Which network service or protocol was used?

The following is an excerpt from the output of tcpdump -nli eth1:

13:03:17.277327 IP 192.168.123.5.1065 > 192.168.5.112.21: Flags [.], ack 1 (truncated)

13:03:17.598624 IP 192.168.5.112.21 > 192.168.123.5.1065: Flags [P.], seq (truncated)

Which network service or protocol was used?
A . FTP
B . HTTP
C . SSH
D . DNS
E . DHCP

View Answer

Answer: A