Which of the following protocols is not implemented at the Internet layer of the TCP/IP protocol
model?

A.
User datagram protocol (UDP)

B.
Internet protocol (IP)

C.
Address resolution protocol (ARP)

D.
Internet control message protocol (ICMP)

Explanation:
UDP (User Datagram Protocol) is a communications method (protocol) that offers a
limited amount of service when messages are exchanged between computers in a network that
uses the Internet Protocol (IP). UDP is an alternative to the Transmission Control Protocol (TCP)
and, together with IP, is sometimes referred to as UDP/IP. Like the Transmission Control Protocol,
UDP uses the Internet Protocol to actually get a data unit (called a datagram) from one computer
to another. Unlike TCP, however, UDP does not provide the service of dividing a message into
packets (datagrams) and reassembling it at the other end. Specifically, UDP doesn’t provide
sequencing of the packets that the data arrives in. UDP is implemented at the Transport layer of
the TCP/IP protocol model.