TCP is a reliable protocol which uses acknowledgements to ensure transfer of information packets. UDP is a non reliable protocol which transfers information even if no acknowledgement is received. UDP is usually applied in audio and video applications where there would be latency if TCP is used, due to acknowledgements.
by
HAROUN MUSA , Supervisor of Sudanese Standard & Metrtology Org Website , Sudanese Standard & Metrology Org
UDP is a connectionless protocol that runs on top of IP (UDP/IP), and TCP is a connection-oriented protocol that runs on top of IP (TCP/IP). Connectionless means that a host can send a message to another host without first establishing a connection with the recipient. The host simply puts a message onto the network with a destination address and hopes that the message arrives. In addition, the transmission or receipt of a UDP packet doesn't guarantee any further communication in either direction. Because a UDP packet doesn't require an existing connection, network systems use UDP primarily for broadcasting messages (i.e., a one-to-many sending, much like unsolicited junk email). The most common UDP packets—DNS registrations and name-resolution queries—are sent to port53.
In contrast, TCP ports support only connection-oriented protocols. A connection-oriented protocol requires that network endpoints establish a channel between them before they transmit messages. Whereas incoming UDP traffic indicates an unsolicited message that doesn't necessarily require a response, incoming TCP messages arrive because someone is trying to establish a point-to-point connection with your system and, in turn, is expecting a response.
