DTLS (TCP vs. UDP)

Transport Layer Security (TLS) known as Secure Sockets Layer (SSL) is an encryption protocol (based on x.509) for secure data transmission.

Datagram Transport Layer Security (DTLS) is based on TLS and uses UDP instead of TCP. The difference between TLS and DTLS is equivalent to the difference between TCP and UDP.

TLS requires the reliability of the data, among other things for decrypting data. If, for example, the data packets arrive out of order, TLS will not be able to perform an integrity check, since the check involves the sequence number of the packets, i.e. after packet N, packet N+1 is expected.

The DTLS specification mainly provides a proposed solution for how the required security can be maintained when using UDP.