Each service provided by a server, such as email or file transfers, uses a specific
port number. The source port number of a service request identifies the client that is requesting
services. The destination port number identifies the specific service. Servers do not use address
information to provide services. Routers and switches use addressing information to move traffic
through the network.
28. What happens if part of an FTP message is not delivered to the destination?
A. The FTP source host sends a query to the destination host.
B. The part of the FTP message that was lost is re-sent.
C. The message is lost because FTP does not use a reliable delivery method.
UDP is not a connection-oriented protocol and does not provide retransmission,
sequencing, or flow control mechanisms. It provides basic transport layer functions with a much
lower overhead than TCP. Lower overhead makes UDP suitable for applications which are
sensitive to delay.