A transaction with UDP takes 2 segments, the request and the reply. With TCP a transaction takes 9 segments. As will be seen in chapter 4 T/TCP can complete a transaction in just 3 segments. A reduction in the case of TCP, but an increase for UDP. The advantage that T/TCP holds over UDP is the reliability.
The main changes with T/TCP over TCP are in the way that it establishes communication with the other host, and how the connection is terminated. These are discussed in chapter 4.