The last mile
Your internet service provider (ISP) links each home to its network. That final stretch of cable, from the ISP to your home, is called the last mile. On this street three homes use three kinds: a phone line, a TV cable and a fibre.
Phone line (DSL)
DSL (digital subscriber line) sends data as high-pitched tones on the copper phone line, above the sound of a voice call. The pair of wires is this home's alone. It runs to a DSLAM, the DSL box at the ISP.
High tones fade quickly in thin copper, so the farther a home is from the DSLAM, the slower DSL gets. VDSL2 gives about 100 Mb/s (megabits per second) at 0.5 km, but only about 50 Mb/s at 1 km.
TV cable
Cable internet uses the coax cable that brings TV. The cable modem speaks DOCSIS, the cable data standard, with a CMTS, the cable box in the ISP building. Your data rides on radio-frequency channels next to the TV channels.
One coax line passes many homes, and they all share it. DOCSIS 3.1 carries up to about 10 Gb/s down and 1 Gb/s up per line, split between everyone online, so busy evenings can feel slower.
Fibre
Fibre to the home (FTTH) brings a thin glass strand right into the house. Data travels as light, about 5 microseconds per kilometre. A small box, the ONT (optical network terminal), turns the light into Ethernet for your router.
Most FTTH uses GPON. A passive splitter, needing no power, copies the light from the OLT (the ISP's fibre box) to up to 64 homes. They share 2.488 Gb/s down and 1.244 Gb/s up; each ONT keeps only its own data.
Choosing a link
Most links give more speed down (to you) than up (from you), because homes mostly download. A common VDSL2 plan is 80 down and 20 up Mb/s. Cable and GPON are lopsided too, though fibre can be built symmetric.
Fixed wireless and 4G or 5G home routers reach the ISP by radio from a nearby mast instead of a cable. They are quick to set up, but speed depends on signal strength and on how many people share the mast.
Every last-mile link ends at the ISP: the DSLAM, the CMTS, the OLT, the mast. They hand traffic to the ISP's routers, which give each home a public address like 203.0.113.21 and carry it onward.
What is going on, line by line
;; step 1/10 · last-mile · local ;; at the dsl modem, cable modem, fibre ont, isp building the "last mile" = the access link between a home and the ISP DSL copper phone pair → DSLAM (VDSL2, ITU-T G.993.2) cable shared TV coax → CMTS (DOCSIS 3.1, CableLabs) fibre glass + splitter → OLT (GPON, ITU-T G.984) radio 4G/5G mast → ISP (fixed wireless, 3GPP) whatever the link, a router at home joins it to your LAN (home network)
VDSL2 rates by distance are typical planning figures for profile 17a; real lines vary. 80/20 Mb/s is a common retail plan. DOCSIS 3.1 and GPON figures are the shared capacity of one line, not one home's speed. Many DSL lines today are fibre to the cabinet (FTTC): the DSLAM sits in a street cabinet, so the copper part is short.