UDP (user datagram protocol) is a simple protocol. It provides no reliability, i.e. it sends the datagrams that the application writes to the IP layer, but there is no guarantee that they ever reach their destination. Services offered by UDP are:
1. IP
2. Port numbers
3. Optional checksum
Fields:
1. Source port
2. Destination port
3. Length field
4. Checksum
UDP checksum covers the UDP header and the UDP data. With UDP checksum is optional, while with TCP it is mandatory.
