The concepts behind the Physical Package Protocol can be divided into two main areas, the Data and Switching Protocols which determine how Packages are handled and the Physical Assets that do the physical work. For more information click on the links below.
Data and Switching Protocols:
Physical Package Protocol Dispatch Number - How each Package is addressed.
Service Auctioning - How the Package finds the best route to it's destination.
Switching and Sorting Protocols - How Packages in Package Routers are handled.
The Dispatch Data Log - How charges are calculated and paid.
Physical Asset Standards:
Top Image CC 3.0: Track Gauges in China Railway Museum