There's something in-between traditional (IP style) packets and traditional (TDM / ISDN style) circuit switching, where you use packets with no bandwidth guaran

There's something in-between traditional (IP style) packets and traditional (TDM / ISDN style) circuit switching, where you use packets with no bandwidth guarantees, but address them by connection number, not endpoint address. This still requires you to set up a connection beforehand, but doesn't require you to reserve resources you might not be using.