Tcp Tutorial-10

The User Datagram Protocol or the UDP Protocol

is the standard protocol used by all systems for communications. TCP is used to break down the data to be

transported into smaller datagrams, before they (the datagrams) are sent across a network. Thus we can say that TCP is used where more than a single or multiple datagrams are involved.

Sometimes, the data to be transported is able to fit into a single datagram. We do not need to break the data into smaller datagrams as the size of the data is pretty small. The perfect example of such data is the DNS system. To send out the query for a particular domain name, a single datagram is more than enough. Also the IP that is returned by the Domain Name Server does not require more than one datagram for transportation. So in such cases instead of making use of the complex TCP protocol, applications fall back to the UDP protocol.

The UDP protocol works almost the way TCP works. But the only differences being that TCP breaks the data to be transferred into smaller chunks, does sequencing by inserting a sequence number in the header and no error control. Thus we can conclude by saying that the UDP protocol is an unreliable protocol with no way to confirm that the data has reached the destination.

The UDP protocol does insert a USP header to the single datagram it is transporting. The UDP header contains the Source and Destination IP Addresses and Port Numbers and also the Checksum value. The UDP header is comparatively smaller than the TCP Header.

It is used by those applications where small chunks of data are involved. It offers services to the User's Network Applications like NFS(Network File Sharing) and SNMP.

Read RFC 768 for further in depth details about the UDP protocol.