Between major networks, BGP. Inside the major network to your cable headend or similar: OSPF or IS-IS or something else - in the largest ISPs, a combination of

Between major networks, BGP. Inside the major network to your cable headend or similar: OSPF or IS-IS or something else - in the largest ISPs, a combination of iBGP to get things to right area and then OSPF, IS-IS or EIGRP in medium areas. Inside your house: almost always static routes, no protocol for exchanging reachability info.