1-- ftp is file transfer protocol. ftp is a application that works in application
layer of osi model.

one good reason to use ftp is to download files. ftp is much fater than
standard http downloads

2--UDP is nothing but user datagram protocol this protocol works at
transport layer of osi model.
udp is un reliable ,connectionless datagram protocol " unreliable" merely
means that the protocol has no technique for verifying that the data
reached the other end of network correctly
3--swithes are network device .
to improve network performance switches were developed.it keeps the
table mac address per port to make switching decision

4--router is network device to send packets between different network routers are used