Unreliable Datagram Protocol
Packet Oriented, not stream oriented like TCP/IP
Much faster but no error correction
NFS, TFTP, and FSP use UDP/IP
Must fit data into packets of about 60,000 bytes or less
The User Datagram Protocol, UDP for short, provides unguaranteed, connectionless transmission of data across an IP network. By contrast, TCP sockets provide reliable, connection-oriented transmission of data.
Both TCP and UDP split data into packets called datagrams. However TCP includes extra headers in the datagram to enable retransmission of lost packets and reassembly of packets into the correct order if they arrive out of order. UDP does not provide this.
Given these disadvantages you may well wonder why anyone would prefer UDP to TCP. The answer is speed. UDP can be up to three times faster than TCP; and there are many applications for which reliable transmission of data is not nearly as important as spee
Telephone vs. snail mail analogy.
Protocols that use UDP include NFS, FSP, and TFTP.