All of the following are true of Internet Protocol (IP), except: 

a. to send messages using IP, higher-layer data must be encapsulated into IP datagrams. 

b. encapsulated datagrams are sent to the Data Link Layer, where they are further encapsulated into frames.

c. on the Network Layer, IP puts Transport Layer messages, including the headers and trailers of all higher layers, into the data field of an IP datagram. 

d. it allows routers to determine which routes are available and which is the most efficient to a destination.