The interplanetary ferry system is how yinrih got around Focus before the invention of the mass router, and it's still how bulk cargo is transported afterward.
It was formerly run by the Bright Way before the War of dissolution, but now operates as a series of independent but interconnected spaceports and spacelines similar to how the aviation industry works on Earth.
Ferries are strictly spacefaring craft, unable to land on a planet's surface. Spaceports exist atop space elevators, or in the case of Yih, an array of freely orbiting structures that are accessed by smaller shuttle craft.
Spacers like to joke that ferries have “accidental gravity” because ferries have a constant acceleration of around 0.88 g (or the same gravity as Yih). This allows them to get from one point on the outer belt to the opposite side of the system in about 84 Earth days. They can accelerate faster, and some spacelines offer routes that use an acceleration of 1 g, which cuts off a lot of travel time at the cost of a higher gravity.
They operate by accelerating for half the trip, and decelerating for the second half.
They're set up like Victorian era / pre WW I steam ships, with cabins of various levels of opulence as well as common areas and food service.
Passenger ferries persist for a time after the mass router is invented, but eventually they're used for just cargo and the occasional pleasure cruise.