tunnels require specific support in each USB4 router, just to support passing them through to further USB4 routers. However, end-to-end tunnels require support of a USB4 router only when the data is ingested into the tunnel and at the target, to the point where the tunnel ends.

Note: USB 2.0 is not part of any tunnel. That functionality is provided by maintaining a physically and logically separate USB 2.0 connection in parallel to a USB4 connection over the dedicated wires, just as it was handled with USB 3.x and its backward compatibility