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

多项选择题Which three protocols use UDP as a transport protocol by default?（）

A. HTTP
B. TFTP
C. DNS
D. SNMP
E. SMTP

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

多项选择题Which two statements are true of a network mask?（）

A. A subnet mask specifies the portion of an IP address that is in a binary format.
B. A subnet mask specifies the portion of an IP address that is in a decimal format.
C. A subnet mask specifies the portion of an IP address that represents a network prefix.
D. A subnet mask specifies the portion of an IP address that represents network hosts.

单项选择题What is the purpose of a network mask?（）

A. It is used in conjunction with the wildcard mask to determine the number of hosts on a network
B. It is used to define which parts of the IP address are allocated to host addresses and network prefixes
C. It is used to hide subnets from external networks by masking the subnets with NAT
D. It is used to differentiate a network as a classful network or a classless network