your network runs a DHCP client that asks “give me an IP.” Practical: Default lease is 24 h. Reservations (bind a MAC to a specific IP) are how you give your NAS, printer, and Pi-hole stable addresses. Debug: if a device can't get online, check ipconfig /all (Windows) or ip a (Linux) — if there's no IP under DHCP, the server is unreachable. See also: IP Address (IPv4), Router, MAC Address.

DNS (Domain Name System)

#
The phone book of the internet. Translates unmolai.com to 104.21.x.x. Hierarchical: root servers → TLD (.com) → authoritative servers for the domain. Practical: Three things to know for home: (1) recursive resolver — your ISP's, or 1.1.1.1 (Cloudflare), 8.8.8.8 (Google), 9.9.9.9 (Quad9). (2) Pi-hole / AdGuard Home — a local resolver that blocks ads network-wide. (3) local DNS — your router's DHCP hands out its own IP as DNS so the local resolver is used. Debug: nslookup unmolai.com or dig unmolai.com. See also: DDNS (Dynamic DNS), Pihole / AdGuard Home, Router.

DDNS (Dynamic DNS)

#
A service that maps a stable hostname to your changing home IP address. Your home IP changes every few weeks (CGNAT aside); DDNS keeps myhouse.duckdns.org pointing at whatever IP your router has today. Practical: For a farm or home with remote-access needs (security camera, Home Assistant, VPN back to your network), DDNS is the simplest way to find your network from the road. Free providers: DuckDNS, No-IP, afraid.org. Most home routers have a DDNS client built in. See also: DNS (Domain Name System), CGNAT (Carrier-Grade NAT), Port Forwarding.

Default Gateway

#
The router that forwards traffic to other networks. Your laptop's default gateway is typically your router's IP (192.168.1.1). Without it, you can talk to anything on your local subnet, but not to the internet. Practical: Three things to know: (1) the gateway IP is the router's IP, (2) it's handed out by DHCP, (3) it must be on the same subnet as your device. Debug: if you can ping your router but not 8.8.8.8, the gateway is misconfigured. See also: Router, Subnet / Subnetting, NAT (Network Address Translation).

DMZ (Demilitarized Zone)

#
A network segment exposed to the internet while the rest of the LAN stays protected. In home routers, the “DMZ host” setting forwards all ports to one device — a poor man's port-forwarding. Practical: Don't use a home-router DMZ for anything you care about. If you need to expose a service, port-forward only the specific port and put the device on a VLAN or guest network. See also: Firewall, Port Forwarding, VLAN (Virtual LAN).
Letter

E

2 terms

ESPHome

#
A framework for flashing ESP32 / ESP8266 boards with YAML configs that read sensors, control outputs, and integrate natively with Home Assistant (auto-discovery, no MQTT broker needed). Practical: The fastest way to build a custom sensor: write 20 lines of YAML, flash over USB, the device shows up in Home Assistant. See also: Home Assistant (HASS), MQTT (Message Queuing Telemetry Transport).

Ethernet

#
The wired networking standard. 10BASE-T = 10 Mbps, 100BASE-TX = 100 Mbps (“Fast Ethernet”), 1000BASE-T = 1 Gbps (“Gigabit”), 10GBASE-T = 10 Gbps. Practical: Cat5e handles Gigabit fine for runs up to 100 m. Cat6 for 10 Gbps or runs near power cables. Watch for: auto-negotiation is reliable; mismatches usually show up as “100 Mbps instead of 1 Gbps” on the link light. See also: Switch (Network), Router, MTU (Maximum Transmission Unit).
Letter

F

3 terms

Firewall

#
A device or software that filters traffic based on rules: allow, deny, or rate-limit. Home routers run a stateful firewall (tracks connections, blocks unsolicited inbound). Linux has iptables / nftables. Practical: Three rules: (1) default deny inbound — block anything from the internet you didn't ask for. (2) default allow outbound from LAN — your devices can reach out. (3) log denied packets — when you can't connect, the log tells you which rule blocked you. See also: Port Forwarding, Stateful Inspection, DMZ (Demilitarized Zone).

Failover

#
Automatic switch to a backup link when the primary fails. Starlink + 4G cellular with a dual-WAN router: if Starlink drops, 4G takes over in 5–30 seconds. Practical: For a farm with critical monitoring (irrigation, livestock, security), dual-WAN failover is cheap insurance. See also: Load Balancer, WAN (Wide Area Network).

Failover (Network)

#
When a primary network link fails, traffic automatically shifts to a backup. Starlink + 4G with a dual-WAN router: Starlink drops → 4G takes over in seconds. Practical: For farm monitoring (irrigation, livestock), failover is cheap insurance. Watch for: some routers do “fail-back” (return to primary when it's back) — this can cause flapping. See also: Load Balancer, WAN (Wide Area Network), Failover.
Letter

G

1 term

Gateway (Network)

#
A device that routes traffic between two networks. Your home router is a gateway between your LAN and the ISP. A LoRaWAN gateway routes LoRaWAN packets from sensors to a network server over Ethernet/Wi-Fi/cellular. Practical: If you have only one router, you have one gateway. If you add a second one (e.g. a farm setup with multiple buildings), you need routing rules. See also: Router, Default Gateway, LoRaWAN Gateway.
Letter

H

2 terms

HTTP / HTTPS

#
HTTP = Hypertext Transfer Protocol, the language of web pages. HTTPS = HTTP over TLS (Transport Layer Security), which encrypts the connection. Practical: For IoT: every device with a web UI (router, NAS, camera, Home Assistant, even a smart toaster) speaks HTTP or HTTPS. Port 80 is HTTP, 443 is HTTPS. Watch for: self-signed certs on IoT devices generate scary browser warnings — click through once to get in, or replace with Let's Encrypt if the device supports ACME. See also: Port Number, TLS / SSL, MQTT 3.1.1.

Home Assistant (HASS)

#
Open-source home automation platform. Runs on a Raspberry Pi, mini PC, or in Docker. Pulls in hundreds of devices and services (Zigbee, Z-Wave, MQTT, Modbus, Tuya, HomeKit, etc.) into one local-first dashboard. Practical: The de-facto hub for a serious home/farm IoT setup. No cloud dependency, runs on your LAN, integrates with everything. Getting started: flash Home Assistant OS to a Raspberry Pi 4/5, plug in a Zigbee/Z-Wave USB dongle, start adding devices. See also: Zigbee, Z-Wave, MQTT (Message Queuing Telemetry Transport), Node-RED.
Letter

I

3 terms

IP Address (IPv4)

#
A 32-bit number that identifies a device on an IP network. Written as four octets: 192.168.1.50. Total address space: ~4.3 billion. Practical: Three ranges reserved for private use (RFC 1918): 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16. Special addresses: 127.0.0.1 is the loopback (“this machine”); 169.254.x.x is link-local (DHCP failed); 0.0.0.0 is the “any” address (a server binding to it listens on all interfaces). See also: IP Address (IPv6), Subnet / Subnetting, NAT (Network Address Translation), CGNAT (Carrier-Grade NAT).

IP Address (IPv6)

#
A 128-bit address. Written as 8 groups of 4 hex digits: 2001:0db8:85a3:0000:0000:8a2e:0370:7334. Address space: ~3.4 × 10³⁸. Practical: Your ISP probably gives you a /64 prefix; your router assigns the rest via SLAAC or DHCPv6. Special addresses: ::1 is loopback, fe80::/10 is link-local (like 169.254.x.x in IPv4), fd00::/8 is ULA (private, like 10.0.0.0/8). Why care: every IoT device should support IPv6 — the world is running out of IPv4 and CGNAT makes things messy. See also: IP Address (IPv4), CGNAT (Carrier-Grade NAT), SLAAC (Stateless Address Autoconfiguration).

ISP (Internet Service Provider)

#
The company that gives you internet: cable (Comcast, Rogers), fiber (Verizon Fios, Bell Fibe), DSL, fixed wireless (Starlink, Rise Broadband), 5G home internet (T-Mobile, Verizon). Practical: For a farm, the choice is often between (1) Starlink (good coverage, ~100 Mbps, $80–$120/mo), (2) fixed wireless from a local WISP (often cheaper, faster, but line-of-sight), (3) cellular (variable, data caps). Always ask about static IP, CGNAT, and data caps before signing. See also: CGNAT (Carrier-Grade NAT), Starlink (Dish-to-Satellite), CPE (Customer Premises Equipment).
Letter

J

1 term

Jitter

#
Variation in latency from packet to packet. Important for real-time traffic (voice, video, gaming). 30 ms ± 5 ms is fine; 30 ms ± 50 ms is a stuttery VoIP call. Practical: Wi-Fi has high jitter (~5–20 ms) compared to wired Ethernet (~0.1 ms). For a security camera or VoIP, wired is worth the cable. See also: Latency, QoS (Quality of Service).
Letter

L

2 terms

Latency

#
How long a single packet takes to get from A to B. Measured in milliseconds (ms). Distinct from bandwidth (capacity) and throughput (actual). Practical: Four reference points: (1) local LAN ping = < 1 ms. (2) continental US internet = 20–80 ms RTT. (3) transatlantic = 80–150 ms. (4) geostationary satellite (Starlink's predecessor) = 600+ ms. Watch for: high latency makes voice / video calls choppy, gaming miserable, and TCP transfers slow. See also: Bandwidth (Network), Throughput, Jitter.

Load Balancer

#
A device that distributes traffic across multiple servers. Used by big sites (Google, Facebook) and overkill at home — but the principle applies: a UniFi gateway with two ISPs can load-balance outbound traffic. Practical: For a farm: if you have Starlink + a 4G cellular link, a dual-WAN router (UniFi Dream Machine, MikroTik) can use both. See also: Router, WAN (Wide Area Network), Failover.
Letter

M

7 terms

MAC Address

#
A 48-bit hardware address burned into every Ethernet and Wi-Fi device. Written as 6 hex bytes: AA:BB:CC:DD:EE:FF. The first 3 bytes identify the manufacturer (OUI). Practical: MAC addresses live at Layer 2; IP addresses at Layer 3. A switch forwards by MAC; a router forwards by IP. Privacy: modern OSes randomize Wi-Fi MAC addresses per network (called MAC randomization) to defeat tracking. See also: ARP (Address Resolution Protocol), Ethernet.

MTU (Maximum Transmission Unit)

#
The largest single packet a link will carry, in bytes. Ethernet default: 1500. PPPoE (used by most DSL and some fiber): 1492. Practical: If a connection mysteriously drops large packets, MTU mismatch is the cause. Test with ping -M do -s 1472 example.com — if 1472 works but 1473 doesn't, your MTU is 1500. For WireGuard / VPN: tunnel MTU is usually 1420 to avoid fragmentation. See also: Ethernet, PPPoE (Point-to-Point Protocol over Ethernet), VPN (Virtual Private Network).

Mesh Network

#
A network topology where every node talks to its neighbors, and traffic is forwarded hop-by-hop. Wi-Fi mesh (eero, Google Nest Wifi, TP-Link Deco): your devices see one SSID, but data hops between APs. LoRa mesh: same idea on sub-GHz radio. Practical: Mesh is the right answer for a multi-building farm where pulling cable is impractical. Watch for: each hop halves the available bandwidth (half-duplex). See also: Access Point (AP), LoRaWAN.

MQTT (Message Queuing Telemetry Transport)

#
A lightweight pub/sub protocol designed for low-bandwidth, unreliable IoT networks. A broker (Mosquitto, HiveMQ) holds messages; clients publish and subscribe to topics. Practical: The default IoT protocol for home automation. Home Assistant, Node-RED, ESPHome, every smart sensor — they all speak MQTT. Topic structure: home/garage/temperature. QoS levels: 0 (fire and forget), 1 (at least once), 2 (exactly once). Default port: 1883 (plain) or 8883 (TLS). See also: Broker (MQTT), Home Assistant (HASS), Modbus.

Modbus

#
A serial communication protocol from 1979, still the lingua franca of industrial sensors, PLCs, and solar inverters. Two variants: Modbus RTU (binary, over RS-485) and Modbus TCP (binary, over Ethernet). Practical: Every solar inverter (SMA, Fronius, Enphase), most electricity meters, many HVAC controllers speak Modbus. Reading a register: request: 0x01 0x04 0x00 0x00 0x00 0x02 [CRC] (function code 04 = read input register, address 0, count 2). The simplymodbus.ca reference is canonical. See also: RS-485 / RS-422, Modbus TCP (port 502), Controller Area Network (CAN).

mDNS / Bonjour

#
Multicast DNS, port 5353. Resolves myprinter.local to an IP without a real DNS server. Apple's Bonjour, Google Chrome's discovery, every IoT device that advertises itself. Practical: The reason ping raspberrypi.local works on your LAN. Watch for: mDNS is multicast and doesn't cross VLANs by default — to use mDNS across VLANs, your router needs an mDNS reflector (most do, but disabled by default for security). See also: DNS (Domain Name System), VLAN (Virtual LAN).

MTU (Maximum Transmission Unit)

#
The largest single packet that can pass through a network segment. Default Ethernet: 1500 bytes. Default PPPoE (used by most DSL): 1492. WireGuard: 1420. Practical: MTU mismatch is the classic “web loads but SSH doesn't” problem. Test with ping -M do -s 1472 destination — if 1472 works and 1473 doesn't, your MTU is 1500. See also: WireGuard, MTU (Maximum Transmission Unit).
Letter

N

4 terms

NTP (Network Time Protocol)

#
The protocol that keeps clocks synchronized. Your router or Pi runs an NTP client; public NTP servers (pool.ntp.org, time.cloudflare.com) keep them within milliseconds of true UTC. Practical: Almost every networked device has an NTP client. If your security camera timestamps are off by an hour, it's probably set to the wrong timezone after a DST change — not an NTP failure. Debug: ntpq -p (Linux) shows the time sources. See also: DNS (Domain Name System), Router.

NAT (Network Address Translation)

#
The mechanism that lets every device on your home network share one public IP. Your router rewrites the source port of every outbound packet and remembers the mapping, so the response (to that port) gets back to the right device. Practical: NAT is why you can't easily reach a device on your home LAN from the internet without port forwarding. It also breaks some protocols (VoIP, online gaming) that need inbound connections. See also: CGNAT (Carrier-Grade NAT), Port Forwarding, Default Gateway.

NMEA 2000 / NMEA 0183

#
Marine networking standards. NMEA 0183 = old, ASCII, RS-422, 4800 baud. NMEA 2000 = newer, binary, based on CAN bus at 250 kbps. Practical: Used on boats for chartplotters, GPS, depth sounders, AIS, autopilots. On a farm, you might meet NMEA 2000 on tractors and combines with yield monitors. To bridge to Ethernet: Yacht Devices NGT-1 or Actisense NGT-1. See also: Controller Area Network (CAN), Modbus.

Node-RED

#
A visual flow-based programming tool, popular for IoT glue. Drag nodes onto a canvas, wire them together, deploy. Built-in nodes for MQTT, HTTP, Modbus, Home Assistant, databases, dashboards. Practical: The right tool when you have data flowing between systems and need to transform it: MQTT topic arrives → look up a value in a database → publish to another topic → trigger an action. Ships as a Home Assistant add-on. See also: MQTT (Message Queuing Telemetry Transport), Home Assistant (HASS).
Letter

O

1 term

OSI Model (7 Layers)

#
The theoretical 7-layer model of networking. In practice, the 4-layer TCP/IP model is what the internet uses. Practical: Don't memorize the layers for their own sake — know which device lives at which layer: L1 (physical) = cable, fiber, radio. L2 (data link) = switch, bridge, MAC address. L3 (network) = router, IP address. L4 (transport) = TCP, UDP, port number. L7 (application) = HTTP, MQTT, DNS. When debugging: “is the problem L1 (cable)? L2 (MAC/ARP)? L3 (IP/routing)? L4 (port blocked)?” See also: TCP/IP Model (4 Layers), Router, Switch (Network).
Letter

P

6 terms

Packet

#
A unit of data on a network. At Layer 3 (IP), a packet has a header (source/dest IP, length, TTL) and a payload (usually a TCP or UDP segment). At Layer 2 (Ethernet), the same unit is called a frame, with a different header (source/dest MAC, EtherType). Practical: For IoT, packet size matters: small, frequent packets (a sensor reading every 10 s) are fine on most networks; large, bursty packets (a camera streaming) need bandwidth planning. See also: MTU (Maximum Transmission Unit), TCP (Transmission Control Protocol), UDP (User Datagram Protocol).

Port Number

#
A 16-bit number (0–65535) that identifies an application on a device. 192.168.1.50:443 = the HTTPS server on 192.168.1.50. Practical: Memorize the common ones: 22 = SSH, 53 = DNS, 80 = HTTP, 443 = HTTPS, 1883 = MQTT, 8883 = MQTT over TLS, 502 = Modbus TCP, 5353 = mDNS, 8080 = alt-HTTP. Watch for: ports below 1024 are “privileged” on Linux — only root can bind them. See also: Port Forwarding, Firewall.

Port Forwarding

#
A NAT rule that says: incoming traffic to port X on the public IP gets sent to port Y on internal IP Z. Used to expose a service (web server, security camera, game console) to the internet. Practical: Configure on your router. Three rules: (1) only forward what you need (security), (2) point to a static DHCP reservation so the internal IP doesn't change, (3) put the device on a guest VLAN if your router supports it. See also: NAT (Network Address Translation), Port Number, Firewall.

PoE (Power over Ethernet)

#
A standard that sends DC power over Ethernet cables. PoE (802.3af) = 15 W, PoE+ (802.3at) = 30 W, PoE++ (802.3bt) = 60–90 W. Practical: An outdoor security camera or a Wi-Fi AP can be powered by a single Ethernet cable run back to a PoE switch — no separate power run, no electrician needed. Watch for: “passive PoE” (non-standard, common on Ubiquiti) is NOT 802.3af — plugging a passive-PoE device into a real PoE switch can fry it. See also: Ethernet, Switch (Network).

Pihole / AdGuard Home

#
A network-wide ad blocker. Runs as a DNS server on your LAN; blocks requests to ad/tracker domains. Every device on the network benefits (no extensions needed on each). Practical: Easy install on a Raspberry Pi: curl -sSL https://install.pi-hole.net | bash. Configure your router's DHCP to hand out the Pi-hole's IP as DNS. Watch for: some sites break if you block the wrong domain — whitelist liberally. See also: DNS (Domain Name System), DHCP (Dynamic Host Configuration Protocol).

PPPoE (Point-to-Point Protocol over Ethernet)

#
The protocol most DSL and some fiber ISPs use to authenticate a session. Adds 8 bytes of overhead per packet, dropping the MTU from 1500 to 1492. Practical: Most home routers auto-configure PPPoE with credentials from your ISP. If a connection works for a browser but breaks for large downloads, the MTU is the first thing to check. See also: MTU (Maximum Transmission Unit), ISP (Internet Service Provider).
Letter

Q

1 term

QoS (Quality of Service)

#
Router features that prioritize certain traffic over others. Real-time (VoIP, video) gets low latency; bulk (file sync, backups) gets best-effort. Practical: On a busy network, QoS is the difference between a smooth Zoom call and a choppy one. Most home routers have a simple QoS: “prioritize video calls.” MikroTik and pfSense have powerful queue trees (per-protocol, per-IP, per-time). See also: Jitter, Latency, Router.
Letter

R

1 term

Router

#
A device that forwards packets between networks, using IP addresses. Your home router: connects your LAN to your ISP's network. Practical: A Wi-Fi router is a router + switch + AP + firewall in one box. On a farm with multiple buildings, you might have a router at each building, all connecting back to a central router at the house. See also: Switch (Network), Access Point (AP), Gateway (Network).
Letter

S

5 terms

Switch (Network)

#
A device that connects devices on the same LAN, forwarding Ethernet frames by MAC address. A 5-port switch is what you plug your PC, NAS, and printer into. Practical: Unmanaged = dumb, no config, $20. Managed = VLANs, link aggregation, port mirroring, $100+. For a small home, unmanaged is fine. For a farm with multiple VLANs (house, barn, guest), you want at least one managed switch. See also: Router, VLAN (Virtual LAN), MAC Address.

SSID (Service Set Identifier)

#
The name of a Wi-Fi network. “SmithHome”, “xfinitywifi”, “ATT-WIFI-9F2E” — all SSIDs. Practical: Best practice: one SSID per band (or one combined if your AP supports it). Don't broadcast a hidden SSID (security through obscurity, plus devices leak it anyway). See also: Wi-Fi (802.11), Access Point (AP), WPA2 / WPA3.

Subnet / Subnetting

#
A subdivision of an IP network. 192.168.1.0/24 is a subnet containing addresses 192.168.1.0 to 192.168.1.255. The /24 means the first 24 bits are the network, last 8 are hosts (254 usable). Practical: For a home network, one /24 is fine. For a farm: one /24 per building (192.168.1.0/24 = house, 192.168.2.0/24 = barn, etc.) with a router between. See also: CIDR (Classless Inter-Domain Routing), VLAN (Virtual LAN).

SLAAC (Stateless Address Autoconfiguration)

#
The IPv6 way for a device to pick its own IP. Combines the router's advertised prefix with a self-generated interface ID (usually derived from the MAC address). Practical: Most home networks have SLAAC enabled by default. If you want a stable IPv6 address (e.g. for a server), use DHCPv6 with a reservation. See also: IP Address (IPv6), DHCP (Dynamic Host Configuration Protocol).

Stateful Inspection

#
A firewall that tracks the state of every connection: source/dest IP+port, sequence numbers, flags. Allows return traffic for an outbound connection; blocks unsolicited inbound. Practical: Default behavior of every home router and every modern OS firewall. Watch for: some services (VoIP, multiplayer games, FTP in active mode) need extra rules because they use dynamic ports. See also: Firewall, NAT (Network Address Translation).
Letter

T

7 terms

TCP/IP Model (4 Layers)

#
The practical model the internet uses: Link (Ethernet, Wi-Fi), Internet (IP), Transport (TCP, UDP), Application (HTTP, MQTT, SSH, DNS). Practical: When something doesn't work, walk up the stack: can you ping the gateway (Internet layer)? Can you telnet example.com 443 (Transport layer)? Does curl https://example.com work (Application layer)? See also: OSI Model (7 Layers), TCP (Transmission Control Protocol), UDP (User Datagram Protocol).

TCP (Transmission Control Protocol)

#
Connection-oriented, reliable transport. Every byte is acknowledged; lost bytes are retransmitted; order is preserved. Practical: Web (HTTP), email (SMTP), SSH, MQTT-over-TCP all use TCP. Watch for: TCP overhead = 20–60 bytes per segment + an extra round-trip to set up the connection (the “three-way handshake”). For a sensor reading every 10 s, that's fine. For a 1000 Hz control loop, use UDP. See also: UDP (User Datagram Protocol), TCP/IP Model (4 Layers), Three-Way Handshake.

Throughput

#
The actual data rate you achieve, after all protocol overhead, retransmissions, congestion, and signal quality. Always less than bandwidth. Practical: 1 Gbps Ethernet = ~940 Mbps TCP throughput. Wi-Fi 6 1.2 Gbps PHY = ~700 Mbps in a clean room, ~200 Mbps in a real house. LoRaWAN SF7 = ~5 kbps. Debug: iperf3 -c server for LAN throughput. See also: Bandwidth (Network), Latency.

Thread / Matter

#
Thread = a low-power IPv6 mesh protocol (IEEE 802.15.4, 2.4 GHz) for IoT. Matter = a unified application-layer standard (built on Thread, Wi-Fi, or Ethernet) backed by Apple, Google, Amazon, and the CSA. Practical: Matter is the “works with everything” promise: a Matter device works with HomeKit, Google Home, Alexa, SmartThings without bridges. As of 2026, adoption is real but uneven — check device compatibility. Thread requires a border router (Apple TV 4K, Nest Hub, HomePod mini, etc.). See also: Zigbee, Home Assistant (HASS).

Tailscale / ZeroTier

#
Zero-config mesh VPNs. They handle NAT traversal, key distribution, and authentication. Practical: For remote access to your home/farm network without dealing with CGNAT, port forwarding, or DDNS: install Tailscale on the devices, log in with the same account, they see each other as if on the same LAN. Watch for: the free personal tier covers ~100 devices; commercial use has different pricing. See also: VPN (Virtual Private Network), CGNAT (Carrier-Grade NAT), NAT (Network Address Translation).

TLS / SSL

#
Transport Layer Security (formerly Secure Sockets Layer). The encryption layer under HTTPS, SMTPS, IMAPS, MQTTS, etc. Practical: For IoT: prefer TLS where available. Self-signed certs on local devices give you a browser warning. Let's Encrypt gives free certs for public domains; Mkcert generates local-trusted certs for LAN devices. Watch for: TLS 1.0 and 1.1 are deprecated — disable them on every server. See also: HTTP / HTTPS, Port Number.

Three-Way Handshake

#
The TCP connection setup: SYN (client → server) → SYN+ACK (server → client) → ACK (client → server). After this, data flows. Practical: Three round-trips before the first byte. On a 50 ms RTT link, that's 100 ms before a connection is usable. Why care: this is why TLS 1.3 is faster (1 round-trip handshake vs 2); why QUIC (used by HTTP/3) eliminates it (0 round-trips on a repeat connection). See also: TCP (Transmission Control Protocol).
Letter

U

1 term

UDP (User Datagram Protocol)

#
Connectionless, unreliable transport. Send a packet, hope it arrives. No handshake, no acknowledgements, no order. Practical: DNS, NTP, VoIP, video streaming, mDNS, MQTT (in its native form), LoRaWAN all use UDP. Watch for: UDP packets get dropped on congested networks — for critical data, you add reliability at the application layer (MQTT QoS 1/2, DTLS, or a custom retry). See also: TCP (Transmission Control Protocol), MQTT (Message Queuing Telemetry Transport).
Letter

V

2 terms

VLAN (Virtual LAN)

#
A way to split one physical switch into multiple logical networks. Devices on VLAN 10 can talk to each other; devices on VLAN 20 can't, even if they're plugged into the same switch. Practical: A common home/farm setup: VLAN 10 = trusted devices, VLAN 20 = IoT (smart bulbs, cameras), VLAN 30 = guest. Your router handles the routing + firewall between them. Watch for: VLANs require a managed switch and a router that supports VLAN tagging (802.1Q). UniFi, MikroTik, pfSense, OPNsense all do. See also: Switch (Network), VLAN (Virtual LAN).

VPN (Virtual Private Network)

#
An encrypted tunnel between two networks (or a device and a network). The most common protocols: WireGuard (fast, modern, default in Linux 5.6+), OpenVPN (mature, widely supported), IPSec (enterprise, complex). Practical: Use a VPN to (1) reach your home network from a coffee shop, (2) connect two sites (house and barn) over the internet, (3) bypass geo-restrictions. For zero-config: Tailscale or ZeroTier. Watch for: the VPN MTU is usually 1420 (tunnel overhead ~80 bytes). See also: WireGuard, Tailscale / ZeroTier, MTU (Maximum Transmission Unit).
Letter

W

3 terms

WAN (Wide Area Network)

#
The network outside your LAN — typically the internet, or a long-distance link between two sites. Your router's WAN port is the one that connects to the modem or to the next-site router. Practical: Dual-WAN = two internet links (Starlink + 4G) for failover. SD-WAN = software that routes per-application across multiple WANs. See also: Router, Failover, Load Balancer.

Wi-Fi (802.11)

#
The IEEE 802.11 family of wireless LAN standards. 2.4 GHz and 5 GHz (6 GHz in 6E/7) bands. Practical: Standards worth knowing: 802.11n (Wi-Fi 4) = 2009, 2.4/5 GHz, 150–600 Mbps. 802.11ac (Wi-Fi 5) = 2014, 5 GHz, 433–1733 Mbps. 802.11ax (Wi-Fi 6/6E) = 2020, OFDMA, 1200+ Mbps. 802.11be (Wi-Fi 7) = 2024, 320 MHz, 30 Gbps. Watch for: the 2.4 GHz band is congested in residential areas; in a farm it can be cleaner. See also: SSID (Service Set Identifier), WPA2 / WPA3, Band Steering.

WPA2 / WPA3

#
Wi-Fi security standards. WPA2 (2004) = AES-CCMP, the long-time default. WPA3 (2018) = SAE handshake (defeats offline dictionary attacks), forward secrecy, mandatory on Wi-Fi 6E/7 certified devices. Practical: Use WPA2-Personal (AES) or WPA3-Personal on every network. Disable WEP and WPA1 (deprecated, breakable in seconds). For older IoT devices, you may need a separate SSID on WPA2 — or a guest VLAN. See also: SSID (Service Set Identifier), Wi-Fi (802.11).
Letter

Z

2 terms

Zigbee

#
A low-power mesh radio protocol for home automation, IEEE 802.15.4 based, 2.4 GHz, ~250 kbps, range ~10–30 m indoor. Practical: Used by IKEA Tradfri, Philips Hue, Aqara, Sonoff Zigbee devices. Requires a coordinator: a USB dongle (ZBT-1, ConBee, CC2652) or a hub (Hue Bridge, Home Assistant Yellow). Watch for: Zigbee and Wi-Fi both use 2.4 GHz and can interfere — keep APs 1+ channel apart from the Zigbee channels (11, 15, 20, 25). See also: Thread / Matter, Z-Wave, Home Assistant (HASS).

Z-Wave

#
A low-power mesh radio for home automation, sub-GHz (908.42 MHz in North America, 868.42 MHz in Europe), ~100 kbps, range ~30 m indoor. Practical: Used by older SmartThings, Aeotec, Zooz, Inovelli devices. Watch for: Z-Wave and Zigbee are competitors — pick one ecosystem per device category. Z-Wave's sub-GHz means it doesn't share spectrum with Wi-Fi (less interference, longer range), but it requires Z-Wave-specific chips. See also: Zigbee, Thread / Matter.

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6. Quick reference tables

6.1 Port cheat sheet (memorize these)

PortProtocolNotes
22SSHremote shell, encrypted
53DNSboth UDP and TCP
67/68DHCPserver / client (UDP)
80HTTPunencrypted — use 443 instead when possible
123NTPtime sync (UDP)
443HTTPSHTTP over TLS
502Modbus TCPindustrial control
5353mDNS / Bonjour / Avahizero-config LAN discovery (UDP)
5683CoAPconstrained IoT (UDP)
5684CoAPs (DTLS)encrypted CoAP
1883MQTTthe default IoT pub/sub
8883MQTT over TLSMQTTS
8884MQTT over QUICMQTT 5 over QUIC
1900SSDP / UPnPdevice discovery multicast (UDP)
51820WireGuarddefault VPN port (UDP)
554RTSPIP camera streaming

6.2 Troubleshooting checklist (walk up the stack)

When something doesn’t work, walk the TCP/IP stack from the bottom. Most bugs are at L1, L2, or L3.

  1. Layer 1 (cable / radio): link light on the switch/AP? Replace the cable. Move closer to the AP. Check the SSID.
  2. Layer 2 (MAC / ARP): can you arp -a the gateway? Can the switch see the MAC?
  3. Layer 3 (IP / routing): can you ping the gateway? Can you ping 8.8.8.8 (public IP)?
  4. Layer 4 (port): can you telnet example.com 443 or nc -zv example.com 443? If not, a firewall is blocking.
  5. Layer 7 (app): can you curl https://example.com? Does the service respond? Is the cert valid?
  6. DNS: if ping 8.8.8.8 works but ping example.com doesn’t, it’s DNS. Try nslookup example.com 1.1.1.1 to bypass your resolver.

6.3 Common home / farm subnet layouts

Use caseRangeNotes
Home LAN (single subnet)192.168.1.0/24default for most home routers
Home + guest + IoT (3 VLANs)192.168.1.0/24, 192.168.2.0/24, 192.168.3.0/24router on a managed switch
Small farm (one building)192.168.10.0/24router + AP + sensors
Multi-building farm192.168.10.0/24 (house), 192.168.11.0/24 (barn), 192.168.12.0/24 (field), etc.router in each building, WireGuard or fiber between
Site-to-site VPNuse non-overlapping rangese.g. house 10.0.1.0/24, barn 10.0.2.0/24
IoT / lab sandbox10.10.10.0/24isolated from main LAN

6.4 IPv4 vs IPv6 at a glance

ConceptIPv4IPv6
Address size32 bits128 bits
Address space~4.3 × 10⁹~3.4 × 10³⁸
Notation192.168.1.12001:db8::1
Header size20–60 bytes40 bytes (fixed)
Private ranges10/8, 172.16/12, 192.168/16fc00::/7 (ULA)
Loopback127.0.0.1::1
Link-local169.254/16fe80::/10
ConfigurationDHCP or staticSLAAC, DHCPv6, or static
NATalmost always needed (CGNAT)not needed (end-to-end)
Multicast224.0.0.0/4ff00::/8

6.5 Which protocol for which job?

RangeBandwidthPowerBest protocol
< 10 m (one room)anylowBLE, Zigbee, Thread, Wi-Fi
10–100 m (one building)lowlowZigbee, Thread, Z-Wave, Wi-Fi
100 m – 2 km (one farm)lowlowLoRaWAN, NB-IoT, LTE-M
2–20 km (rural)lowlowLoRaWAN + outdoor gateway, cellular, satellite (Iridium)
Wired (any distance < 100 m)highlowEthernet (Cat5e/6)
Backhaul (site to site)highanyFiber, Point-to-Point radio (Ubiquiti airMAX, Mimosa)

6.6 Default debugging tools (on a Linux/macOS box)

# Layer 1
ip link                     # list interfaces and link state
iw dev wlan0 link           # Wi-Fi link state
ethtool eth0                # Ethernet link state, speed, duplex

# Layer 2
arp -a                      # ARP table
ip neigh                    # same on modern Linux
bridge link                 # bridge ports and their state

# Layer 3
ip a                        # interfaces + IPs
ip route                    # routing table
ping -c 4 8.8.8.8           # public IP reachability
traceroute unmolai.com      # path to a host

# Layer 4
nc -zv example.com 443      # is a port open?
ss -tlnp                    # listening TCP sockets
ss -ulnp                    # listening UDP sockets

# Layer 7
dig unmolai.com @1.1.1.1    # DNS resolution
curl -v https://unmolai.com # full HTTP trace
mosquitto_sub -h broker.local -t 'home/#' -v  # MQTT subscribe

# Wi-Fi
iw dev wlan0 scan           # list nearby APs
iw dev wlan0 link           # current association

# Bluetooth
bluetoothctl scan on       # discover nearby BLE devices
bluetoothctl devices

7. Further reading

Start here (free, high quality):

  • 🔥 Home Assistant docs — home-assistant.io
  • 🔥 The Things Network LoRaWAN docs — thethingsnetwork.org
  • 🔥 ChirpStack LoRaWAN server docs — chirpstack.io
  • 🔥 Mosquitto MQTT broker docs — mosquitto.org
  • 📚 Computer Networking: A Top-Down Approach (Kurose & Ross) — the canonical textbook
  • 📚 Beej’s Guide to Network Programming — beej.us

Specifications (canonical, free):

Stay current:

Last updated: July 2026. Maintained as a living document — if a term on your co-op isn't here, add it.