Which three protocols use UDP as a transport protocol by default?（）

多项选择题You have been asked to develop an application that uses only connection-oriented protocols. Which two protocols can you use?（）

A. PPP
B. UDP
C. TCP
D. ICMP

多项选择题Which two characteristics describe the UDP protocol?（）

A. limited error checking
B. defined timers
C. no recovery mechanisms
D. three-way handshake